Modular fuel cell architectures for power generation

Abstract

Methods, systems, and apparatus for modular fuel cell architectures for power generation. In some implementations, an array of modules is configured to output an AC voltage as a combination of multiple AC module voltages generated based on DC input from one or more fuel cell stacks. Each of the modules can include a plurality of input ports configured to receive the DC input from the one or more fuel cell stacks. In some cases, the modules are configured to receive different DC input voltages from electrical taps at different intermediate locations among fuel cells of a fuel cell stack that are electrically coupled in series. In some cases, the modules are configured to selectively receive power from multiple fuel cell stacks or multiple fuel cell strings coupled together in parallel. The modules include a power output connection and a local control device configured to control the module.

Description

[0001] MODULAR FUEL CELL ARCHITECTURES FOR POWER GENERATION

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application is an International Application which claims priority to U.S. Provisional Patent Application No. 63 / 616,142, filed December 29, 2023. The disclosure of the foregoing application is hereby incorporated by reference in its entirety.

[0004] FIELD

[0005] The subject matter described herein relates generally to systems, devices, and methods for power generation using modular fuel cell architectures.

[0006] BACKGROUND

[0007] Fuel cells can provide renewable energy with few or no greenhouse gas emissions. For example, hydrogen fuel cells produce electricity with only heat and water as byproducts. However, adoption of fuel cell technology has been more limited than many have expected. Fuel cell systems have traditionally had limited scalability and adjustability, often requiring users to employ an oversized system that is more expensive than is actually needed. Many applications do not make use of fuel cells due to their relatively slow response to applied loads and slow start-up process compared to batteries and other electrical sources. Finally, few systems have the capability to effectively manage fuel cells over their lifetime, as the cells degrade and their capabilities are reduced.

[0008] For these and other reasons, needs exist for improved systems, devices, and methods for power generation using modular fuel cell architectures.

[0009] SUMMARY

[0010] Example embodiments of systems, devices, and methods are provided herein for systems, devices, and methods that generate power using modular arrangements of fuel cells and conversion electronics. Different groups of fuel cells, e.g., fuel cell stacks, are arranged in modules that each have an associated control and conversion electronics. Each module can generate an alternating current (AC) output from its corresponding fuel cell stack, and the AC outputs can be coordinated among the modules to deliver the output power characteristics that are desired. For example, multiple modules can be controlled so that together they provide an AC output phase that combines the power generation capabilities of their respective fuel cells stacks. The system can dynamically couple more or fewer modules to the AC output line to respond to increases or decreases in demand. As another example, multiple modules or multiple groups of modules can be synchronized to provide multiphase power. The various modules can be controlled separately to achieve a variety of configurations, including with differing numbers of AC and direct current (DC) outputs, different voltages, and different power levels, as well as to balance wear and load among different modules.

[0011] The modular system also facilitates the use of fuel cells with batteries and other power sources. For example, the modules that generate AC output using fuel cell stacks can be synchronized with other modules that generate AC output from stored energy in batteries, so that both types of modules contribute concurrently to power a load. As another example, the electronics of a single module can receive input from a fuel cell stack as well as a battery, so that the module can generate AC output from either or both power sources coupled to the module. By combining battery power with fuel cell power at the module level, each module gains the high responsiveness of battery to fluctuation in demand as well as the long-running steady-state power generation capacity of the fuel cell stack. In addition, the peak power capacity of each module is greater than if it were powered by either the battery or the fuel cell stack alone.

[0012] In many conventional systems, DC output of a fuel cell stack undergoes multiple conversion stages before power is delivered to a load. For example, DC output of a fuel cell stack is commonly first stepped up to the level of a DC bus using DC / DC converter, before a DC / AC converter (e.g., an inverter) produces AC output. The intermediate DC / DC conversion stage often leads to electrical inefficiency as well as additional cost and size of the system.

[0013] In some implementations, the modular fuel cell system described herein can achieve high efficiency by directly converting DC output of the fuel cell stack to an AC output. Even when the DC fuel cell output is stepped up to a higher level, stepping directly to the desired output voltage for the AC output can avoid the inefficiency of multiple DC / DC conversions. For example, the fuel cell output can be first matched to a battery voltage or a DC bus voltage before conversion to AC output. In addition, because each fuel cell module has a separate DC / AC converter, modules having fuel cell stacks with different voltages or wear characteristics can still be coupled together and to the load with high efficiency.

[0014] Other systems, devices, methods, features and advantages of the subject matter described herein will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the subject matter described herein, and be protected by the accompanying claims. In no way should the features of the example embodiments be construed as limiting the appended claims, absent express recitation of those features in the claims. BRIEF DESCRIPTION OF FIGURES

[0015] The details of the subject matter set forth herein, both as to its structure and operation, may be apparent by study of the accompanying figures, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the subject matter. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely.

[0016] FIGS. 1A-1C are block diagrams depicting example embodiments of a modular energy system.

[0017] FIGS. 1D-1E are block diagrams depicting example embodiments of control devices for an energy system.

[0018] FIGS. 1F-1G are block diagrams depicting example embodiments of modular energy systems coupled with a load and a charge source.

[0019] FIGS. 2A-2B are block diagrams depicting example embodiments of a module and control system within an energy system.

[0020] FIG. 2C is a block diagram depicting an example embodiment of a physical configuration of a module.

[0021] FIG. 2D is a block diagram depicting an example embodiment of a physical configuration of a modular energy system.

[0022] FIGS. 3A-3C are block diagrams depicting example embodiments of modules having various electrical configurations.

[0023] FIGS. 4A-4F are schematic views depicting example embodiments of energy sources.

[0024] FIGS. 5A-5C are schematic views depicting example embodiments of energy buffers.

[0025] FIGS. 6A-6C are schematic views depicting example embodiments of converters.

[0026] FIGS. 7A-7E are block diagrams depicting example embodiments of modular energy systems having various topologies.

[0027] FIG. 8A is a plot depicting an example output voltage of a module.

[0028] FIG. 8B is a plot depicting an example multilevel output voltage of an array of modules.

[0029] FIG. 8C is a plot depicting an example reference signal and carrier signals usable in a pulse width modulation control technique.

[0030] FIG. 8D is a plot depicting example reference signals and carrier signals usable in a pulse width modulation control technique.

[0031] FIG. 8E is a plot depicting example switch signals generated according to a pulse width modulation control technique. FIG. 8F as a plot depicting an example multilevel output voltage generated by superposition of output voltages from an array of modules under a pulse width modulation control technique.

[0032] FIGS. 9A-9B are block diagrams depicting example embodiments of controllers for a modular energy system.

[0033] FIG. 10A is a block diagram depicting an example embodiment of a multiphase modular energy system having interconnection module.

[0034] FIG. 1 OB is a schematic diagram depicting an example embodiment of an interconnection module in the multiphase embodiment of FIG. 1 OA.

[0035] FIG. IOC is a block diagram depicting an example embodiment of a modular energy system having two subsystems connected together by interconnection modules.

[0036] FIG. 10D is a block diagram depicting an example embodiment of a three-phase modular energy system having interconnection modules supplying auxiliary loads.

[0037] FIG. 10E is a schematic view depicting an example embodiment of the interconnection modules in the multiphase embodiment of FIG. 10D.

[0038] FIG. 1 OF is a block diagram depicting another example embodiment of a three-phase modular energy system having interconnection modules supplying auxiliary loads.

[0039] FIGS. 11A-15B are block diagrams depicting examples of systems for supplying power using fuel cells.

[0040] FIGS. 16A-17B are block diagrams depicting examples of fuel cell stacks and modules supplying power using input from the fuel cell stacks.

[0041] FIG. 18 is a block diagram depicting an example of the main control device controlling a fuel cell system and interacting with a computer system over a network.

[0042] DETAILED DESCRIPTION

[0043] Before the present subject matter is described in detail, it is to be understood that this disclosure is not limited to the particular embodiments described, as such may, of course, vary. The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

[0044] Before describing the example embodiments pertaining to modular energy systems that emphasize fuel cell power generation, it is first useful to describe these underlying systems in greater detail. With reference to FIGS. 1A through 10F, the following sections describe various applications in which embodiments of the modular energy systems can be implemented, embodiments of control systems or devices for the modular energy systems, configurations of the modular energy system embodiments with respect to charging sources and loads, embodiments of individual modules, embodiments of topologies for arrangement of the modules within the systems, embodiments of control methodologies, embodiments of balancing operating characteristics of modules within the systems, and embodiments of the use of interconnection modules.

[0045] Examples of Applications

[0046] Stationary applications are those in which the modular energy system is located in a fixed location during use, although it may be capable of being transported to alternative locations when not in use. The module-based energy system resides in a static location while providing electrical energy for consumption by one or more other entities, or storing or buffering energy for later consumption. Examples of stationary applications in which the embodiments disclosed herein can be used include, but are not limited to: energy systems for use by or within one or more residential structures or locales, energy systems for use by or within one or more industrial structures or locales, energy systems for use by or within one or more commercial structures or locales, energy systems for use by or within one or more governmental structures or locales (including both military and non-military uses), energy systems for charging the mobile applications described below (e.g., a charge source or a charging station), and systems that convert solar power, wind, geothermal energy, fossil fuels, or nuclear reactions into electricity for storage. Stationary applications often supply loads such as grids and microgrids, motors, and data centers. A stationary energy system can be used in either a storage or non-storage role.

[0047] Mobile applications, sometimes referred to as traction applications, are generally ones where a module-based energy system is located on or within an entity, and stores and provides electrical energy for conversion into motive force by a motor to move or assist in moving that entity. Examples of mobile entities with which the embodiments disclosed herein can be used include, but are not limited to, electric and / or hybrid entities that move over or under land, over or under sea, above and out of contact with land or sea (e.g., flying or hovering in the air), or through outer space. Examples of mobile entities with which the embodiments disclosed herein can be used include, but are not limited to, vehicles, trains, trams, ships, vessels, aircraft, and spacecraft. Examples of mobile vehicles with which the embodiments disclosed herein can be used include, but are not limited to, those having only one wheel or track, those having only two-wheels or tracks, those having only three wheels or tracks, those having only four wheels or tracks, and those having five or more wheels or tracks. Examples of mobile entities with which the embodiments disclosed herein can be used include, but are not limited to, a car, a bus, a truck, a motorcycle, a scooter, a bicycle, an industrial vehicle, a mining vehicle, a flying vehicle (e.g., a plane, a helicopter, a drone, etc.), a maritime vessel (e.g., commercial shipping vessels, ships, yachts, boats or other watercraft), a submarine, a locomotive or rail-based vehicle (e.g., a train, a tram, etc.), a military vehicle, a spacecraft, and a satellite.

[0048] In describing embodiments herein, reference may be made to a particular stationary application (e.g., grid, micro-grid, data centers, cloud computing environments) or mobile application (e.g., an electric car). Such references are made for ease of explanation and do not mean that a particular embodiment is limited for use to only that particular mobile or stationary application. Embodiments of systems providing power to a motor can be used in both mobile and stationary applications. While certain configurations may be more suitable to some applications over others, all example embodiments disclosed herein are capable of use in both mobile and stationary applications unless otherwise noted.

[0049] Module-based Energy System Examples

[0050] FIG. 1 A is a block diagram depicts an example embodiment of a module-based energy system 100. Here, system 100 includes control system 102 communicatively coupled with N power supply modules or converter modules 108-1 through 108-N, over communication paths or links 106-1 through 106-N, respectively. Modules 108 can be configured to convert energy and output the energy as needed to a load 101 (and / or other modules 108). Each module 108 includes or is associated with a source of energy, such as a battery, one or more fuel cells, a photovoltaic panel, or other energy source. The source of energy for a module 108 can be included in the module 108 (e.g., housed within or attached to the module 108) or can be coupled to the module 108 to provide energy but can be external and separate from the module 108 itself (e.g., a fuel cell, a photovoltaic panel, etc.).

[0051] When fuel cells are used as the source of energy for one or more power supply modules or converter modules 108, multiple modules 108 may receive energy from the same fuel cell stack. A fuel cell stack typically includes a set of multiple individual fuel cells that are combined in series. Each individual fuel cell generates electricity in the form of direct current (DC) from electrochemical reactions that take place in the fuel cell. Each individual fuel cell may produce a relatively low voltage, such as approximately 1 V or less. Fuel cells can be combined in series into strings or strands each comprising multiple fuel cells, and one or more of these fuel cell strings or fuel cell strands is included in each fuel cell stack. The fuel cell stack can be a modular assembly of standardized fuel cells integrated into a single assembly. Each fuel cell stack has an associated balance-of-plant that includes other supporting components, such as pumps, sensors, heat exchangers, gaskets, compressors, recirculation blowers, and so on. As used herein, each fuel cell stack has a corresponding balance-of-plant supporting its operation, even though the additional components are not specifically discussed. In some implementations, a fuel cell stack includes a single set of fuel cells electrically coupled in series, but in other implementations, a fuel cell stack may include sets of fuel cells electrically coupled in parallel. As discussed below, multiple fuel cell stacks can also be coupled in parallel, for example, to provide higher current output than a single fuel cell stack.

[0052] One example type of fuel cell is a proton-exchange membrane fuel cell (PEMFC). These fuel cells generally have two electrodes, a cathode and an anode, that are separated by an electrolyte. The cathode is typically made of a porous, conductive material such as carbon, and the anode is typically made of a material that is catalytically active, such as platinum or palladium. The electrolyte is a material, which could be solid or liquid, that allows ions to pass through but blocks electrons. When fuel (e.g., hydrogen gas) is supplied to the anode and oxidant (e.g., oxygen gas) is supplied to the cathode, a chemical reaction occurs at the electrodes to produce electricity. At the anode, the fuel is oxidized, releasing electrons and protons. The protons pass through the electrolyte to the cathode, while the presence of the electron-blocking membrane forces electrons to flow through an external circuit as electricity. At the cathode, the protons and electrons are recombined with oxygen to form water, which completes the process. Other types of fuel cells, using other fuels or other mechanisms of operation, may additionally or alternatively be used.

[0053] Any number of two or more modules 108 can be used (e.g., N is greater than or equal to two). Modules 108 can be connected to each other in a variety of manners as will be described in more detail with respect to FIGS. 7A-7E. For ease of illustration, in FIGS. 1A-1C, modules 108 are shown connected in series, or as a one dimensional array, where the Nth module is coupled to load 101.

[0054] System 100 is configured to supply power to load 101. Load 101 can be any type of load such as a motor or a grid. System 100 is also configured to store power received from a charge source. FIG. IF is a block diagram depicting an example embodiment of system 100 with a power input interface 151 for receiving power from a charge source 150 and a power output interface for outputting power to load 101. In this embodiment system 100 can receive and store power over interface 151 at the same time as outputting power over interface 152. FIG. 1G is a block diagram depicting another example embodiment of system 100 with a switchable interface 154. In this embodiment, system 100 can select, or be instructed to select, between receiving power from charge source 150 and outputting power to load 101. System 100 can be configured to supply multiple loads 101, including both primary and auxiliary loads, and / or receive power from multiple charge sources 150 (e.g., a utility-operated power grid and a local renewable energy source (e.g., solar)).

[0055] FIG. IB depicts another example embodiment of system 100. Here, control system 102 is implemented as a main control device (MCD) 112 communicatively coupled with N different local control devices (LCDs) 114-1 through 114-N over communication paths or links 115-1 through 115-N, respectively. Each LCD 114-1 through 114-N is communicatively coupled with one module 108-1 through 108-N over communication paths or links 116-1 through 116-N, respectively, such that there is a 1 : 1 relationship between LCDs 114 and modules 108.

[0056] EIG. 1C depicts another example embodiment of system 100. Here, MCD 112 is communicatively coupled with M different LCDs 114-1 to 114-M over communication paths or links 115-1 to 115-M, respectively. Each LCD 114 can be coupled with and control two or more modules 108. In the example shown here, each LCD 114 is communicatively coupled with two modules 108, such that M LCDs 114-1 to 114-M are coupled with 2M modules 108-1 through 108- 2M over communication paths or links 116-1 to 116-2M, respectively.

[0057] Control system 102 can be configured as a single device (e.g., EIG. 1A) for the entire system 100 or can be distributed across or implemented as multiple devices (e.g., FIGS. 1B-1C). In some embodiments, control system 102 can be distributed between LCDs 114 associated with the modules 108, such that no MCD 112 is necessary and can be omitted from system 100.

[0058] Control system 102 can be configured to execute control using software (instructions stored in memory that are executable by processing circuitry), hardware, or a combination thereof. The one or more devices of control system 102 can each include processing circuitry 120 and memory 122 as shown here. Example implementations of processing circuitry and memory are described further below.

[0059] Control system 102 can have a communicative interface for communicating with devices 104 external to system 100 over a communication link or path 105. For example, control system 102 (e.g., MCD 112) can output data or information about system 100 to another control device 104 (e.g., the Electronic Control Unit (ECU) or Motor Control Unit (MCU) of a vehicle in a mobile application, grid controller in a stationary application, etc.).

[0060] Communication paths or links 105, 106, 115, 116, and 118 (FIG. 2B) can each be wired (e.g., electrical, optical) or wireless communication paths that communicate data or information bidirectionally, in parallel or series fashion. Data can be communicated in a standardized (e.g., IEEE, ANSI) or custom (e.g., proprietary) format. In automotive applications, communication paths 115 can be configured to communicate according to FlexRay or CAN protocols. Communication paths 106, 115, 116, and 118 can also provide wired power to directly supply the operating power for system 102 from one or more modules 108. For example, the operating power for each LCD 114 can be supplied only by the one or more modules 108 to which that LCD 114 is connected and the operating power for MCD 112 can be supplied indirectly from one or more of modules 108 (e.g., such as through a car’s power network).

[0061] Control system 102 is configured to control one or more modules 108 based on status information received from the same or different one or more of modules 108. Control can also be based on one or more other factors, such as requirements of load 101. Controllable aspects include, but are not limited to, one or more of voltage, current, phase, and / or output power of each module 108.

[0062] Status information of every module 108 in system 100 can be communicated to control system 102, which can independently control every module 108-1... 108-N. Other variations are possible. For example, a particular module 108 (or subset of modules 108) can be controlled based on status information of that particular module 108 (or subset), based on status information of a different module 108 that is not that particular module 108 (or subset), based on status information of all modules 108 other than that particular module 108 (or subset), based on status information of that particular module 108 (or subset) and status information of at least one other module 108 that is not that particular module 108 (or subset), or based on status information of all modules 108 in system 100.

[0063] The status information can be information about one or more aspects, characteristics, or parameters of each module 108. Types of status information include, but are not limited to, the following aspects of a module 108 or one or more components thereof (e.g., energy source, energy buffer, converter, monitor circuitry): State of Charge (SOC) (e.g., the level of charge of an energy source relative to its capacity, such as a fraction or percent) of the one or more energy sources of the module, State of Health (SOH) (e.g., a figure of merit of the condition of an energy source compared to its ideal conditions) of the one or more energy sources of the module, temperature of the one or more energy sources or other components of the module, capacity of the one or more energy sources of the module, voltage of the one or more energy sources and / or other components of the module, current of the one or more energy sources and / or other components of the module, State of Power (SOP) (e.g., the available power limitation of the energy source during discharge and / or charge), State of Energy (SOE) (e.g., the present level of available energy of an energy source relative to the maximum available energy of the source), and / or the presence of absence of a fault in any one or more of the components of the module.

[0064] LCDs 114 can be configured to receive the status information from each module 108, or determine the status information from monitored signals or data received from or within each module 108, and communicate that information to MCD 112. In some embodiments, each LCD 114 can communicate raw collected data to MCD 112, which then algorithmically determines the status information on the basis of that raw data. MCD 112 can then use the status information of modules 108 to make control determinations accordingly. The determinations may take the form of instructions, commands, or other information (such as a modulation index described herein) that can be utilized by LCDs 114 to either maintain or adjust the operation of each module 108. For example, MCD 112 may receive status information and assess that information to determine a difference between at least one module 108 (e.g., a component thereof) and at least one or more other modules 108 (e.g., comparable components thereof). For example, MCD 112 may determine that a particular module 108 is operating with one of the following conditions as compared to one or more other modules 108: with a relatively lower or higher SOC, with a relatively lower or higher SOH, with a relatively lower or higher capacity, with a relatively lower or higher voltage, with a relatively lower or higher current, with a relatively lower or higher temperature, or with or without a fault. In such examples, MCD 112 can output control information that causes the relevant aspect (e.g., output voltage, current, power, temperature) of that particular module 108 to be reduced or increased (depending on the condition). In this manner, the utilization of an outlier module 108 (e.g., operating with a relatively lower SOC or higher temperature), can be reduced so as to cause the relevant parameter of that module 108 (e.g., SOC or temperature) to converge towards that of one or more other modules 108.

[0065] The determination of whether to adjust the operation of a particular module 108 can be made by comparison of the status information to predetermined thresholds, limits, or conditions, and not necessarily by comparison to statuses of other modules 108. The predetermined thresholds, limits, or conditions can be static thresholds, limits, or conditions, such as those set by the manufacturer that do not change during use. The predetermined thresholds, limits, or conditions can be dynamic thresholds, limits, or conditions, that are permitted to change, or that do change, during use. For example, MCD 112 can adjust the operation of a module 108 if the status information for that module 108 indicates it to be operating in violation (e.g., above or below) of a predetermined threshold or limit, or outside of a predetermined range of acceptable operating conditions. Similarly, MCD 112 can adjust the operation of a module 108 if the status information for that module 108 indicates the presence of an actual or potential fault (e.g., an alarm, or warning) or indicates the absence or removal of an actual or potential fault. Examples of a fault include, but are not limited to, an actual failure of a component, a potential failure of a component, a short circuit or other excessive current condition, an open circuit, an excessive voltage condition, a failure to receive a communication, the receipt of corrupted data, and the like. Depending on the type and severity of the fault, the faulty module’s utilization can be decreased to avoid damaging the module, or the module’s utilization can be ceased altogether. For example, if a fault occurs in a given module, then MCD 112 or LCD 114 can cause that module to enter a bypass state as described herein.

[0066] MCD 112 can control modules 108 within system 100 to achieve or converge towards a desired target. The target can be, for example, operation of all modules 108 at the same or similar levels with respect to each other, or within predetermined thresholds limits, or conditions. This process is also referred to as balancing or seeking to achieve balance in the operation or operating characteristics of modules 108. The term “balance” as used herein does not require absolute equality between modules 108 or components thereof, but rather is used in a broad sense to convey that operation of system 100 can be used to actively reduce disparities in operation (or operative state) between modules 108 that would otherwise exist.

[0067] MCD 112 can communicate control information to LCD 114 for the purpose of controlling the modules 108 associated with the LCD 114. The control information can be, e.g., a modulation index and a reference signal as described herein, a modulated reference signal, or otherwise. Each LCD 114 can use (e.g., receive and process) the control information to generate switch signals that control operation of one or more components (e.g., a converter) within the associated module(s) 108. In some embodiments, MCD 112 generates the switch signals directly and outputs them to LCD 114, which relays the switch signals to the intended module component.

[0068] All or a portion of control system 102 can be combined with a system external control device 104 that controls one or more other aspects of the mobile or stationary application. When integrated in this shared or common control device (or subsystem), control of system 100 can be implemented in any desired fashion, such as one or more software applications executed by processing circuitry of the shared device, with hardware of the shared device, or a combination thereof. Non-exhaustive examples of external control devices 104 include: a vehicular ECU or MCU having control capability for one or more other vehicular functions (e.g., motor control, driver interface control, traction control, etc.); a grid or micro-grid controller having responsibility for one or more other power management functions (e.g., load interfacing, load power requirement forecasting, transmission and switching, interface with charge sources (e.g., diesel, solar, wind), charge source power forecasting, back up source monitoring, asset dispatch, etc.); and a data center control subsystem (e.g., environmental control, network control, backup control, etc.).

[0069] FIGS. ID and IE are block diagrams depicting example embodiments of a shared or common control device (or system) 132 in which control system 102 can be implemented. In FIG. ID, common control device 132 includes main control device 112 and external control device 104. Main control device 112 includes an interface 141 for communication with LCDs 114 over path 115, as well as an interface 142 for communication with external control device 104 over internal communication bus 136. External control device 104 includes an interface 143 for communication with main control device 112 over bus 136, and an interface 144 for communication with other entities (e.g., components of the vehicle or grid) of the overall application over communication path 136. In some embodiments, common control device 132 can be integrated as a common housing or package with devices 112 and 104 implemented as discrete integrated circuit (IC) chips or packages contained therein. In FIG. IE, external control device 104 acts as common control device 132, with the main control functionality implemented as a component within device 104. The main control device 112 can be or include software or other program instructions stored and / or hardcoded within memory of device 104 and executed by processing circuitry thereof. The component can also contain dedicated hardware. The component can be a self-contained module or core, with one or more internal hardware and / or software interfaces (e.g., application program interface (API)) for communication with the operating software of external control device 104. External control device 104 can manage communication with LCDs 114 over interface 141 and other devices over interface 144. In various embodiments, device 104 / 132 can be integrated as a single IC chip, can be integrated into multiple IC chips in a single package, or integrated as multiple semiconductor packages within a common housing.

[0070] In the embodiments of FIGS. ID and IE, the main control functionality of system 102 is shared in common device 132, however, other divisions of shared control or permitted. For example, part of the main control functionality can be distributed between common device 132 and a dedicated MCD 112. In another example, both the main control functionality and at least part of the local control functionality can be implemented in common device 132 (e.g., with remaining local control functionality implemented in LCDs 114). In some embodiments, all of control system 102 is implemented in common device (or subsystem) 132. In some embodiments, local control functionality is implemented within a device shared with another component of each module 108, such as a Battery Management System (BMS).

[0071] Examples of Modules within Cascaded Energy Systems

[0072] Module 108 can include one or more energy sources and a power electronics converter and, if desired, an energy buffer. FIGS. 2A-2B are block diagrams depicting additional example embodiments of system 100 with module 108 having a power converter 202, an energy buffer 204, and an energy source 206. Converter 202 can be a voltage converter or a current converter. The embodiments are described herein with reference to voltage converters, although the embodiments are not limited to such. Converter 202 can be configured to convert a direct current (DC) signal from energy source 206 into an alternating current (AC) signal and output it over power connection 110 (e.g., with the converter 202 acting as an inverter). Converter 202 can also receive an AC or DC signal over connection 110 and apply it to energy source 206 with either polarity in a continuous or pulsed form. Converter 202 can be or include an arrangement of switches (e.g., power transistors) such as a half bridge of full bridge (H-bridge). In some embodiments converter 202 includes only switches and the converter (and the module as a whole) does not include a transformer. Converter 202 can be also (or alternatively) be configured to perform AC to DC conversion (e.g., a rectifier) such as to charge a DC energy source from an AC source, DC to DC conversion, and / or AC to AC conversion (e.g., in combination with an AC -DC converter). In some embodiments, such as to perform AC-AC conversion, converter 202 can include a transformer, either alone or in combination with one or more power semiconductors (e.g., switches, diodes, thyristors, and the like). In other embodiments, such as those where weight and cost is a significant factor, converter 202 can be configured to perform the conversions with only power switches, power diodes, or other semiconductor devices and without a transformer.

[0073] Energy source 206 is preferably a robust energy storage device capable of outputting direct current and having an energy density suitable for energy storage applications for electrically powered devices. Energy source 206 can be an electrochemical battery, such as a single battery cell or multiple battery cells connected together in a battery module or array, or any combination thereof. FIGS. 4A-4D are schematic diagrams depicting example embodiments of energy source 206 configured as a single battery cell 402 (FIG. 4A), a battery module with a series connection of multiple (e.g., four) cells 402 (FIG. 4B), a battery module with a parallel connection of single cells 402 (FIG. 4C), and a battery module with a parallel connection with legs having two cells 402 each (FIG. 4D). A non-exhaustive list of examples of battery types is set forth elsewhere herein.

[0074] Energy source 206 can also be a high energy density (HED) capacitor, such as an ultracapacitor or supercapacitor. An HED capacitor can be configured as a double layer capacitor (electrostatic charge storage), pseudocapacitor (electrochemical charge storage), hybrid capacitor (electrostatic and electrochemical), or otherwise, as opposed to a solid dielectric type of a typical electrolytic capacitor. The HED capacitor can have an energy density of 10 to 100 times (or higher) that of an electrolytic capacitor, in addition to a higher capacity. For example, HED capacitors can have a specific energy greater than 1.0 watt hours per kilogram (Wh / kg), and a capacitance greater than 10-100 farads (F). As with the batteries described with respect to FIGS. 4A-4D, energy source 206 can be configured as a single HED capacitor or multiple HED capacitors connected together in an array (e.g., series, parallel, or a combination thereof).

[0075] Energy source 206 can also be a fuel cell. The fuel cell can be a single fuel cell, multiple fuel cells connected in series or parallel, or a fuel cell module. Examples of fuel cell types include proton-exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), solid acid fuel cells, alkaline fuel cells, high temperature fuel cells, solid oxide fuel cells, molten electrolyte fuel cells, and others. As with the batteries described with respect to FIGS. 4A-4D, energy source 206 can be configured as a single fuel cell or multiple fuel cells connected together in an array (e.g., series, parallel, or a combination thereof). The aforementioned examples of source classes (e.g., batteries, capacitors, and fuel cells) and types (e.g., chemistries and / or structural configurations within each class) are not intended to form an exhaustive list, and those of ordinary skill in the art will recognize other variants that fall within the scope of the present subject matter.

[0076] Energy buffer 204 can dampen or fdter fluctuations in current across the DC line or link (e.g., +VDCL and -VDCL as described below), to assist in maintaining stability in the DC link voltage. These fluctuations can be relatively low (e.g., kilohertz) or high (e.g., megahertz) frequency fluctuations or harmonics caused by the switching of converter 202, or other transients. These fluctuations can be absorbed by buffer 204 instead of being passed to source 206 or to ports 103 and IO4 of converter 202.

[0077] Power connection 110 is a connection for transferring energy or power to, from and through module 108. Module 108 can output energy from energy source 206 to power connection 110, where it can be transferred to other modules of the system or to a load. Module 108 can also receive energy from other modules 108 or a charging source (DC charger, single phase charger, multi -phase charger). Signals can also be passed through module 108 bypassing energy source 206. The routing of energy or power into and out of module 108 is performed by converter 202 under the control of LCD 114 (or another entity of system 102).

[0078] In the embodiment of FIG. 2A, LCD 114 is implemented as a component separate from module 108 (e.g., not within a shared module housing) and is connected to and capable of communication with converter 202 via communication path 116. In the embodiment of FIG. 2B, LCD 114 is included as a component of module 108 and is connected to and capable of communication with converter 202 via internal communication path 118 (e.g., a shared bus or discrete connections). LCD 114 can also be capable of receiving signals from, and transmitting signals to, energy buffer 204 and / or energy source 206 over paths 116 or 118.

[0079] Module 108 can also include monitor circuitry 208 configured to monitor (e.g., collect, sense, measure, and / or determine) one or more aspects of module 108 and / or the components thereof, such as voltage, current, temperature or other operating parameters that constitute status information (or can be used to determine status information by, e.g., LCD 114). A main function of the status information is to describe the state of the one or more energy sources 206 of the module 108 to enable determinations as to how much to utilize the energy source in comparison to other sources in system 100, although status information describing the state of other components (e.g., voltage, temperature, and / or presence of a fault in buffer 204, temperature and / or presence of a fault in converter 202, presence of a fault elsewhere in module 108, etc.) can be used in the utilization determination as well. Monitor circuitry 208 can include one or more sensors, shunts, dividers, fault detectors, Coulomb counters, controllers or other hardware and / or software configured to monitor such aspects. Monitor circuitry 208 can be separate from the various components 202, 204, and 206, or can be integrated with each component 202, 204, and 206 (as shown in FIGS. 2A-2B), or any combination thereof. In some embodiments, monitor circuitry 208 can be part of or shared with a Battery Management System (BMS) for a battery energy source 204. Discrete circuitry is not needed to monitor each type of status information, as more than one type of status information can be monitored with a single circuit or device, or otherwise algorithmically determined without the need for additional circuits.

[0080] LCD 114 can receive status information (or raw data) about the module components over communication paths 116, 118. LCD 114 can also transmit information to module components over paths 116, 118. Paths 116 and 118 can include diagnostics, measurement, protection, and control signal lines. The transmitted information can be control signals for one or more module components. The control signals can be switch signals for converter 202 and / or one or more signals that request the status information from module components. For example, LCD 114 can cause the status information to be transmitted over paths 116, 118 by requesting the status information directly, or by applying a stimulus (e.g., voltage) to cause the status information to be generated, in some cases in combination with switch signals that place converter 202 in a particular state.

[0081] The physical configuration or layout of module 108 can take various forms. In some embodiments, module 108 can include a common housing in which all module components, e.g., converter 202, buffer 204, and source 206, are housed, along with other optional components such as an integrated LCD 114. In other embodiments, the various components can be separated in discrete housings that are secured together. FIG. 2C is a block diagram depicting an example embodiment of a module 108 having a first housing 220 that holds an energy source 206 of the module and accompanying electronics such as monitor circuitry, a second housing 222 that holds module electronics such as converter 202, energy buffer 204, and other accompany electronics such as monitor circuitry, and a third housing 224 that holds LCD 114 (not shown) for the module 108. In alternative embodiments the module electronics and LCD 114 can be housed within the same single housing. In still other embodiments, the module electronics, LCD 114, and energy source(s) can be housed within the same single housing for the module 108. Electrical connections between the various module components can proceed through the housings 220, 222, 224 and can be exposed on any of the housing exteriors for connection with other devices such as other modules 108 or MCD 112.

[0082] Modules 108 of system 100 can be physically arranged with respect to each other in various configurations that depend on the needs of the application and the number of loads. For example, in a stationary application where system 100 provides power for a microgrid, modules 108 can be placed in one or more racks or other frameworks. Such configurations may be suitable for larger mobile applications as well, such as maritime vessels. Alternatively, modules 108 can be secured together and located within a common housing, referred to as a pack. A rack or a pack may have its own dedicated cooling system shared across all modules. Pack configurations are useful for smaller mobile applications such as electric cars. System 100 can be implemented with one or more racks (e.g., for parallel supply to a microgrid) or one or more packs (e.g., serving different motors of the vehicle), or combination thereof. FIG. 2D is a block diagram depicting an example embodiment of system 100 configured as a pack with nine modules 108 electrically and physically coupled together within a common housing 230.

[0083] Examples of these and further configurations are described in Int’l. Appl. No. PCT7US20 / 25366, filed March 27, 2020 and titled Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto, which is incorporated by reference herein in its entirety for all purposes.

[0084] FIGS. 3A-3C are block diagrams depicting example embodiments of modules 108 having various electrical configurations. These embodiments are described as having one LCD 114 per module 108, with the LCD 114 housed within the associated module, but can be configured otherwise as described herein. FIG. 3 A depicts a first example configuration of a module 108A within system 100. Module 108 A includes energy source 206, energy buffer 204, and converter 202A. Each component has power connection ports (e.g., terminals, connectors) into which power can be input and / or from which power can be output, referred to herein as IO ports. Such ports can also be referred to as input ports or output ports depending on the context.

[0085] Energy source 206 can be configured as any of the energy source types described herein (e.g., a battery as described with respect to FIGS. 4A-4D, an HED capacitor, a fuel cell, or otherwise). Ports IO1 and IO2 of energy source 206 can be connected to ports IO1 and IO2, respectively, of energy buffer 204. Energy buffer 204 can be configured to buffer or filter high and low frequency energy pulsations arriving at buffer 204 through converter 202, which can otherwise degrade the performance of module 108. The topology and components for buffer 204 are selected to accommodate the maximum permissible amplitude of these high frequency voltage pulsations. Several (non-exhaustive) example embodiments of energy buffer 204 are depicted in the schematic diagrams of FIGS. 5A-5C. In FIG. 5 A, buffer 204 is an electrolytic and / or film capacitor CEB, in FIG. 5B buffer 204 is a Z-source network 710, formed by two inductors LEBI and LEB2 and two electrolytic and / or film capacitors CEBI and CEB2, and in FIG. 5C buffer 204 is a quasi Z-source network 720, formed by two inductors LEBI and LEB2, two electrolytic and / or film capacitors CEBI and CEB2 and a diode DEB.

[0086] Ports IO3 and IO4 of energy buffer 204 can be connected to ports IO1 and IO2, respectively, of converter 202A, which can be configured as any of the power converter types described herein. FIG. 6A is a schematic diagram depicting an example embodiment of converter 202 A configured as a DC-AC converter that can receive a DC voltage at ports 101 and 102 and switch to generate pulses at ports 103 and 104. Converter 202A can include multiple switches, and here converter 202A includes four switches S3, S4, S5, S6 arranged in a full bridge configuration. Control system 102 or LCD 114 can independently control each switch via control input lines 118- 3 to each gate.

[0087] The switches can be any suitable switch type, such as power semiconductors like the metal-oxide-semiconductor field-effect transistors (MOSFETs) shown here, insulated gate bipolar transistors (IGBTs), or gallium nitride (GaN) transistors. Semiconductor switches can operate at relatively high switching frequencies, thereby permitting converter 202 to be operated in pulsewidth modulated (PWM) mode if desired, and to respond to control commands within a relatively short interval of time. This can provide a high tolerance of output voltage regulation and fast dynamic behavior in transient modes.

[0088] In this embodiment, a DC line voltage VDCL can be applied to converter 202 between ports 101 and 102. By connecting VDCL to ports 103 and 104 by different combinations of switches S3, S4, S5, S6, converter 202 can generate three different voltage outputs at ports 103 and 104: +VDCL, 0, and -VDCL. A switch signal provided to each switch controls whether the switch is on (closed) or off (open). To obtain +VDCL, switches S3 and S6 are turned on while S4 and S5 are turned off, whereas -VDCL can be obtained by turning on switches S4 and S5 and turning off S3 and S6. The output voltage can be set to zero (including near zero) or a reference voltage by turning on S3 and S5 with S4 and S6 off, or by turning on S4 and S6 with S3 and S5 off. These voltages can be output from module 108 over power connection 110. Ports 103 and 104 of converter 202 can be connected to (or form) module IO ports 1 and 2 of power connection 110, so as to generate the output voltage for use with output voltages from other modules 108.

[0089] The control or switch signals for the embodiments of converter 202 described herein can be generated in different ways depending on the control technique utilized by system 100 to generate the output voltage of converter 202. In some embodiments, the control technique is a PWM technique such as space vector pulse-width modulation (SVPWM) or sinusoidal pulse-width modulation (SPWM), or variations thereof. FIG. 8A is a graph of voltage versus time depicting an example of an output voltage waveform 802 of converter 202. For ease of description, the embodiments herein will be described in the context of a PWM control technique, although the embodiments are not limited to such. Other classes of techniques can be used. One alternative class is based on hysteresis, examples of which are described in Inf 1 Publ. Nos. WO 2018 / 231810A1, WO 2018 / 232403 Al, and WO 2019 / 183553A1, which are incorporated by reference herein for all purposes. Each module 108 can be configured with multiple energy sources 206 (e.g., two, three, four, or more). Each energy source 206 of module 108 can be controllable (switchable) to supply power to connection 110 (or receive power from a charge source) independent of the other sources 206 of the module. For example, all sources 206 can output power to connection 110 (or be charged) at the same time, or only one (or a subset) of sources 206 can supply power (or be charged) at any one time. In some embodiments, the sources 206 of the module can exchange energy between them, e.g., one source 206 can charge another source 206. Each of the sources 206 can be configured as any energy source described herein (e.g., battery, FLED capacitor, fuel cell). Each of the sources 206 can be the same class (e.g., each can be a battery, each can be an HED capacitor, or each can be a fuel cell), or a different class (e.g., a first source can be a battery and a second source can be an HED capacitor or fuel cell, or a first source can be an HED capacitor and a second source can be a fuel cell).

[0090] FIG. 3B is a block diagram depicting an example embodiment of a module 108B in a dual energy source configuration with a primary energy source 206A and secondary energy source 206B. Ports IO1 and IO2 of primary source 202 A can be connected to ports IO1 and IO2 of energy buffer 204. Module 108B includes a converter 202B having an additional IO port. Ports IO3 and IO4 of buffer 204 can be connected ports IO1 and IO2, respectively, of converter 202B. Ports IO1 and IO2 of secondary source 206B can be connected to ports 105 and 102, respectively, of converter 202B (also connected to port 104 of buffer 204).

[0091] In this example embodiment of module 108B, primary energy source 202A, along with the other modules 108 of system 100, supplies the average power needed by the load. Secondary source 202B can serve the function of assisting energy source 202 by providing additional power at load power peaks, or absorbing excess power, or otherwise.

[0092] As mentioned both primary source 206A and secondary source 206B can be utilized simultaneously or at separate times depending on the switch state of converter 202B. If at the same time, an electrolytic and / or a film capacitor (CES) can be placed in parallel with source 206B as depicted in FIG. 4E to act as an energy buffer for the source 206B, or energy source 206B can be configured to utilize an HED capacitor in parallel with another energy source (e.g., a battery or fuel cell) as depicted in FIG. 4F.

[0093] FIGS. 6B and 6C are schematic views depicting example embodiments of converters 202B and 202C, respectively. Converter 202B includes switch circuitry portions 601 and 602A. Portion 601 includes switches S3 through S6 configured as a full bridge in similar manner to converter 202A, and is configured to selectively couple IO1 and IO2 to either of 103 and 104, thereby changing the output voltages of module 108B. Portion 602A includes switches SI and S2 configured as a half bridge and coupled between ports 101 and 102. A coupling inductor Lc is connected between port 105 and a nodel present between switches SI and S2 such that switch portion 602A is a bidirectional converter that can regulate (boost or buck) voltage (or inversely current). Switch portion 602A can generate two different voltages at nodel, which are +VDCL2 and 0, referenced to port 102, which can be at virtual zero potential. The current drawn from or input to energy source 202B can be controlled by regulating the voltage on coupling inductor Lc, using, for example, a pulse-width modulation technique or a hysteresis control method for commutating switches SI and S2. Other techniques can also be used.

[0094] Converter 202C differs from that of 202B as switch portion 602B includes switches SI and S2 configured as a half bridge and coupled between ports 105 and 102. A coupling inductor Lc is connected between port 101 and a nodel present between switches SI and S2 such that switch portion 602B is configured to regulate voltage.

[0095] Control system 102 or LCD 114 can independently control each switch of converters 202B and 202C via control input lines 118-3 to each gate. In these embodiments and that of FIG. 6A, LCD 114 (not MCD 112) generates the switching signals for the converter switches. Alternatively, MCD 112 can generate the switching signals, which can be communicated directly to the switches, or relayed by LCD 114. In some embodiments, driver circuitry for generating the switching signals can be present in or associated with MCD 112 and / or LCD 114.

[0096] The aforementioned zero voltage configuration for converter 202 (turning on S3 and S5 with S4 and S6 off, or turning on S4 and S6 with S3 and S5 off) can also be referred to as a bypass state for the given module. This bypass state can be entered if a fault is detected in the given module, or if a system fault is detected warranting shut-off of more than one (or all modules) in an array or system. A fault in the module can be detected by LCD 114 and the control switching signals for converter 202 can be set to engage the bypass state without intervention by MCD 112. Alternatively, fault information for a given module can be communicated by LCD 114 to MCD 112, and MCD 112 can then make a determination whether to engage the bypass state, and if so, can communicate instructions to engage the bypass state to the LCD 114 associated with the module having the fault, at which point LCD 114 can output switching signals to cause engagement of the bypass state.

[0097] In embodiments where a module 108 includes three or more energy sources 206, converters 202B and 202C can be scaled accordingly such that each additional energy source 206B is coupled to an additional IO port leading to an additional switch circuitry portion 602A or 602B, depending on the needs of the particular source. For example a dual source converter 202 can include both switch portions 202 A and 202B.

[0098] Modules 108 with multiple energy sources 206 are capable of performing additional functions such as energy sharing between sources 206, energy capture from within the application (e.g., regenerative braking), charging of the primary source by the secondary source even while the overall system is in a state of discharge, and active filtering of the module output. The active filtering function can also be performed by modules having a typical electrolytic capacitor instead of a secondary energy source. Examples of these functions are described in more detail in IntT. Appl. No. PCT / US20 / 25366, filed March 27, 2020 and titled Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto, and IntT. Publ. No. WO 2019 / 183553, filed March 22, 2019, and titled Systems and Methods for Power Management and Control, both of which are incorporated by reference herein in their entireties for all purposes.

[0099] Each module 108 can be configured to supply one or more auxiliary loads with its one or more energy sources 206. Auxiliary loads are loads that require lower voltages than the primary load 101. Examples of auxiliary loads can be, for example, an on-board electrical network of an electric vehicle, or an HVAC system of an electric vehicle. The load of system 100 can be, for example, one of the phases of the electric vehicle motor or electrical grid. This embodiment can allow a complete decoupling between the electrical characteristics (terminal voltage and current) of the energy source and those of the loads.

[0100] FIG. 3C is a block diagram depicting an example embodiment of a module 108C configured to supply power to a first auxiliary load 301 and a second auxiliary load 302, where module 108C includes an energy source 206, energy buffer 204, and converter 202B coupled together in a manner similar to that of FIG. 3B. First auxiliary load 301 requires a voltage equivalent to that supplied from source 206. Load 301 is coupled to IO ports 3 and 4 of module 108C, which are in turn coupled to ports IO1 and IO2 of source 206. Source 206 can output power to both power connection 110 and load 301. Second auxiliary load 302 requires a constant voltage lower than that of source 206. Load 302 is coupled to IO ports 5 and 6 of module 108C, which are coupled to ports IO5 and IO2, respectively, of converter 202B. Converter 202B can include switch portion 602 having coupling inductor Lc coupled to port IO5 (FIG. 6B). Energy supplied by source 206 can be supplied to load 302 through switch portion 602 of converter 202B. It is assumed that load 302 has an input capacitor (a capacitor can be added to module 108C if not), so switches SI and S2 can be commutated to regulate the voltage on and current through coupling inductor Lc and thus produce a stable constant voltage for load 302. This regulation can step down the voltage of source 206 to the lower magnitude voltage is required by load 302.

[0101] Module 108C can thus be configured to supply one or more first auxiliary loads in the manner described with respect to load 301, with the one or more first loads coupled to IO ports 3 and 4. Module 108C can also be configured to supply one or more second auxiliary loads in the manner described with respect to load 302. If multiple second auxiliary loads 302 are present, then for each additional load 302 module 108C can be scaled with additional dedicated module output ports (like 5 and 6), an additional dedicated switch portion 602, and an additional converter IO port coupled to the additional portion 602.

[0102] Energy source 206 can thus supply power for any number of auxiliary loads (e.g., 301 and 302), as well as the corresponding portion of system output power needed by primary load 101. Power flow from source 206 to the various loads can be adjusted as desired.

[0103] Module 108 can be configured as needed with two or more energy sources 206 (FIG. 3B) and to supply first and / or second auxiliary loads (FIG. 3C) through the addition of a switch portion 602 and converter port IO5 for each additional source 206B or second auxiliary load 302. Additional module IO ports (e.g., 3, 4, 5, 6) can be added as needed. Module 108 can also be configured as an interconnection module to exchange energy (e.g., for balancing) between two or more arrays, two or more packs, or two or more systems 100 as described further herein. This interconnection functionality can likewise be combined with multiple source and / or multiple auxiliary load supply capabilities.

[0104] Control system 102 can perform various functions with respect to the components of modules 108 A, 108B, and 108C. These functions can include management of the utilization (amount of use) of each energy source 206, protection of energy buffer 204 from over-current, over-voltage and high temperature conditions, and control and protection of converter 202.

[0105] For example, to manage (e.g., adjust by increasing, decreasing, or maintaining) utilization of each energy source 206, LCD 114 can receive one or more monitored voltages, temperatures, and currents from each energy source 206 (or monitor circuitry). The monitored voltages can be at least one of, preferably all, voltages of each elementary component independent of the other components (e.g., each individual battery cell, HED capacitor, and / or fuel cell) of the source 206, or the voltages of groups of elementary components as a whole (e.g., voltage of the battery array, HED capacitor array, and / or fuel cell array). Similarly the monitored temperatures and currents can be at least one of, preferably all, temperatures and currents of each elementary component independent of the other components of the source 206, or the temperatures and currents of groups of elementary components as a whole, or any combination thereof. The monitored signals can be status information, with which LCD 114 can perform one or more of the following: calculation or determination of a real capacity, actual State of Charge (SOC) and / or State of Health (SOH) of the elementary components or groups of elementary components; set or output a warning or alarm indication based on monitored and / or calculated status information; and / or transmission of the status information to MCD 112. LCD 114 can receive control information (e.g., a modulation index, synchronization signal) from MCD 112 and use this control information to generate switch signals for converter 202 that manage the utilization of the source 206. To protect energy buffer 204, LCD 114 can receive one or more monitored voltages, temperatures, and currents from energy buffer 204 (or monitor circuitry). The monitored voltages can be at least one of, preferably all, voltages of each elementary component of buffer 204 (e.g., of CEB, CEBI, CEB2, LEBI, LEB2, DEB) independent of the other components, or the voltages of groups of elementary components or buffer 204 as a whole (e.g., between 101 and IO2 or between 103 and 104). Similarly the monitored temperatures and currents can be at least one of, preferably all, temperatures and currents of each elementary component of buffer 204 independent of the other components, or the temperatures and currents of groups of elementary components or of buffer 204 as a whole, or any combination thereof. The monitored signals can be status information, with which LCD 114 can perform one or more of the following: set or output a warning or alarm indication; communicate the status information to MCD 112; or control converter 202 to adjust (increase or decrease) the utilization of source 206 and module 108 as a whole for buffer protection.

[0106] To control and protect converter 202, LCD 114 can receive the control information from MCD 112 (e.g., a modulated reference signal, or a reference signal and a modulation index), which can be used with a PWM technique in LCD 114 to generate the control signals for each switch (e.g., SI through S6). LCD 114 can receive a current feedback signal from a current sensor of converter 202, which can be used for overcurrent protection together with one or more fault status signals from driver circuits (not shown) of the converter switches, which can carry information about fault statuses (e.g., short circuit or open circuit failure modes) of all switches of converter 202. Based on this data, LCD 114 can make a decision on which combination of switching signals to be applied to manage utilization of module 108, and potentially bypass or disconnect converter 202 (and the entire module 108) from system 100.

[0107] If controlling a module 108C that supplies a second auxiliary load 302, LCD 114 can receive one or more monitored voltages (e.g., the voltage between IO ports 5 and 6) and one or more monitored currents (e.g., the current in coupling inductor Lc, which is a current of load 302) in module 108C. Based on these signals, LCD 114 can adjust the switching cycles (e.g., by adjustment of modulation index or reference waveform) of SI and S2 to control (and stabilize) the voltage for load 302.

[0108] Cascaded Energy System Topology Examples

[0109] Two or more modules 108 can be coupled together in a cascaded array that outputs a voltage signal formed by a superposition of the discrete voltages generated by each module 108 within the array. FIG. 7A is a block diagram depicting an example embodiment of a topology for system 100 where N modules 108-1, 108-2 . . . 108-N are coupled together in series to form a serial array 700. In this and all embodiments described herein, N can be any integer greater than one. Array 700 includes a first system IO port SIO1 and a second system IO port SIO2 across which is generated an array output voltage. Array 700 can be used as a DC or single phase AC energy source for DC or AC single-phase loads, which can be connected to SIO1 and SIO2 of array 700. FIG. 8A is a plot of voltage versus time depicting an example output signal produced by a single module 108 having a 48 volt energy source. FIG. 8B is a plot of voltage versus time depicting an example single phase AC output signal generated by array 700 having six 48V modules 108 coupled in series.

[0110] System 100 can be arranged in a broad variety of different topologies to meet varying needs of the applications. System 100 can provide multi-phase power (e.g., two-phase, three- phase, four-phase, five-phase, six-phase, etc.) to a load by use of multiple arrays 700, where each array can generate an AC output signal having a different phase angle.

[0111] FIG. 7B is a block diagram depicting system 100 with two arrays 700-PA and 700-PB coupled together. Each array 700 is one-dimensional, formed by a series connection of N modules 108. The two arrays 700-PA and 700-PB can each generate a single-phase AC signal, where the two AC signals have different phase angles PA and PB (e.g., 180 degrees apart). IO port 1 of module 108-1 of each array 700-PA and 700-PB can form or be connected to system IO ports SIO1 and SIO2, respectively, which in turn can serve as a first output of each array that can provide two phase power to a load (not shown). Or alternatively ports SIO1 and SIO2 can be connected to provide single phase power from two parallel arrays. IO port 2 of module 108-N of each array 700- PA and 700- PB can serve as a second output for each array 700- PA and 700- PB on the opposite end of the array from system IO ports SIO1 and SIO2, and can be coupled together at a common node and optionally used for an additional system IO port SIO3 if desired, which can serve as a neutral. This common node can be referred to as a rail, and IO port 2 of modules 108-N of each array 700 can be referred to as being on the rail side of the arrays.

[0112] FIG. 7C is a block diagram depicting system 100 with three arrays 700-PA, 700-PB, and 700-PC coupled together. Each array 700 is one-dimensional, formed by a series connection of N modules 108. The three arrays 700-1 and 700-2 can each generate a single-phase AC signal, where the three AC signals have different phase angles PA, PB, PC (e.g., 120 degrees apart). IO port 1 of module 108-1 of each array 700-PA, 700-PB, and 700-PC can form or be connected to system IO ports SIO1, SIO2, and SIO3, respectively, which in turn can provide three phase power to a load (not shown). IO port 2 of module 108-N of each array 700-PA, 700-PB, and 700-PC can be coupled together at a common node and optionally used for an additional system IO port SIO4 if desired, which can serve as a neutral.

[0113] The concepts described with respect to the two-phase and three-phase embodiments of FIGS. 7B and 7C can be extended to systems 100 generating still more phases of power. For example, a non-exhaustive list of additional examples includes: system 100 having four arrays 700, each of which is configured to generate a single phase AC signal having a different phase angle (e.g., 90 degrees apart): system 100 having five arrays 700, each of which is configured to generate a single phase AC signal having a different phase angle (e.g., 72 degrees apart); and system 100 having six arrays 700, each array configured to generate a single phase AC signal having a different phase angle (e.g., 60 degrees apart).

[0114] System 100 can be configured such that arrays 700 are interconnected at electrical nodes between modules 108 within each array. FIG. 7D is a block diagram depicting system 100 with three arrays 700-PA, 700-PB, and 700-PC coupled together in a combined series and delta arrangement. Each array 700 includes a first series connection of M modules 108, where M is two or greater, coupled with a second series connection of N modules 108, where N is two or greater. The delta configuration is formed by the interconnections between arrays, which can be placed in any desired location. In this embodiment, IO port 2 of module 108-(M+N) of array 700-PC is coupled with IO port 2 of module 108-M and IO port 1 of module 108-(M+l) of array 700-PA, IO port 2 of module 108-(M+N) of array 700-PB is coupled with IO port 2 of module 108-M and IO port 1 of module 108-(M+l) of array 700-PC, and IO port 2 of module 108-(M+N) of array 700- PA is coupled with IO port 2 of module 108-M and IO port 1 of module 108-(M+l) of array 700-

[0115] PB.

[0116] FIG. 7E is a block diagram depicting system 100 with three arrays 700-PA, 700-PB, and 700-PC coupled together in a combined series and delta arrangement. This embodiment is similar to that of FIG. 7D except with different cross connections. In this embodiment, IO port 2 of module 108-M of array 700-PC is coupled with IO port 1 of module 108-1 of array 700-PA, IO port 2 of module 108-M of array 700-PB is coupled with IO port 1 of module 108-1 of array 700-

[0117] PC, and IO port 2 of module 108-M of array 700-PA is coupled with IO port 1 of module 108-1 of array 700-PB. The arrangements of FIGS. 7D and 7E can be implemented with as little as two modules in each array 700. Combined delta and series configurations enable an effective exchange of energy between all modules 108 of the system (interphase balancing) and phases of power grid or load, and also allows reducing the total number of modules 108 in an array 700 to obtain the desired output voltages.

[0118] In the embodiments described herein, although it is advantageous for the number of modules 108 to be the same in each array 700 within system 100, such is not required and different arrays 700 can have differing numbers of modules 108. Further, each array 700 can have modules 108 that are all of the same configuration (e.g., all modules are 108A, all modules are 108B, all modules are 108C, or others) or different configurations (e.g., one or more modules are 108A, one or more are 108B, and one or more are 108C, or otherwise). As such, the scope of topologies of system 100 covered herein is broad.

[0119] Control Methodology Examples

[0120] As mentioned, control of system 100 can be performed according to various methodologies, such as hysteresis or PWM. Several examples of PWM include space vector modulation and sine pulse width modulation, where the switching signals for converter 202 are generated with a phase shifted carrier technique that continuously rotates utilization of each module 108 to equally distribute power among them.

[0121] FIGS. 8C-8F are plots depicting an example embodiment of a phase-shifted PWM control methodology that can generate a multilevel output PWM waveform using incrementally shifted two-level waveforms. An X-level PWM waveform can be created by the summation of (X-l) / 2 two-level PWM waveforms. These two-level waveforms can be generated by comparing a reference waveform Vref to carriers incrementally shifted by 3607(X-l). The carriers are triangular, but the embodiments are not limited to such. A nine-level example is shown in FIG. 8C (using four modules 108). The carriers are incrementally shifted by 3607(9-1) = 45° and compared to Vref. The resulting two-level PWM waveforms are shown in FIG. 8E. These two-level waveforms may be used as the switching signals for semiconductor switches (e.g., SI though S6) of converters 202. As an example with reference to FIG. 8E, for a one-dimensional array 700 including four modules 108 each with a converter 202, the 0° signal is for control of S3 and the 180° signal for S6 of the first module 108-1, the 45° signal is for S3 and the 225° signal for S6 of the second module 108-2, the 90 signal is for S3 and the 270 signal is for S6 of the third module 108-3, and the 135 signal is for S3 and the 315 signal is for S6 of the fourth module 108-4. The signal for S3 is complementary to S4 and the signal for S5 is complementary to S6 with sufficient dead-time to avoid shoot through of each half-bridge. FIG. 8F depicts an example single phase AC waveform produced by superposition (summation) of output voltages from the four modules 108.

[0122] An alternative is to utilize both a positive and a negative reference signal with the first (N- l) / 2 carriers. A nine-level example is shown in FIG. 8D. In this example, the 0° to 135° switching signals (FIG. 8E) are generated by comparing +Vref to the 0° to 135° carriers of FIG. 8D and the 180° to 315° switching signals are generated by comparing -Vref to the 0° to 135° carriers of FIG. 8D. However, the logic of the comparison in the latter case is reversed. Other techniques such as a state machine decoder may also be used to generate gate signals for the switches of converter 202.

[0123] In multi-phase system embodiments, the same carriers can be used for each phase, or the set of carriers can be shifted as a whole for each phase. For example, in a three phase system with a single reference voltage (Vref), each array 700 can use the same number of carriers with the same relative offsets as shown in FIGS. 8C and 8D, but the carriers of the second phase are shift by 120 degrees as compared to the carriers of the first phase, and the carriers of the third phase are shifted by 240 degrees as compared to the carriers of the first phase. If a different reference voltage is available for each phase, then the phase information can be carried in the reference voltage and the same carriers can be used for each phase. In many cases the carrier frequencies will be fixed, but in some example embodiments, the carrier frequencies can be adjusted, which can help to reduce losses in EV motors under high current conditions.

[0124] The appropriate switching signals can be provided to each module by control system 102. For example, MCD 112 can provide Vref and the appropriate carrier signals to each LCD 114 depending upon the module or modules 108 that LCD 114 controls, and the LCD 114 can then generate the switching signals. Or all LCDs 114 in an array can be provided with all carrier signals and the LCD can select the appropriate carrier signals.

[0125] The relative utilizations of each module 108 can adjusted based on status information to perform balancing or of one or more parameters as described herein. Balancing of parameters can involve adjusting utilization to minimize parameter divergence over time as compared to a system where individual module utilization adjustment is not performed. The utilization can be the relative amount of time a module 108 is discharging when system 100 is in a discharge state, or the relative amount of time a module 108 is charging when system 100 is in a charge state.

[0126] As described herein, modules 108 can be balanced with respect to other modules in an array 700, which can be referred to as intra array or intraphase balancing, and different arrays 700 can be balanced with respect to each other, which can be referred to as interarray or interphase balancing. Arrays 700 of different subsystems can also be balanced with respect to each other. Control system 102 can simultaneously perform any combination of intraphase balancing, interphase balancing, utilization of multiple energy sources within a module, active filtering, and auxiliary load supply.

[0127] FIG. 9A is a block diagram depicting an example embodiment of an array controller 900 of control system 102 for a single-phase AC or DC array. Array controller 900 can include a peak detector 902, a divider 904, and an intraphase (or intra array) balance controller 906. Array controller 900 can receive a reference voltage waveform (Vr) and status information about each of the N modules 108 in the array (e.g., state of charge (SOCi), temperature (Ti), capacity (Qi), and voltage (Vi)) as inputs, and generate a normalized reference voltage waveform (Vm) and modulation indexes (Mi) as outputs. Peak detector 902 detects the peak (Vpk) of Vr, which can be specific to the phase that controller 900 is operating with and / or balancing. Divider 904 generates Vm by dividing Vr by its detected Vpk. Intraphase balance controller 906 uses Vpk along with the status information (e.g., SOCi, Ti, Qi, Vi, etc.) to generate modulation indexes Mi for each module 108 within the array 700 being controlled. The modulation indexes and Vm can be used to generate the switching signals for each converter 202. The modulation index can be a number between zero and one (inclusive of zero and one). For a particular module 108, the normalized reference Vm can be modulated or scaled by Mi, and this modulated reference signal (Vmm) can be used as Vref (or -Vref) according to the PWM technique described with respect to FIGS. 8C-8F, or according to other techniques. In this manner, the modulation index can be used to control the PWM switching signals provided to the converter switching circuitry (e.g., S3-S6 or S1-S6), and thus regulate the operation of each module 108. For example, a module 108 being controlled to maintain normal or full operation may receive an Mi of one, while a module 108 being controlled to less than normal or full operation may receive an Mi less than one, and a module 108 controlled to cease power output may receive an Mi of zero. This operation can be performed in various ways by control system 102, such as by MCD 112 outputting Vm and Mi to the appropriate LCDs 114 for modulation and switch signal generation, by MCD 112 performing modulation and outputting the modulated Vmm to the appropriate LCDs 114 for switch signal generation, or by MCD 112 performing modulation and switch signal generation and outputting the switch signals to the LCDs or the converters 202 of each module 108 directly. Vm can be sent continually with Mi sent at regular intervals, such as once for every period of the Vm, or one per minute, etc.

[0128] Controller 906 can generate an Mi for each module 108 using any type or combination of types of status information (e.g., SOC, temperature (T), Q, SOH, voltage, current) described herein. For example, when using SOC and T, a module 108 can have a relatively high Mi if SOC is relatively high and temperature is relatively low as compared to other modules 108 in array 700. If either SOC is relatively low or T is relatively high, then that module 108 can have a relatively low Mi, resulting in less utilization than other modules 108 in array 700. Controller 906 can determine Mi such that the sum of module voltages does not exceed Vpk. For example, Vpk can be the sum of the products of the voltage of each module’s source 206 and Mi for that module (e.g., Vpk = M1V1+M2V2+M3V3 . . . +MNVN, etc). A different combination of modulation indexes, and thus respective voltage contributions by the modules, may be used but the total generated voltage should remain the same.

[0129] Controller 900 can control operation, to the extent it does not prevent achieving the power output requirements of the system at any one time (e.g., such as during maximum acceleration of an EV), such that SOC of the energy source(s) in each module 108 remains balanced or converges to a balanced condition if they are unbalanced, and / or such that temperature of the energy source(s) or other component (e.g., energy buffer) in each module remains balanced or converges to a balanced condition if they are unbalanced. Power flow in and out of the modules can be regulated such that a capacity difference between sources does not cause an SOC deviation. Balancing of SOC and temperature can indirectly cause some balancing of SOH. Voltage and current can be directly balanced if desired, but in many embodiments the main goal of the system is to balance SOC and temperature, and balancing of SOC can lead to balance of voltage and current in a highly symmetric systems where modules are of similar capacity and impedance.

[0130] Since balancing all parameters may not be possible at the same time (e.g., balancing of one parameter may further unbalance another parameter), a combination of balancing any two or more parameters (SOC, T, Q, SOH, V, I) may be applied with priority given to either one depending on the requirements of the application. Priority in balancing can be given to SOC over other parameters (T, Q, SOH, V, I), with exceptions made if one of the other parameters (T, Q, SOH, V, I) reaches a severe unbalanced condition outside a threshold.

[0131] Balancing between arrays 700 of different phases (or arrays of the same phase, e.g., if parallel arrays are used) can be performed concurrently with intraphase balancing. FIG. 9B depicts an example embodiment of an Q-phase (or Q-array) controller 950 configured for operation in an Q-phase system 100, having at least Q arrays 700, where Q is any integer greater than one. Controller 950 can include one interphase (or interarray) controller 910 and Q intraphase balance controllers 906-PA . . . 906-PQ for phases PA through PQ, as well as peak detector 902 and divider 904 (FIG. 9A) for generating normalized references VmPA through VmPQ from each phasespecific reference VrPA through VrPQ. Intraphase controllers 906 can generate Mi for each module 108 of each array 700 as described with respect to FIG. 9A. Interphase balance controller 910 is configured or programmed to balance aspects of modules 108 across the entire multidimensional system, for example, between arrays of different phases. This may be achieved through injecting common mode to the phases (e.g., neutral point shifting) or through the use of interconnection modules (described herein) or through both. Common mode injection involves introducing a phase and amplitude shift to the reference signals VrPA through VrPQ to generate normalized waveforms VmPA through VmPQ to compensate for unbalance in one or more arrays, and is described further in IntT. Appl. No. PCT / US20 / 25366 incorporated herein.

[0132] Controllers 900 and 950 (as well as balance controllers 906 and 910) can be implemented in hardware, software or a combination thereof within control system 102. Controllers 900 and 950 can be implemented within MCD 112, distributed partially or fully among LCDs 114, or may be implemented as discrete controllers independent of MCD 112 and LCDs 114.

[0133] Interconnection (IC) Module Examples

[0134] Modules 108 can be connected between the modules of different arrays 700 for the purposes of exchanging energy between the arrays, acting as a source for an auxiliary load, or both. Such modules are referred to herein as interconnection (IC) modules 108IC. IC module 108IC can be implemented in any of the already described module configurations (108A, 108B, 108C) and others to be described herein. IC modules 108IC can include any number of one or more energy sources, an optional energy buffer, switch circuitry for supplying energy to one or more arrays and / or for supplying power to one or more auxiliary loads, control circuitry (e.g., a local control device), and monitor circuitry for collecting status information about the IC module itself or its various loads (e.g., SOC of an energy source, temperature of an energy source or energy buffer, capacity of an energy source, SOH of an energy source, voltage and / or current measurements pertaining to the IC module, voltage and / or current measurements pertaining to the auxiliary load(s), etc.).

[0135] FIG. 10A is a block diagram depicting an example embodiment of a system 100 capable of producing Q-phase power with Q arrays 700-PA through 700-PQ, where Q can be any integer greater than one. In this and other embodiments, IC module 108IC can be located on the rail side of arrays 700 such the arrays 700 to which module 108IC are connected (arrays 700-PA through 700-PQ in this embodiment) are electrically connected between module 108IC and outputs (e.g., SIO1 through SIOQ) to the load. Here, module 108IC has Q IO ports for connection to IO port 2 of each module 108-N of arrays 700-PA through 700-PQ. In the configuration depicted here, module 108IC can perform interphase balancing by selectively connecting the one or more energy sources of module 108IC to one or more of the arrays 700-PA through 700-PQ (or to no output, or equally to all outputs, if interphase balancing is not required). System 100 can be controlled by control system 102 (not shown, see FIG. 1A).

[0136] FIG. 10B is a schematic diagram depicting an example embodiment of module 108IC. In this embodiment module 108IC includes an energy source 206 connected with energy buffer 204 that in turn is connected with switch circuitry 603. Switch circuitry 603 can include switch circuitry units 604-PA through 604-PQ for independently connecting energy source 206 to each of arrays 700-PA through 700-PQ, respectively. Various switch configurations can be used for each unit 604, which in this embodiment is configured as a half-bridge with two semiconductor switches S7 and S8. Each half bridge is controlled by control lines 118-3 from LCD 114. This configuration is similar to module 108A described with respect to FIG. 3 A. As described with respect to converter 202, switch circuitry 603 can be configured in any arrangement and with any switch types (e.g., MOSFET, IGBT, Silicon, GaN, etc.) suitable for the requirements of the application.

[0137] Switch circuitry units 604 are coupled between positive and negative terminals of energy source 206 and have an output that is connected to an IO port of module 108IC. Units 604-PA through 604-PQ can be controlled by control system 102 to selectively couple voltage +Vic or -Vic to the respective module I / O ports 1 through Q. Control system 102 can control switch circuitry 603 according to any desired control technique, including the PWM and hysteresis techniques mentioned herein. Here, control circuitry 102 is implemented as LCD 114 and MCD 112 (not shown). LCD 114 can receive monitoring data or status information from monitor circuitry of module 108IC. This monitoring data and / or other status information derived from this monitoring data can be output to MCD 112 for use in system control as described herein. LCD 114 can also receive timing information (not shown) for purposes of synchronization of modules 108 of the system 100 and one or more carrier signals (not shown), such as the sawtooth signals used in PWM (FIGS. 8C-8D).

[0138] For interphase balancing, proportionally more energy from source 206 can be supplied to any one or more of arrays 700-PA through 700-PQ that is relatively low on charge as compared to other arrays 700. Supply of this supplemental energy to a particular array 700 allows the energy output of those cascaded modules 108-1 thru 108-N in that array 700 to be reduced relative to the unsupplied phase array(s).

[0139] For example, in some example embodiments applying PWM, LCD 114 can be configured to receive the normalized voltage reference signal (Vm) (from MCD 112) for each of the one or more arrays 700 that module 108IC is coupled to, e.g., VmPA through VmPQ. LCD 114 can also receive modulation indexes MiPA through MiPQ for the switch units 604-PA through 604-PQ for each array 700, respectively, from MCD 112. LCD 114 can modulate (e.g., multiply) each respective Vm with the modulation index for the switch section coupled directly to that array (e.g., VmA multiplied by MiA) and then utilize a carrier signal to generate the control signal(s) for each switch unit 604. In other embodiments, MCD 112 can perform the modulation and output modulated voltage reference waveforms for each unit 604 directly to LCD 114 of module 108IC. In still other embodiments, all processing and modulation can occur by a single control entity that can output the control signals directly to each unit 604.

[0140] This switching can be modulated such that power from energy source 206 is supplied to the array(s) 700 at appropriate intervals and durations. Such methodology can be implemented in various ways.

[0141] Based on the collected status information for system 100, such as the present capacity (Q) and SOC of each energy source in each array, MCD 112 can determine an aggregate charge for each array 700 (e.g., aggregate charge for an array can be determined as the sum of capacity times SOC for each module of that array). MCD 112 can determine whether a balanced or unbalanced condition exists (e.g., through the use of relative difference thresholds and other metrics described herein) and generate modulation indexes MiPA through MiPQ accordingly for each switch unit 604-PA through 604-PQ.

[0142] During balanced operation, Mi for each switch unit 604 can be set at a value that causes the same or similar amount of net energy over time to be supplied by energy source 206 and / or energy buffer 204 to each array 700. For example, Mi for each switch unit 604 could be the same or similar, and can be set at a level or value that causes the module 108IC to perform a net or time average discharge of energy to the one or more arrays 700-PA through 700-PQ during balanced operation, so as to drain module 108IC at the same rate as other modules 108 in system 100. In some embodiments, Mi for each unit 604 can be set at a level or value that does not cause a net or time average discharge of energy during balanced operation (causes a net energy discharge of zero). This can be useful if module 108IC has a lower aggregate charge than other modules in the system.

[0143] When an unbalanced condition occurs between arrays 700, then the modulation indexes of system 100 can be adjusted to cause convergence towards a balanced condition or to minimize further divergence. For example, control system 102 can cause module 108IC to discharge more to the array 700 with low charge than the others, and can also cause modules 108-1 through 108-N of that low array 700 to discharge relatively less (e.g., on a time average basis). The relative net energy contributed by module 108IC increases as compared to the modules 108-1 through 108-N of the array 700 being assisted, and also as compared to the amount of net energy module 108IC contributes to the other arrays. This can be accomplished by increasing Mi for the switch unit 604 supplying that low array 700, and by decreasing the modulation indexes of modules 108-1 through 108-N of the low array 700 in a manner that maintains Vout for that low array at the appropriate or required levels, and maintaining the modulation indexes for other switch units 604 supplying the other higher arrays relatively unchanged (or decreasing them).

[0144] The configuration of module 108IC in FIGS. 10A-10B can be used alone to provide interphase or interarray balancing for a single system, or can be used in combination with one or more other modules 108IC each having an energy source and one or more switch portions 604 coupled to one or more arrays. For example, a module 108IC with switch portions 604 coupled with different arrays 700 can be combined with a second module 108IC having one switch portion 604 coupled with one array 700 such that the two modules combine to service a system 100 having +l arrays 700. Any number of modules 108IC can be combined in this fashion, each coupled with one or more arrays 700 of system 100.

[0145] Furthermore, IC modules can be configured to exchange energy between two or more subsystems of system 100. FIG. 10C is a block diagram depicting an example embodiment of system 100 with a first subsystem 1000-1 and a second subsystem 1000-2 interconnected by IC modules. Specifically, subsystem 1000-1 is configured to supply three-phase power, PA, PB, and PC, to a first load (not shown) by way of system I / O ports SIO1, SIO2, and SIO3, while subsystem 1000-2 is configured to supply three-phase power PD, PE, and PF to a second load (not shown) by way of system I / O ports SIO4, SIO5, and SIO06, respectively. For example, subsystems 1000-1 and 1000-2 can be configured as different packs supplying power for different motors of an EV or as different racks supplying power for different microgrids.

[0146] In this embodiment each module 108IC is coupled with a first array of subsystem 1000-1 (via IO port 1) and a first array of subsystem 1000-2 (via IO port 2), and each module 108IC can be electrically connected with each other module 108IC by way of I / O ports 3 and 4, which are coupled with the energy source 206 of each module 108IC as described with respect to module 108C of FIG. 3C. This connection places sources 206 of modules 108IC-1, 108IC-2, and 108IC-3 in parallel, and thus the energy stored and supplied by modules 108IC is pooled together by this parallel arrangement. Other arrangements such as serious connections can also be used. Modules 108IC are housed within a common enclosure of subsystem 1000-1, however the interconnection modules can be external to the common enclosure and physically located as independent entities between the common enclosures of both subsystems 1000.

[0147] Each module 108IC has a switch unit 604-1 coupled with IO port 1 and a switch unit 604-2 coupled with I / O port 2, as described with respect to FIG. 10B. Thus, for balancing between subsystems 1000 (e.g., inter-pack or inter-rack balancing), a particular module 108IC can supply relatively more energy to either or both of the two arrays to which it is connected (e.g., module 108IC-1 can supply to array 700-PA and / or array 700-PD). The control circuitry can monitor relative parameters (e.g., SOC and temperature) of the arrays of the different subsystems and adjust the energy output of the IC modules to compensate for imbalances between arrays or phases of different subsystems in the same manner described herein as compensating for imbalances between two arrays of the same rack or pack. Because all three modules 108IC are in parallel, energy can be efficiently exchanged between any and all arrays of system 100. In this embodiment, each module 108IC supplies two arrays 700, but other configurations can be used including a single IC module for all arrays of system 100 and a configuration with one dedicated IC module for each array 700 (e.g., six IC modules for six arrays, where each IC module has one switch unit 604). In all cases with multiple IC modules, the energy sources can be coupled together in parallel so as to share energy as described herein.

[0148] In systems with IC modules between phases, interphase balancing can also be performed by neutral point shifting (or common mode injection) as described above. Such a combination allows for more robust and flexible balancing under a wider range of operating conditions. System 100 can determine the appropriate circumstances under which to perform interphase balancing with neutral point shifting alone, interphase energy injection alone, or a combination of both simultaneously.

[0149] IC modules can also be configured to supply power to one or more auxiliary loads 301 (at the same voltage as source 206) and / or one or more auxiliary loads 302 (at voltages stepped down from source 302). FIG. 10D is a block diagram depicting an example embodiment of a three-phase system 100 A with two modules 108IC connected to perform interphase balancing and to supply auxiliary loads 301 and 302. FIG. 10E is a schematic diagram depicting this example embodiment of system 100 with emphasis on modules 108IC-1 ad 108IC-2. Here, control circuitry 102 is again implemented as LCD 114 and MCD 112 (not shown). The LCDs 114 can receive monitoring data from modules 108IC (e.g., SOC of ESI, temperature of ESI, Q of ESI, voltage of auxiliary loads 301 and 302, etc.) and can output this and / or other monitoring data to MCD 112 for use in system control as described herein. Each module 108IC can include a switch portion 602A (or 602B described with respect to FIG. 6C) for each load 302 being supplied by that module, and each switch portion 602 can be controlled to maintain the requisite voltage level for load 302 by LCD 114 either independently or based on control input from MCD 112. In this embodiment, each module 108IC includes a switch portion 602A connected together to supply the one load 302, although such is not required.

[0150] FIG. 1 OF is a block diagram depicting another example embodiment of a three-phase system configured to supply power to one or more auxiliary loads 301 and 302 with modules 108IC-1, 108IC-2, and 108IC-3. In this embodiment, modules 108IC-1 and 108IC-2 are configured in the same manner as described with respect to FIGS. 10D-10E. Module 108IC-3 is configured in a purely auxiliary role and does not actively inject voltage or current into any array 700 of system 100. In this embodiment, module 108IC-3 can be configured like module 108C of FIG. 3B, having a converter 202B,C (FIGS. 6B-6C) with one or more auxiliary switch portions 602A, but omitting switch portion 601. As such, the one or more energy sources 206 of module 108IC-3 are interconnected in parallel with those of modules 108IC-1 and 108IC-2, and thus this embodiment of system 100 is configured with additional energy for supplying auxiliary loads 301 and 302, and for maintaining charge on the sources 206A of modules 108IC-1 and 108IC-2 through the parallel connection with the source 206 of module 108IC-3.

[0151] The energy source 206 of each IC module can be at the same voltage and capacity as the sources 206 of the other modules 108-1 through 108-N of the system, although such is not required. For example, a relatively higher capacity can be desirable in an embodiment where one module 108IC applies energy to multiple arrays 700 (FIG. 10A) to allow the IC module to discharge at the same rate as the modules of the phase arrays themselves. If the module 108IC is also supplying an auxiliary load, then an even greater capacity may be desired so as to permit the IC module to both supply the auxiliary load and discharge at relatively the same rate as the other modules.

[0152] Power Generation Using Fuel Cells FIGS. 11A-15B illustrate several different example arrangements in which fuel cell stacks 1112 are used to provide AC power to a load or power grid 1150 (referred to simply as “load 1150” below). In each example, fuel cell stacks 1112 provide DC output that is converted to AC output by arrays 700 of modules 108. As discussed above, each module 108 can include, or one or more modules 108 can be associated with, a local control device (LCD) 114 (see, e.g., FIGS. 1C, 2A, 2B, 3A-3C), and the modules 108 are controlled and managed by a main control device (MCD) 112. The examples show how arrays 700 of modules 108 can be used to provide AC output for different AC phases. In some examples, each fuel cell stack 1112 provides power for a single AC phase, so a three-phase AC system uses three fuel cell stacks 1112 (see, e.g., FIG. 11 A). In other examples, a fuel cell stack 1112 provides the energy for multiple AC phases (see, e.g., FIG. 1 IB).

[0153] A fuel cell stack 1112 can include multiple strings of fuel cells, including multiple strings coupled in parallel to provide sufficiently high current output for each of the three phases of AC output. In addition, or as an alternative, a fuel cell stack 1112 can include multiple strings of fuel cells in series, and the DC voltage across different spans or subsets of the fuel cells can be used to provide the DC input for different phases of AC output.

[0154] In some implementations, power generated from the fuel cell stacks 1112 is supplemented with energy stored by batteries. For example, some modules 108 generate AC output from power generated by fuel cell stacks 1112, and other modules 108 generate AC output from energy stored in batteries, and the AC outputs from both types of modules are combined and delivered to the load 1150 (see FIGS. 12A-12B). As another example, each individual module 108 is configured to receive power from a fuel cell stack 1112 and a battery (which may be included in the module or may be external to the module 108), so the module 108 can generate AC output based on input from either or both types of sources (see FIGS. 13A-14B).

[0155] A fuel cell stack (FCS) 1112 includes multiple fuel cells that are electrically coupled together, allowing higher voltage and / or current to be generated than an individual fuel cell would generate alone. Each fuel cell includes an anode and a cathode separated by an electrolyte. As mentioned above, the fuel cells can be proton-exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), solid acid fuel cells, alkaline fuel cells, high temperature fuel cells, solid oxide fuel cells, molten electrolyte fuel cells, and others. Many fuel cells individually generate an output of approximately 1 V or less, so each fuel cell stack 1112 can include multiple fuel cells coupled in series to produce a combined output having a higher voltage that is appropriate for the application. A fuel cell stack 1112 can be arranged in strings or groups of fuel cells, where the fuel cells in each string or group are coupled in series, e.g., current-coupled or daisy-chained. In some implementations, multiple fuel cell stacks 1112 can be coupled together in series or in parallel. In general, adding fuel cells to a fuel cell stack 1112, with the additional fuel cells coupled in series. increases the voltage output capacity of the fuel cell stack 1112. Coupling fuel cell stacks 1112 in parallel increases the current output capacity compared to a single fuel cell stack 1112. Various example arrangements of fuel cell stacks 1112 are shown in FIGS. 16A-16H.

[0156] FIG. 11 A illustrates a system 1100 that uses a fuel cell system 1110 to generate AC output that is delivered to the load 1150 via an AC bus 1105. The fuel cell system 1110 generates three phases of AC output that are supplied on the AC bus 1105, although the system 1100 can be configured to alternatively provide more or fewer phases of AC output. The system 1100 includes a main control device (MCD) 112 that coordinates power delivery. The system 1100 also includes fuel tanks 1120 that store an appropriate fuel for the fuel cell system 1110, such as hydrogen gas for polymer electrolyte membrane (PEM) or proton exchange membrane fuel cells. Other loads can also make use of the generated AC power, such as AC ancillary loads 1152 and an AC -DC converter 1160. The AC-DC converter 1160 provides DC output on a DC bus 1107 for control systems and DC loads 1162.

[0157] The fuel cell system 1110 includes multiple arrays 700 of power supply modules or converter modules 108. In particular, the example includes N arrays 700, labeled 700-PA to 700- PN, where N is an integer. Each of the arrays 700-PA to 700-PN receives input DC power generated by a different fuel cell stack (FCS) 1112-1 to 1112-N.

[0158] The modules 108 are each labeled 108D to signify that, unlike the modules 108 A, 108B, and 108C discussed above, the modules 108D do not necessarily each include a separate energy source 206 such as a battery. Instead, the modules 108D are configured to receive input DC power from one or more external sources, such as a fuel cell 1112. The modules 108D can optionally receive input from multiple external sources, such as multiple fuel cells 1112, a fuel cell 1112 and a battery, a fuel cell 1112 and a photovoltaic panel, and so on. Each module 108D can include features as discussed above, such as an LCD 114, an optional energy buffer 204, a converter 202, and a power connection 110 to supply output AC power, for example, as shown in FIGS. 3A-3C. In addition, the modules 108D may each include additional components, such as one or more DC- DC converters or voltage regulators to additionally supply output DC power that may be at a different voltage than the DC input from the fuel cell 1112.

[0159] In the example, there is a separate array 700 for each of three phases of AC output, e.g., a first array 700-PA for phase A, a second array 700-PB for phase B, and a third array 700-PC for phase C. Additional arrays 700, such as array 700-PN, can be provided in the fuel cell system 1110 but are not currently connected to provide any of the phases of AC power. These additional arrays 700 and fuel cell stacks 1112 may be connected as needed, under control of the MCD 112, to supplement power generation for phases A, B, or C, or to provide power instead of the arrays 700-PA to 700-PC in case of failure or maintenance. In the example of FIG. 11A, each of the arrays 700-PA to 700-PC is shown generating a different phase of AC output for the load 1150. However, each phase of AC output can be generated using multiple arrays 700 and their associated fuel cell stacks 1112, for example, with multiple arrays 700 providing synchronized AC output to the same phase.

[0160] The arrays 700-PA to 700-PN can each operate as described with respect to FIGS. 7A to 10F. For example, each array 700 can include multiple modules 108 coupled in series (e.g., daisy chained) and controlled so that the sum of their outputs provides one phase of combined AC output on the AC bus. In the example, the array 700-PA includes M modules 108D-A1 to 108D-AM, the array 700-PA includes M modules 108D-B1 to 108D-BM, and the array 700-PC includes M modules 108D-C1 to 108D-CM, where M is an integer and may be the same integer or a different integer for each array 700.

[0161] In the fuel cell system 1110, each of the modules 108D can have a LCD 114 (see, e.g., FIGS. 1A-1C, 2A-2C, 3A-3C) that manages and adjusts output of the module 108D. The LCDs 114 of the modules 108D can also send status information about their own operation to the MCD 112, which tracks and uses that information in generating instructions. The LCD 114 for each module 108 can send information to and receive information from the MCD 112 through a control interface 1125, which can allow bidirectional communication. In addition, the MCD 112 can receive sensor data and status data from, and send control information to, the control systems and DC loads 1162 through a control interface 1126. Each of the modules 108D can have its own identifier or address, so the MCD 112 can direct control information to each module 108D individually. The control interface 1125 can be implemented in any appropriate communication techniques and protocols, such as using digital signals, analog signals, packet-based communications, and so on.

[0162] The control interface 1125 enables the MCD 112 to receive status information from the modules 108D-A1 to 108D-NM and the fuel cell stacks 1112-A to 1112-N, as well as for the MCD 112 to send control signals to control the modules 108D-A1 to 108D-NM and the fuel cell stacks 1112-A to 1112-N. For example, the status information can include temperature, voltage levels, current levels, operating time, current settings, and so on. The MCD 112 can receive status information about the fuel cell stacks 1112-A to 1112-N from sensors or control systems of the fuel cell stacks 1112-A to 1112-N. In addition, the LCDs 114 of one or more of the modules 108D in each array 700-PA to 700-PD can receive sensor information about, and can monitor the operation of, the corresponding fuel cell stack 1112.

[0163] As discussed further below with respect to FIG. 18, the MCD 112 can perform various control functions to control the operation of the fuel cell stacks 1112-A to 1112-N as well as control the operation of the of the modules 108D in the arrays 700-PA to 700-PN. In some implementations, the MCD 112 controls the assignment arrays 700-PA to 700-PN to the different phases of the AC bus 1105. The arrays 700-PA to 700-PN can be coupled in the fuel cell system 1110 in a reconfigurable or switchable manner, so that the number of arrays 700 and fuel cell stacks 1112 used to supply each AC phase can be programmably changed through activation of switching elements according to instructions from the MCD 112. In some implementations, the modules 108D are also connected through an programmable interconnect or switchable connection, so that the topology or interconnections of modules 108D within each array 700 can also be changed by the MCD 112.

[0164] The MCD 112 also determines and instructs the AC output characteristics of the different arrays 700-PA to 700-PN, such as the voltage, frequency, and timing or phase for each array’s AC output. In some implementations, each of the arrays 700-PA to 700-PN can approximate a sinusoidal waveform using a combination stepped DC outputs from the modules 108D in the array, as described above with respect to FIGS. 8A to 8F. The MCD 112 also monitors the AC bus 1105 and sends control signals to change the operation of the arrays 700 and their modules 108D as needed to adjust voltage output, adjust current output capacity, and so on.

[0165] For example, the MCD 112 can instruct the modules 108D-A1 to 108D-AM of a first array 700-PA to, operating together, provide 120V RMS at 60Hz synchronized to a first AC output phase, instruct the modules 108D-B1 to 108D-BM of a second array 700=PB to together provide 120V RMS at 60Hz synchronized to a second AC output phase, and instruct the modules 108D-C1 to 108D-CM of a third array 700-PC to provide 120V RMS at 60Hz synchronized to a third AC output phase. As another example, the MCD 112 may instruct other outputs, such as (1) two or more arrays 700 each providing 120V RMS at 60Hz for the same phase, coupled in parallel to provide higher current capacity, or (2) multiple arrays 700 each providing 120V RMS at 60Hz for the same phase, coupled in series to provide a higher AC voltage (e.g., 240V RMS for two modules arrays 700, 480V for four arrays 700 in series, etc.).

[0166] The MCD 112 can provide synchronization signals to enable each array 700-PA to 700-PN to synchronize its AC output with the phase of the AC bus 1105 output it is instructed to supply. The MCD 112 can output synchronization signals that include, for example, a digital signal, an analog signal, a clock signal, etc. The MCD 112 and LCDs 114 can use packet-based communication to synchronize timing using the precision time protocol (PTP) or other techniques. In some implementations, the fuel cell system 1110, or individual arrays 700-PA to 700-PN, may include circuitry to sense the frequency and / or phase of a line of the AC bus 1105 to which they are coupled, in order to synchronize output of the arrays 700-PA to 700-PN with a power grid with or without synchronization signals from the MCD 112. Each array 700-PA to 700-PN converts the DC input received from its associated fuel cell stack 1112 to AC output with the voltage level, frequency, phase, and / or other characteristics instructed by the MCD 112.

[0167] Each fuel cell stack 1112 can also include sensors to monitor the condition of the fuel cell stack 1112, such as the DC output voltage and current levels, as well as other fuel cell parameters such as temperature, pressure, gas flow rate, and so on. The MCD 112 can monitor these parameters for the fuel cell stack 1112 to track the status of the associated fuel cell stack 1112 and to schedule maintenance operations. As an example, the MCD 112 can monitor the temperature of each fuel cell stack 1112-A to 1112-N and detect if the temperature exceeds a threshold or is outside a target operating range. The MCD 112 can take actions to manage a high temperature condition, such as to increase cooling (e.g., increase coolant circulation, engage a fan or increase fan speed, etc.), to reduce output, etc.

[0168] The MCD 112, along with potentially one or more remote computing devices, can track usage and performance of the fuel cell stacks 1112, fuel cell strings within fuel cell stacks 1112, and / or individual fuel cells. With this information, the capability and characteristics of the fuel cell stacks 1112 can be determined or estimated, including characteristics such as the lifespan, current capacity, voltage capacity, stage in a maintenance cycle, and so on. This tracking enables the MCD 112 to use fuel cells effectively, even if they have degraded or are undergoing maintenance operations. For example, based on the sensed conditions indicated by the LCDs 114 and tracked usage data, the MCD 112 may determine that certain fuel cell stacks 1112 have degraded and have lower voltage capacity than other fuel cell stacks. As a result, the MCD 112 may assign, as an example, four of the degraded fuel cell stacks 1112 to be used together to provide the desired output, where only two or three fuel cell stacks 1112 at full capacity are assigned for the same level of output.

[0169] The fuel cell system 1110 can include one or more modules 108D and associated fuel cell stacks 1112 that are available but not currently used for power generation. For example, one or more arrays 700, each with an associated fuel cell stack 1112, can be held in reserve for the MCD 112 to assign, as needed, to be coupled to an AC output phase. For example, in response to an increase in current demand of the load 1150, the MCD 112 can connect an additional array 700-PN to generate power. As another example, the MCD 112 can cause one or more arrays 700 that were held in reserve to begin supplying power in response to a performance decrease of other arrays 700. Similarly, the MCD 112 can switch a redundant or unused array 700 in place of another array 700 to respond to a failure in an array 700 or fuel cell stack 1112, to balance wear and lifespan among arrays 700 and their fuel cell stacks 1112, to manage temperature and pressure among the various fuel cell stacks 1112, or to facilitate purging cycles (e.g., to release water, nitrogen, or impurities from the anodes of some or all fuel cells to recover performance) or other maintenance on the fuel cell stacks 1112.

[0170] In some implementations, the MCD 112 can also control the fuel cell stacks 1112, or communicate with a controller of the fuel cell stack, to adjust the fuel rate, timing of maintenance cycles, and other operating parameters of the associated fuel cell stack 1112.

[0171] To facilitate reconfiguration or dynamic adjustments to the arrangements of the modules 108D into arrays 700, the modules 108D can be coupled together with programmable switching elements to couple or decouple module outputs from each other and from the various phase output lines of the AC bus 1105. For example, the fuel cell system 1110 can include switching elements to couple each of multiple modules 108D to each of the different AC output phases of the AC bus 1105.

[0172] When a reconfigurable arrangement is used, the MCD 112 determines an arrangement or topology for the modules 108D and sends instructions to configure the modules 108D and their interconnections. This can include determining the number of modules 108D to couple to each phase of AC output, assigning specific modules 108D to particular AC output phases, and determining appropriate connections to be established among the modules 108D. The MCD 112 sends this information to the modules 108D through the control interface 1125, for example, through instructions that specify for each module 108D which connections to the AC bus 1105 and / or to other modules 108D should be established.

[0173] In each module 108D, the LCD 114 receives control instructions from the MCD 112 that are addressed for that module 108D, such as are provided through a control line to the module 108D or through data packets that specify an address or identifier for the module 108D. The LCD 114 can include one or more feedback control loops to monitor and adjust output of the module 108D to the timing and output voltage instructed by the MCD 112.

[0174] Each module 108D converts the DC input received from its associated fuel cell stack 1112 to a AC module output having the instructed AC output characteristics. As discussed above for FIGS. 8A-8E, individual modules 108D may not directly output a sine wave, but rather may output components that, when summed, approximate a sine wave. Thus, the AC module output may be that module’s component or portion of the AC approximation to be generated. Together, the modules 108D in an array provide the voltage level, frequency, phase, and / or other characteristics instructed by the MCD 112. In some implementations, individual modules 108D may be configured to individually provide a full AC output, whether as a true sine wave or as an approximated sine wave, and in those implementations, individual modules 108D may each provide the AC output with the characteristics instructed for the corresponding phase of the AC bus 1105. The MCD 112 can also instruct changes in the operation of the associated fuel cell stack 1112. For example, the MCD 112 can start up or shut down operation of a fuel cell stack 1112, increase or decrease the fuel rate of the fuel cell stack 1112, initiate or terminate fuel cell purging (e.g., to release water, nitrogen, or impurities from the anodes of some or all fuel cells to recover performance), adjust load to balance temperature along different portions of the fuel cell stack 1112, and so on. The MCD 112 can instruct these changes for any of various reasons, such as to achieve outputs specified for the system, to maintain output at a desired level in response to changing conditions (e.g., changes in load demand), to respond to failures or reduced fuel cell stack 1112 output, or to perform maintenance or prolong lifespan of the fuel cell stack 1112. If a separate fuel cell controller is integrated with the fuel cell stack 1112, the MCD 112 can communicate with the fuel cell controller to adjust output and operation of the fuel cell stack 1112 as needed.

[0175] FIG. 1 IB illustrates a system 1101 that has the same components and arrangement as the system 1100 of FIG. 11 A, except that the fuel cell system 1110 includes a single fuel cell stack 1112, rather than multiple fuel cell stacks 1112. In this example, three arrays 700-PA to 700-PC each output a different AC phase but receive power generated by the same fuel cell stack 1112.

[0176] As discussed below, several different arrangements can be used to couple multiple arrays 700 to the fuel cell stack 1112. As an example, the three arrays 700-PA to 700-PC can be coupled to receive the DC output of the fuel cell stack 1112 in parallel. As another example, the fuel cell stack 1112 can include multiple strings of fuel cells in series, and the DC voltage across different spans or subsets of the fuel cells can be provided as input to different arrays 700-PA to 700-PC and used to provide the DC input for different phases of AC output.

[0177] FIG. 12A illustrates a system 1200 that has the same components and arrangement as the system 1100 of FIG. 11 A, with an additional battery system 1210 to supplement the power generated by the fuel cell system 1110. The battery system 1210 can include multiple modules 108 A, each having one or more battery cells. The battery system 1210 can organize the modules 108 A into arrays 700-1 to 700-3 within the battery system 1210, and generate AC output from the arrays 700-1 to 700-3, which are coupled to the AC bus 1105. Overall, the battery system 1210 can include X arrays, where X is an integer, that each include multiple modules 108 (e.g., any of modules 108 A, 108B, 108C, etc. discussed above). In the arrays 700-1 to 700-3 of the battery system 1210, each of the modules 108 includes an energy source 206, such as one or more batteries, which can both provide energy for the module 108 to supply AC power to the AC bus 1105 at times and be charged from energy received from the AC bus 1105 at other times. The AC output from the battery system 1210 is synchronized with the AC bus 1105, so that the battery system 1210 and the fuel cell system 1100 each simultaneously supply power to the load 1150 through the AC bus 1105. In the example of FIG. 12A, the battery system 1210 is coupled directly to the AC bus 1105, and the fuel cell system 1110 is also coupled directly to the AC bus 1105. The battery system 1210 and the fuel cell system 1110 can thus operate independently and are each separately synchronized to the AC bus 1105.

[0178] The MCD 112 controls the battery system 1210 through a control interface 1225, which can allow bidirectional communication. The control interface 1225 can transmit analog control signals, digital control signals, packet-based communications, or communication in other forms. Each module 108 A in the battery system 1210 can include sensors to detect status information about the output of the module 108 A and the condition of the associated battery or batteries. For example, each module 108 A can determine and provide to the MCD 112 values of parameters such as of voltage output, current output, temperature, battery state of charge, and so on. The MCD 112 can send control signals that adjust the arrangement or topology in which the modules 108 A are coupled to each other in the arrays 700 and how the arrays 700 are coupled to the AC bus 1105. For example, the MCD 112 can instruct different amounts of modules 108A to be connected in an array 700 for each phase of the AC bus 1105. As load demands change, the MCD 112 can increase or decrease the number of modules 108 A or arrays 700 supplying power to each phase of the AC bus 1105. In addition, the MCD 112 can assign specific modules 108 A in the topology according to their individual addresses or identifiers, to account for the varying status of the batteries (e.g., temperature, state of charge, internal resistance, remaining lifespan, etc.) to balance load and wear among the modules 108 A and their batteries. The battery system 1210 can couple the modules 108 A and arrays 700 in a reconfigurable or switchable manner, with programmable switching elements to couple or decouple module outputs from each other and from the various phase output lines of the AC bus 1105, as discussed above for the modules 108D of the fuel cell system 1110.

[0179] The MCD 112 also controls load balancing between the fuel cell system 1110 and the battery system 1210. In general, the battery system 1210 can vary its output more quickly than the fuel cell system 1110. As a result, the presence of the battery system 1210 increases the capacity to handle transient demand and rapid increases in demand that exceed the current output of the fuel cell system 1110. When the average demand of the load 1150 increases (e.g., when a rolling average over a time period rises to a threshold), the MCD 112 can adjust the configuration and output of the fuel cell system 1110, such as to increase the fuel rate in the fuel cell stacks 1112 and / or to start up additional fuel cell stacks 1112. These actions can increase the current output of the fuel cell system 1110, but often require time to take effect. While the fuel cell system 1110 is increasing its output, the battery system 1210 can supply the additional current that is needed.

[0180] In addition, the MCD 112 can facilitate charging of the batteries in the battery system 1210. For example, when the fuel cell system 1110 is producing output greater than the demands of the load 1150, the MCD 112 can instruct the battery system 1210 to draw power from the AC bus 1105 to charge the batteries in the battery system 1210 instead of supplying power to the AC bus 1105. Although the output of the fuel cell system 1110 may change more slowly than that of the battery system 1210, the fuel cell system 1110 can use the fuel in the fuel tanks 1120 to generate more energy than can be stored in the battery system 1210 at any given time. As another example, in some implementations, the batteries in the battery system 1210 can receive DC output from the modules 108D or from the fuel cell stacks 1112 without intermediate conversion to AC, which can increase efficiency by avoiding additional conversions.

[0181] The fuel cell system 1110 and the battery system 1210 complement each other. The fuel cell system 1110 can generate power consistently for as long as fuel is available. If the output of the fuel cell system 1110 does not match the demand of the load 1150, the battery system 1210 can respond quickly to supply additional power to the AC bus 1105, or to draw excess power from the AC bus 1105 for battery charging. As a result, the battery system 1210 can address the difference between output of the fuel cell system 1110 and the load demand over the course of adjusting the fuel cell system 1110 to a new operating point and even before the MCD 112 detects or initiates the adjustment.

[0182] FIG. 12B illustrates a system 1201 that has the same components and arrangement as the system 1200 of FIG. 12 A, except that the fuel cell system 1110 includes a single fuel cell stack 1112, rather than multiple fuel cell stacks 1112. In this example, the three arrays 700-PA to 700- PC provide the output for the three phases of AC output on the AC bus 1105. In some implementations, the fuel cell stack 1112 can include multiple strings of fuel cells in series, and the DC voltage across different spans or subsets of the fuel cells can be provided to different arrays 700-PA to 700-PC (and / or to different modules 108D within the arrays 700-PA to 700-PC) used to provide the DC input for different phases of AC output.

[0183] The MCD 112 can also control the division of DC output among the modules 108D, within and across the various arrays 700-PA to 700-PN. For example, some modules 108D may be assigned to provide DC output to the DC bus 1107, while other modules 108D may be assigned to provide AC output to the AC bus 1105. In some cases, different modules 108D may be assigned to provide different levels of DC output, or to provide both DC and AC output.

[0184] FIG. 13A illustrates a system 1300 that uses a fuel cell system 1310 and a battery system 1315 to supply AC output to the load 1150 via the AC bus 1105. By contrast with the system 1200 of FIG. 12A, the system 1300 arrays 700 of modules 108D that each receive input from batteries and fuel cell stacks 1112, instead of using a set of arrays 700 producing AC output from fuel cell stacks 112 and another set of arrays 700 producing AC output from energy stored in batteries. In FIG. 13 A, each module 108D is coupled to receive input from one or more batteries as well as from one or more fuel cell stacks 1112. For example, in the first array 700-PA, the module 108D-1A has one or more batteries BT1A, which may be housed within or located external to the module 108D-1A. Other modules 108D in the array 700-PA similarly have one or more batteries, as do the modules 108D in the other arrays 700-PB to 700-PN. For example, the modules 108D- 1A to 108D-MA have corresponding batteries BT1A to BTMA, the modules 108D-1B to 108D- MB have corresponding batteries BT1B to BTMB, the modules 108D-1C to 108D-MC have corresponding batteries BT1C to BTMC, and so on.

[0185] Each module 108D is configured to provide its components of the AC output of its array 700 based on the DC input from its associated battery, a fuel cell stack 1112, or both. Each module 108D can be configured to use DC input from a fuel cell stack 1112 to charge its battery also.

[0186] As discussed above for the system 1200, the combination of power generation with the fuel cell system 1310 and stored energy in the battery system 1315 provides a versatile and reliable power supply. In the system 1300, each module 108D benefits from the long-term, stable power generation from a fuel cell stack 1112, as well as the stored energy of a battery to handle transient power demands and short-term variations in load. This allows high capacity and high responsiveness to changes in load, both at the level of individual modules 108D, for the arrays 700, and for the system 1300 as a whole.

[0187] In the example, the arrays 700-PA to 700-PN are shown as part of the battery system 1315, with each array 700-PA to 700-PN receiving DC input from a corresponding fuel cell stack 1112-A to 1112-N of a separate fuel cell system 1310. Nevertheless, as an alternative, the modules 108D can be part of the fuel cell system 1310, with the modules 108D each receiving input from one or more batteries of the battery system 1315. As another alternative, the battery system 1315 and the fuel cell system 1310 can be integrated into a single system, with each module 108D including or being associated with one or more fuel cell stacks 1112 and one or more batteries.

[0188] The system 1300 includes many of the elements of the system 1200, including the MCD 112 that coordinates power delivery, the fuel tanks 1120, and the AC ancillary loads 1152. In the system 1300, instead of using an AC -DC converter, the battery system 1315 provides DC output on the DC bus 1107 for control systems and DC loads 1162.

[0189] In the system 1300, the MCD 112 can adjust the arrangement or topology in which the modules 108D are coupled to each other and to the AC bus 1105. For example, as discussed above, the MCD 112 can assign specific modules 108D and / or groups of modules 108D to supply power to specific output lines (e.g., specific phases) of the AC bus 1105. This can include assigning multiple modules 108D to be coupled together in parallel, and / or assigning multiple modules 108D to be coupled together in series, to form the arrays 700-PA to 700-PN. The MCD 112 provides instructions and control signals to specify the configuration for the modules 108D through the control interface 1225. The battery system 1315 can couple the modules 108D in a reconfigurable or switchable manner, with programmable switches to couple or decouple module inputs and outputs from each other and from the various phase output lines of the AC bus 1105, as discussed above for the modules 108D of the fuel cell system 1110.

[0190] The modules 108D can each receive input from sensors that detect conditions of the associated batteries and fuel cell stacks 1112. The modules 108D provide the sensed information to the MCD 112, which uses the information to assign the output characteristics and operating mode for the modules 108D. In some implementations, the MCD 112 instructs the modules 108D the output characteristics to provide and also sets parameters of the fuel cell stacks 1112, such as the fuel rate. Each module 108D can use power generated by its associated fuel cell stack 1112 as the primary source of DC input for conversion to the module’s AC output. The battery associated with the module 108D can provide additional stored power as needed to meet load demands in excess of what is provided by the fuel cell stack 1112. In addition, the battery can provide stored energy to maintain output of the module 108D while the output of the fuel cell stack 1112 is reduced due to maintenance, such as during a purging cycle (e.g., to release water, nitrogen, or impurities from the anodes of some or all fuel cells to recover performance). In each module 108D, the LCD 114 can control the balance of power from the battery and the fuel cell stack 1112, according to the policies or settings specified by the MCD 112, to charge the battery when the fuel cell stack 1112 supplies power beyond what is needed by the load 1150 and to discharge the battery when the fuel cell stack 1112 supplies less power than is needed by the load 1150. In addition, or as an alternative, the LCDs 114 can adjust this balance based on a predetermined policy, such as to adjust the balance of sourcing power to maintain battery charge above a minimum threshold level or to maintain temperature of the battery or fuel cell stack 1112 below a maximum threshold level. As another example, the MCD 112 can monitor the status of the battery and the fuel cell stack 1112 of each module 108D, and can send instructions for each module 108D, which the LCDs 114 each carry out.

[0191] EIG. 13B illustrates a system 1301 that has the same components and arrangement as the system 1300 of EIG. 13 A, except that the fuel cell system 1110 includes a single fuel cell stack 1112, rather than multiple fuel cell stacks 1112. DC output of the single fuel cell stack 1112 is provided as input to the modules 108D of the arrays 700-PA to 700-PN, and the modules 108D also receive input from their respective batteries. Thus, in this example, the power generated by one fuel cell stack 1112 contributes to the supply of AC output of multiple phases of AC output on the AC bus 1105. The division of the output among the various arrays 700 can be controlled by the MCD 112. The system 1301 demonstrates that the relationship between fuel cell stacks 1112 to batteries, or between fuel cell stacks 1112 and arrays 700, is not required to be one-to-one. By coupling the fuel cell stack 1112 to each of the modules 108D of each of the arrays 700-PA to 700- PN, the power generated by the fuel cell stack 1112 is distributed to each of the modules 108D and the respective batteries (e.g., BT1A-BTMA, BT1B-BTMB, BT1C-BTMB, etc.) can supplement power delivery with their stored energy. In general, the relationship between fuel cell stacks 1112 and arrays 700 can be one-to-one (e.g., as shown in FIG. 13A), one-to-many (e.g., as shown in FIG. 13B), many-to-one (e.g., with multiple fuel cell stacks 1112 in parallel for a single array 700), or many-to-many (e.g., with arrays 700 receiving power from multiple fuel cell stacks 1112, and fuel cell stacks 1112 providing input to multiple arrays 700).

[0192] FIG. 14A illustrates a system 1400 that has the same components and arrangement as the system 1300 of FIG. 13 A, except that instead of a single DC bus 1107, the system 1400 includes two DC buses: a high-voltage DC bus (“HV DC Bus”) 1410 and a low- voltage DC bus (“LV DC Bus”) 1412. The low DC voltage is used to power the control systems and DC loads 1162 and the MCD 112, and the high DC voltage is used to power other DC ancillary loads 1402. The arrays 700 can provide the DC bus voltages through any of various techniques. For example, the modules 108D can include one or more DC-DC converters to provide the high and low DC voltages. As another example, the high and low DC voltages can be generated by having individual modules 108D providing DC outputs, for example, based on the voltage of the associated batteries, and then coupling DC outputs from the different modules 108D in series. In this manner, an array 700 can use the combination of DC voltages from different modules 108D to reach a desired DC output for either of the DC busses. In some implementations, individual arrays 700 may provide output of both the high and low DC output voltages. As another example, one array 700 (or set of arrays 700) may provide the low DC voltage, and another array 700 (or a different set of arrays 700) may provide the high DC voltage. With these techniques, an array 700 or set of arrays 700 can be configured to provide one, two, three, or more different DC voltage outputs, as needed and instructed by the MCD 112, in addition to providing AC output to the AC bus 1105.

[0193] FIG. 14B illustrates a system 1401 that has the same components and arrangement as the system 1400 of FIG. 14 A, except that the fuel cell system 1110 includes a single fuel cell stack 1112, rather than multiple fuel cell stacks 1112. The DC output of the single fuel cell stack 1112 is provided as input to each of the different modules 108D, which also receive input from their respective batteries (e.g., batteries BT1A-BTMA for modules 108D-1A to 108D-MA, batteries BT1B-BTMB for modules 108D-1B to 108D-MB, batteries BT1C-BTMC for modules 108D-1C to 108D-MC, etc.). Thus, in this example, the power generated by one fuel cell stack 1112 contributes to the supply of AC output of multiple phases of AC output on the AC bus 1105. FIG. 15A illustrates a system 1500 that has the same components and arrangement as the system 1100 of FIG. 11 A, with the two DC buses instead of one, and with the DC output being provided by the arrays 700 of modules 108D rather than by an AC -DC converter. The system 1500 includes two DC buses, similar to FIGS. 14A-14B: a high-voltage DC bus (“HV DC Bus”) and a low-voltage DC bus (“LV DC Bus”). Both DC bus voltages are provided by the arrays as discussed above for FIG. 14A. The low DC voltage is used to power the control systems and DC loads 1162 and the MCD 112, and the high DC voltage is used to power other DC ancillary loads 1402.

[0194] FIG. 15B illustrates a system 1501 that has the same components and arrangement as the system 1500 of FIG. 15A, except that only a single fuel cell stack 1112 is used, instead of multiple separate fuel cell stacks 1112. As a result, the arrays 700-PA to 700-PC each generate their respective phased of AC output based on DC input from the same fuel cell stack 1112.

[0195] FIGS. 16A-16F illustrate examples of different arrangements of fuel cell stacks 1112 and modules 108D. As discussed above, each fuel cell stack 1112 can include multiple individual fuel cells. The fuel cells can be arranged in strings 1610, each of which includes multiple fuel cells electrically coupled in series. Each fuel cell stack 1112 includes one or more strings 1610 of fuel cells, with strings 1610 of fuel cells optionally being coupled in series and / or in parallel with each other.

[0196] FIG. 16A illustrates a fuel cell stack 1112a that includes multiple fuel cell strings 1610. The example shows three fuel cell strings 1610, but more or fewer can be used. The fuel cell stack 1112a has four output ports, DC_1 to DC_4. The negative terminals of each of the fuel cell strings 1610 are electrically coupled together to share the same voltage potential at one output (DC_4) of the fuel cell stack 1112a. The positive terminals of the fuel cell strings 1610 are not coupled together, and instead are each provided as separate outputs of the fuel cell stack 1112a. As a result, the three fuel cell strings 1610 can be separately and independently used by the arrays 700-PA to 700-PC to generate three phases of AC output to the load 1150.

[0197] Each of the arrays 700-PA to 700-PC receives DC input from a different one of the output ports DC_1, DC_2, and DC_3, so the arrays 700-PA to 700-PC receive power from different fuel cell strings 1610 to provide their respective AC output phases. The output at port DC_4, coupled to the voltage potential shared by the negative terminals of the fuel cell strings 1610, is provided to each of the arrays 700-PA to 700-PC. For example, the array 700-PA uses the voltage across ports DC_1 and DC_4 as input to generate the AC output at port VA, the array 700-PB uses the voltage across ports DC_2 and DC_4 as input to generate the AC output VB, and the array 700-PC uses the voltage across ports DC_3 and DC_4 as input to generate the AC output Vc. FIG. 16B illustrates another example of a fuel cell stack 1112b, which includes multiple fuel cell strings 1610 arranged in series. The example shows three fuel cell strings 1610, but more or fewer can be used. Arrays 700-PA to 700-PC respectively generate different AC output phases VA, VB, VC based on different fuel cell strings 1610 or subsets of the fuel cells in the fuel cell stack 1112b.

[0198] The fuel cell stack 1112b has electrical taps located between the fuel cell strings 1610, and those electrical taps are connected to output ports DC_1 to DC_4 that are coupled to the arrays 700-PA to 700-PC. The arrays 700-PA to 700-PC receive DC input across different spans of the fuel cells. For example, the array 700-PA receives DC input across output ports DC_1 and output DC_2 from a first fuel cell string 1610, the array 700-PB receives DC input across output DC_2 and output DC_3 from a second fuel cell string 1610, and the array 700-PC receives DC input across output DC_3 and output DC_4 from a third fuel cell string 1610.

[0199] In some implementations, the electrical taps in the fuel cell stack 1112b are distributed at regular intervals along the fuel cells, so that there is a consistent number of cells between each electrical tap. For example, each fuel cell string 1610 may include 60 fuel cells, and an electrical tap can be placed between each fuel cell string 1610 so that the electrical taps are each separated by 60 fuel cells. Depending on the application and desired voltage and current output needs, other sizes of fuel cell strings 1610 and other numbers of fuel cells between electrical taps can be used (e.g., 200, 100, 50, 20, 8, 4, 2, 1, etc.).

[0200] In the examples of FIGS. 16A and 16B, each array 700-PA to 700-PC is shown connected by a positive and negative connection, with each array 700-PA to 700-PC receiving a single DC input voltage (e.g., the voltage across one fuel cell string 1610). In each array 700-PA to 700-PC, each of the modules 108D can receive the same DC input voltage. In some implementations, each array 700-PA to 700-PC may have connections across multiple different spans of fuel cell strings 1610. For example, for the fuel cell stack 1112a of FIG. 16A, each of the arrays 700-PA to 700-PC can be coupled to each of the DC output ports DC_1 to DC_4, allowing the arrays 700-PA to 700- PC, under the control of the MCD 112, to select which of the fuel cell strings 1610 to use at a given time. Similarly, for the fuel cell stack 1112b of FIG. 16B, each of the arrays 700-PA to 700-PC can be coupled to each of the DC output ports DC_1 to DC_4, allowing the arrays 700-PA to 700- PC, under the control of the MCD 112, to select which span of fuel cell strings 1610 to use at a given time. By selecting to use the voltage between different spans of the fuel cell strings 1610 in the fuel cell stack 1112b, different voltage levels of DC input can be achieved. The electrical taps can allow the system to select to use the DC voltage across a span of one, two, or three of the fuel cell strings 1610 connected in series. FIG. 16C shows an example in which each of three arrays 700-PA to 700-PC is coupled to a different fuel cell stack 1112a-A to 1112a-C. Each of the fuel cell stacks 1112a-A to 1112a-C provides output at four ports DC_1 to DC_4 to its corresponding array 700-PA to 700-PC. The arrays 700-PA to 700-PC have the option to provide DC input from different spans of fuel cells, e.g., different fuel cell strings 1610, to different modules 108D. In general, within each array 700- PA to 700-PC, the modules 108D are loaded in a manner that balances current flow among them, at least over period of time such as an AC cycle or a few AC cycles. As a result, loading each fuel cell string 1610 with the same number modules 108D can achieve balanced current flowthrough the fuel cell stack 1112a.

[0201] In the example of FIG. 16C, each module 108D has four DC input ports, DC_1 to DC_4. The ports DC_1, DC_2, and DC_3 coupled to the three positive terminals of the respective fuel cell strings 1610. The port DC_4 is coupled to the voltage potential shared by the negative terminals of the fuel cell strings 1610. Each module 108D also has a port for AC output and a port E for a neutral return wire.

[0202] By providing separate DC input ports coupled to the positive terminals from different fuel cell strings 1610, the module 108E gains the versatility to utilize the fuel cell strings 1610 in various ways. This includes the modules 108D adaptively changing how different fuel cell strings 1610 are used, as instructed by the MCD 112 or in response to the locally-sensed condition of each fuel cell string 1610, e.g., temperature, pressure, sensed voltage, recent or historical current output capacity, wear level or usage history, position in maintenance cycle (e.g., purging or not), etc. If the fuel cell strings 1610 include the same or similar number of fuel cells, and so provide the same or similar DC voltage, the module 108D has the option to couple two or more of the fuel cell strings 1610 in parallel, through connections made within the module 108D. Nevertheless, if the module 108D senses that the temperature or pressure in one of the fuel cell strings 1610 exceeds a target operating range, or is significantly higher than the other fuel cell strings 1610, the module 108D can temporarily disconnect or reduce the load on that fuel cell string 1610.

[0203] The modules 108D can be configured to couple the fuel cell strings 1610 in any of various different configurations. For example, each module 108D can couple fuel cell strings 1610 directly in parallel when their output voltages differ by less than a maximum amount, and when current demand is greater than a predetermined threshold level. As another example, the modules 108D can be configured to make separate connections from the different fuel cell strings 1610 to different DC- AC converters and / or DC-DC converters to use the fuel cell strings 1610 independently. As another example, the modules 108D can couple the fuel cell strings 1610 through a transformer. The module 108D can include a transformer with multiple windings, and the DC output of each fuel cell string 1610 can be coupled to a corresponding DC-AC converter. The DC-AC converters can each drive a corresponding winding of the transformer to combine the power from each fuel cell string 1610.

[0204] If the number of fuel cells or the DC output voltages are significantly different for different fuel cell strings 1610, the modules 108D can use the DC output voltages from different fuel cell strings 1610 separately. For example, if one of the fuel cell strings 1610 is sensed to currently have a low voltage output (e.g., due to buildup of contaminants or a need for maintenance), the modules 108D can couple that fuel cell string 1610 to a DC-DC converter to provide power for a DC bus that requires lower power output than the AC bus.

[0205] Using the inputs on the ports DC_1 to DC_3, the modules 108D can each selectively use the output from two or more of the fuel cell strings 1610 — as instructed by the MCD 112 or as selected locally by the LCD 114 in response to sensed voltages or other conditions — to provide desired AC and / or DC outputs while managing various aspects of the fuel cell strings 1610. For example, the modules 108D can selectively use the fuel cell strings 1610 to perform load balancing among the fuel cell strings 1610, to add or remove the number of fuel cell strings 1610 used in response to changes in demand, to even out wear or usage across the fuel cell strings 1610, to manage temperature and pressure in the fuel cell strings 1610 (e.g., by disconnecting or reducing load for a fuel cell string that exceeds a temperature or pressure threshold), and to maintain output while one or more fuel cell strings are in different operating states (e.g., ramping up, ramping down, performing purging, etc.).

[0206] FIG. 16D shows an example in which each of three arrays 700-PA to 700-PC is coupled to a different fuel cell stack 1112b-A to 1112b-C. Each of the fuel cell stacks 1112b-A to 1112b-C provides output at four ports DC_1 to DC_4 to its corresponding array 700-PA to 700-PC. The arrays 700-PA to 700-PC have the option to provide DC input from different spans of fuel cells, e.g., different fuel cell strings 1610, to different modules 108D or achieve different input voltages. As an example, in the array 700-PA, the module 108D-A1 may receive DC input as the voltage across ports DC_1 and DC_2, the module 108D-A2 may receive DC input as the voltage across ports DC_2 and DC_3, and the module 108D-AM may receive DC input as the voltage across ports DC_3 and DC_4. As another example, to achieve a higher input voltage, all of the modules 108D- A1 to 108D-A2 may each receive input of the voltage across ports DC_1 and DC_4. As another example, if one of the fuel cell strings 1610 has need of maintenance or is not performing well, the top fuel cell string 1610 may be disconnected and the modules can use the voltage across ports DC_2 and DC_4.

[0207] In general, within each array 700-PA to 700-PC, the modules 108D are loaded in a manner that balances current flow among them, at least over period of time such as an AC cycle or a few AC cycles. For example, as discussed with respect to FIGS. 8A-8E, each module 108 can provide an AC module output that is not a sine wave, but rather a component that, when combined with the AC module outputs of the other modules 108, approximates a sine wave. The different AC module outputs are not current balanced in an instantaneous sense, because they have different voltages and currents over the course of a single AC cycle, but the overall amount of power or current supplied by each module 108 in the array 700 over the course of a single AC cycle is similar. As a result, loading each fuel cell string 1610 with the same number modules 108D can achieve balanced current flow through the fuel cell stack 1112b.

[0208] The connection of the electrical taps with the input ports of the modules 108D enable the modules 108D to select different subsets or spans of the fuel cell strings 1610 to use at different times and for different uses. For example, in the fuel cell stack 1112b-A, the three fuel cell strings 1610 are labeled Fl, F2, and F3. There is an intermediate tap 1650a between strings Fl and F2, and another intermediate tap 1650b between the strings F2 and F3. Similar intermediate taps are included in the other fuel cell stacks 1112b-B, 1112b-C. The set of cell strings 1610 labeled Fl, F2, and F3 are all part of the same fuel cell stack 1112b- A, and share the same balance of plant and are coupled in series.

[0209] The modules 108D can include programmable switching elements (e.g., transistors, relays, etc.) that enable different subsets or spans of the fuel cells to be used, e.g., coupled to the inputs of a DC-AC converter, DC-DC converter, or other components in the module 108D. For example, using the voltage across different pairs of the input ports DC_1 to DC_4, the modules 108D-A1 to 108D-AM can select and access the voltage across any Fl, F2, or F3 individually, or across the combination of Fl and F2 in series, the combination of F2 and F3 in series, or across the combination of Fl, F2, and F3 in series.

[0210] In general, when selecting among different spans of fuel cell strings 1610, the modules 108D can switch between different spans over time to balance loading, achieve desired output characteristics, or to coordinate maintenance. This can include shifting over the course of days, hours, minutes, seconds, or fractions of seconds. In some cases, the modules 108D can change the selection of which span of fuel cell strings 1610 is used for a given phase of AC output at a more fine-grained level, even within a single sinusoidal AC output cycle.

[0211] The versatility to select different subsets or spans of the fuel cells in the fuel cell stack 1112b gives the modules 108D the capability to adjust or vary the use of the different fuel cell strings 1610 to achieve various advantages. For example, the modules 108D can perform maintenance for one or more fuel cell strings 1610 (e.g., purging) while using other fuel cell strings 1610 to continue providing output without disruption. Similarly, the modules 108D can vary the amount of fuel cell strings 1610 used to respond to changes in load demand. The modules 108D can also change which subset of fuel cells is used to balance the wear and usage time for different fuel cell strings 1610, as well as to balance load, temperature, and pressure among the fuel cell strings 1610. Various scenarios and advantages for selectively coupling different spans of fuel cells in the fuel cell stack 1112b are discussed further below.

[0212] As a simple example, arrays 700 of modules 108D can use different fuel cell strings 1610, or different spans of multiple fuel cell strings 1610 to generate different phases of AC outputs, such as is shown in FIG. 16B by using Fl (e.g., voltage across DC_1 and DC_2) to provide AC output at port VA, using F2 (e.g., voltage across DC_2 and DC_3) to provide AC output at port VB, and using F3 (e.g., voltage across DC_3 and DC_4) to provide AC output at port Vc. However, the modules 108D can additionally or alternatively use different spans across the fuel cell strings 1610, e.g., using different pairs of the inputs DC_1 to DC_4, in a variety of other ways.

[0213] For example, referring to FIG. 16D, the modules 108D can each use the different voltages at the respective input ports DC_1 to DC_4 to achieve high conversion efficiency. The LCD 114 in the modules 108D can increase or decrease the number of fuel cells that are selected (e.g., the number of fuel cell strings 1610 in a span provided as input to a converter) to achieve a voltage near the desired output level. This can minimize or eliminate DC / DC conversion loss in some cases by allowing the voltage across the selected span of fuel cells to be used directly. For example, the LCD 114 can sense the voltage at the various ports DC_1 to DC_4. When the LCD 114 determines that a particular port provides a voltage sufficiently close to a desired DC output voltage, the LCD 114 can set programmable switches to couple that port to the DC bus. Even when the closest voltage of the electrical tap is not precisely at the DC voltage desired, identifying and using the closest voltage can reduce the amount of conversion and thus the loss incurred. As an example, a fuel cell stack 1112b may include 48 cells that each provide approximately IV, and the fuel cell stack 1112b can be arranged with fuel cell strings 1610 of 2 cells each. As a result, electrical taps would be provided between every 2 fuel cells, allowing a selection from among the taps to provide a DC voltage that is within 2 volts of the desired level. To achieve a 35V output, the LCD 114 can select a subset spanning 34 fuel cells and step up the voltage IV to achieve 35V, or select a subset spanning 36 cells and step the voltage down IV to achieve 35V. In general, DC- DC converters are more efficient when the absolute value of the difference between the input voltage and the output voltage is smaller, and the electrical taps between fuel cell strings 1610 enable the modules 108D to keep the difference between the input voltage used for conversion and the output voltage low. In practice, a hydrogen fuel cell may provide differing voltages depending on the condition of the cell, fuel rate, load, and other factors. In examples discussed herein, a cell voltage of IV is used for convenience, but in practice the LCD 114 of the modules 108D would sense the actual voltages and adjust control to achieve the desired voltage output. The modules 108D can also use the different voltages at the respective input ports DC_1 to DC_4 to respond to changing loads. In many cases, as current draw increases, voltage output of fuel cells decreases. The LCD 114 in the modules 108D can change (e.g., increase) the span of fuel cells to maintain a desired output voltage in response to higher loads, or decrease the span to maintain voltage as load decreases. As current draw from the fuel cell stack increases, if fuel concentration remains the same, voltage can decrease significantly. The LCD 114 can quickly switch to using a larger span of fuel cells to boost the voltage for the needed current level, at least temporarily, to gain an immediate boost to the voltage. Traditional fuel cell stacks often have relatively low capacity to respond to changes in load demand. However, the ability to dynamically change the voltage used by switching which span of fuel cells is used gives a much higher responsiveness than traditional processes of changing a fuel cell’s fuel rate or bringing additional fuel cells into operation. In some cases, a change in the span of fuel cell strings 1610 used may be temporary, such as until a spike in load demand decreases or while the fuel rate is increased and fuel cell voltages increase to previous levels, at which time the span of fuel cell strings 1610 used can be returned to the previous level. To provide headroom or margin for dynamic adjustment in the span used, the LCD 114 can operate in normal condition using a span of less than all of the fuel cell strings 1610. Thus, the LCD 114 may leave one or more fuel cell strings 1610 available in reserve as spare capacity that provides a margin or headroom to respond to load increases. Even if the LCD 114 and / or the MCD 112 requests an increase or decrease to the fuel rate to compensate for detected or predicted change in load demand, the ability to increase or decrease voltage nearly instantly by changing the span of fuel cell strings 1610 used can improve short-term performance before changes to fuel cell operation, such as fuel rate increases, take effect.

[0214] The modules 108D can also use the different voltages at the respective input ports DC_1 to DC_4 to generate AC output. One technique for generating the AC output is to progressively span different amounts of fuel cells at the output, using the electrical taps, in a pattern that approximates a sinusoidal output. By controlling switching to increase and decrease the number of fuel cells spanned between the input and output, the modules 108D can simulate or approximate a sinusoidal AC output with DC outputs. For example, one phase of AC output can span zero cells for a brief period at the midpoint of the AC cycle to provide 0V. Then, the modules 108D can provide, on the AC bus, DC output spanning 2 cells to provide 2V of DC output for a period including the time when the sinusoidal AC output would provide 2V (e.g., the time when the sinusoid increases from IV to 3 V). Then, the modules 108D can switch to provide the DC voltage from spanning 4 fuel cells to provide 4V during the period that the sinusoidal output would range from 3 V to 5V. The modules 108D can progressively change the amount of fuel cells spanned to increase and decrease the voltage at the AC output, including reversing the polarity to achieve negative portions of the AC output. While this represents a single module 108D approximating a sine wave output, multiple modules 108D in an array 700 can have their AC outputs connected in series so that their AC module output voltages sum to the AC voltage that is needed for the load 1150. The MCD 112 can coordinate the connections among modules and the timing and output voltages of each modules 108D to achieve the desired AC output characteristics.

[0215] The modules 108D can also use the different voltages at the respective input ports DC_1 to DC_4 to balance load among fuel cell strings 1610 within the fuel cell stack 1112b or to balance load among multiple fuel cell stacks 1112. For example, three fuel cell strings 1610 can each have 96 fuel cells at approximately IV per cell for approximately 96V DC across each fuel cell string 1610. In this example, the peak voltages +170V or -170V of 120V RMS AC output can be obtained using only two of the three fuel cell strings 1610. The modules 108D can shift which fuel cell strings 1610 are used over time, e.g., using Fl and F2 for a period of time, then using F2 and F3 for a period of time, to balance the load among the fuel cell strings 1610.

[0216] The modules 108D can include a DC-DC converter to convert from the voltage provided by a selected span of fuel cells (e.g., Fl, F2, F3, Fl + F2, F2 + F3, Fl + F2 + F3) to a desired output. This can allow the modules 108D to provide desired AC and DC output voltages at levels between those of the electrical taps between fuel cell strings 1610, as well as to maintain voltage output at desired levels even as current levels (and consequently voltage output per fuel cell) is changing. This arrangement can still be much more efficient than conventional systems that convert from fuel cell stack output to a fixed DC bus level before performing DC-AC conversion. The modules 108D can convert directly from any of the fuel cell output voltages across any pair of input ports DC_1 to DC_4 directly to the desired output voltage, thus avoiding the inefficiency of intermediate conversion to a fixed DC bus level. In some implementations, a DC-DC converter can be used to generate the simulated or approximated AC output. For example, according to the portion of the AC cycle, the modules 108D can select a span of fuel cells that is near the voltage level currently needed, and can use a DC-DC converter to step up or step down the voltage slightly as needed to provide the DC voltage step needed (e.g., at levels between those of the electrical taps between fuel cell strings 1610). This can provide the progressive, stepped DC outputs that approximate an AC output. In general, the technique of progressively stepping up and stepping down DC-DC conversion to create a stepped DC output can be used by any of the module 108 to generate a simulated or approximated AC output.

[0217] The modules 108D can also use the connections of the different electrical taps at the respective input ports DC_1 to DC_4 to perform maintenance on the fuel cell strings 1610 without disrupting AC output to the load 1150. When maintenance is needed for a fuel cell string 1610, the modules 108D can select a pair of the inputs DC_1 to DC_4 that avoids those fuel cells, to allow maintenance to be performed for that fuel cell string 1610 while power output is derived from the selected span of fuel cell strings 1610. For example, when a particular fuel cell string 1610 is in a purging process, the modules 108D can use the voltage across other fuel cell strings 1610 to generate the output to the load 1150. Purging and other maintenance can be staggered in time for different fuel cell strings 1610, so that maintenance is performed for each fuel cell string 1610 in turn without interrupting the output of the modules 108D.

[0218] The modules 108D can also use the connections of the different electrical taps at the respective input ports DC_1 to DC_4 to manage heat or pressure. For example, in response to sensed temperature or pressure in the different fuel cell strings 1610, the modules 108D can select pairs of input ports DC_1 to DC_4 to avoid spans of fuel cell strings 1610 that have temperature or pressure above a threshold level. For example, the LCD can have a set of rules for temperature, and can reduce load or duty cycle when temperature exceeds a threshold, or when it exceeds a particular temperature for at least a minimum amount of time. As another example, the modules 108D can proactively spread usage around to different fuel cell strings 1610 over time in a planned rotation or cycle.

[0219] The modules 108D can also use the connections of the different electrical taps at the respective input ports DC_1 to DC_4 to deal with fuel cell failures. When one or more fuel cells in a fuel cell string 1610 fail, the modules 108D can select one or more spans across other fuel cell strings 1610 to avoiding failed or low-output cells.

[0220] The modules 108D can also use the connections of the different electrical taps at the respective input ports DC_1 to DC_4 to extend the lifespan of fuel cells. For example, the modules 108D can use different fuel cell strings 1610 at different times to balance wear and degradation across various fuel cell strings 1610. This allows the individual cells to be used at a lower average output or for a lower total percentage of the time that the modules 108D provides power, which can extend the lifespan of the fuel cells and delay the amount of time between maintenance.

[0221] The modules 108D can also use the connections of the different electrical taps at the respective input ports DC_1 to DC_4 to extend the useful life of fuel cells after they have degraded. The selective use over different spans of fuel cells can extend the useful life of fuel cells by using effectively cells that have degraded beyond original design tolerances, to allow use past their original design lifespan. The modules 108D can identify and track the performance of each fuel cell string 1610 (and potentially for each individual fuel cell), and can route around fuel cell strings 1610 using the switches when needed. In addition, when voltage output is low across a fuel cell string 1610, the modules 108D can increase the number of fuel cell strings 1610 spanned to achieve the higher voltage needed. In other words, a larger number of lower-performing cells can be used together to approximate the performance of a smaller number of high-performing cells. As a result, the fuel cell stack 1112b can still be used effectively when some of the fuel cells are degraded or inoperable, because the modules 108D can use an alternative span of fuel cells when higher current is needed or to combine a span of multiple fuel cell strings 1610 to provide the combined voltage needed. The modules 108D can use lower-performing cells during times of low current draw or low total power demand.

[0222] Although the example of FIG. 16D shows the modules 108D, the same techniques can be used by any of the other modules 108 discussed herein, such as the module 108E that includes or operates with one or more batteries. For example, any of the modules 108 can be configured with multiple DC input ports, including one or more electrical taps at intermediate locations between fuel cell strings 1610 of a fuel cell stack 1112b, so the modules 108 can dynamically select and adjust which spans of fuel cell strings 1610 are used at different times, under local control of the LCD 114 and / or as instructed by the MCD 112.

[0223] FIG. 16E shows another example that shows multiple fuel cell stacks 1112c that can be used in parallel. In particular, N fuel cell stacks 1112c-l to 1112-cN can be provided, where N is a positive integer. The fuel cell stacks 1112c-l to 1112-cN can each be coupled in parallel to each of three arrays 700-PA to 700-PC. Each fuel cell stack 1112c-l to 1112-cN has an associated switching element SI to SN that connects or disconnects the fuel cell stack 1112c-l to 1112-cN to the arrays 700-PA to 700-PC. This arrangement allows the amount of power to be adjusted by adding or removing fuel cell stacks 1112c-l to 1112c-N, which can help respond to changes in load demand. In addition, the arrangement provides the ability to selectively add or remove fuel cell stacks 1112c-l to 1112c-N from power generation for repair or maintenance, while the arrays 700- PA to 700-PB continue to provide output based on power from other fuel cell stacks coupled in parallel.

[0224] Fuel cells do require some time to begin operation and start producing power, so full load output from a reserve fuel cell stack will not be available immediately, unlike a battery. In some implementations, higher responsiveness can be achieved by operating some or all of the fuel cell stacks 1112c-l to 1112c-N at a low output level, and then increased load demand can be met by switching to a higher output level. This can maintain an effective balance of plant and produce a faster response than starting a fuel cell stack 1112c from a completely off state.

[0225] Each fuel cell stack 1112c-l to 1112c-N optionally includes multiple sets of fuel cell strings 1610. The connections between the different sets of fuel cell stacks 1112c-l to 1112c-N are configurable, so that different sets of fuel cell stacks 1112c-l to 1112c-N can be selectively coupled according to instructions from the MCD 112. For example, a programmable switching element SI, S2, SN can be placed between, for example, the positive terminal of each fuel cell stacks 1112c-l to 1112c-N and the DC+ port of the modules 108D in the arrays 700-PA to 700-PB, so that the MCD 112 can selectively couple the fuel cell stacks 1112c-l to 1112c-N in different combinations at different times. The switching elements SI to SN can be implemented using transistors, relays, switches, or other types of switching elements. For example, a single fuel cell stack 1112c may be connected when low power output is needed by the load 1150. The MCD 112 can use the switching elements SI to SN to select any combination of the different fuel cell stacks 1112c-l to 1112c-N to provide DC input in this manner. As the electrical current demand of the load 1150 increases, the MCD 112 can set the switching elements Sl-SN to couple one or more of the other fuel cell stacks 1112c-2 to 1112c-N in parallel to provide greater power output.

[0226] As another example, the MCD 112 can selectively couple different fuel cell stacks 1112c-l to 1112c-N, or combinations of fuel cell stacks 1112c-l to 1112c-N, at different times to balance wear and usage time. Similarly, the MCD 112 can adjust the connections based on sensed conditions, such as to disconnect or reduce load on one or more of the fuel cell stacks 1112c-l to 1112c-N in response to pressure or temperature exceeding a threshold. The MCD 112 can also selectively connect the fuel cell stacks 1112c-l to 1112c-N to perform maintenance (e.g., purging) with one group while one or more of the other groups remain connected to provide power. In addition to, or instead of selectively connecting the fuel cell stacks 1112c-l to 1112c-N, the MCD 112 can manage electrical output, temperature, pressure, and other characteristics by adjusting the fuel rate or other operating for the fuel cells, and these adjustments can be made separately for each fuel cell stacks 1112c-l to 1112c-N.

[0227] FIG. 16F shows an example in which each array 700-PA to 700-PN has multiple fuel cell stacks 112c that can be selectively coupled in parallel. For example, the array 700-PA can receive input from one or more of the fuel cell stacks 1112c-Al to 1112c-AN, the array 700-PB can be receive input from one or more of the fuel cell stacks 1112c-Bl to 1112c-BN, and the array 700- PC can be receive input from one or more of the fuel cell stacks 1112c-Cl to 1112c-CN. The fuel cell stacks 1112c each have an associated switching element, labeled S1A-SNA, S1B-SNB, S1C- SNC, that can be electrically controlled by the MCD 112 or another control system. For example, the fuel cell stack 1112c-Al can be coupled or decoupled from providing power to the array 700- PA using switching element SI A, the fuel cell stack 1112c-Al can be coupled or decoupled from providing power to the array 700-PA using switching element S2A, and so on.

[0228] Each fuel cell stack 1112c can be as simple as a single fuel cell string 1610. In other implementations, as shown, each fuel cell stack 1112c can include multiple fuel cell strings 1610 arranged in series, where each fuel cell stack 1112c provides the voltage across the fuel cell stack 1112c as a whole. As with the example of FIG. 16E, each fuel cell stack 1112c has a switching element SI to SN that can be used to connect or disconnect the fuel cell stack 1112c under the control of the MCD 112. This allows for power generation capacity to be added or removed according to load demand, and for individual fuel cell stacks 1112c to be selectively added and removed from operation without disrupting the overall output of the arrays 700-PA to 700-PN.

[0229] FIG. 16G shows another example showing fuel cell stacks 1112d that include both electrical taps between fuel cell strings 1610 and switching elements to facilitate coupling of multiple fuel cell stacks 1112d in parallel. Each fuel cell stack 1112d includes multiple fuel cell strings 1610 in series, with electrical taps between the fuel cell strings 1610. Each fuel cell stack 1112d includes multiple switching elements SI to S3, for example, a switching element SI to selectively connect the full series of fuel cell strings 1610 as well as switching elements S2, S3 to selectively connect electrical taps between fuel cell strings 1610. This results in a hybrid arrangement that allows selective coupling of different fuel cell stacks 1112d- 1 to 1112d-N, as in FIGS. 16E and 16F, as well as drawing power from intermediate positions in the fuel cell stacks 1112d- 1 to 1112d-N using intermediate taps, as in FIGS. 16B and 16D.

[0230] In the example of FIG. 16G, a single array 700-PA is illustrated, which receives input at four input ports DC_1 to DC_4 and provides a single phase of AC output, VA. Other arrays 700, such as arrays 700-PB and 700-PC, can be used to provide other AC output phases. Other arrays 700 may each have their own set of one or more fuel cell stacks 1112d, or may receive the same inputs as the array 700-PA.

[0231] For the array 700-PA, the first input port DC_1 is arranged to receive input from the positive terminal of each fuel cell stack 1112d- 1 to 1112d-N, and the last input port DC_4 is coupled to the negative terminal of each fuel cell stack 1112d- 1 to 1112d-N. The input port DC_2 couples to a first set intermediate taps through the switching elements S2, and the input port DC_3 couples to a second set of intermediate taps through the switching elements S3.

[0232] By setting the switching elements SI, the voltages across any or all of the fuel cell stacks 1112d- 1 to 1112d-N (e.g., across any one, or across any combination or sub-combination) can be coupled to the input port DC_1. The MCD 112 can control the operation of the various fuel cell stacks 1112d- 1 to 1112d-N and set the switching elements. The electrical taps between fuel cell strings 1610 can also be selectively coupled to corresponding input ports DC_2 and DC_3. For example, the electrical taps below the top fuel cell stack 1610 of each fuel cell stack 1112d- 1 to 1112d-N can be selectively coupled to the input port DC_2 through switching elements S2, respectively. Similarly, the electrical taps below the second fuel cell stack 1610 of each fuel cell stack 1112d- 1 to 1112d-N can be selectively coupled to the input port DC_3 through switching elements S3, respectively. The lowest-potential terminals of the fuel cell stacks 1112d- 1 to 1112d- N groups are coupled together to input port DC_4.

[0233] The arrangement of fuel cell strings 1610 and switching elements SI -S3 provides the versatility to select current capacity and voltage used as input to the modules 108D of the array 700-PA. For example, the settings of the switching elements determine which particular fuel cell stacks 1112d- 1 to 1112d-N are used as well as the total number of fuel cell stacks 1112d- 1 to 1112d-N that are used. The voltages across different combinations of ports DC_1 to DC_4 allows different voltages to be selected. With the arrangement shown, the MCD 112 can select and change the number of fuel cell strings 1610 used in parallel across each pair of input ports DC_1 to DC_4. The MCD 112 can also select and change which specific fuel cell strings 1610 are used, e.g., by setting the switching elements S1-S3 to specify which fuel cell strings 1610 from fuel cell stacks 1112d- 1 to 1112d-N will be connected. The module 108D of the array 700-PA can be instructed to draw input using the voltage across any pair of the input ports DC_1 to DC_4 (e.g., across DC_1 and DC_2; across DC_2 and DC_3; across DC_3 and DC_4; across DC_1 and DC_3; across DC_2 and DC_4; across DC_1 and DC_4), or multiple pairs concurrently, to source the power needed to generate their respective outputs. In addition, the MCD 112 can control the switching elements SI -S3 to provide the input at any pair of the input ports DC_1 to DC_4 using any one of the fuel cell stacks 1112d- 1 to 1112d-N individually, or use any two or more of the fuel cell stacks 1112d- 1 to 1112d-N coupled in parallel.

[0234] For example, the MCD 112 may initially instruct the modules 108D of the array 700-PA to use the voltage between input ports DC_2 and DC_4 to generate an AC output, with only the switching element S2 of the fuel cell stack 1112d- 1 closed to connect only the lower two fuel cell strings 1610 of the fuel cell stack 1112d-l. Current through the top fuel cell string 1610 of the fuel cell stack 1112d- 1 can be used to charge a battery or power another load, to maintain a balance of current through the different fuel cell strings 1610 of the fuel cell stack 1112d-l. If the load demand increases or if this span across the group G1 is unable to provide desired voltage and / or current characteristics, the MCD 112 can instruct the switching element S2 of the fuel cell stack 1112d-2 to add the lower two fuel cell strings 1610 from the fuel cell stack 1112d-2 in parallel across the same input ports (e.g., DC_2 and DC_4). The MCD 112 can additionally or alternatively close the switching element S2 of the fuel cell stack 1112d-N to add the lower two fuel cell strings 1610 from the fuel cell stack 1112d-N in parallel across the same input ports (e.g., DC_2 and DC_4). The same techniques can be used to select or vary which fuel cell strings 1610, and the amount of fuel cell strings 1610, that are coupled across any of the pairs of input ports DC_1 to DC_4.

[0235] FIG. 16H illustrates another example that includes multiple fuel cell stacks 1112b- 1 to 1112b-N. Similar to FIG. 16G, each of the fuel cell stacks 1112b- 1 to 1112b-N has intermediate taps that are provided to access voltages at different portions of the fuel cell stacks 1112b- 1 to 1112b-N. However, the connections between the various fuel cell strands 1610 are not tied together at input ports of the modules 108D of the array 700-PA and are not coupled through switching elements. Instead, the outputs from different points in the fuel cell stacks 1112b- 1 to 1112b-N are provided to separate input ports of the modules 108D.

[0236] For example, the highest-potential points on the fuel cell stacks 1112b- 1 to 1112b-N are provided to separate input ports DC l-l to DC l-N, the intermediate taps below the first fuel cell string 1610 of each fuel cell stack 1112b- 1 to 1112b-N are provided to input ports DC 2-1 to DC_2-N, the intermediate taps below the second fuel cell string 1610 of each fuel cell stack 1112b- 1 to 1112b-N are provided to input ports DC 3-1 to DC 3-N, and the lowest-potential connections of each fuel cell stack 1112b- 1 to 1112b-N are provided to input ports DC 4-1 to DC 4-N.

[0237] This arrangement provides a high degree of versatility by allowing the modules 108D to select and combine different fuel cell strings 1610 in series or in parallel. This arrangement also relies on the modules 108D to include switching circuitry to make the connections as needed. In addition, diodes or other protection circuitry can be used to limit or disallow connections that would cause short circuits or loops. As another example, the LCD 114 of each module 108D can include logic that limits the connections of the various input ports that can be made.

[0238] For each of the fuel cell stacks 1112 shown in FIGS. 16A-16H, alternative implementations can be used. For example, additional fuel cell strings 1610 can be added in series or in parallel. Similarly, multiple fuel cell strings 1610 can be aggregated or combined, or individual fuel cell strings 1610 can be subdivided into smaller strings coupled in series.

[0239] The various electrical connections and ports of the example fuel cell stacks in FIGS. 16A- 16H provide the system many options for selecting the desired DC voltage to draw (e.g., by using voltage at different ports or across spans of different pairs of ports) as well as many options for the desired current capacity (e.g., by selectively drawing power from one fuel cell stack, or from two, three, or more different fuel cell stacks coupled in parallel). The MCD 112 and the LCDs 114 can electrically or programmably adjust the power source utilization, such as by changing the state of switching elements to couple or decouple fuel cell stacks 1112, or by selecting within modules 108 which of different input ports to draw power from (e.g., where the input ports of the modules 108 connect to different output ports on the fuel cell stacks 1112, including at intermediate taps between fuel cell strings 1610). These settings can be changed dynamically according to factors such as the desired output voltage or output current, power needs of the load, the state of the respective fuel cell stacks 1112, maintenance needs and wear leveling to increase longevity, and so on.

[0240] The connections used to source power can be set at any appropriate level of granularity, such as (1) shared for the system as a whole (e.g., the same for all three phases), (2) separately for each phase or for each array 700 but shared within the modules 108 of each array 700, or (3) separately for each module 108 within each array 700. This versatility can facilitate the efficient use of fuel cell stacks with diverse characteristics, such as different numbers of fuel cells, different maintenance states (e.g., recently purged vs. not recently purged, new vs. worn or degraded, etc.), different output levels, and so on. For example, the versatility for modules 108 to select voltages from different intermediate taps can allow modules 108 to select and use the input that is sensed to be closest to the desired input level or desired output level, to minimize the voltage difference needed in performing conversions, which can increase efficiency. As another example, the versatility in the input connections to the modules 108 can allow modules 108 to use fuel cell stacks 1112 past their typical normal life, by cycling or rotating among different fuel cell stacks 1112 to limit wear, using multiple fuel cell stacks 1112 at lower output levels, allowing more frequent purging or other maintenance with seamless switchover to other fuel cell stacks 1112, and so on.

[0241] The high versatility that the different input connections of FIGS. 16A-16H provide can also present the risk of improper connections, however, if ports are connected to cause short circuits, loops, reverse current flows, or other undesired behavior. As a result, the system can include passive and / or passive mechanisms to enforce the desired behavior and protect against improper connections. For example, the connections between some or all of the fuel cell strings 1610 to the modules 108 can be made through diodes arranged to block reverse currents. Similarly, the fuel cell stacks 1112 and / or the modules 108 can include current limiters, fuses, short circuit protection or other features to prevent overcurrent conditions or faults.

[0242] As another example, the mechanisms in the various modules 108 that connect different input voltages from the fuel cell stacks 1112 to the internal components of the modules 108 (such as a DC-AC converter 202) or to the DC or AC output connections of the modules 108 can be structured to disallow certain combinations, such as reverse polarity of DC outputs or to internally connect ports that would result in a short circuit. This may limit the set of possible connections, but is an acceptable tradeoff to preserve the reliability of the system. In some cases, logic in the LCDs 114 and / or the MCD 112, whether in hardware, software or firmware, permits only a predetermined set of connections or port combinations to be used together. For example, the MCD 112 can include rules or look-up tables that designate allowed connections, and / or which specify disallowed combinations, so that the MCD 112 will only instruct modules 108 to use mappings of input ports to internal nodes or external outputs that are permitted. The same information can also be stored at or provided to the LCDs 114 so that they can also enforce modules 108 using only safe and reliable connections of input ports to other components.

[0243] In general, the current flowing through a fuel cell stack 1112 should be balanced so that substantially the same current flows through all of the fuel cells in the fuel cell stack 1112. Various of the configurations shown in FIGS. 16A-16H allow power to be drawn to or diverted to different paths from different fuel cell strings 1610 or sets of fuel cells in the same fuel cell stack 1112. The MCD 112 can manage this to reduce or eliminate the difference in current flow among fuel cells of each individual fuel cell stack. The techniques for AC output generation described in FIGS. 7A to 8E allow the because the modules 108 in an array 700 to provide substantially equal power output over an AC cycle, which allow the MCD 112 to balance loading on different fuel cell strings 1610 by assigning substantially equal numbers of modules 108 within an array to draw power from each fuel cell string 1610. As a result, the current draw from, and the current flow through, different fuel cell strings 1610 in a fuel cell stack 1112 can be distributed and still maintain an even flow of current through the fuel cell stack 1112 overall. Additional elements such as capacitors can be used to provide energy buffers to help balance the current flow and avoid disparities. In addition, to the extent there is excess current from one or more fuel cell strings 1610, or one or more fuel cell strings 1610 cannot be loaded evenly with others, the current can be routed for battery charging to make use of the generated power and maintain balance current flow through the fuel cell stack 1112. For example, if one of the fuel cell strings 1610 provides significantly lower voltage than the others, the MCD 112 can assign that fuel cell string 1610 to provide output to a battery charger, which may have its own converter(s) that can tolerate low voltage or significant variation in voltage, and for which the battery charging application is not time-critical and can tolerate significant variation in power or current being supplied. The other fuel cell strings 1610 which are performing well can be used by the modules 108 in their normal capacity, without the need for the LCDs to coordinate current balancing through the fuel cell stack 1112, since the MCD 112 handles this management task through its assignments to the modules 108. The LCDs 114 can each carry out the instructions given by the MCD 112 for their respective modules 108.

[0244] FIGS. 17A and 17B illustrate examples of using different examples of fuel cell stacks 1112 with arrays 700-PA to 700-PC of modules 108E, where each of the modules 108D which are configured to use power from fuel cell stacks 1112 as well as from batteries. More generally, any of the examples of FIGS. 16A-16H can use modules 108E in place of modules 108D, where the modules 108E each have one or more batteries and a DC-DC converter, in addition to other features of modules 108 discussed above.

[0245] FIG. 17A shows an example in which a fuel cell stack 1112c is used to provide input power to three different arrays of modules 108E, labelled as arrays 700-PA to 700-PC. As discussed above, each of the modules 108E includes, or is otherwise coupled to, one or more batteries. Each fuel cell stack 1112c-l to 1112c-N has only two output terminals, and so these two terminals provide DC power to the modules 108E of each of the arrays 700-PA to 700-PC. In effect, the modules 108E are each coupled in parallel to the fuel cell stacks 1112c-l to 1112c-N, so that each module 108E receives the same voltage at its DC+ terminal and the same voltage at the DC- terminal. As with other examples, the MCD 112 can open or close switching elements SI to Sn to change the number of fuel cell stacks 1112c that are connected in parallel.

[0246] FIG. 17B shows an example in which a fuel cell stack 1112a provides input modules 108E of multiple arrays 700-PA to 700-PC. In the fuel cell stack 1112a, the positive terminals of the fuel cell strings 1610 are made available as different outputs. Each of the modules 108E is coupled to the positive terminal of a different fuel cell string 1610, through respective input ports DC 1+, DC 2+, and DC 3+. The modules 108E also each have an input port labelled DC-, which is coupled to a shared voltage potential at the negative terminal of each of the fuel cell strings 1610.

[0247] FIG. 18 is a block diagram depicting an example 1800 of the main control device 112 controlling a fuel cell system 1110 and interacting with a computer system 1810 over a network 1802. The MCD 112 can perform control functions to manage the fuel cell stacks 1112 and the arrays 700 of modules 108.

[0248] As discussed above, the MCD 112 can track usage and performance of the fuel cell stacks 1112, including potentially tracking status over time at more fine-grained levels of individual fuel cell strings 1610 within fuel cell stacks 1112 and / or individual fuel cells. The MCD 112 can communicate with a computer system 1810 over a communication network 1802, such as the Internet, to more effectively manage the fuel cell stacks 1112. For example, the 1810 can be a remote server or a cloud computing system that stores usage and performance data and may additionally perform additional modeling and prediction to facilitate effective management.

[0249] The control interface 1125 carries information from sensors of the fuel cell stacks 1112-A to 1112-N, such as temperature, pressure, fuel rate, voltage output, current output, operating status (e.g., on or off, parameters within predetermined ranged, etc.), and so on. In some implementations, each fuel cell stack 1112-A to 1112-N has a controller that provides the information to the MCD 112.

[0250] In some implementations, in each array 700-PA to 700-PN, the LCD 114 of one or more of the modules 108D receives and processes status information about the associated fuel cell stack 1112. For example, some local monitoring tasks may be delegated to the LCDs 114, such as to monitor for certain conditions (e.g., temperature above a threshold, output voltage below a threshold, etc.), and to send a message to the MCD 112 to indicate when one of the conditions is detected. Similarly, the LCDs 114 may aggregate information about the associated fuel cell stacks 1112 over a predetermined duration or time window (e.g., periods of 1 minute, 5 minutes, 15 minutes, 1 hour, etc.) and then send aggregated reports for the time window to the MCD 112.

[0251] With information about usage and status of the fuel cell stacks 1112-A to 1112-N, the capability and characteristics of the fuel cell stacks 1112 can be determined or estimated, including characteristics such as the lifespan, current capacity, voltage capacity, stage in a maintenance cycle, and so on. This tracking enables the MCD 112 to use fuel cells effectively, even if they have degraded or are undergoing maintenance operations. For example, based on the sensed conditions indicated by the LCDs 114 and tracked usage data, the MCD 112 may determine that certain fuel cell stacks 1112 have degraded and have lower voltage capacity than other fuel cell stacks. As a result, the MCD 112 may assign, as an example, four of the degraded fuel cell stacks 1112 to be used together to provide the desired output, where only two or three fuel cell stacks 1112 at full capacity would be assigned for the same level of output.

[0252] The processing to perform modeling and generate predictions about maintenance and lifespan for fuel cell stacks 1112 can be performed at the MCD 112 or at another processing system, such as the computer system 1810. The system can use a separate identifier or address for different components, such as individual arrays 700, individual modules 108, individual batteries, individual fuel cell stacks 1112, and individual fuel cell strings 1610. This facilitates monitoring and tracking, as well as sending specific commands that can be effectively routed to the appropriate device. For example, the MCD 112 can specify settings or profiles for each individual component, based on its maintenance and lifespan prediction models.

[0253] In some implementations, digital twin models 1830 are created for fuel cell stacks 1112 and / or other components in the fuel cell system 1110, including batteries that operate together with the fuel cell system 1110. Each digital twin model 1830 can be a virtual model of the actual device, used to simulate the behavior of the device, including results of wear and usage over time. The MCD 112 and / or the computer system 1810 can use status data collected regularly over the lifetime of a fuel cell stack 1112, making incremental updates for the specific circumstances and conditions the fuel cell stack 1112 experiences. For example, when a fuel cell stack 1112 is used, the time and duration of use, ambient temperature, internal temperature, pressure, fuel rate, output current, output voltage, and other parameters can be sampled repeatedly. Using characterization data for that model of fuel cell stack 1112, which can be obtained through observation of other fuel cell stacks 1112 over their lifetimes and under various usage conditions, the digital twin model can reflect the wear and capability expected for the actual physical fuel cell stack 1112 instance being modeled. As a result, use at higher temperature or for longer durations can be shown in the model 1830 to place greater wear on the device, leading to earlier estimates of potential failure or output degradation and recommendations for preventative maintenance to be performed earlier. By accumulating usage and status data repeatedly for each individual fuel cell stack 1112 (or other component of the system 1110), the maintenance schedule, duty cycle, loading, and other parameters can be customized for each fuel cell stack 1112 to improve the lifespan and quality of output generated. In some implementations, predictive models 1832 are also used. For example, machine learning models can be trained using example data, such as time series data including the usage and status of different fuel cell stacks 1112. For example, the example data can indicate (1) conditions and loading experienced by different fuel cell stacks 1112, (2) maintenance actions performed, and (3) outcomes achieved (e.g., power output capabilities, failures experienced, etc.). Using these example datasets, machine learning models such as neural networks can be trained to leam the correlations between the usage and conditions and the maintenance actions performed, and their impact on the probability of the outcomes achieved, whether positive or negative. The models 1832 can be trained to predict maintenance that will increase the likelihood of positive outcomes (e.g., long lifespan, maintained voltage and current capacity, etc.) and decrease the likelihood of negative outcome (e.g., degraded output capacity, failure, etc.). As a result, the models 1832 can be used to predict timing of and / or selection of maintenance actions for a fuel cell stack 1112, given a usage history and / or current status of the fuel cell stack 1112. In other words, the models 1832 can receive feature values indicative of a particular fuel cell stack’s past history (e.g., maintenance history, usage history, time series of status data, etc.) and current status. In response, the models 1832 can output predictions of which maintenance actions to perform, and timing at which to perform the actions (e.g., immediately, in the next day, in the next week etc.). The models 1832 can also be trained to output the predicted future results, such as future output voltage and / or output current capacity, if the maintenance actions are performed or are not performed.

[0254] In some implementations, the MCD 112 and / or the computer system 1810 can use the models 1830, 1832 to repeatedly and automatically assess the need for maintenance of each of the fuel cell stacks 1112- A to 1112-N, and can schedule and initiate the maintenance to improve performance and lifespan. For example, the MCD 112 and / or the computer system 1810 can continually update predictions for the fuel cell stacks 1112-A to 1112-N as new status reports are provided. If a maintenance action is determined to be appropriate for a fuel cell stack 1112-A based on the models 1830, 1832, then the MCD 112 can initiate a transition for another fuel cell stack 1112 to take over power generation so the fuel cell stack 1112-A can be maintained without interrupting power delivery.

[0255] In general, models such as the digital twin models 1830 and the predictive models 1832 can be used to select and schedule a variety of actions, such as the purging of fuel cells, decreasing of output to limit wear, selecting an appropriate number of fuel cell stacks 1112 to use in parallel to avoid undue stress or to supply needed power given the diminished capacity of the fuel cell stacks, and so on. In many cases, the MCD 112 can adjust a control setting to reduce the acceptable maximum output from a fuel cell stack 1112 if the fuel cell stack 1112 is damaged or if there is a preference to increase its lifespan. The predictive maintenance and management can be helpful for managing fleets of vehicles that use fuel cell stacks 1112. The models 1830, 1830 can provide a fleet operator information about the trends across multiple fuel cell stacks 1112 and multiple vehicles, along with plans or schedules for replacing components to maintain performance and avoid failures. By detecting problematic conditions at early stages, or by predicting them ahead of time, the system can be controlled to achieve better reliability (e.g., uptime) as well as better and more consistent performance. Fleet operators use these techniques to improve vehicle range and to extend the life of the vehicle. As an example, the MCD 112 or the computer system 1810 can predict the capability of a fuel cell stack 1112 power plant of a vehicle, which can determine the driving range available. With this information, the computer system 1810 or another system can assign the vehicle to routes that fit within the capability of the fuel cell stack 1112. As a result, even if a fuel cell stack 1112 of a vehicle has degraded, the effectively life of the fuel cell power system can be extended by appropriately matching the power capability to the task or route assigned.

[0256] Because the MCD 112 receives reports from each of the many components of the fuel cell system 1110, the MCD 112 can effectively control the fuel cell stacks 1112- A to 1112-N to meet the current and predicted future needs of the loads. The MCD 112 can issue instructions over the control interface 1125 to start up additional fuel cell stacks 1112 when additional power is needed or is predicted based on previous usage patterns to be needed soon. Similarly, the MCD 112 can balance the power capacity needs with the capabilities that are monitored and predicted for the individual fuel cell stacks 1112- A to 1112-N. In many cases, the fuel cell stacks 1112- A to 1112-N can have local controllers that maintain operation at a particular set point, e.g., to operate pumps and other components to provide a fuel rate that is instructed. Nevertheless, the MCD 112, with information about the load on the system 1110 and other conditions, has the information to determine when changes to the set point are needed. For example, based on voltage levels reported, current drawn by the loads, temperatures reported, or other parameters, the MCD 112 can instruct particular fuel cell stacks 1112-A to 1112-N to increase or decrease fuel rate and other parameters.

[0257] In addition to monitoring conditions and tracking usage, the MCD 112 can perform a variety of other control functions. For example, the MCD 112, can detect and respond to failures to keep continuity of power output, for example, activating a reserve fuel cell stack 1112 to take the place of one that has failed or is not providing the desired output. More generally, the MCD 112 can instruct fuel cell stacks 1112 to start up or shut down according to load conditions. Similarly, the MCD 112 can control the state of switching elements to selectively couple (e.g., couple or decouple depending on the setting and circumstances) specific fuel cell stacks 1112 to the inputs of particular modules 108 in arrays 700. The MCD 112 can also assign modules 108 to arrays 700 and adjust topologies for those arrays 700 (e.g., the number of modules 108 per array 700, the interconnections between modules within arrays 700, etc.). The MCD 112 can also coordinate the overall output of the fuel cell system 1110, such as by setting the AC output voltages, AC output frequencies, AC phases, DC output voltages, and other characteristics. The MCD 112 can coordinate the specific output characteristics needed for each module 108 so that together the modules 108 in each array 700 provide the needed output.

[0258] In systems that include or interface with batteries, the MCD 112 can instruct the modules 108 and any battery systems to adjust the amount of power to be sourced from the fuel cell stacks 1112 and batteries. For example, the MCD 112 can designate which fuel cell stacks 1112 to be used for charging batteries, and times when batteries should be charged and discharged, and to what extent. Depending on the implementation, some of these functions may be implemented using policies that are carried out by the LCDs 114 of the modules 108, such as to charge a battery when its state of charge decreases below a threshold or to source power from a battery when the state of charge is above a threshold and the load is above a certain level. Even in these situations, the MCD 112 can set and adjust the policies and thresholds to be used, and can instruct the LCDs accordingly.

[0259] In general, the MCD 112 can monitor a condition of the fuel cell stacks 1112- A to 112-N based on information provided by the modules 108D-A1 to 108D-NM and / or from controllers or sensors of the fuel cell stacks 1112-A to 1112-N themselves. The MCD 112 can provide, based on the monitored condition of the fuel cell stacks 1112-A to 1112-N, control signals that adjust the operation of the fuel cell stacks 1112-A to 112-N, the operation of the modules 108D-A1 to 108D- NM, or both. For example, the MCD 112 can send instructions to the local control devices that configure (e.g., set or adjust) outputs of the power supply modules. The information provided by the local control devices indicates one or more operating parameters of the fuel cell stacks 1112-A to 1112-N, wherein the one or more operating parameters of a fuel cell stack 1112 comprise a voltage output, an electrical current output, a temperature, a pressure, a fuel rate, a configuration, an operating state, a duration of operation, or a maintenance status. In some cases, one or more of the LCDs 114 is configured to monitor the one or more operating parameters of a fuel cell stack and communicate to the main control device whether the one or more operating parameters are within a predetermined range or satisfy a predetermined threshold.

[0260] The MCD 112 is configured to provide control signals via the control interface 1125 that instruct AC output characteristics for individual modules 108D-A1 to 108D-NM. The instructed AC output characteristics can specify at least one of an AC output voltage, a AC output frequency, an AC output phase, a connection over which to provide AC output, or whether to enable or disable AC output from the module 108D-A1 to 108D-NM. The system 1110 can be configured to provide multiple phases of AC output to an AC bus 1105, and the MCD 112 can be configured to assign different subsets of the modules 108 to provide the respective phases of AC output. The MCD 112 sends control signals via the control interface 1125 to cause the LCDs 114 to provide AC output at the phases to which the modules 108D-A1 to 108D-NM are assigned. The control signals can include synchronization signals to synchronize AC module outputs of the modules 108D-A1 to 108D-NM. In some implementations, the control signals comprise control signals that instruct a topology for electrical connections to be established among the modules 108D-A1 to 108D-NM or with the AC bus 1105.

[0261] The MCD 112 can send control signals that instruct a change to operation of one or more fuel cell stacks 1112-A to 1112-N, including at least one of a change to a fuel rate for a fuel cell stack 1112, a change to a pressure of a fuel cell stack 1112, a change to begin or end a purging cycle for a fuel cell stack 1112, or a change to start or stop power generation with a fuel cell stack 1112.

[0262] The MCD 112 can be configured to send control signals to instruct a subset of the modules 108D-A1 to 108D-NM to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the modules 108D-A1 to 108D-NM coupled in series. The MCD 112 can be configured to send control signals to instruct a subset of the modules 108D-A1 to 108D-NM to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the modules 108 coupled in parallel. The MCD 112 can be configured to track usage of the one or more fuel cell stacks based on the information from the LCDs 114 and send control signals to vary usage of the modules 108D-A1 to 108D-NM to balance wear among multiple fuel cell stacks. The MCD 112 can be configured to (i) determine, based on the information from the LCDs 114 or the fuel cell stacks 1112-A to 1112-N, when a temperature of at least one of the one or more fuel cell stacks 1112-A to 1112-N exceeds a threshold and (ii) send control signals to reduce output of one or more modules 108D-A1 to 108D-NM receiving power from the fuel cell stack determined to have a temperature that exceeds the threshold.

[0263] The MCD 112 can also use the versatility afforded by the arrangements of FIGS. 16A-16H to manage performance in the system, including the selection of different inputs to the modules 108D-A1 to 108D-NM. As shown in FIG. 16C and 16D, each individual module 108 may have input ports to receive inputs for different fuel cell strands 1610, and the LCD 114 can selectively couple different inputs to the DC-AC converter 202 according to the condition of the fuel cell stack 1112, the load, and other conditions. The MCD 112 can use its information about the overall system 1110 to instruct modules 108 to use specific inputs, or to change inputs as conditions change, to adjust output and balance wear and loading. For example, the MCD 112 can instruct the LCDs 114 of the modules 108D-A1 to 108D- NM to change the inputs used to provide power to the DC-AC converters to balance load or wear among the fuel cells over time. This can include setting or changing which span of fuel cells, or which fuel cell strand(s) 1610, in a fuel cell stack 1112 are used by a particular module. In some cases, the MCD 112 is configured to (i) detect a decrease in performance of one or more fuel cells in a fuel cell stack 1112- A to 1112-N and (ii) instruct the LCDs 114 to change the inputs that their respective modules use to provide power to the DC-AC converters in response to detecting the decrease in performance. The MCD 112 can be configured to (i) detect a change in load demand and (ii) change the inputs used to provide power to the DC-AC converters in response to detecting the change in load demand. The MCD 112 can be configured to (i) identify one or more of the fuel cells or fuel cell stacks that are designated for a maintenance operation and (ii) instruct the LCDs 114 to change the inputs used to provide power to the DC-AC converters to draw power during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation. The MCD 112 can be configured to (i) receive sensor data indicating a condition of a fuel cell stack and (ii) instruct the LCDs 114 to change the inputs used to provide power to the DC-AC converter based on the sensor data. The MCD 112 can instruct the LCDs 114 of the modules 108D-A1 to 108D-NM to change the inputs used to provide power to the DC-AC converter in response to determining that the temperature of one or more fuel cells exceeds a threshold.

[0264] In general, the use of intermediate taps between multiple fuel cell strings 1610, as shown in FIG. 16D, enables access to and power draw from intermediate points in the fuel cell stack 1112, for a more fine-grained level of control than is afforded in other systems. Although the current through a series-connected set of fuel cells typically needs to be balanced, because the modules 108 in an array 700 share the load substantially evenly, they can be distributed across different spans of fuel cell strings 1610 and still maintain an even flow of current through the fuel cell stack 1112. In addition, to the extent there is excess current from one or more fuel cell strings 1610, the current can be routed for battery charging to make use of the generated power and maintain balance current flow through the fuel cell stack 1112.

[0265] One advantage of this approach is the ability for the MCD 112 and / or the LCDs 114 to select between different spans of fuel cells to improve output. The MCD 112 and / or the LCDs 114 can obtain different voltage levels across different spans of fuel cell strings 1610, and so can use different taps to get different DC output voltages. This allows modules 108 to achieve consistent output and adjust for changes in fuel cell stack performance, even when one fuel cell string 1610 is weaker than another, or if one fuel cell string 1610 becomes damaged. Different spans of fuel cell strings 1610 can be used for different purposes. In some cases, the full set of strings 1610 (e.g., the full fuel cell stack 1112) can be used to obtain a high voltage for output, but use subsets of the fuel cells or shorter spans of fuel cells for battery charging or lower DC output.

[0266] The intermediate taps between fuel cell strings 1610 also allow advanced control and monitoring. For example, the MCD 112 and / or the LCDs 114 can monitor and track the use and status of each fuel cell string 1610 on a fine-grained basis, and can also vary which spans of fuel cell strings 1610 are used, to increase lifespan and balance wear and to manage temperature and pressure separately for each fuel cell string 1610. The MCD 112 and / or the LCDs 114 can track the usage, lifespan, and health of fuel cell strings individually. The MCD 112 receives sensor data for each fuel cell string 1610 and can send control data affecting the use and loading of each fuel cell string 1610, including separately managing purge cycles for each fuel cell string 1610. This level of control helps the MCD 112 manage purge and maintenance cycles without causing downtime. For example, it allow timing the purge cycles as needed separately for each fuel cell string 1610, based on total usage over time for each and also the sensor outputs or diagnostics for each. The MCD 112 can optimize purging events because it can characterize the condition of the fuel cell strings 1610 to a higher degree.

[0267] In some cases, the fuel cell strand may FCS may have different anode and cathode configurations at the intermediate taps to be able to handle power output effectively. For example, compared to other anodes and cathodes of other fuel cells not at the intermediate taps, the electrodes providing the intermediate taps may include additional sensors, thicker or differently shaped material, or other changes, in addition to the presence of wiring to enable electrical connections.

[0268] The MCD 112 can manage the output of the different fuel cell strings 1610, so that overall RMS currents through the fuel cell strings 1610 of a fuel cell stack 1112 are within a certain tolerance of each other over a period. For example, the MCD 112 can monitor and manage the currents to try to balance current over the course of a particular time period, such as a second or less. In general, fuel cells in the same fuel cell stack 1112 need to pass the same current. The MCD 112 can coordinate to achieve this, using rapid switching in the loading across one span of fuel cells 1610, then another, then another, over a second or less. In addition, or as an alternative, the MCD 112 can selectively load a battery charging system, a capacitor, or other current sink to draw current needed to balance the flow through the fuel cell stack 1112.

[0269] Of course, the MCD 112 also benefits from the versatility of other fuel cell stack configurations, such as configurations that include multiple fuel cell strands 1610 that can be used individually or in parallel (see, e.g., FIG. 16C, 16H) and configurations where multiple fuel cell stacks can be selectively coupled in parallel using switching elements (see, e.g., 16E-16G). The MCD 112 can determine when conditions are appropriate to connect additional fuel cell stacks 1112 or fuel cell strands 1610 using the switching elements (e.g., when load is increasing, voltage output is decreasing, when current output meets a threshold, when battery state-of-charge reaches or falls below a threshold and more charging current is needed, in advance of a requested or predicted increase in power draw from the load, and so on), and then send instructions or control signals to the switching elements to connect additional power sources. Similarly, the MCD 112 can determine when conditions are appropriate to disconnect fuel cell stacks 1112 or fuel cell strands 1610 using the switching elements (e.g., when load is decreasing, voltage output is increasing, when battery state of charge reaches or rises above a threshold and charging current can be decreased, in advance of a requested or predicted decrease in power draw from the load, and so on), and then send instructions or control signals to the switching elements to disconnect power sources. The MCD 112 can also control the switching elements to manage wear across multiple fuel cell stacks 1112 and / or fuel cell strands 1610 within a fuel cell stack, by periodically changing the settings of the switching elements to rotate or alternate among using different sets of fuel cells to manage temperature, pressure, usage duration, and so on, as well as to allow fuel cells to be decoupled for purging or other maintenance without removing power. As a result, the MCD 112, optionally in cooperation with the LCDs 114, can cycle through the usage of different sets of fuel cells in a seamless manner that manages operating parameters (e.g., temperature, pressure, fuel rates, etc.) within desired ranges or limits, while still preserving consistent and reliable output to the loads.

[0270] The MCD 112 can also manage the state of batteries associated with the system, such as in FIGS. 13A-14B. When managing fuel cell stacks 1112, the MCD 112 can adjust the fuel flow rate to adjust output (e.g., reduce fuel rate to reduce output, increase fuel flow rate to increase output). If the fuel cells are not contaminated, the fuel flow rate is a main parameter. For batteries, the MCD 112 can control how deeply discharged the batteries are allowed to become (e.g., how low of a state of charge is permitted), the maximum temperatures permitted when drawing power and charging the batteries, the charging rate (e.g., level of charging current provided) when the battery is charged, etc. The MCD 112 can change the values of these parameters from one application or configuration to another to suit the demands of the load. Similarly, the MCD 112 can adjust the values of these parameters dynamically over time, to respond to changes in load demand or other changes. For example, if load demand suddenly spikes, the MCD 112 may permit batteries to temporarily supply power at a higher temperature or state of charge for a brief period, while also controlling additional fuel cell stacks 1112 to begin initializing so they can soon take over the additional current supply and / or charge the batteries. Similarly, as components wear over time or as the models 1830, 1832 predict that wear will occur, the MCD 112 may change the values of the parameters to adjust the balance of energy sourcing to meet requirements and extend lifespan given the reduced actual or predicted future capacity of the batteries and fuel cell stacks 1112.

[0271] The MCD 112 can take steps to adjust the balance of power sourced from the fuel cell stacks 1112 and batteries, as well as balance the wear and increase the lifespan of fuel cell stacks 1112, batteries, or system a whole. Often, the MCD 112 operates with a bias set by an operator or system designer to achieve a desired tradeoff. For example, some configurations may prefer using batteries to provide peak current output, potentially at the cost of running at higher temperatures and lower state-of-charge, which may impact lifespan. By contrast, some configurations may prefer reliability and lifespan instead. In addition, different applications may require different levels of energy held in reserve in batteries than others. The MCD 112 can store the settings, including policies, rules, thresholds, and other values that specify the desired cooperation and balance between use of batteries and fuel cell stacks 1112. The MCD 112 can monitor the conditions that occur, and implement those settings by sending control signals (e.g., instructions) to the various LCDs 114 of the modules 108 to make changes as needed. This can involve providing temperature thresholds, current limits, charging procedures, and other parameters for operating batteries. The LCDs 114 of the modules 108 can then operate as instructed, sourcing power from or charging their respective batteries when the corresponding conditions specified by the MCD 112 are satisfied, and operating with the limits (e.g., current limits, temperature limits, etc.) specified. In addition, the MCD 112 can provide operating parameters for fuel cell stacks 1112, such as the amounts of power to be generated from each, temperature threshold, current thresholds, pressure thresholds, etc. The MCD 112 may, in some implementations, directly control fuel cell stacks 1112 to adjust fuel rate, start up or shut down, purging, etc. In other implementations, the MCD 112 can provide instructions to the LCDs 114 or to a controller of the fuel cell stack 1112 if present.

[0272] As another example of managing batteries and fuel cell stacks 1112 together, if the MCD 112 detects that performance of a fuel cell stack 1112 is degrading, the MCD 112 can switch the amount or proportion of power used by some or all modules 108 in an array 700 to satisfy more of the load demand using energy from the battery. As another example, the MCD 112 can meet increased demand by increases the fuel rate to a fuel cell stack so the system reduces the number of charge cycles placed on the batteries, which can increase battery lifespan but may require more frequent purging or other maintenance of the fuel cell stack 1112. Of course, this more frequent maintenance of a fuel cell stack 1112 may not be a problem if there are other fuel cell stacks 1112 in reserve, e.g., the MCD 112 can perform a seamless switchover between the fuel cell stacks 1112 as discussed, can use switching elements to allow multiple fuel cell stacks 1112 to be initialized and connected before taking one offline for maintenance, and / or can cycle among different fuel cell stacks 1112 to distribute the overall usage and wear.

[0273] In making the control decisions to balance between batteries and fuel cell stacks 1112, the MCD 112 can use information about the configuration of the system, such as the specified output requirements (e.g., peak current, average current, minimum and maximum voltages, etc.), historical usage and loading, the physical characteristics of the batteries (e.g., number of batteries, capacity, age, number of charge cycles, battery chemistry type, etc.), the physical characteristics of the fuel cell stacks 1112 (e.g., number of fuel cell stacks, number of cells per fuel cell stack, age, wear, fuel cell type, etc.). The MCD 112 uses this information, together with the preferences of the operator about howto balance output characteristics (e.g., peak current, responsiveness to transient demand, responsiveness to changes in steady-state load demand, etc.) with preserving the lifespan of the batteries and the fuel cell stacks (e.g., by limiting the rate of battery charging, limiting temperature, limiting the number of battery charge cycles, etc.). The MCD 112 can also use information from the digital twin models 1830 and the predictive models 1832, beyond simply determining when maintenance is needed, to predict the effects of different settings combinations and to optimize the overall system for the desired objectives or tradeoffs. For example, the MCD 112 can provide various proposed sets of settings, for batteries and / or fuel cell stacks 1112, and use the models 1830, 1832 to predict the outcomes at current and future times. From these various predictions, the MCD 112 can select the set of settings that best fits the objectives or preferences set for the current application. Since components may not wear equally or linearly, the balance in utilization between different fuel cell stacks 1112 or between fuel cell stacks 1112 and batteries may need to change over time, potentially in gradual or incremental steps, to continue to meet the system designer’s objectives for lifespan and output capability.

[0274] Various aspects of the present subject matter are set forth below, in review of, and / or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following embodiments. In other words, an emphasis is on the fact that each feature of the embodiments can be combined with each and every other feature unless explicitly stated or taught otherwise.

[0275] The term “module” as used herein refers to one of two or more devices or sub-systems within a larger system. The module can be configured to work in conjunction with other modules of similar size, function, and physical arrangement (e.g., location of electrical terminals, connectors, etc.). Modules having the same function and energy source(s) can be configured identical (e.g., size and physical arrangement) to all other modules within the same system (e.g., rack or pack), while modules having different functions or energy source(s) may vary in size and physical arrangement. While each module may be physically removable and replaceable with respect to the other modules of the system (e.g., like wheels on a car, or blades in an information technology (IT) blade server), such is not required. For example, a system may be packaged in a common housing that does not permit removal and replacement any one module, without disassembly of the system as a whole. However, any and all embodiments herein can be configured such that each module is removable and replaceable with respect to the other modules in a convenient fashion, such as without disassembly of the system.

[0276] The term “output” is used herein in a broad sense, and does not preclude functioning in a bidirectional manner as both an output and an input. Similarly, the term “input” is used herein in a broad sense, and does not preclude functioning in a bidirectional manner as both an input and an output.

[0277] The terms “terminal” and “port” are used herein in a broad sense, can be either unidirectional or bidirectional, can be an input or an output, and do not require a specific physical or mechanical structure, such as a female or male configuration.

[0278] Various aspects of the present subject matter are set forth below, in review of, and / or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following implementations. In other words, an emphasis is on the fact that each feature of the implementations can be combined with each and every other feature unless explicitly stated otherwise or logically implausible.

[0279] In some aspects, a power supply system includes: an array of power supply modules configured to output an AC voltage as a combination of AC module voltages from multiple power supply modules, wherein the AC voltage is generated based on DC input from one or more fuel cell stacks including multiple groups of fuel cells, wherein each group of fuel cells includes multiple fuel cells that are electrically coupled in series, and the multiple groups of fuel cells are arranged to be selectively coupled in parallel with each other, the power supply modules each including: input ports configured to receive DC input from the one or more fuel cell stacks; a DC- AC converter configured to electrically couple with the one or more fuel cell stacks and configured to convert the DC input from the one or more fuel cell stacks to the AC module voltage; a power connection configured to output the AC module voltage of the power supply module; and a local control device configured to control the DC-AC converter to provide the AC module voltage to the power connection, wherein the local control device is configured to cause DC input from the respective groups of fuel cells to be selectively provided as input to the DC-AC converter.

[0280] In some aspects, a power supply system includes: an array of power supply modules configured to output an AC voltage as a combination of multiple AC module voltages, wherein the AC voltage is generated based on DC input from a fuel cell stack that includes multiple fuel cells that are electrically coupled in series, each of the power supply modules including: a plurality of input ports configured to receive the DC input from the fuel cell stack, wherein the plurality of input ports include input ports to respectively receive different DC input voltages from electrical taps at different intermediate locations among the fuel cells that are electrically coupled in series; a DC-AC converter configured to electrically couple with the fuel cell stack and configured to convert the DC input from the fuel cell stack to the AC module voltage; a power output connection configured to output the AC module voltage of the power supply module; and a local control device configured to control the DC-AC converter to provide the AC module voltage to the power output connection, wherein the local control device is configured to select from among the DC outputs of different subsets of the fuel cells to provide power to generate the AC module voltage.

[0281] Various implementations of the aspects of the disclosure are possible and may include one or more features, as described herein. For instance, in some implementations, at least a first power supply module of the power supply modules includes one or more switching elements configured to set which of the plurality of inputs are coupled to the DC-AC power converter; and the local control device of the first power supply module is configured to control the switching elements to adjust which combinations of the input ports provide input to the DC-AC converter of the first power supply module.

[0282] In some implementations, the electrical taps are each spaced apart by multiple fuel cells, such that each pair of the input ports provides a voltage across a different span of multiple fuel cells coupled in series.

[0283] In some implementations, the local control devices of the power supply modules are configured to synchronize a frequency and phase of the AC module voltages to a frequency and phase of an AC bus.

[0284] In some implementations, the local control devices of the power supply modules are configured to change the inputs used to provide power to the DC-AC converters to balance load or wear among the fuel cells over time.

[0285] In some implementations, the local control devices of the power supply modules are configured to (i) detect a decrease in performance of one or more fuel cells in the fuel cell stack and (ii) change the inputs used to provide power to the DC-AC converters in response to detecting the decrease in performance.

[0286] In some implementations, the local control devices of the power supply modules are configured to (i) detect a change in load demand and (ii) change the inputs used to provide power to the DC-AC converter in response to detecting the change in load demand.

[0287] In some implementations, the local control devices of the power supply modules are configured to (i) identify one or more of the fuel cells that are designated for a maintenance operation and (ii) change the inputs used to provide power to the DC-AC converter to draw power during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation.

[0288] In some implementations, the local control devices of the power supply modules are configured to (i) receive sensor data indicating a condition of the fuel cell stack and (ii) change the inputs used to provide power to the DC-AC converter based on the sensor data.

[0289] In some implementations, the sensor data includes a temperature of one or more of the fuel cells, and wherein the local control devices of the power supply modules are configured to change the inputs used to provide power to the DC-AC converter in response to determining that the temperature of one or more of the fuel cells exceeds a threshold.

[0290] In some implementations, the power supply modules each include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC-DC converters; and the local control devices of the power supply modules are configured to control which pair of the input ports provides input to the one or more DC-DC converters.

[0291] In some implementations, the local control devices are configured to determine a DC output voltage to be provided at the DC output port and to select the pair of the input ports based on the DC output voltage to be provided.

[0292] In some implementations, the DC-AC converters are configured to provide the AC module voltages as a series of progressively varied DC outputs that together approximate a sinusoidal output.

[0293] In some implementations, the power supply system includes three arrays of power supply modules, wherein each of the three arrays of power supply modules is configured to provide AC output at a different phase.

[0294] In some implementations, the power supply modules of the three arrays receive power generated by the same fuel cell stack.

[0295] In some implementations, the power supply modules of the three arrays receive power generated by different fuel cell stacks.

[0296] In some implementations, the power supply modules are configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

[0297] In some implementations, the power supply modules are each configured to couple with or to include one or more batteries; and each of the power supply module is configured to generate its AC module output based on power concurrently drawn from the one or more batteries and from the fuel cell stack.

[0298] In some implementations, the power supply modules are configured to couple with or to include one or more batteries; and the power supply modules are configured to switch between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the fuel cell stack.

[0299] In some implementations, the power supply modules are configured to couple with or to include one or more batteries; and the power supply modules are configured to charge the one or more batteries with power received from the fuel cell stack.

[0300] In some implementations, the local control device is configured to select DC outputs of different subsets of the fuel cells by adjusting which combinations of the input ports provide input to the DC-AC converter.

[0301] In some aspects, a power supply system includes: an array of power supply modules configured to output an AC voltage as a combination of multiple AC module voltages, wherein the AC voltage is generated based on DC input from a fuel cell stack that includes multiple fuel cells that are electrically coupled in series, each of the power supply modules including: a plurality of input ports configured to receive the DC input from the fuel cell stack, wherein the plurality of input ports include input ports to respectively receive different DC input voltages from electrical taps at different intermediate locations among the fuel cells that are electrically coupled in series; a power output connection configured to output the AC module voltage of the power supply module; and a local control device configured to control the power supply module to provide the AC module voltage to the power output connection, wherein the local control device is configured to select from among the DC outputs of different subsets of the fuel cells to provide power to generate the AC module voltage.

[0302] Various implementations of the aspects of the disclosure are possible and may include one or more features, as described herein. For instance, in some implementations, the power supply system includes a main control device configured to adjust which of the groups of fuel cells are coupled to the input ports and how many of the groups are coupled to the input ports.

[0303] In some implementations, the system includes one or more switching elements arranged between the groups of fuel cells and the DC-AC converter, wherein the local control devices or a main control device is configured to control the one or more switching elements to selectively couple the respective groups of fuel cells from an input to the DC-AC converter.

[0304] In some implementations, the one or more switching elements includes one or more switches, transistors, or relays.

[0305] In some implementations, the one or more switching elements comprise a switching element for each of the groups of fuel cells, and wherein the switching elements are configured to enable each of the groups of fuel cells to selectively provide input to the DC-AC converter independent of whether the other groups of fuel cells provide input to the DC-AC converter. In some implementations, the input ports of the power supply module comprise a first input port and a second input port; the one or more fuel cell stacks comprise (i) a first output port to couple with the first input port and (ii) a second output port to couple with the second input port; the one or more fuel cell stacks include a switching element for each group of fuel cells; for each of the groups of fuel cells, the switching element for the group of fuel cells is configured to selectively provide DC output across the corresponding group of fuel cells at the first output port and the second output port; and the local control devices or a main control device is configured to provide one or more control signals to cause the switching elements to set which of the groups of fuel cells provide DC output at the first output port and the second output port.

[0306] In some implementations, the input ports of the power supply module include input ports configured to separately receive DC input voltages across the respective groups of fuel cells; and the power supply module includes the one or more switching elements, and the one or more switching elements are controlled by the local control device to set which of the input ports provide input to the DC-AC converter.

[0307] In some implementations, the one or more switching elements are controllable by the local control device to provide, as input to the DC-AC converter, DC input selected from among each of the individual groups of fuel cells and combinations of multiple of the groups of fuel cells.

[0308] In some implementations, the local control device is configured to synchronize a frequency and phase of the AC module voltage to a frequency and phase of an AC bus.

[0309] In some implementations, the local control device is configured to change which of the groups of fuel cells provide input to the DC-AC converter to balance load or wear among the fuel cells over time.

[0310] In some implementations, the local control devices are configured to (i) detect a decrease in performance of one or more fuel cells in the fuel cell stack and (ii) change which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the decrease in performance.

[0311] In some implementations, the local control devices are configured to (i) detect a change in load demand and (ii) change which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the change in load demand.

[0312] In some implementations, the local control devices are configured to (i) identify one or more of the groups of fuel cells that are designated for a maintenance operation and (ii) change which of the groups of fuel cells provide input to the DC-AC converter during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation. In some implementations, the local control devices are configured to (i) receive sensor data indicating a status of the one or more fuel cell stacks and (ii) change which of the groups of fuel cells provide input to the DC-AC converter based on the sensor data.

[0313] In some implementations, the sensor data indicates a temperature of one or more of the fuel cells, and wherein the local control device is configured to change which of the groups of fuel cells provide input to the DC-AC converter in response determining that the temperature of one or more of the fuel cells exceeds a threshold.

[0314] In some implementations, at least some of the power supply modules include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC- DC converters; and at least some of the local control devices are configured to control which of the groups of fuel cells provide input to the one or more DC-DC converters.

[0315] In some implementations, the DC-AC converter is configured to provide the AC module voltage as a series of progressively varied DC outputs that together approximate a sinusoidal output.

[0316] In some implementations, the DC-AC converter is configured to concurrently provide three different AC module voltages at different phases.

[0317] In some implementations, the power supply module is configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

[0318] In some implementations, the input ports of the power supply module are configured to couple with output ports of the one or more fuel cell stacks that separately provide voltages across each of the respective groups of fuel cells, and wherein the power supply module includes a set of switching elements that are configured to (i) selectively couple the groups of fuel in parallel to the input of the DC-AC converter and (ii) selectively couple the groups of fuel in parallel to the input of the DC-AC converter.

[0319] In some implementations, the power supply module is configured to couple with one or more batteries; and the power supply module is configured to generate the AC module output based on power concurrently drawn from the one or more batteries and the one or more fuel cell stacks.

[0320] In some implementations, the power supply module is configured to couple with one or more batteries; and the power supply module is configured to switch between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the one or more fuel cell stacks.

[0321] In some implementations, the power supply module is configured to couple with one or more batteries; and the power supply module is configured to charge the one or more batteries with power received from the one or more fuel cell stacks. In some aspects, a power supply system includes: a plurality of power supply modules electrically coupled together, wherein the power supply modules are configured to output an alternating current (AC) signal including a superposition of AC module voltages from the plurality of power supply modules, each of the plurality of power supply modules including: a DC-AC converter configured to electrically couple with one or more fuel cell stacks and configured to convert the DC input from the one or more fuel cell stacks to the AC module voltage; a power connection configured to output an AC module voltage of the power supply module; and a local control device configured to control the DC-AC converter to route energy from the one or more fuel cell stacks to the power connection; and a main control device that is configured to control the plurality of power supply modules via a control interface, wherein the main control device is configured to (i) monitor a condition of the one or more fuel cell stacks based on information provided by the power supply modules and (ii) provide, based on the monitored condition of the one or more fuel cell stacks, control signals to the local control devices to configure outputs of the power supply modules.

[0322] Various implementations of the aspects of the disclosure are possible and may include one or more features, as described herein. For instance, in some implementations, the information provided by the local control devices indicates one or more operating parameters of the one or more fuel cell stacks, wherein the one or more operating parameters comprise a voltage output of the one or more fuel cell stacks, an electrical current output of the one or more fuel cell stacks, a temperature of the one or more fuel cell stacks, a pressure of the one or more fuel cell stacks, a fuel rate of the one or more fuel cell stacks, a configuration of the one or more fuel cell stacks, an operating state of the one or more fuel cell stacks, a duration of operation for the one or more fuel cell stacks, or a maintenance status of the one or more fuel cell stacks.

[0323] In some implementations, the plurality of power supply modules includes a first power supply module that is configured to receive power from a fuel cell stack that includes multiple fuel cell strings, wherein each of the respective fuel cell strings includes multiple fuel cells coupled together in series; and the first power supply module is configured to provide, to the main control device, information indicating the one or more the operating parameters for each of the multiple fuel cell strings.

[0324] In some implementations, one or more of the local control devices is configured to (i) monitor the one or more operating parameters of a fuel cell stack and (ii) communicate to the main control device whether the one or more operating parameters are within a predetermined range or satisfy a predetermined threshold.

[0325] In some implementations, the main control device is configured to provide control signals via the control interface that instruct AC output characteristics for individual power supply modules, wherein the instructed AC output characteristics specify at least one of an AC output voltage, a AC output frequency, an AC output phase, a connection over which to provide AC output, or whether to enable or disable AC output from the power supply module.

[0326] In some aspects, a method includes: receiving DC input from a fuel cell stack at a plurality of input ports of power supply modules of a power supply system, wherein each of the power supply modules comprises a plurality of input ports, and each of the power supply modules receives different DC input voltages from electrical taps at different intermediate locations among fuel cells of the fuel cell stack that are electrically coupled in series; converting the DC input from the fuel cell stack to AC module voltages, wherein each of the power supply modules has a separate DC-AC converter that is used to convert DC input to the corresponding AC module voltage for the power supply module, wherein each of the power supply modules uses a separate local control device to select from among the DC outputs of different subsets of the fuel cells to provide power to generate the corresponding AC module voltage; and outputting the AC module voltages generated by the power supply modules.

[0327] Various implementations of the aspects of the disclosure are possible and may include one or more features, as described herein. For instance, in some implementations, the method includes: setting, for at least a first power supply module of the power supply modules, which of the plurality of inputs are coupled to the DC-AC power converter of the first power supply module using one or more switching elements of the first power supply module; and controlling, by the local control device of the first power supply module, the one or more switching elements to adjust which combinations of the input ports of the first power supply module provide input to the DC-AC converter of the first power supply module.

[0328] In some implementations, the electrical taps are each spaced apart by multiple fuel cells, such that each pair of the input ports provides a voltage across a different span of multiple fuel cells coupled in series.

[0329] In some implementations, the method includes synchronizing, using the local control devices of the power supply modules, a frequency and phase of the AC module voltages to a frequency and phase of an AC bus.

[0330] In some implementations, the method includes changing, using the local control devices of the power supply modules, the DC inputs used to provide power to the DC-AC converters to balance load or wear among the fuel cells over time.

[0331] In some implementations, the method includes: detecting a decrease in performance of one or more fuel cells in the fuel cell stack; and changing the inputs used to provide power to the DC- AC converters in response to detecting the decrease in performance. In some implementations, the method includes: detecting a change in load demand; and changing the inputs used to provide power to the DC-AC converter in response to detecting the change in load demand.

[0332] In some implementations, the method includes: identifying one or more of the fuel cells that are designated for a maintenance operation; and changing the inputs used to provide power to the DC-AC converter to draw power during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation.

[0333] In some implementations, the method includes: receiving sensor data indicating a condition of the fuel cell stack; and changing the inputs used to provide power to the DC-AC converter based on the sensor data.

[0334] In some implementations, the sensor data includes a temperature of one or more of the fuel cells, and wherein the local control devices of the power supply modules are configured to change the inputs used to provide power to the DC-AC converter in response to determining that the temperature of one or more of the fuel cells exceeds a threshold.

[0335] In some implementations, the power supply modules each include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC-DC converters; and the local control devices of the power supply modules are configured to control which pair of the input ports provides input to the one or more DC-DC converters.

[0336] In some implementations, the local control devices are configured to determine a DC output voltage to be provided at the DC output port and to select the pair of the input ports based on the DC output voltage to be provided.

[0337] In some implementations, the DC-AC converters are configured to provide the AC module voltages as a series of progressively varied DC outputs that together approximate a sinusoidal output.

[0338] In some implementations, the method includes three arrays of power supply modules, wherein each of the three arrays of power supply modules is configured to provide AC output at a different phase.

[0339] In some implementations, the power supply modules of the three arrays receive power generated by the same fuel cell stack.

[0340] In some implementations, the power supply modules of the three arrays receive power generated by different fuel cell stacks.

[0341] In some implementations, the power supply modules are configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus. In some implementations, the power supply modules are each coupled with or include one or more batteries; and each of the power supply module generates its AC module output based on power concurrently drawn from the one or more batteries and from the fuel cell stack.

[0342] In some implementations, the power supply modules are coupled with or include one or more batteries; and the method includes switching, for one or more of the power supply modules, between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the fuel cell stack.

[0343] In some implementations, the power supply modules are configured to couple with or to include one or more batteries; and the method includes charging the one or more batteries with power received from the fuel cell stack.

[0344] In some implementations, the method includes selecting, by one or more of the local control devices, DC outputs of different subsets of the fuel cells by adjusting which combinations of the input ports provide input to the DC-AC converter.

[0345] In some aspects, a method includes: generating an AC voltage as a combination of AC module voltages from multiple power supply modules in an array of power supply modules, wherein the AC voltage is generated based on DC input from one or more fuel cell stacks comprising multiple groups of fuel cells, wherein each group of fuel cells includes multiple fuel cells that are electrically coupled in series, and the multiple groups of fuel cells are arranged to be selectively coupled in parallel with each other, wherein the power supply modules each generate the corresponding AC module voltage with operations that include: receiving DC input from the one or more fuel cell stacks; converting the DC input from the one or more fuel cell stacks to the AC module voltage using a DC-AC converter configured to electrically couple with the one or more fuel cell stacks; and controlling the DC-AC converter, using a local control device, to provide the AC module voltage to a power connection, wherein the local control device is configured to cause DC input from the respective groups of fuel cells to be selectively provided as input to the DC-AC converter.

[0346] Various implementations of the aspects of the disclosure are possible and may include one or more features, as described herein. For instance, in some implementations, the method includes using a main control device to control which of the groups of fuel cells are coupled to the input ports and how many of the groups are coupled to the input ports.

[0347] In some implementations, the method includes controlling one or more switching elements to selectively couple the respective groups of fuel cells from an input to the DC-AC converter of one or more power supply modules.

[0348] In some implementations, the one or more switching elements comprise one or more switches, transistors, or relays. In some implementations, the one or more switching elements comprise a switching element for each of the groups of fuel cells, and wherein the switching elements are configured to enable each of the groups of fuel cells to selectively provide input to the DC-AC converter independent of whether the other groups of fuel cells provide input to the DC-AC converter.

[0349] In some implementations, the input ports of the power supply module comprise a first input port and a second input port; the one or more fuel cell stacks comprise (i) a first output port to couple with the first input port and (ii) a second output port to couple with the second input port; the one or more fuel cell stacks include a switching element for each group of fuel cells; for each of the groups of fuel cells, the switching element for the group of fuel cells is configured to selectively provide DC output across the corresponding group of fuel cells at the first output port and the second output port; and the local control devices or a main control device is configured to provide one or more control signals to cause the switching elements to set which of the groups of fuel cells provide DC output at the first output port and the second output port.

[0350] In some implementations, the input ports of the power supply module include input ports configured to separately receive DC input voltages across the respective groups of fuel cells; and the power supply module includes the one or more switching elements, and the one or more switching elements are controlled by the local control device to set which of the input ports provide input to the DC-AC converter.

[0351] In some implementations, the one or more switching elements are controllable by the local control device to provide, as input to the DC-AC converter, DC input selected from among each of the individual groups of fuel cells and combinations of multiple of the groups of fuel cells.

[0352] In some implementations, the method includes synchronizing a frequency and phase of the AC module voltages to a frequency and phase of an AC bus.

[0353] In some implementations, the method includes changing which of the groups of fuel cells provide input to the DC-AC converters to balance load or wear among the fuel cells over time.

[0354] In some implementations, the method includes: detecting a decrease in performance of one or more fuel cells in the fuel cell stack; and changing which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the decrease in performance.

[0355] In some implementations, the method includes: detecting a change in load demand; and changing which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the change in load demand.

[0356] In some implementations, the method includes: identifying one or more of the groups of fuel cells that are designated for a maintenance operation; and changing which of the groups of fuel cells provide input to the DC-AC converter during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation. In some implementations, the method includes: receiving sensor data indicating a status of the one or more fuel cell stacks; and changing which of the groups of fuel cells provide input to the DC-AC converter based on the sensor data.

[0357] In some implementations, the sensor data indicates a temperature of one or more of the fuel cells, and wherein the local control device is configured to change which of the groups of fuel cells provide input to the DC-AC converter in response determining that the temperature of one or more of the fuel cells exceeds a threshold.

[0358] In some implementations, at least some of the power supply modules include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC- DC converters; and at least some of the local control devices are configured to control which of the groups of fuel cells provide input to the one or more DC-DC converters.

[0359] In some implementations, the DC-AC converter is configured to provide the AC module voltage as a series of progressively varied DC outputs that together approximate a sinusoidal output.

[0360] In some implementations, the DC-AC converter is configured to concurrently provide three different AC module voltages at different phases.

[0361] In some implementations, the power supply module is configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

[0362] In some implementations, the input ports of the power supply module are configured to couple with output ports of the one or more fuel cell stacks that separately provide voltages across each of the respective groups of fuel cells, and wherein the power supply module comprises a set of switching elements that are configured to (i) selectively couple the groups of fuel in parallel to the input of the DC-AC converter and (ii) selectively couple the groups of fuel in parallel to the input of the DC-AC converter.

[0363] In some implementations, the power supply module is configured to couple with one or more batteries; and the power supply module is configured to generate the AC module output based on power concurrently drawn from the one or more batteries and the one or more fuel cell stacks.

[0364] In some implementations, the power supply module is configured to couple with one or more batteries; and the power supply module is configured to switch between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the one or more fuel cell stacks.

[0365] In some implementations, the power supply module is configured to couple with one or more batteries; and the power supply module is configured to charge the one or more batteries with power received from the one or more fuel cell stacks. In some aspects, a method includes: controlling a plurality of power supply modules via a control interface, wherein the plurality of power supply modules are electrically coupled together, wherein the power supply modules are configured to output an alternating current (AC) signal comprising a superposition of AC module voltages from the plurality of power supply modules, and wherein each of the power supply modules comprises a DC-AC converter and a local control device configured to control the DC-AC converter to route energy from the one or more fuel cell stacks to a power connection; monitoring a condition of the one or more fuel cell stacks based on information provided by the power supply modules; and providing, based on the monitored condition of the one or more fuel cell stacks, control signals to the local control devices to configure outputs of the power supply modules.

[0366] Various implementations of the aspects of the disclosure are possible and may include one or more features, as described herein. For instance, in some implementations, the information provided by the local control devices indicates one or more operating parameters of the one or more fuel cell stacks, wherein the one or more operating parameters comprise a voltage output of the one or more fuel cell stacks, an electrical current output of the one or more fuel cell stacks, a temperature of the one or more fuel cell stacks, a pressure of the one or more fuel cell stacks, a fuel rate of the one or more fuel cell stacks, a configuration of the one or more fuel cell stacks, an operating state of the one or more fuel cell stacks, a duration of operation for the one or more fuel cell stacks, or a maintenance status of the one or more fuel cell stacks.

[0367] In some implementations, the plurality of power supply modules comprises a first power supply module that is configured to receive power from a fuel cell stack that includes multiple fuel cell strings, wherein each of the respective fuel cell strings comprises multiple fuel cells coupled together in series; and the first power supply module is configured to provide information indicating the one or more the operating parameters for each of the multiple fuel cell strings.

[0368] In some implementations, one or more of the local control devices is configured to (i) monitor the one or more operating parameters of a fuel cell stack and (ii) communicate whether the one or more operating parameters are within a predetermined range or satisfy a predetermined threshold.

[0369] In some implementations, the method includes providing control signals, via the control interface, that instruct AC output characteristics for individual power supply modules, wherein the instructed AC output characteristics specify at least one of an AC output voltage, a AC output frequency, an AC output phase, a connection over which to provide AC output, or whether to enable or disable AC output from the power supply module.

[0370] In some implementations, the power supply system is configured to provide multiple phases of AC output to an AC bus; and the method includes: assigning different subsets of the power supply modules to provide the respective phases of AC output; and sending control signals via the control interface to cause the local control devices to provide AC output at the phases to which the power supply modules are assigned.

[0371] In some implementations, the control signals comprise one or more synchronization signals to synchronize AC module outputs of the power supply modules.

[0372] In some implementations, the control signals comprise control signals that instruct a topology for electrical connections to be established among the power supply modules or with an AC bus.

[0373] In some implementations, the control signals comprise control signals that instruct a change to operation of at least one of the one or more fuel cell stacks, including at least one of a change to a fuel rate for a fuel cell stack, a change to a pressure of a fuel cell stack, a change to begin or end a purging cycle for a fuel cell stack, or a change to start or shut down power generation with a fuel cell stack.

[0374] In some implementations, the method includes sending control signals to instruct a subset of the power supply modules to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the power supply modules coupled in series.

[0375] In some implementations, the method includes sending control signals to instruct a subset of the power supply modules to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the power supply modules coupled in parallel.

[0376] In some implementations, the method includes: tracking usage of the one or more fuel cell stacks based on the information from the local control devices; and sending control signals to vary usage of the power supply modules to balance wear among multiple fuel cell stacks.

[0377] In some implementations, the method includes determining, based on the information from the local control devices, when a temperature of at least one of the one or more fuel cell stacks exceeds a threshold; and sending control signals to reduce output of one or more power supply modules receiving power from the fuel cell stack determined to have a temperature that exceeds the threshold.

[0378] Other embodiments of these aspects include corresponding systems, apparatus, and computer programs, configured to perform the actions of the methods, encoded on computer storage devices. A system of one or more computers can be so configured by virtue of software, firmware, hardware, or a combination of them installed on the system that in operation cause the system to perform the actions. One or more computer programs can be so configured by virtue having instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions. While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a combination can in some cases be excised from the combination.

[0379] Processing circuitry can include one or more processors, microprocessors, controllers, and / or microcontrollers, each of which can be a discrete or stand-alone chip or distributed amongst (and a portion of) a number of different chips. Any type of processing circuitry can be implemented, such as, but not limited to, personal computing architectures (e.g., such as used in desktop PC’s, laptops, tablets, etc.), programmable gate array architectures, proprietary architectures, custom architectures, and others. Processing circuitry can include a digital signal processor, which can be implemented in hardware and / or software. Processing circuitry can execute software instructions stored on memory that cause processing circuitry to take a host of different actions and control other components.

[0380] Processing circuitry can also perform other software and / or hardware routines. For example, processing circuitry can interface with communication circuitry and perform analog-to- digital conversions, encoding and decoding, other digital signal processing, multimedia functions, conversion of data into a format (e.g., in-phase and quadrature) suitable for provision to communication circuitry, and / or can cause communication circuitry to transmit the data (wired or wirelessly).

[0381] Processing circuitry can also be adapted to execute the operating system and any software applications, and perform those other functions not related to the processing of communications transmitted and received.

[0382] Computer program instructions for carrying out operations in accordance with the described subject matter may be written in any combination of one or more programming languages, including computer and programming languages. A non-exhaustive list of examples includes hardware description languages (HDLs), SystemC, C, C++, C#, Objective-C, Matlab, Simulink, SystemVerilog, SystemVHDL, Handel-C, Python, Java, JavaScript, Ruby, HTML, Smalltalk, Transact-SQL, XML, PHP, Golang (Go), “R” language, and Swift, to name a few.

[0383] Memory, storage, and / or computer readable media can be shared by one or more of the various functional units present, or can be distributed amongst two or more of them (e.g., as separate memories present within different chips). Memory can also reside in a separate chip of its own.

[0384] To the extent the embodiments disclosed herein include or operate in association with memory, storage, and / or computer readable media, then that memory, storage, and / or computer readable media are non-transitory. Accordingly, to the extent that memory, storage, and / or computer readable media are covered by one or more claims, then that memory, storage, and / or computer readable media is only non-transitory. The terms “non-transitory” and “tangible” as used herein, are intended to describe memory, storage, and / or computer readable media excluding propagating electromagnetic signals, but are not intended to limit the type of memory, storage, and / or computer readable media in terms of the persistency of storage or otherwise. For example, “non-transitory” and / or “tangible” memory, storage, and / or computer readable media encompasses volatile and non-volatile media such as random access media (e.g., RAM, SRAM, DRAM, FRAM, etc.), read-only media (e.g., ROM, PROM, EPROM, EEPROM, flash, etc.) and combinations thereof (e.g., hybrid RAM and ROM, NVRAM, etc.) and variants thereof.

[0385] It should be noted that all features, elements, components, functions, and steps described with respect to any embodiment provided herein are intended to be freely combinable and substitutable with those from any other embodiment. If a certain feature, element, component, function, or step is described with respect to only one embodiment, then it should be understood that that feature, element, component, function, or step can be used with every other embodiment described herein unless explicitly stated otherwise. This paragraph therefore serves as antecedent basis and written support for the introduction of claims, at any time, that combine features, elements, components, functions, and steps from different embodiments, or that substitute features, elements, components, functions, and steps from one embodiment with those of another, even if the following description does not explicitly state, in a particular instance, that such combinations or substitutions are possible. It is explicitly acknowledged that express recitation of every possible combination and substitution is overly burdensome, especially given that the permissibility of each and every such combination and substitution will be readily recognized by those of ordinary skill in the art.

[0386] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0387] While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that these embodiments are not to be limited to the particular form disclosed, but to the contrary, these embodiments are to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, any features, functions, steps, or elements of the embodiments may be recited in or added to the claims, as well as negative limitations that define the inventive scope of the claims by features, functions, steps, or elements that are not within that scope.

Claims

CLAIMS1. A power supply system comprising: an array of power supply modules configured to output an AC voltage as a combination of multiple AC module voltages, wherein the AC voltage is generated based on DC input from a fuel cell stack that includes multiple fuel cells that are electrically coupled in series, each of the power supply modules comprising: a plurality of input ports configured to receive the DC input from the fuel cell stack, wherein the plurality of input ports include input ports to respectively receive different DC input voltages from electrical taps at different intermediate locations among the fuel cells that are electrically coupled in series; a DC-AC converter configured to electrically couple with the fuel cell stack and configured to convert the DC input from the fuel cell stack to the AC module voltage; a power output connection configured to output the AC module voltage of the power supply module; and a local control device configured to control the DC-AC converter to provide the AC module voltage to the power output connection, wherein the local control device is configured to select from among the DC outputs of different subsets of the fuel cells to provide power to generate the AC module voltage.

2. The power supply system of any preceding claim, wherein at least a first power supply module of the power supply modules comprises one or more switching elements configured to set which of the plurality of inputs are coupled to the DC-AC power converter; and wherein the local control device of the first power supply module is configured to control the one or more switching elements to adjust which combinations of the input ports provide input to the DC-AC converter of the first power supply module.

3. The power supply system of any preceding claim, wherein the electrical taps are each spaced apart by multiple fuel cells, such that each pair of the input ports provides a voltage across a different span of multiple fuel cells coupled in series.

4. The power supply system of any preceding claim, wherein the local control devices of the power supply modules are configured to synchronize a frequency and phase of the AC module voltages to a frequency and phase of an AC bus.

5. The power supply system of any preceding claim, wherein the local control devices of the power supply modules are configured to change the inputs used to provide power to the DC-AC converters to balance load or wear among the fuel cells over time.

6. The power supply system of any preceding claim, wherein the local control devices of the power supply modules are configured to (i) detect a decrease in performance of one or more fuel cells in the fuel cell stack and (ii) change the inputs used to provide power to the DC-AC converters in response to detecting the decrease in performance.

7. The power supply system of any preceding claim, wherein the local control devices of the power supply modules are configured to (i) detect a change in load demand and (ii) change the inputs used to provide power to the DC-AC converter in response to detecting the change in load demand.

8. The power supply system of any preceding claim, wherein the local control devices of the power supply modules are configured to (i) identify one or more of the fuel cells that are designated for a maintenance operation and (ii) change the inputs used to provide power to the DC- AC converter to draw power during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation.

9. The power supply system of any preceding claim, wherein the local control devices of the power supply modules are configured to (i) receive sensor data indicating a condition of the fuel cell stack and (ii) change the inputs used to provide power to the DC-AC converter based on the sensor data.

10. The power supply system of claim 9, wherein the sensor data includes a temperature of one or more of the fuel cells, and wherein the local control devices of the power supply modules are configured to change the inputs used to provide power to the DC-AC converter in response to determining that the temperature of one or more of the fuel cells exceeds a threshold.

11. The power supply system of any preceding claim, wherein the power supply modules each include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC-DC converters; and wherein the local control devices of the power supply modules are configured to control which pair of the input ports provides input to the one or more DC-DC converters.

12. The power supply system of claim 11, wherein the local control devices are configured to determine a DC output voltage to be provided at the DC output port and to select the pair of the input ports based on the DC output voltage to be provided.

13. The power supply system of any preceding claim, wherein the DC-AC converters are configured to provide the AC module voltages as a series of progressively varied DC outputs that together approximate a sinusoidal output.

14. The power supply system of any preceding claim, comprising three arrays of power supply modules, wherein each of the three arrays of power supply modules is configured to provide AC output at a different phase.

15. The power supply system of claim 14, wherein the power supply modules of the three arrays receive power generated by the same fuel cell stack.

16. The power supply system of claim 14, wherein the power supply modules of the three arrays receive power generated by different fuel cell stacks.

17. The power supply system of any preceding claim, wherein the power supply modules are configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

18. The power supply system of any preceding claim, wherein the power supply modules are each configured to couple with or to include one or more batteries; and wherein each of the power supply module is configured to generate its AC module output based on power concurrently drawn from the one or more batteries and from the fuel cell stack.

19. The power supply system of any preceding claim, wherein the power supply modules are configured to couple with or to include one or more batteries; and wherein the power supply modules are configured to switch between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the fuel cell stack.

20. The power supply system of any preceding claim, wherein the power supply modules are configured to couple with or to include one or more batteries; and wherein the power supply modules are configured to charge the one or more batteries with power received from the fuel cell stack.

21. The power supply system of any preceding claim, wherein the local control device is configured to select DC outputs of different subsets of the fuel cells by adjusting which combinations of the input ports provide input to the DC-AC converter.

22. A power supply system comprising: an array of power supply modules configured to output an AC voltage as a combination of multiple AC module voltages, wherein the AC voltage is generated based on DC input from a fuel cell stack that includes multiple fuel cells that are electrically coupled in series, each of the power supply modules comprising: a plurality of input ports configured to receive the DC input from the fuel cell stack, wherein the plurality of input ports include input ports to respectively receive different DC input voltages from electrical taps at different intermediate locations among the fuel cells that are electrically coupled in series; a power output connection configured to output the AC module voltage of the power supply module; and a local control device configured to control the power supply module to provide the AC module voltage to the power output connection, wherein the local control device is configured to select from among the DC outputs of different subsets of the fuel cells to provide power to generate the AC module voltage.

23. A power supply system comprising: an array of power supply modules configured to output an AC voltage as a combination of AC module voltages from multiple power supply modules, wherein the AC voltage is generated based on DC input from one or more fuel cell stacks comprising multiple groups of fuel cells, wherein each group of fuel cells includes multiple fuel cells that are electrically coupled in series, and the multiple groups of fuel cells are arranged to be selectively coupled in parallel with each other, the power supply modules each comprising: input ports configured to receive DC input from the one or more fuel cell stacks;a DC-AC converter configured to electrically couple with the one or more fuel cell stacks and configured to convert the DC input from the one or more fuel cell stacks to the AC module voltage; a power connection configured to output the AC module voltage of the power supply module; and a local control device configured to control the DC-AC converter to provide the AC module voltage to the power connection, wherein the local control device is configured to cause DC input from the respective groups of fuel cells to be selectively provided as input to the DC-AC converter.

24. The power supply system of claim 23, comprising a main control device configured to adjust which of the groups of fuel cells are coupled to the input ports and how many of the groups are coupled to the input ports.

25. The power supply system of claim 23 or 24, further comprising one or more switching elements arranged between the groups of fuel cells and the DC-AC converter, wherein the local control devices or a main control device is configured to control the one or more switching elements to selectively couple the respective groups of fuel cells from an input to the DC-AC converter.

26. The power supply system of claim 25, wherein the one or more switching elements comprise one or more switches, transistors, or relays.

27. The power supply system of claim 25 or 26, wherein the one or more switching elements comprise a switching element for each of the groups of fuel cells, and wherein the switching elements are configured to enable each of the groups of fuel cells to selectively provide input to the DC-AC converter independent of whether the other groups of fuel cells provide input to the DC- AC converter.

28. The power supply system of any of claims 25 to 27, wherein the input ports of the power supply module comprise a first input port and a second input port; wherein the one or more fuel cell stacks comprise (i) a first output port to couple with the first input port and (ii) a second output port to couple with the second input port; wherein the one or more fuel cell stacks include a switching element for each group of fuel cells;wherein, for each of the groups of fuel cells, the switching element for the group of fuel cells is configured to selectively provide DC output across the corresponding group of fuel cells at the first output port and the second output port; and wherein the local control devices or a main control device is configured to provide one or more control signals to cause the switching elements to set which of the groups of fuel cells provide DC output at the first output port and the second output port.

29. The power supply system of any of claims 25 to 28, wherein the input ports of the power supply module include input ports configured to separately receive DC input voltages across the respective groups of fuel cells; and wherein the power supply module includes the one or more switching elements, and the one or more switching elements are controlled by the local control device to set which of the input ports provide input to the DC-AC converter.

30. The power supply system of claim 29, wherein the one or more switching elements are controllable by the local control device to provide, as input to the DC-AC converter, DC input selected from among each of the individual groups of fuel cells and combinations of multiple of the groups of fuel cells.

31. The power supply system of any of claims 23 to 30, wherein the local control device is configured to synchronize a frequency and phase of the AC module voltage to a frequency and phase of an AC bus.

32. The power supply system of any of claims 23 to 31, wherein the local control device is configured to change which of the groups of fuel cells provide input to the DC-AC converter to balance load or wear among the fuel cells over time.

33. The power supply system of any of claims 23 to 32, wherein the local control devices are configured to (i) detect a decrease in performance of one or more fuel cells in the fuel cell stack and (ii) change which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the decrease in performance.

34. The power supply system of any of claims 23 to 33, wherein the local control devices are configured to (i) detect a change in load demand and (ii) change which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the change in load demand.

35. The power supply system of any of claims 23 to 34, wherein the local control devices are configured to (i) identify one or more of the groups of fuel cells that are designated for a maintenance operation and (ii) change which of the groups of fuel cells provide input to the DC- AC converter during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation.

36. The power supply system of any of claims 23 to 35, wherein the local control devices are configured to (i) receive sensor data indicating a status of the one or more fuel cell stacks and (ii) change which of the groups of fuel cells provide input to the DC-AC converter based on the sensor data.

37. The power supply system of any of claims 23 to 36, wherein the sensor data indicates a temperature of one or more of the fuel cells, and wherein the local control device is configured to change which of the groups of fuel cells provide input to the DC-AC converter in response determining that the temperature of one or more of the fuel cells exceeds a threshold.

38. The power supply system of any of claims 23 to 37, wherein at least some of the power supply modules include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC-DC converters; and wherein at least some of the local control devices are configured to control which of the groups of fuel cells provide input to the one or more DC-DC converters.

39. The power supply system of any of claims 23 to 38, wherein the DC-AC converter is configured to provide the AC module voltage as a series of progressively varied DC outputs that together approximate a sinusoidal output.

40. The power supply system of any of claims 23 to 39, wherein the DC-AC converter is configured to concurrently provide three different AC module voltages at different phases.

41. The power supply system of any of claims 23 to 40, wherein the power supply module is configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

42. The power supply system of any of claims 23 to 41, wherein the input ports of the power supply module are configured to couple with output ports of the one or more fuel cell stacks that separately provide voltages across each of the respective groups of fuel cells, and wherein the power supply module comprises a set of switching elements that are configured to (i) selectively couple the groups of fuel in parallel to the input of the DC-AC converter and (ii) selectively couple the groups of fuel in parallel to the input of the DC-AC converter.

43. The power supply system of any of claims 23 to 42, wherein the power supply module is configured to couple with one or more batteries; and wherein the power supply module is configured to generate the AC module output based on power concurrently drawn from the one or more batteries and the one or more fuel cell stacks.

44. The power supply system of any of claims 23 to 43, wherein the power supply module is configured to couple with one or more batteries; and wherein the power supply module is configured to switch between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the one or more fuel cell stacks.

45. The power supply system of any of claims 23 to 44, wherein the power supply module is configured to couple with one or more batteries; and wherein the power supply module is configured to charge the one or more batteries with power received from the one or more fuel cell stacks.

46. A power supply system, comprising: a plurality of power supply modules electrically coupled together, wherein the power supply modules are configured to output an alternating current (AC) signal comprising a superposition of AC module voltages from the plurality of power supply modules, each of the plurality of power supply modules comprising: a DC-AC converter configured to electrically couple with one or more fuel cell stacks and configured to convert the DC input from the one or more fuel cell stacks to the AC module voltage; a power connection configured to output an AC module voltage of the power supply module; and a local control device configured to control the DC-AC converter to route energy from the one or more fuel cell stacks to the power connection; anda main control device that is configured to control the plurality of power supply modules via a control interface, wherein the main control device is configured to (i) monitor a condition of the one or more fuel cell stacks based on information provided by the power supply modules and (ii) provide, based on the monitored condition of the one or more fuel cell stacks, control signals to the local control devices to configure outputs of the power supply modules.

47. The power supply system of claim 46, wherein the information provided by the local control devices indicates one or more operating parameters of the one or more fuel cell stacks, wherein the one or more operating parameters comprise a voltage output of the one or more fuel cell stacks, an electrical current output of the one or more fuel cell stacks, a temperature of the one or more fuel cell stacks, a pressure of the one or more fuel cell stacks, a fuel rate of the one or more fuel cell stacks, a configuration of the one or more fuel cell stacks, an operating state of the one or more fuel cell stacks, a duration of operation for the one or more fuel cell stacks, or a maintenance status of the one or more fuel cell stacks.

48. The power supply system of claim 47, wherein the plurality of power supply modules comprises a first power supply module that is configured to receive power from a fuel cell stack that includes multiple fuel cell strings, wherein each of the respective fuel cell strings comprises multiple fuel cells coupled together in series; and wherein the first power supply module is configured to provide, to the main control device, information indicating the one or more the operating parameters for each of the multiple fuel cell strings.

49. The power supply system of claim 47 or 48, wherein one or more of the local control devices is configured to (i) monitor the one or more operating parameters of a fuel cell stack and (ii) communicate to the main control device whether the one or more operating parameters are within a predetermined range or satisfy a predetermined threshold.

50. The power supply system of any of claims 47 to 49, wherein the main control device is configured to provide control signals via the control interface that instruct AC output characteristics for individual power supply modules, wherein the instructed AC output characteristics specify at least one of an AC output voltage, a AC output frequency, an AC output phase, a connection over which to provide AC output, or whether to enable or disable AC output from the power supply module.

51. The power supply system of any of claims 46 to 50, wherein the power supply system is configured to provide multiple phases of AC output to an AC bus; and wherein the main control device is configured to (i) assign different subsets of the power supply modules to provide the respective phases of AC output and (ii) send control signals via the control interface to cause the local control devices to provide AC output at the phases to which the power supply modules are assigned.

52. The power supply system of any of claims 46 to 51, wherein the control signals comprise one or more synchronization signals to synchronize AC module outputs of the power supply modules.

53. The power supply system of any of claims 46 to 52, wherein the control signals comprise control signals that instruct a topology for electrical connections to be established among the power supply modules or with an AC bus.

54. The power supply system of any of claims 46 to 53, wherein the control signals comprise control signals that instruct a change to operation of at least one of the one or more fuel cell stacks, including at least one of a change to a fuel rate for a fuel cell stack, a change to a pressure of a fuel cell stack, a change to begin or end a purging cycle for a fuel cell stack, or a change to start or shut down power generation with a fuel cell stack.

55. The power supply system of any of claims 46 to 54, wherein the main control device is configured to send control signals to instruct a subset of the power supply modules to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the power supply modules coupled in series.

56. The power supply system of any of claims 46 to 55, wherein the main control device is configured to send control signals to instruct a subset of the power supply modules to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the power supply modules coupled in parallel.

57. The power supply system of any of claims 46 to 56, wherein the main control device is configured to (i) track usage of the one or more fuel cell stacks based on the information from the local control devices and (ii) send control signals to vary usage of the power supply modules to balance wear among multiple fuel cell stacks.

58. The power supply system of any of claims 46 to 57, wherein the main control device is configured to (i) determine, based on the information from the local control devices, when a temperature of at least one of the one or more fuel cell stacks exceeds a threshold and (ii) send control signals to reduce output of one or more power supply modules receiving power from the fuel cell stack determined to have a temperature that exceeds the threshold.

59. A method comprising: receiving DC input from a fuel cell stack at a plurality of input ports of power supply modules of a power supply system, wherein each of the power supply modules comprises a plurality of input ports, and each of the power supply modules receives different DC input voltages from electrical taps at different intermediate locations among fuel cells of the fuel cell stack that are electrically coupled in series; converting the DC input from the fuel cell stack to AC module voltages, wherein each of the power supply modules has a separate DC-AC converter that is used to convert DC input to the corresponding AC module voltage for the power supply module, wherein each of the power supply modules uses a separate local control device to select from among the DC outputs of different subsets of the fuel cells to provide power to generate the corresponding AC module voltage; and outputting the AC module voltages generated by the power supply modules.

60. The method of claim 59, comprising: setting, for at least a first power supply module of the power supply modules, which of the plurality of inputs are coupled to the DC-AC power converter of the first power supply module using one or more switching elements of the first power supply module; and controlling, by the local control device of the first power supply module, the one or more switching elements to adjust which combinations of the input ports of the first power supply module provide input to the DC-AC converter of the first power supply module.

61. The method of any one of claims 59 to 60, wherein the electrical taps are each spaced apart by multiple fuel cells, such that each pair of the input ports provides a voltage across a different span of multiple fuel cells coupled in series.

62. The method of any one of claims 59 to 61, synchronizing, using the local control devices of the power supply modules, a frequency and phase of the AC module voltages to a frequency and phase of an AC bus.

63. The method of any one of claims 59 to 62, changing, using the local control devices of the power supply modules, the DC inputs used to provide power to the DC-AC converters to balance load or wear among the fuel cells over time.

64. The method of any one of claims 59 to 63, comprising: detecting a decrease in performance of one or more fuel cells in the fuel cell stack; and changing the inputs used to provide power to the DC-AC converters in response to detecting the decrease in performance.

65. The method of any one of claims 59 to 64, comprising: detecting a change in load demand; and changing the inputs used to provide power to the DC-AC converter in response to detecting the change in load demand.

66. The method of any one of claims 59 to 65, comprising: identifying one or more of the fuel cells that are designated for a maintenance operation; and changing the inputs used to provide power to the DC-AC converter to draw power during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation.

67. The method of any one of claims 59 to 66, comprising: receiving sensor data indicating a condition of the fuel cell stack; and changing the inputs used to provide power to the DC-AC converter based on the sensor data.

68. The method of claim 67, wherein the sensor data includes a temperature of one or more of the fuel cells, and wherein the local control devices of the power supply modules are configured to change the inputs used to provide power to the DC-AC converter in response to determining that the temperature of one or more of the fuel cells exceeds a threshold.

69. The method of any one of claims 59 to 68, wherein the power supply modules each include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC-DC converters; andwherein the local control devices of the power supply modules are configured to control which pair of the input ports provides input to the one or more DC-DC converters.

70. The method of claim 69, wherein the local control devices are configured to determine a DC output voltage to be provided at the DC output port and to select the pair of the input ports based on the DC output voltage to be provided.

71. The method of any one of claims 59 to 70, wherein the DC-AC converters are configured to provide the AC module voltages as a series of progressively varied DC outputs that together approximate a sinusoidal output.

72. The method of any one of claims 59 to 71, comprising three arrays of power supply modules, wherein each of the three arrays of power supply modules is configured to provide AC output at a different phase.

73. The method of claim 72, wherein the power supply modules of the three arrays receive power generated by the same fuel cell stack.

74. The method of claim 72, wherein the power supply modules of the three arrays receive power generated by different fuel cell stacks.

75. The method of any one of claims 59 to 74, wherein the power supply modules are configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

76. The method of any one of claims 59 to 75, wherein the power supply modules are each coupled with or include one or more batteries; and wherein each of the power supply module generates its AC module output based on power concurrently drawn from the one or more batteries and from the fuel cell stack.

77. The method of any one of claims 59 to 76, wherein the power supply modules are coupled with or include one or more batteries; and wherein the method includes switching, for one or more of the power supply modules, between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the fuel cell stack.

78. The method of any one of claims 59 to 77, wherein the power supply modules are configured to couple with or to include one or more batteries; and wherein the method includes charging the one or more batteries with power received from the fuel cell stack.

79. The method of any one of claims 59 to 78, comprising selecting, by one or more of the local control devices, DC outputs of different subsets of the fuel cells by adjusting which combinations of the input ports provide input to the DC-AC converter.

80. A method comprising: generating an AC voltage as a combination of AC module voltages from multiple power supply modules in an array of power supply modules, wherein the AC voltage is generated based on DC input from one or more fuel cell stacks comprising multiple groups of fuel cells, wherein each group of fuel cells includes multiple fuel cells that are electrically coupled in series, and the multiple groups of fuel cells are arranged to be selectively coupled in parallel with each other, wherein the power supply modules each generate the corresponding AC module voltage with operations that include: receiving DC input from the one or more fuel cell stacks; converting the DC input from the one or more fuel cell stacks to the AC module voltage using a DC-AC converter configured to electrically couple with the one or more fuel cell stacks; and controlling the DC-AC converter, using a local control device, to provide the AC module voltage to a power connection, wherein the local control device is configured to cause DC input from the respective groups of fuel cells to be selectively provided as input to the DC-AC converter.

81. The method of claim 80, comprising using a main control device to control which of the groups of fuel cells are coupled to the input ports and how many of the groups are coupled to the input ports.

82. The method of claim 80 or 81, comprising controlling one or more switching elements to selectively couple the respective groups of fuel cells from an input to the DC-AC converter of one or more power supply modules.

83. The method of claim 82, wherein the one or more switching elements comprise one or more switches, transistors, or relays.

84. The method of claim 82 or 83, wherein the one or more switching elements comprise a switching element for each of the groups of fuel cells, and wherein the switching elements are configured to enable each of the groups of fuel cells to selectively provide input to the DC-AC converter independent of whether the other groups of fuel cells provide input to the DC-AC converter.

85. The method of any of claims 82 to 84, wherein the input ports of the power supply module comprise a first input port and a second input port; wherein the one or more fuel cell stacks comprise (i) a first output port to couple with the first input port and (ii) a second output port to couple with the second input port; wherein the one or more fuel cell stacks include a switching element for each group of fuel cells; wherein, for each of the groups of fuel cells, the switching element for the group of fuel cells is configured to selectively provide DC output across the corresponding group of fuel cells at the first output port and the second output port; and wherein the local control devices or a main control device is configured to provide one or more control signals to cause the switching elements to set which of the groups of fuel cells provide DC output at the first output port and the second output port.

86. The method of any of claims 82 to 85, wherein the input ports of the power supply module include input ports configured to separately receive DC input voltages across the respective groups of fuel cells; and wherein the power supply module includes the one or more switching elements, and the one or more switching elements are controlled by the local control device to set which of the input ports provide input to the DC-AC converter.

87. The method of claim 86, wherein the one or more switching elements are controllable by the local control device to provide, as input to the DC-AC converter, DC input selected from among each of the individual groups of fuel cells and combinations of multiple of the groups of fuel cells.

88. The method of any of claims 80 to 87, comprising synchronizing a frequency and phase of the AC module voltages to a frequency and phase of an AC bus.

89. The method of any of claims 80 to 88, comprising changing which of the groups of fuel cells provide input to the DC-AC converters to balance load or wear among the fuel cells over time.

90. The method of any of claims 80 to 89, comprising: detecting a decrease in performance of one or more fuel cells in the fuel cell stack; and changing which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the decrease in performance.

91. The method of any of claims 80 to 90, comprising: detecting a change in load demand; and changing which of the groups of fuel cells provide input to the DC-AC converters in response to detecting the change in load demand.

92. The method of any of claims 80 to 91, comprising: identifying one or more of the groups of fuel cells that are designated for a maintenance operation; and changing which of the groups of fuel cells provide input to the DC-AC converter during the maintenance operation from fuel cells other than the fuel cells that are designated for the maintenance operation.

93. The method of any of claims 80 to 92, comprising: receiving sensor data indicating a status of the one or more fuel cell stacks; and changing which of the groups of fuel cells provide input to the DC-AC converter based on the sensor data.

94. The method of any of claims 80 to 93, wherein the sensor data indicates a temperature of one or more of the fuel cells, and wherein the local control device is configured to change which of the groups of fuel cells provide input to the DC-AC converter in response determining that the temperature of one or more of the fuel cells exceeds a threshold.

95. The method of any of claims 80 to 94, wherein at least some of the power supply modules include one or more DC-DC converters and a DC output port configured to provide an output of the one or more DC-DC converters; and wherein at least some of the local control devices are configured to control which of the groups of fuel cells provide input to the one or more DC-DC converters.

96. The method of any of claims 80 to 95, wherein the DC-AC converter is configured to provide the AC module voltage as a series of progressively varied DC outputs that together approximate a sinusoidal output.

97. The method of any of claims 80 to 96, wherein the DC-AC converter is configured to concurrently provide three different AC module voltages at different phases.

98. The method of any of claims 80 to 97, wherein the power supply module is configured to provide the DC input to the DC-AC converter without an intermediate conversion to a DC bus.

99. The method of any of claims 80 to 98, wherein the input ports of the power supply module are configured to couple with output ports of the one or more fuel cell stacks that separately provide voltages across each of the respective groups of fuel cells, and wherein the power supply module comprises a set of switching elements that are configured to (i) selectively couple the groups of fuel in parallel to the input of the DC-AC converter and (ii) selectively couple the groups of fuel in parallel to the input of the DC-AC converter.

100. The method of any of claims 80 to 99, wherein the power supply module is configured to couple with one or more batteries; and wherein the power supply module is configured to generate the AC module output based on power concurrently drawn from the one or more batteries and the one or more fuel cell stacks.

101. The method of any of claims 80 to 100, wherein the power supply module is configured to couple with one or more batteries; and wherein the power supply module is configured to switch between (i) generating the AC module output based on power from the one or more batteries and (ii) generating the AC module output based on power from the one or more fuel cell stacks.

102. The method of any of claims 80 to 101, wherein the power supply module is configured to couple with one or more batteries; and wherein the power supply module is configured to charge the one or more batteries with power received from the one or more fuel cell stacks.

103. A method comprising: controlling a plurality of power supply modules via a control interface, wherein the plurality of power supply modules are electrically coupled together, wherein the power supply modules are configured to output an alternating current (AC) signal comprising a superposition of AC module voltages from the plurality of power supply modules, and wherein each of the power supply modules comprises a DC-AC converter and a local control device configured to control the DC-AC converter to route energy from the one or more fuel cell stacks to a power connection; monitoring a condition of the one or more fuel cell stacks based on information provided by the power supply modules; and providing, based on the monitored condition of the one or more fuel cell stacks, control signals to the local control devices to configure outputs of the power supply modules.

104. The method of claim 103, wherein the information provided by the local control devices indicates one or more operating parameters of the one or more fuel cell stacks, wherein the one or more operating parameters comprise a voltage output of the one or more fuel cell stacks, an electrical current output of the one or more fuel cell stacks, a temperature of the one or more fuel cell stacks, a pressure of the one or more fuel cell stacks, a fuel rate of the one or more fuel cell stacks, a configuration of the one or more fuel cell stacks, an operating state of the one or more fuel cell stacks, a duration of operation for the one or more fuel cell stacks, or a maintenance status of the one or more fuel cell stacks.

105. The method of claim 104, wherein the plurality of power supply modules comprises a first power supply module that is configured to receive power from a fuel cell stack that includes multiple fuel cell strings, wherein each of the respective fuel cell strings comprises multiple fuel cells coupled together in series; and wherein the first power supply module is configured to provide information indicating the one or more the operating parameters for each of the multiple fuel cell strings.

106. The method of claim 104 or 105, wherein one or more of the local control devices is configured to (i) monitor the one or more operating parameters of a fuel cell stack and (ii)communicate whether the one or more operating parameters are within a predetermined range or satisfy a predetermined threshold.

107. The method of any of claims 104 to 106, comprising providing control signals, via the control interface, that instruct AC output characteristics for individual power supply modules, wherein the instructed AC output characteristics specify at least one of an AC output voltage, a AC output frequency, an AC output phase, a connection over which to provide AC output, or whether to enable or disable AC output from the power supply module.

108. The method of any of claims 103 to 107, wherein the power supply system is configured to provide multiple phases of AC output to an AC bus; and wherein the method includes: assigning different subsets of the power supply modules to provide the respective phases of AC output; and sending control signals via the control interface to cause the local control devices to provide AC output at the phases to which the power supply modules are assigned.

109. The method of any of claims 103 to 108, wherein the control signals comprise one or more synchronization signals to synchronize AC module outputs of the power supply modules.

110. The method of any of claims 103 to 109, wherein the control signals comprise control signals that instruct a topology for electrical connections to be established among the power supply modules or with an AC bus.

111. The method of any of claims 103 to 110, wherein the control signals comprise control signals that instruct a change to operation of at least one of the one or more fuel cell stacks, including at least one of a change to a fuel rate for a fuel cell stack, a change to a pressure of a fuel cell stack, a change to begin or end a purging cycle for a fuel cell stack, or a change to start or shut down power generation with a fuel cell stack.

112. The method of any of claims 103 to 111, comprising sending control signals to instruct a subset of the power supply modules to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the power supply modules coupled in series.

113. The method of any of claims 103 to 112, comprising sending control signals to instruct a subset of the power supply modules to provide a phase of AC output on an AC bus by having AC module outputs of the subset of the power supply modules coupled in parallel.

114. The method of any of claims 103 to 113, comprising: tracking usage of the one or more fuel cell stacks based on the information from the local control devices; and sending control signals to vary usage of the power supply modules to balance wear among multiple fuel cell stacks.

115. The method of any of claims 103 to 114, comprising determining, based on the information from the local control devices, when a temperature of at least one of the one or more fuel cell stacks exceeds a threshold; and sending control signals to reduce output of one or more power supply modules receiving power from the fuel cell stack determined to have a temperature that exceeds the threshold.

116. A system configured to perform the operations of the method of any of claims 59 to 115.

117. One or more machine-readable media storing instructions that are operable, when executed by one or more processors, to cause a system to perform the operations of any of claims 59 to 115.

118. A control system configured to cause a system to perform the operations of any of claims 59 to 115.

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