Energy system islanding detection

Abstract

A system, device, and method for an energy system includes one or more modules configured to connect to a power grid. Each module outputs a respective voltage and / or current waveform to a load. A controller is configured to periodically cause at least a portion of the one or more modules to output increased voltage and / or current levels at specified harmonic frequencies. An islanding detector is configured to detect when one or more modules are in an islanding condition based on grid impedance.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present disclosure relates generally to energy systems and systems, devices, and methods for detecting islanding conditions. [Background technology]

[0002] In electrical engineering, power engineering, and the power industry, power conversion is the conversion of electrical energy from one form to another, for example, converting between AC and DC, regulating voltage or frequency, or some combination of these. A power converter is an electrical or electromechanical device for converting electrical energy. A power converter can be as simple as a transformer for changing the voltage of AC (e.g., alternating current) power, but can also be implemented using much more complex systems. The term "power converter" can also refer to a class of electrical machinery used to convert one frequency of alternating current to another. Power conversion systems often incorporate redundancy and voltage regulation.

[0003] Safety standards for grid support utility bidirectional inverters typically require that the inverter should cease energizing and disconnect from the area electric power system (AEPS) when an unintentional islanding condition occurs. This is often referred to as anti-islanding protection. An islanding condition is a condition in which only a portion of the AEPS is energized by the local electronic power system (EPS), while that portion is electrically isolated from other portions of the AEPS. Summary of the Invention [Means for solving the problem]

[0004] Techniques for detecting islanding conditions can be broadly classified into three categories, including passive, active, and communication-based. In the active category, harmonic injection is one of the common approaches. Harmonic injection islanding detection increases the harmonic content of the output waveform, leading to higher total harmonic distortion (THD). Increased THD results in certain performance degradation for the EPS, including lower power factor, higher peak current, and lower efficiency.

[0005] This specification describes exemplary implementations of systems, devices, and methods for module-based energy systems, including devices that are broadly relevant to many applications and configured to detect islanding conditions. For example, a master control device can detect an islanding condition by periodically injecting additional harmonic signals, such as harmonic currents and / or harmonic voltages, onto the output of each, or at least one, of the modules in an array of cascaded modules and measuring the output impedance of the module's converter at the harmonic frequencies. The described methods and systems for detecting islanding conditions can be used in other inverter topologies in addition to arrays of cascaded modules. By injecting harmonic signals periodically, rather than continuously, the accuracy of islanding detection is increased and the THD introduced by the harmonic signals is reduced.

[0006] The master control device is configured to generate control information including a normalized reference signal for each module and a modulation index for at least one of the modules. One or more modules can be associated with and controlled by one or more local control devices configured to use the modulation index to scale the normalized reference signal, for example, by outputting a reference signal and dividing the reference signal by its peak value prior to adjusting the magnitude of the reference signal. To inject harmonic signals for islanding detection, the master control device can adjust the control information to cause the local control devices to adjust the switching of their modules to increase the amplitude of current at harmonic frequencies.

[0007] When an islanding condition is detected, the master control device disconnects the array of cascaded modules from the grid and switches from current control mode to voltage control mode. In voltage control mode, the master control device causes the modules to output waveforms that track the grid's last normal voltage, frequency, and phase. When the grid returns to normal operation, the master control module reconnects the array of cascaded modules to the grid and switches back to current control mode based on the grid's current voltage, frequency, and phase. The master control device's current controller adjusts the fundamental current based on load demand, and the harmonic current controller periodically injects harmonic currents for islanding condition detection.

[0008] Other systems, devices, methods, features, and advantages of the subject matter described herein will be, or become, apparent to one with skill in the art upon examination of the following figures and detailed description. [Brief explanation of the drawings]

[0009] [Figure 1A] 1A-1C are block diagrams depicting embodiments of modular energy systems. [Figure 1B]1A-1C are block diagrams depicting embodiments of modular energy systems. [Figure 1C] 1A-1C are block diagrams depicting embodiments of modular energy systems.

[0010] [Figure 1D] 1D-1E are block diagrams depicting examples of control devices for energy systems. [Figure 1E] 1D-1E are block diagrams depicting examples of control devices for energy systems.

[0011] [Figure 1F] 1F-1G are block diagrams depicting examples of modular energy systems coupled with loads and charging sources. [Figure 1G] 1F-1G are block diagrams depicting examples of modular energy systems coupled with loads and charging sources.

[0012] [Figure 2A] 2A-2B are block diagrams depicting examples of modules and control systems within an energy system. [Figure 2B] 2A-2B are block diagrams depicting examples of modules and control systems within an energy system.

[0013] [Figure 2C] FIG. 2C is a block diagram depicting an example of the physical configuration of the modules.

[0014] [Figure 2D] FIG. 2D is a block diagram depicting an example of the physical configuration of a modular energy system.

[0015] [Figure 3A]3A-3C are block diagrams depicting embodiments of modules having various electrical configurations. [Figure 3B] 3A-3C are block diagrams depicting embodiments of modules having various electrical configurations. [Figure 3C] 3A-3C are block diagrams depicting embodiments of modules having various electrical configurations.

[0016] [Figure 4A] 4A-4F are schematic diagrams depicting examples of energy sources. [Figure 4B] 4A-4F are schematic diagrams depicting examples of energy sources. [Figure 4C] 4A-4F are schematic diagrams depicting examples of energy sources. [Figure 4D] 4A-4F are schematic diagrams depicting examples of energy sources. [Figure 4E] 4A-4F are schematic diagrams depicting examples of energy sources. [Figure 4F] 4A-4F are schematic diagrams depicting examples of energy sources.

[0017] [Figure 5A] 5A-5C are schematic diagrams depicting examples of energy buffers. [Figure 5B] 5A-5C are schematic diagrams depicting examples of energy buffers. [Figure 5C] 5A-5C are schematic diagrams depicting examples of energy buffers.

[0018] [Figure 6A] 6A-6C are schematic diagrams depicting embodiments of the transducer. [Figure 6B] 6A-6C are schematic diagrams depicting embodiments of the transducer. [Figure 6C] 6A-6C are schematic diagrams depicting embodiments of the transducer.

[0019] [Figure 7A] 7A-7E are block diagrams depicting examples of modular energy systems having various topologies. [Figure 7B] 7A-7E are block diagrams depicting examples of modular energy systems having various topologies. [Figure 7C] 7A-7E are block diagrams depicting examples of modular energy systems having various topologies. [Figure 7D] 7A-7E are block diagrams depicting examples of modular energy systems having various topologies. [Figure 7E] 7A-7E are block diagrams depicting examples of modular energy systems having various topologies.

[0020] [Figure 8A] FIG. 8A is a plot depicting an example output voltage of the module.

[0021] [Figure 8B] FIG. 8B is a plot depicting an exemplary multi-level output voltage of an array of modules.

[0022] [Figure 8C] FIG. 8C is a plot depicting exemplary reference and carrier signals that can be used in a pulse width modulation control technique.

[0023] [Figure 8D] FIG. 8D is a plot depicting exemplary reference and carrier signals that can be used in a pulse width modulation control technique.

[0024] [Figure 8E] FIG. 8E is a plot depicting an exemplary switch signal generated according to a pulse width modulation control technique.

[0025] [Figure 8F] FIG. 8F is a plot depicting an exemplary multi-level output voltage generated by superposition of output voltages from an array of modules under pulse width modulation control techniques.

[0026] [Figure 9A] 9A-9B are block diagrams depicting an embodiment of a controller for a modular energy system. [Figure 9B] 9A-9B are block diagrams depicting an embodiment of a controller for a modular energy system.

[0027] [Figure 10A] FIG. 10A is a block diagram depicting an example of a multi-phase modular energy system having interconnected modules.

[0028] [Figure 10B] FIG. 10B is a schematic diagram depicting an embodiment of an interconnect module in the multi-phase embodiment of FIG. 10A.

[0029] [Figure 10C] FIG. 10C is a block diagram depicting an example of a modular energy system having two subsystems wired together by an interconnect module.

[0030] [Figure 10D] FIG. 10D is a block diagram depicting an example of a three-phase modular energy system having interconnected modules supplying auxiliary loads.

[0031] [Figure 10E] FIG. 10E is a schematic diagram depicting an embodiment of an interconnect module in the multi-phase embodiment of FIG. 10D.

[0032] [Figure 10F]FIG. 10F is a block diagram depicting another embodiment of a three-phase modular energy system having interconnected modules supplying auxiliary loads.

[0033] [Figure 11A] FIG. 11A is a block diagram depicting an example of a grid-connected system in which an energy system is connected to a load and a grid.

[0034] [Figure 11B] FIG. 11B is an electrical equivalent diagram depicting an example of a grid-connected system in which an energy system is connected to a load and a grid.

[0035] [Figure 12A] 12A-12B are block diagrams depicting an embodiment of a master control device. [Figure 12B] 12A-12B are block diagrams depicting an embodiment of a master control device.

[0036] [Figure 13] FIG. 13 is a block diagram of an embodiment of an islanding detector.

[0037] [Figure 14] FIG. 14 is a flow diagram depicting an example embodiment of a method for detecting an islanding condition and operating an energy system based on whether an islanding condition is detected.

[0038] [Figure 15] FIG. 15 is a flow diagram depicting an embodiment of a method for one or more modules to adjust control information for injecting disturbances onto the output of the modules. DETAILED DESCRIPTION OF THE INVENTION

[0039] (Detailed explanation) Before the present subject matter is described in detail, it is to be understood that the present disclosure is not limited to particular embodiments described. 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.

[0040] Before describing example implementations of modular energy systems and their communication interfaces, it is useful to first describe these underlying systems in more detail. With reference to Figures 1A-10F, the following sections describe various applications in which exemplary modular energy systems may be implemented, exemplary control systems or devices for modular energy systems, configurations of exemplary modular energy systems relative to charging sources and loads, exemplary individual modules, exemplary topologies for arranging modules in the system, exemplary control methodologies, exemplary balanced operating characteristics of modules in the system, and exemplary uses of interconnected modules.

[0041] (Example of use) A stationary application is one in which a modular energy system resides at a fixed location during use but may be capable of being transported to an alternative location when not in use. A module-based energy system provides electrical energy for consumption by one or more other entities while residing at a static location, or stores or buffers energy for later consumption. Examples of stationary applications include, but are not limited to, energy systems for use by or within one or more residential structures or locations, energy systems for use by or within one or more industrial structures or locations, energy systems for use by or within one or more commercial structures or locations, energy systems for use by or within one or more government structures or locations (including both military and non-military uses), energy systems for charging mobile applications described below (e.g., charging sources or charging stations), and systems that convert solar power, wind power, 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. Static energy systems can be used in either a storage or non-storage role.

[0042] Mobile applications, sometimes referred to as traction applications, are generally those in which a modular energy system is located on or within an entity to store and provide electrical energy for conversion into motive force by a motor to move or assist in moving the entity. Examples of mobile entities include, but are not limited to, electric and / or hybrid entities that move over land or underground, over or under the sea, above land or sea without contact therewith (e.g., flying or hovering in the air), or through space. Examples of mobile entities also include, but are not limited to, cars, trains, trams, ships, watercraft, aircraft, and spacecraft. Examples of mobile vehicles include, but are not limited to, those with only one wheel or track, those with only two wheels or tracks, those with only three wheels or tracks, those with only four wheels or tracks, and those with five or more wheels or tracks. Examples of mobile entities also include, but are not limited to, cars, buses, trucks, motorcycles, scooters, industrial vehicles, mining vehicles, air vehicles (e.g., airplanes, helicopters, drones, etc.), marine vessels (e.g., commercial carriers, ships, yachts, boats, or other water vehicles), submarines, locomotives or rail-based vehicles (e.g., trains, trams, etc.), military vehicles, spacecraft, and satellites.

[0043] Reference may be made herein to particular stationary applications (e.g., grids, microgrids, data centers, cloud computing environments) or mobile applications (e.g., electric vehicles). Such references are made for ease of explanation and do not imply that a particular implementation is limited for use only in that particular mobile or stationary application. Implementations of systems that provide power to motors can be used in both mobile and stationary applications. While certain configurations may be more suitable for some applications than others, all example implementations disclosed herein are capable of use in both mobile and stationary applications unless otherwise stated.

[0044] (Example of a module-based energy system) FIG. 1A is a block diagram depicting an example of a module-based energy system 100. Here, system 100 includes a control system 102 communicatively coupled to N converter source modules 108-1 through 108-N via communication paths or links 106-1 through 106-N, respectively. The modules 108 are configured to store energy and output energy to a load 101 (or other modules 108) as needed. In these implementations, any number of two or more modules 108 can be used (e.g., N is greater than or equal to two). The modules 108 can be wired together in various manners, as will be described in more detail with respect to FIGS. 7A-7E. For ease of illustration, in FIGS. 1A-1C, the modules 108 are shown wired in series or as a one-dimensional array, with the Nth module coupled to the load 101.

[0045] System 100 is configured to supply power to load 101. Load 101 can be any type of load, such as a motor or grid 1130. System 100 is also configured to store power received from a charging source. FIG. 1F is a block diagram depicting an embodiment of system 100 with a power input interface 151 for receiving power from charging source 150 and a power output interface for outputting power to load 101. In this implementation, system 100 can receive and store power via interface 151 while simultaneously outputting power via interface 152. FIG. 1G is a block diagram depicting another embodiment of system 100 with a switchable interface 154. In this implementation, system 100 can select, or be instructed to select, between receiving power from charging source 150 and outputting power to load 101. The system 100 can be configured to supply multiple loads 101, including both primary and auxiliary loads, and / or receive power from multiple charging sources 150 (e.g., a utility operating power grid 1130 and local renewable energy sources (e.g., solar)).

[0046] 1B depicts another embodiment of system 100. Here, control system 102 is implemented as a master control device (MCD) 112 that is communicatively coupled to N different local control devices (LCDs) 114-1 to 114-N via communication paths or links 115-1 to 115-N, respectively. Each LCD 114-1 to 114-N is communicatively coupled to one module 108-1 to 108-N via communication paths or links 116-1 to 116-N, respectively, such that a 1:1 relationship exists between the LCD 114 and the module 108. In some implementations, two or more modules 108 can share an LCD 114.

[0047] 1C depicts another embodiment of system 100, in which MCD 112 is communicatively coupled to M different LCDs 114-1 through 114-M via communication paths or links 115-1 through 115-M, respectively. Each LCD 114 is coupled to and can control two or more modules 108. In the illustrated embodiment, each LCD 114 is communicatively coupled to two modules 108, such that M LCDs 114-1 through 114-M are coupled to 2M modules 108-1 through 108-2M via communication paths or links 116-1 through 116-2M, respectively.

[0048] The control system 102 can be configured as a single device for the entire system 100 (e.g., FIG. 1A), or can be distributed across or implemented as multiple devices (e.g., FIGS. 1B-1C). In some implementations, the control system 102 can be distributed among the LCDs 114 associated with the modules 108, such that any MCDs 112 are not required and may be omitted from the system 100.

[0049] Control system 102 can be configured to perform control using software (instructions stored in memory executable by processing circuitry), hardware, or a combination thereof. One or more devices of control system 102 may each include processing circuitry 120 and memory 122, as shown here. Exemplary implementations of processing circuitry and memory are described further below.

[0050] The control system 102 may have a communication interface for communicating with devices 104 external to the system 100 via communication links or paths 105. For example, the control system 102 (e.g., the MCD 112) may output data or information about the system 100 to another control device 104 (e.g., a vehicle's electronic control unit (ECU) or motor control unit (MCU) in a mobile application, a grid controller in a stationary application, etc.).

[0051] Each of the communication paths or links 105, 106, 115, 116, and 118 (FIG. 2B) can be a wired (e.g., electrical, optical) or wireless communication path that communicates data or information bidirectionally, in parallel or serial fashion. Data can be communicated in a standardized (e.g., IEEE, ANSI) or custom (e.g., proprietary) format. In automotive applications, the communication path 115 can be configured to communicate according to the FlexRay or CAN protocol. The communication paths 106, 115, 116, and 118 also provide wired power and can directly supply operating power for the system 102 from one or more modules 108. For example, operating power for each LCD 114 can be supplied solely by the one or more modules 108 to which the LCD 114 is wired, while operating power for the MCD 112 can be indirectly supplied from one or more of the modules 108 (e.g., through the vehicle's power network, etc.).

[0052] The 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 the modules 108. The control can also be based on one or more other factors, such as the requirements of the load 101. Controllable aspects include, but are not limited to, one or more of the voltage, current, phase, and / or output power of each module 108.

[0053] Status information for all modules 108 in system 100 can be communicated to control system 102, which can independently control all modules 108-1...108-N. Other variations are possible. For example, a particular module 108 (or a subset of modules 108) can be controlled based on status information for that particular module 108 (or subset), based on status information for a different module 108 that is not the particular module 108 (or subset), based on status information for all modules 108 other than the particular module 108 (or subset), based on status information for the particular module 108 (or subset) and status information for at least one other module 108 that is not the particular module 108 (or subset), or based on status information for all modules 108 in system 100.

[0054] 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 the module 108 or one or more of its components (e.g., energy source, energy buffer, converter, monitor circuitry): the state of charge (SOC) of one or more energy sources of the module (e.g., the level of charge of the energy source relative to its capacity, such as a fraction or percent); the state of health (SOH) of one or more energy sources of the module (e.g., a figure of merit of the condition of the energy source compared to its ideal condition); the temperature of one or more energy sources or other components of the module; the capacity of one or more energy sources of the module; the voltage of one or more energy sources and / or other components of the module; the current of one or more energy sources and / or other components of the module; the state of power (SOP) (e.g., the available power limit of the energy source during discharge and / or charge); the state of energy (SOE) (e.g., the current level of available energy of the energy source relative to the maximum available energy of the source); and / or the presence or absence of a fault within any one or more of the module's components.

[0055] The LCD 114 can be configured to receive status information from each module 108 or determine status information from monitored signals or data received from or within each module 108 and communicate that information to the MCD 112. In some implementations, each LCD 114 can communicate raw collected data to the MCD 112, which then algorithmically determines status information based on the raw data. The MCD 112 can then use the module 108 status information to make control decisions as appropriate. Decisions may take the form of instructions, commands, or other information (such as the modulation index described herein) that can be utilized by the LCD 114 to either maintain or adjust the operation of each module 108.

[0056] For example, the MCD 112 may receive status information, evaluate the information, and determine differences between at least one module 108 (e.g., its components) and at least one or more other modules 108 (e.g., its comparable components). For example, the MCD 112 may determine that a particular module 108 is operating with one of the following conditions compared to one or more other modules 108: a relatively low or high SOC, a relatively low or high SOH, a relatively low or high capacity, a relatively low or high voltage, a relatively low or high current, a relatively low or high temperature, or the presence or absence of a fault. In such an example, the MCD 112 may output control information to reduce or increase (depending on the condition) a relevant aspect (e.g., output voltage, current, power, temperature) of that particular module 108. In this manner, the utilization of an outlier module 108 (e.g., operating with a relatively low SOC or high temperature) can be reduced to cause the relevant parameters (e.g., SOC or temperature) of that module 108 to converge toward those of one or more other modules 108.

[0057] The decision whether to adjust the operation of a particular module 108 may be made by comparing the status information with predetermined thresholds, limits, or conditions, not necessarily by comparison with the status of other modules 108. The predetermined thresholds, limits, or conditions may be static thresholds, limits, or conditions, such as those set by a manufacturer, that do not change during use. The predetermined thresholds, limits, or conditions may be dynamic thresholds, limits, or conditions that are allowed to change or change during use. For example, the MCD 112 may adjust the operation of a module 108 if the status information for that module 108 indicates that it is violating (e.g., above or below) a predetermined threshold or limit or is operating outside a predetermined range of acceptable operating conditions. Similarly, the MCD 112 may 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 the absence or removal of an actual or potential fault. Examples of faults include, but are not limited to, actual failure of a component, potential failure of a component, short circuit or other excessive current condition, open circuit, excessive voltage condition, poor reception of communications, reception of corrupted data, and the like. Depending on the type and severity of the fault, the amount of utilization of the faulty module can be reduced to avoid damaging the module, or utilization of the module can be stopped entirely. For example, if a fault occurs in a given module, MCD 112 or LCD 114 can cause that module to enter a bypass state, as described herein.

[0058] The MCD 112 can control the modules 108 in the system 100 to achieve or converge toward a desired target. The target can be, for example, that the operation of all modules 108 is at the same or similar level relative to one another, or within a predetermined threshold, limit, or condition. This process can also be referred to as seeking to achieve balance, or equilibrium, in the operation or operating characteristics of the modules 108. The term “balance,” as used herein, does not require absolute equality between the modules 108 or their components, but rather is used broadly to convey that the operation of the system 100 can be used to actively reduce inequalities in operation (or operating states) between the modules 108 that would otherwise exist.

[0059] The MCD 112 can communicate control information to the LCD 114 for purposes of controlling the module 108 associated with the LCD 114. The control information can be, for example, a modulation index and reference signal as described herein, a reference signal, or others. Each LCD 114 can use (e.g., receive and process) the control information and generate switch signals that control the operation of one or more components (e.g., converters) in the associated module 108. In some implementations, the MCD 112 generates the switch signals directly and outputs them to the LCD 114, which relays the switch signals to the intended module components.

[0060] All or a portion of the control system 102 can be combined with a system external control device 104 that controls one or more other aspects of a mobile or stationary application. When integrated within this shared or common control device (or subsystem), control of the system 100 can be implemented in any desired manner, such as by one or more software applications executed by processing circuitry of the shared device, by hardware of the shared device, or a combination thereof. Non-exhaustive examples of external control device 104 include an on-board ECU or MCU having control capabilities for one or more other on-board functions (e.g., motor control, driver interface control, traction control, etc.), a grid or microgrid controller responsible for one or more other power management functions (e.g., load interfacing, load power requirement prediction, transmission and switching, interfacing with charging sources (e.g., diesel, solar, wind), charging source power prediction, backup source monitoring, asset dispatch, etc.), and a data center control subsystem (e.g., environmental control, network control, backup control, etc.).

[0061] 1D and 1E are block diagrams depicting an example of a shared or common control device (or system) 132 in which control system 102 may be implemented. In FIG. 1D , common control device 132 includes master control device 112 and external control device 104. Master control device 112 includes interface 141 for communication with LCD 114 via path 115 and interface 142 for communication with external control device 104 via internal communication bus 136. External control device 104 includes interface 143 for communication with master control device 112 via bus 136 and interface 144 for communication with other entities in the overall application (e.g., components of a vehicle or grid 1130) via communication path 136. In some implementations, 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.

[0062] In FIG. 1E , the external control device 104 acts as a common control device 132, with master control functionality implemented as a component within the device 104. This component 112 can be or include software or other program instructions stored and / or hard-coded in the device 104's memory and executed by its processing circuitry. 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 interfaces (APIs)) for communication with the external control device 104's operating software. The external control device 104 can manage communication with the LCD 114 via interface 141 and with other devices via interface 144. In various implementations, the devices 104 / 132 can be integrated as a single IC chip, integrated into multiple IC chips in a single package, or integrated as multiple semiconductor packages in a common housing.

[0063] 1D and 1E, the master control functionality of the system 102 is shared within the common device 132; however, other divisions of shared control are also possible. For example, a portion of the master control functionality can be distributed between the common device 132 and the dedicated MCD 112. In another embodiment, both the master control functionality and at least a portion of the local control functionality can be implemented within the common device 132 (e.g., the remaining local control functionality is implemented within the LCD 114). In some implementations, the control system 102 is implemented entirely within the common device (or subsystem) 132. In some implementations, the local control functionality is implemented within a device shared with another component of each module 108, such as a battery management system (BMS).

[0064] (Example of modules in a cascaded energy system) The module 108 can include one or more energy sources, a power electronics converter, and, optionally, an energy buffer. Figures 2A-2B are block diagrams depicting additional examples of the system 100 with a module 108 having a power converter 202, an energy buffer 204, and an energy source 206. The converter 202 can be a voltage converter or a current converter. While implementations are described herein with reference to a voltage converter, implementations are not limited thereto. The converter 202 can be configured to convert a direct current (DC) signal from the energy source 204 to an alternating current (AC) signal and output it via the power wiring 110 (e.g., an inverter). The converter 202 can also receive an AC or DC signal via the wiring 110 and apply it to the energy source 204 with either polarity in a continuous or pulsed form. The converter 202 can be or include an arrangement of switches (e.g., power transistors), such as a half-bridge or full-bridge (H-bridge). In some implementations, the converter 202 includes only a switch, and the converter (and the module as a whole) does not include a transformer.

[0065] Converter 202 can also (or alternatively) be configured to perform AC / DC conversion (e.g., a rectifier), DC / DC conversion, and / or AC / AC conversion (e.g., in combination with an AC / DC converter), such as for charging a DC energy source from an AC source. In some implementations, such as for performing 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 implementations, such as those where weight and cost are significant factors, converter 202 can be configured to perform the conversion using only power switches, power diodes, or other semiconductor devices and without a transformer.

[0066] 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 wired together in a battery module or array, or any combination thereof. Figures 4A-4D are schematic diagrams depicting examples of energy source 206 configured as a single battery cell 402 (Figure 4A), a battery module with series wiring of multiple (e.g., four) cells 402 (Figure 4B), a battery module with parallel wiring of single cells 402 (Figure 4C), and a battery module with parallel wiring of tributaries each having two cells 402 (Figure 4D). A non-exhaustive list of example battery types is described elsewhere herein.

[0067] Energy source 206 can also be a high-energy density (HED) capacitor, such as an ultracapacitor or supercapacitor. HED capacitors can be configured as double-layer capacitors (electrostatic charge storage), pseudocapacitors (electrochemical charge storage), hybrid capacitors (electrostatic and electrochemical), or others, as opposed to typical solid-dielectric electrolytic capacitors. In addition to higher capacitance, HED capacitors can have energy densities 10 to 100 times (or higher) than those of electrolytic capacitors. For example, HED capacitors can have specific energies greater than 1.0 watt-hours per kilogram (Wh / kg) and capacitances greater than 10 to 100 farads (F). Similar to the battery described with respect to FIGS. 4A-4D , energy source 206 can be configured as a single HED capacitor or multiple HED capacitors wired together in an array (e.g., in series, parallel, or a combination thereof).

[0068] Energy source 206 can also be a fuel cell. The fuel cell can be a single fuel cell, multiple fuel cells wired in series or parallel, or a fuel cell module. Examples of fuel cell types include proton exchange membrane fuel cells (PEMFCs), phosphoric acid fuel cells (PAFCs), solid acid fuel cells, alkaline fuel cells, high-temperature fuel cells, solid oxide fuel cells, molten electrolyte fuel cells, and others. Similar to the batteries described with respect to FIGS. 4A-4D , energy source 206 can be configured as a single fuel cell or multiple fuel cells wired together in an array (e.g., in series, parallel, or a combination thereof). The foregoing examples of source classes (e.g., batteries, capacitors, and fuel cells) and types (chemical and / or structural configurations within each class) are not intended to form an exhaustive list, and one of ordinary skill in the art will recognize other variations that fall within the scope of the present subject matter.

[0069] The energy buffer 204 may be connected to a DC line or link (e.g., +V DCL and -V DCL ) to help maintain stability in the DC link voltage. These fluctuations may be relatively low (e.g., kilohertz) or high (e.g., megahertz) frequency fluctuations or harmonics or other transient events caused by the switching of converter 202. These fluctuations may be absorbed by buffer 204 instead of being passed to source 206 or ports IO3 and IO4 of converter 202.

[0070] Power wiring 110 is wiring for transporting energy or power to, from, and through modules 108. Modules 108 can output energy from an energy source 206 to power wiring 110, where it can be transported to other modules or loads in the system. Modules 108 can also receive energy from other modules 108 or charging sources (DC chargers, single-phase chargers, multi-phase chargers). Signals can also be passed through module 108 and bypass energy source 206. Distribution of energy or power into and out of modules 108 is performed by converters 202 under the control of LCD 114 (or another entity in system 102).

[0071] In the implementation of Figure 2A, the LCD 114 is implemented as a component separate from the module 108 (e.g., not in a shared module housing) and may be wired to and communicate with the converter 202 via communication path 116. In the implementation of Figure 2B, the LCD 114 is included as a component of the module 108 and may be wired to and communicate with the converter 202 via an internal communication path 118 (e.g., a shared bus or discrete wiring). The LCD 114 may also be capable of receiving signals from and transmitting signals to the energy buffer 204 and / or the energy source 206 via paths 116 or 118.

[0072] The module 108 may also include monitor circuitry 208 configured to monitor (e.g., collect, sense, measure, and / or determine) one or more aspects of the module 108 and / or its components, such as voltage, current, temperature, or other operating parameters that constitute status information (or may be used to determine the status information, e.g., by the LCD 114). A primary function of the status information is to describe the state of one or more energy sources 206 of the module 108 and enable a decision regarding how much to utilize the energy source relative to other sources in the system 100, although status information describing the state of other components (e.g., voltage, temperature, and / or presence of a fault in the buffer 204, temperature and / or presence of a fault in the converter 202, presence of a fault anywhere in the module 108, etc.) may likewise be used in the utilization determination. The monitor circuitry 208 may include one or more sensors, shunts, dividers, fault detectors, coulomb counters, controllers, or other hardware and / or software configured to monitor such aspects. The 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 implementations, the monitor circuitry 208 can be part of or shared with a battery management system (BMS) for the battery energy source 204. Discrete circuitry is not required to monitor each type of status information, as more than one type of status information can be monitored using a single circuit or device or otherwise determined algorithmically without the need for additional circuitry.

[0073] The LCD 114 can receive status information (or raw data) about the module components via communication paths 116, 118. The LCD 114 can also transmit information to the module components via paths 116, 118. Paths 116 and 118 can include diagnostic, 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 the transducer 202 and / or one or more signals requesting status information from the module components. For example, the LCD 114 can cause the status information to be transmitted via paths 116, 118 by directly requesting the status information or, in some cases, by applying a stimulus (e.g., a voltage) to generate the status information in combination with a switch signal that places the transducer 202 in a particular state.

[0074] The physical configuration or layout of module 108 can take a variety of forms. In some implementations, module 108 can include a common housing within which all module components, e.g., converter 202, buffer 204, and source 206, are stored along with other optional components such as an integrated LCD 114. In other implementations, the various components can be separated within discrete housings that are affixed together. FIG. 2C is a block diagram depicting an example of module 108 having a first housing 220 that holds the module's energy source 206 and associated electronics such as monitor circuitry, a second housing 222 that holds module electronics such as converter 202, energy buffer 204, and other associated electronics such as monitor circuitry, and a third housing 224 that holds the LCD 114 (not shown) for module 108. In an alternative implementation, the module electronics and LCD 114 can be housed within the same single housing. In yet other implementations, the module electronics, LCD 114, and energy source can be housed within the same single housing for module 108. Electrical wiring between the various module components can run through housings 220, 222, 224 and can be exposed either on the exterior of the housing for wiring with other modules 108 or other devices such as MCD 112.

[0075] The modules 108 of the system 100 can be physically arranged relative to each other in various configurations, depending on the needs of the application and the number of loads. For example, in a stationary application where the system 100 provides power for a microgrid, the modules 108 can be installed in one or more racks or other framework structures. Such a configuration may also be suitable for larger mobile applications, such as marine vessels. Alternatively, the modules 108 can be affixed together and located in a common housing, referred to as a pack. The rack or pack may have its own dedicated cooling system shared across all modules. A pack configuration is useful for smaller mobile applications, such as electric vehicles. The system 100 can be implemented using one or more racks (e.g., for parallel supply to a microgrid), or one or more packs (e.g., to supply different motors in a vehicle), or a combination thereof. FIG. 2D is a block diagram depicting an example embodiment of the system 100 in which nine modules 108 are configured as a pack, electrically and physically coupled together within a common housing 230.

[0076] Examples of these and further configurations are described in International Application No. PCT / US20 / 25366, filed March 27, 2020, and entitled "Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto," which is incorporated herein by reference in its entirety for all purposes.

[0077] 3A-3C are block diagrams depicting examples of modules 108 having various electrical configurations. These implementations are described as having one LCD 114 per module 108, with the LCD 114 housed within the associated module, but may be otherwise configured as described herein. FIG. 3A depicts a first exemplary configuration of a module 108A within system 100. Module 108A includes an energy source 206, an energy buffer 204, and a converter 202A. Each component has a power wiring port (e.g., terminal, connector), referred to herein as an IO port, into which and / or from which power may be input. Such ports may also be referred to as input or output ports, depending on the context.

[0078] The energy source 206 can be configured as any of the energy source types described herein (e.g., a battery, HED capacitor, fuel cell, or other, as described with respect to FIGS. 4A-4D ). Ports IO1 and IO2 of the energy source 206 can be wired to ports IO1 and IO2, respectively, of the energy buffer 204. The energy buffer 204 can be configured to buffer or filter high and low frequency energy waves arriving at the buffer 204 through the converter 202, which may otherwise degrade the performance of the module 108. The topology and components for the buffer 204 are selected to accommodate the maximum allowable amplitude of these high frequency voltage waves. Several (non-exhaustive) examples of the energy buffer 204 are depicted in the schematic diagrams of FIGS. 5A-5C . In FIG. 5A , the buffer 204 is configured with electrolytic and / or film capacitors C EB 5B, the buffer 204 is connected to two inductors L EB1 and L EB2 and two electrolytic and / or film capacitors C EB1 and C EB2 5C, the buffer 204 is formed by two inductors L EB1and L EB2 and two electrolytic and / or film capacitors C EB1 and C EB2 and diode D EB and a quasi-Z-source network 720 formed by

[0079] Ports IO3 and IO4 of energy buffer 204 can be wired 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 of converter 202A configured as a DC-to-AC converter that can receive DC voltages at ports IO1 and IO2 and switch pulses to be generated at ports IO3 and IO4. Converter 202A can include multiple switches, here converter 202A includes four switches S3, S4, S5, and S6 arranged in a full-bridge configuration. Control system 102 or LCD 114 can control each switch independently via control input line 118-3 to each gate.

[0080] The switches can be any suitable switch type, such as power semiconductors like metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or gallium nitride (GaN) transistors, as shown here. The semiconductor switches operate at a relatively high switching frequency, thereby allowing the converter 202 to be operated in pulse-width modulation (PWM) mode, if desired, and respond to control commands within a relatively short time interval. This can provide high tolerance and fast dynamic behavior of output voltage regulation in transient mode. Furthermore, the switching frequency can depend on the number of converters in the multilevel topology. Therefore, increasing the number of converters can reduce the response time, e.g., from 141 ms to 14 ms.

[0081] In this implementation, the DC line voltage V DCLcan be applied to the converter 202 between ports IO1 and IO2. Different combinations of switches S3, S4, S5, and S6 allow V DCL to ports IO3 and IO4, converter 202 can provide three different voltage outputs: +V DCL , 0, and -V DCL can be generated on ports IO3 and IO4. The switch signal provided to each switch controls whether the switch is turned on (closed) or off (open). DCL To obtain -V, switches S3 and S6 are turned on while S4 and S5 are turned off. DCL 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 turned off, or by turning on S4 and S6 with S3 and S5 turned off. These voltages can be output from the module 108 via the power wiring 110. Ports IO3 and IO4 of the converter 202 can be routed to (or from) module IO ports 1 and 2 of the power wiring 110 to generate an output voltage for use with output voltages from other modules 108.

[0082] Control or switch signals for implementations of the converter 202 described herein can be generated in different ways depending on the control technique utilized by the system 100 to generate the converter 202 output voltage. In some implementations, 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 voltage versus time graph depicting an example of an output voltage waveform 802 of the converter 202. For ease of explanation, implementations herein will be described in the context of PWM control techniques, although implementations are not limited thereto. Other classes of techniques can also be used. One alternative class is based on hysteresis, examples of which are described in International Publication Nos. WO 2018 / 231810 A1, WO 2018 / 232403 A1, and WO 2019 / 183553 A1 (incorporated herein by reference for all purposes).

[0083] Each module 108 can be configured with multiple energy sources 206 (e.g., two, three, four, or more). Each energy source 206 of a module 108 can be controllable (switchable) to supply power to the wiring 110 (or receive power from a charging source) independently of the other sources 206 of the module. For example, all sources 206 can output power to (or be charged with) the wiring 110 simultaneously, or only one (or a subset) of the sources 206 can supply power (or be charged) at any one time. In some implementations, the sources 206 of a module can exchange energy between themselves, e.g., one source 206 can charge another source 206. The sources 206 can each be configured as any energy source described herein (e.g., a battery, a HED capacitor, a fuel cell). The sources 206 can each be of the same class (e.g., each can be a battery, each can be an HED capacitor, or each can be a fuel cell) or of different classes (e.g., the first source can be a battery and the second source can be an HED capacitor or a fuel cell, or the first source can be an HED capacitor and the second source can be a fuel cell).

[0084] 3B is a block diagram depicting an example of module 108B in a dual energy source configuration with a primary energy source 206A and a secondary energy source 206B. Ports IO1 and IO2 of primary source 202A can be wired to ports IO1 and IO2 of energy buffer 204. Module 108B includes converter 202B with an additional IO port. Ports IO3 and IO4 of buffer 204 can be wired to ports IO1 and IO2, respectively, of converter 202B. Ports IO1 and IO2 of secondary source 206B can be wired to ports IO5 and IO2, respectively, of converter 202B (and also to port IO4 of buffer 204).

[0085] In this embodiment of module 108B, primary energy source 202A, along with the other modules 108 of system 100, supplies the average power required by the load. Secondary source 202B can function to supplement energy source 202 by providing additional power at load power peaks, absorbing excess power, or otherwise.

[0086] As mentioned, both the primary source 206A and the secondary source 206B can be utilized simultaneously or at separate times depending on the switch state of the converter 202B. If simultaneously, the electrolytic and / or film capacitors (C ES ) can be placed in parallel with source 206B and act as an energy buffer for source 206B, as depicted in FIG. 4E, or energy source 206B can be configured to utilize a HED capacitor in parallel with another energy source (e.g., a battery or fuel cell), as depicted in FIG. 4F.

[0087] 6B and 6C are schematic diagrams depicting examples of converters 202B and 202C, respectively. Converter 202B includes switch network portions 601 and 602A. Portion 601, in a similar manner to converter 202A, is configured as a full bridge and includes switches S3 to S6 configured to selectively couple IO1 and IO2 to either IO3 or IO4, thereby varying the output voltage of module 108B. Portion 602A is configured as a half bridge and includes switches S1 and S2 coupled between ports IO1 and IO2. A coupled inductor L C However, switch portion 602A is wired between port IO5 and node 1, which exists between switches S1 and S2, so that it is a bidirectional converter that can regulate (boost or buck) voltage (or conversely, current). Switch portion 602A is connected to +V, which is referenced to port IO2, which can be effectively zero potential. DCL2Two different voltages can be generated at node 1, ie, 0 and 0. The current drawn from or input to energy source 202B can be controlled by using, for example, a pulse width modulation technique or a hysteretic control method to commutate switches S1 and S2 through coupled inductor L. C The voltage applied to the output of the power supply can be controlled by adjusting the voltage on the output of the power supply. Other techniques can also be used.

[0088] Converter 202C differs from that of 202B because switch portion 602B includes switches S1 and S2 configured as a half-bridge and coupled between ports IO5 and IO2. C However, switch portion 602B is wired between port IO1 and node 1, which exists between switches S1 and S2, so that it is configured to regulate the voltage.

[0089] The control system 102 or the LCD 114 can independently control each switch of the converters 202B and 202C via the control input line 118-3 to each gate. In these implementations and that of FIG. 6A , the LCD 114 (rather than the MCD 112) generates the switching signals for the converter switches. Alternatively, the MCD 112 can also generate the switching signals, which can be communicated directly to the switches or relayed by the LCD 114. In some implementations, the driver circuitry for generating the switching signals can be present in or associated with the MCD 112 and / or the LCD 114.

[0090] The aforementioned zero-voltage configuration for converter 202 (S3 and S5 on with S4 and S6 off, or S4 and S6 on with S3 and S5 off) may also be referred to as a bypass state for a given module. This bypass state may be entered if a fault is detected within a given module or if a system fault is detected that warrants shutting off more than one (or all) modules in the array or system. A fault within a module may be detected by LCD 114, and a control switching signal for converter 202 may be set to assume the bypass state without intervention by MCD 112. Alternatively, fault information regarding a given module may be communicated by LCD 114 to MCD 112, which may then make a decision on whether to assume the bypass state and, if applicable, may communicate a command to assume the bypass state to the LCD 114 associated with the faulty module, at which point LCD 114 may output a switching signal to assume the bypass state.

[0091] In implementations in which 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 that leads to an additional switch network portion 602A or 602B, depending on the needs of the particular source. For example, dual-source converter 202 can include both switch portions 202A and 202B.

[0092] A module 108 with multiple energy sources 206 can perform additional functions such as energy sharing between sources 206, energy capture from within the application (e.g., regenerative braking), charging a primary source with a secondary source even while the overall system is in a discharge state, and active filtering of the module output. Active filtering functions can also be performed by the module, typically with electrolytic capacitors, in place of a secondary energy source. Examples of these functions are described in further detail in International Application No. PCT / US20 / 25366, filed March 27, 2020, and entitled "Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto," and International Publication No. WO2019 / 183553, filed March 22, 2019, and entitled "Systems and Methods for Power Management and Control," both of which are incorporated herein by reference in their entireties for all purposes.

[0093] Each module 108 can be configured to supply one or more auxiliary loads using its one or more energy sources 206. An auxiliary load is a load that requires a lower voltage than the primary load 101. An example of an auxiliary load can be, for example, an on-board electrical network of an electric vehicle or an HVAC system of an electric vehicle. A load of the system 100 can be, for example, an electric vehicle motor or one of the phases of the electric grid 1130. This implementation can allow for complete decoupling between the electrical characteristics of the energy source (terminal voltage and current) and the electrical characteristics of the load.

[0094] 3C is a block diagram depicting an example of a module 108C configured to supply power to a first auxiliary load 301 and a second auxiliary load 302. The module 108C includes an energy source 206, an energy buffer 204, and a converter 202B coupled together in a manner similar to that of FIG. 3B. The first auxiliary load 301 requires a voltage equal to that supplied by the source 206. The load 301 is coupled to IO ports 3 and 4 of the module 108C, which are in turn coupled to ports IO1 and IO2 of the source 206. The source 206 can output power to both the power line 110 and the load 301. The second auxiliary load 302 requires a constant voltage lower than that of the source 206. The load 302 is coupled to IO ports 5 and 6 of the module 108C, which are coupled to ports IO5 and IO2, respectively, of the converter 202B. Transformer 202B includes a coupled inductor L coupled to port IO5 (FIG. 6B). C The energy provided by the source 206 can be supplied to the load 302 through the switch portion 602 of the converter 202B. The load 302 has an input capacitor (a capacitor can be added to the module 108C if not applicable), and therefore the switches S1 and S2 are connected to the coupled inductor L C It is assumed that the voltage at source 206 is rectified to regulate the voltage and current through it, thus producing a stable constant voltage for load 302. This regulation allows the voltage of source 206 to be stepped down to a lower magnitude voltage required by load 302.

[0095] Module 108C can thus be configured to supply one or more first auxiliary loads in the manner described with respect to load 301, with 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 (such as 5 and 6), additional dedicated switch sections 602, and additional converter IO ports coupled to the additional sections 602.

[0096] Energy source 206 can therefore supply power for any number of auxiliary loads (e.g., 301 and 302) as well as a corresponding portion of the system output power required by primary load 101. The power flow from source 206 to the various loads can be adjusted as desired.

[0097] The module 108 can be configured to supply the first and / or second auxiliary loads (FIG. 3C) using two or more energy sources 206 (FIG. 3B) as needed, through the addition of 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. The module 108 can also be configured as an interconnect module to exchange energy (e.g., for balancing) between two or more arrays, two or more packs, or two or more systems 100 as further described herein. This interconnect functionality can likewise be combined with multiple source and / or multiple auxiliary load supply capabilities.

[0098] The control system 102 may perform various functions for the components of the modules 108A, 108B, and 108C. These functions may include managing the utilization of each energy source 206, protecting the energy buffer 204 from overcurrent, overvoltage, and high temperature conditions, and controlling and protecting the converter 202.

[0099] For example, LCD 114 may receive one or more monitored voltages, temperatures, and currents from each energy source 206 (or monitor circuitry) to manage (e.g., adjust by increasing, decreasing, or maintaining) the utilization of each energy source 206. The monitored voltages may be at least one, and preferably all, of the voltage of each basic component independent of the other components of source 206 (e.g., each individual battery cell, HED capacitor, and / or fuel cell), or the voltage of the group of basic components as a whole (e.g., the voltage of the battery array, HED capacitor array, and / or fuel cell array). Similarly, the monitored temperatures and currents may be at least one, and preferably all, of the temperature and current of each basic component independent of the other components of source 206, or the temperature and current of the group of basic components as a whole, or any combination thereof. The monitored signals may be status information with which the LCD 114 may perform one or more of the following: calculate or determine the actual capacity, actual state of charge (SOC), and / or state of health (SOH) of a basic component or group of basic components, set or output a warning or alarm indication based on the monitored and / or calculated status information, and / or transmit status information to the MCD 112. The LCD 114 may receive control information (e.g., modulation index, synchronization signal) from the MCD 112 and use this control information to generate switch signals for the converter 202 that manage the utilization of the source 206.

[0100] To protect the energy buffer 204, the LCD 114 may receive one or more monitored voltages, temperatures, and currents from the energy buffer 204 (or monitor circuitry). The monitored voltages are monitored for each basic component (e.g., C EB , C EB1 , C EB2 , L EB1 , L EB2 , D EB ) or the voltage of a group of basic components or buffer 204 as a whole (e.g., between IO1 and IO2 or between IO3 and IO4). Similarly, the monitored temperatures and currents may be at least one, preferably all, of the temperature and current of each basic component of buffer 204 independent of other components, or the temperature and current of a group of basic components or buffer 204 as a whole, or any combination thereof. The monitored signals may be status information with which LCD 114 may perform one or more of the following: set or output a warning or alarm indication, communicate status information to MCD 112, or control converter 202 to adjust (increase or decrease) utilization of source 206 and module 108 as a whole for buffer protection.

[0101] To control and protect the converter 202, the LCD 114 can receive control information (e.g., a modulated reference signal, or a reference signal and a modulation index) from the MCD 112, which can be used in conjunction with PWM techniques within the LCD 114 to generate control signals for each switch (e.g., S1 through S6). The LCD 114 can receive current feedback signals from current sensors in the converter 202, which can be used for overcurrent protection, along with one or more fault status signals from the converter switch driver circuits (not shown), which can carry information about the fault status (e.g., short-circuit or open-circuit failure mode) of all switches in the converter 202. Based on this data, the LCD 114 can manage the utilization of the module 108 and potentially make decisions regarding the combination of switching signals to be applied to bypass or disconnect the converter 202 (and the entire module 108) from the system 100.

[0102] When controlling module 108C, which supplies second auxiliary load 302, LCD 114 displays one or more monitored voltages within module 108C (e.g., the voltage between IO ports 5 and 6) and one or more monitored currents (e.g., the current of load 302, the voltage across coupled inductor L C Based on these signals, the LCD 114 can adjust the switching cycles of S1 and S2 to control (and stabilize) the voltage to the load 302 (e.g., by adjusting the modulation index or reference waveform). Cascaded Energy System Topology Example

[0103] Two or more modules 108 can be coupled together in a cascaded array that outputs a voltage signal formed by the superposition of discrete voltages generated by each module 108 in the array. FIG. 7A is a block diagram depicting an example topology for system 100, in which N modules 108-1, 108-2...108-N are coupled together in series to form a series array 700. In this and all implementations described herein, N can be any integer greater than 1. Array 700 includes a first system IO port SI01 and a second system IO port SI02 across which the array output voltage is generated. Array 700 can be used as a DC or single-phase AC energy source for DC or AC single-phase loads that may be wired to SI01 and SI02 of array 700. FIG. 8A is a voltage versus time plot depicting an example output signal produced by a single module 108 with a 48-volt energy source. FIG. 8B is a voltage versus time plot depicting an exemplary single-phase AC output signal generated by an array 700 having six 48V modules 108 coupled in series.

[0104] System 100 can be arranged in a variety of different topologies to meet the varying needs of an application. System 100 can provide multi-phase power (e.g., 2-phase, 3-phase, 4-phase, 5-phase, 6-phase, etc.) to a load through the use of multiple arrays 700, with each array generating an AC output signal having a different phase angle.

[0105] 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 and formed by the series wiring of N modules 108. The two arrays 700-PA and 700-PB can each generate a single-phase AC signal, with the two AC signals having 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 wired to system IO ports SIO1 and SIO2, respectively, which can then serve as the first output of each array, which can provide two-phase power to a load (not shown). Alternatively, ports SIO1 and SIO2 can be wired to provide single-phase power from the two parallel arrays. IO port 2 of module 108-N of each array 700-PA and 700-PB, on the opposite end of the array from system IO ports SIO1 and SIO2, can serve as a second output for each array 700-PA and 700-PB, and can be coupled together at a common node that can optionally be used, as desired, for an additional system IO port SIO3, which can serve as a neutral terminal. This common node can be referred to as the rail, and IO port 2 of module 108-N of each array 700 can be referred to as being on the rail side of the array.

[0106] 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 and formed by the series wiring of N modules 108. Each of the three arrays 700-1 and 700-2 can generate a single-phase AC signal, with the three AC signals having different phase angles PA, PB, and 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 wired to system IO ports SIO1, SIO2, and SIO3, respectively, which can in turn provide three-phase power to a load (not shown). The IO ports 2 of the modules 108-N of each array 700-PA, 700-PB, and 700-PC can be coupled together at a common node, which can optionally be used, as desired, for an additional system IO port SIO4, which can serve as a neutral terminal.

[0107] 7B and 7C can be further extended to systems 100 that generate power in more phases. For example, a non-exhaustive list of additional examples includes a system 100 having four arrays 700 configured to generate single-phase AC signals, each having a different phase angle (e.g., 90 degrees apart), a system 100 having five arrays 700 configured to generate single-phase AC signals, each having a different phase angle (e.g., 72 degrees apart), and a system 100 having six arrays 700, each configured to generate single-phase AC signals, each having a different phase angle (e.g., 60 degrees apart).

[0108] System 100 can be configured such that arrays 700 are interconnected at electrical nodes between modules 108 within each array. Figure 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 wiring of M modules 108 (M is 2 or greater) coupled with a second series wiring of N modules 108 (N is 2 or greater). The delta configuration is formed by the interconnection between the arrays, which can be placed in any desired location. In this implementation, IO port 2 of module 108-(M+N) of array 700-PC is coupled to IO port 2 of module 108-M and IO port 1 of module 108-(M+1) of array 700-PA, IO port 2 of module 108-(M+N) of array 700-PB is coupled to IO port 2 of module 108-M and IO port 1 of module 108-(M+1) of array 700-PC, and IO port 2 of module 108-(M+N) of array 700-PA is coupled to IO port 2 of module 108-M and IO port 1 of module 108-(M+1) of array 700-PB.

[0109] 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 implementation is similar to that of FIG. 7D but with different crossover wiring. In this implementation, IO port 2 of module 108-M of array 700-PC is coupled to IO port 1 of module 108-1 of array 700-PA, IO port 2 of module 108-M of array 700-PB is coupled to IO port 1 of module 108-1 of array 700-PC, and IO port 2 of module 108-M of array 700-PA is coupled to IO port 1 of module 108-1 of array 700-PB. The arrangements of FIGS. 7D and 7E can be implemented with as few as two modules in each array 700. The combined delta and series configuration allows for an effective exchange of energy between all modules 108 of the system (phase-to-phase balance) and the power grid 1130 or load phases, and also allows for a reduction in the total number of modules 108 in the array 700 to obtain the desired output voltage.

[0110] In the implementations described herein, it is advantageous for the number of modules 108 to be the same in each array 700 in system 100, but that is not required, and different arrays 700 can have different numbers of modules 108. Furthermore, 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, etc.) or that are of different configurations (e.g., one or more modules are 108A, one or more modules are 108B, one or more modules are 108C, etc.). Accordingly, the range of topologies of system 100 covered herein is broad.

[0111] In conventional systems, energy sources, typically batteries, are connected together in a non-switchable arrangement (e.g., parallel) resulting in a single output voltage (Vc_out). A conventional inverter oscillates this voltage between positive (+Vc_out) and negative (-Vc_out) and generates an AC signal that, after filtering, is output to the load or grid for each desired phase. The AC signal output by a conventional system is limited to the switching frequency of the conventional inverter. For example, high-power IGBT-based conventional inverters typically have output frequencies below 5 kHz. Conversely, system 100 uses modular converter 202 to provide switching capability for all energy sources 206, and therefore has a dynamic range that exceeds conventional systems, whether for stationary or mobile applications. In implementations where MOSFETs are used for converter 202A (FIG. 6A), the switching frequency (Fsw) of each MOSFET can be in the range of 1 kHz to 2 kHz or greater. If eight modules 108 are present in each phased array 700, the resulting frequency of the ripples in the AC output voltage will be 2Fsw×N=16 kHz to 32 kHz or greater, which allows for the injection of signals at much higher frequencies than conventional systems.

[0112] (Control methodology example) As mentioned, control of the system 100 can be implemented according to various methodologies, such as hysteresis or PWM. Some examples of PWM include space vector modulation and sinusoidal pulse width modulation, where the switching signals for the converters 202 are generated using a phase shifted carrier technique that continuously rotates the utilization of each module 108, distributing power equally among them.

[0113] 8C-8F are plots depicting an example of a phase-shift PWM control methodology that can generate multi-level output PWM waveforms using gradually shifted two-level waveforms. An X-level PWM waveform can be generated by summing (X-1) / 2 two-level PWM waveforms. These two-level waveforms can be generated by comparing a reference waveform Vref with a carrier wave that is gradually shifted by 360° / (X-1). The carrier wave is triangular, but implementations are not limited thereto. A nine-level example is shown in FIG. 8C (using four modules 108). The carrier wave is gradually shifted by 360° / (9-1)=45° and compared to Vref. The resulting two-level PWM waveform is shown in FIG. 8E. These two-level waveforms may be used as switching signals for the semiconductor switches (e.g., S1 to S6) of the converter 202. 8E, for a one-dimensional array 700 including four modules 108, each with a converter 202, the 0° signal is for S3 of the first module 108-1, the 180° signal is for its S6 control, the 45° signal is for S3 of the second module 108-2, the 225° signal is for its S6 control, the 90° signal is for S3 of the third module 108-3, the 270° signal is for its S6 control, and the 135° signal is for S3 of the fourth module 108-4, the 315° signal is for its S6 control. The signal for S3 is the complement of S4, and the signal for S5 is the complement of S6, with sufficient dead time to avoid shoot-through in each half-bridge. FIG. 8F depicts an exemplary single-phase AC waveform produced by the superposition (summation) of the output voltages from four modules 108.

[0114] An alternative is to utilize both positive and negative reference signals along with the first (N-1) / 2 carrier. A nine-level embodiment is shown in FIG. 8D. In this embodiment, the 0° to 135° switching signal (FIG. 8E) is generated by comparing +Vref to the 0° to 135° carrier of FIG. 8D, and the 180° to 315° switching signal is generated by comparing -Vref to the 0° to 135° carrier of FIG. 8D. However, the comparison logic in the latter case is reversed. Other techniques, such as a state machine decoder, may also be used to generate the gate signals for the switches of converter 202.

[0115] In a multi-phase system implementation, the same carrier wave can be used for each phase, or the set of carrier waves 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 carrier waves with the same relative offsets as shown in FIGS. 8C and 8D, but the carrier wave of the second phase is shifted 120 degrees compared to the carrier wave of the first phase, and the carrier wave of the third phase is shifted 240 degrees compared to the carrier wave of the first phase. If different reference voltages are available for each phase, phase information can be carried within the reference voltage, and the same carrier wave can be used for each phase. While in many cases the carrier frequency will be fixed, in some example implementations the carrier frequency can be adjusted, which can help reduce losses in the EV motor under high current conditions.

[0116] An appropriate switching signal can be provided to each module by the control system 102. For example, the MCD 112 can provide Vref and an appropriate carrier signal to each LCD 114 depending on the module or modules 108 that the LCD 114 controls, and the LCD 114 can then generate the switching signal. Or, all LCDs 114 in the array can provide all carrier signals, and the LCD can select the appropriate carrier signal.

[0117] The relative utilization of each module 108 may be adjusted based on the status information, as described herein, to implement one or more parameter balancing. Parameter balancing may involve adjusting utilization to minimize parameter divergence over time compared to a system in which individual module utilization adjustments are not implemented. Utilization may be the relative amount of time a module 108 is discharging when the system 100 is in a discharging state, or the relative amount of time a module 108 is charging when the system 100 is in a charging state.

[0118] As described herein, modules 108 can be balanced relative to other modules in an array 700, which may be referred to as intra-array or intra-phase balancing, and different arrays 700 can also be balanced relative to each other, which may be referred to as inter-array or inter-phase balancing. Arrays 700 of different subsystems can also be balanced relative to each other. The control system 102 can simultaneously perform any combination of intra-phase balancing, inter-phase balancing, utilization of multiple energy sources within a module, active filtering, and auxiliary load supply.

[0119] 9A is a block diagram depicting an example of an array controller 900 of the control system 102 for a single-phase AC or DC array. The array controller 900 may include a peak detector 902, a divider 904, and an intra-phase (or intra-array) balance controller 906. The array controller 900 may receive as inputs a reference voltage waveform (Vr) and status information (e.g., state of charge (SOCi), temperature (Ti), capacity (Qi), and voltage (Vi)) for each of the N modules 108 in the array and generate as outputs a normalized reference voltage waveform (Vrn) and a modulation index (Mi). The peak detector 902 detects the peak (Vpk) of Vr, which may be specific to the phase on which the controller 900 is operating and / or balancing. The divider 904 generates Vrn by dividing Vr by the detected Vpk. The intra-phase balance controller 906 uses Vpk along with status information (eg, SOCi, Ti, Qi, Vi, etc.) to generate a modulation index Mi for each module 108 in the array 700 being controlled.

[0120] The modulation index and Vrn can be used to generate a switching signal for each converter 202. The modulation index can be a number between zero and one (inclusive). For a particular module 108, a normalized reference Vrn can be modulated or scaled by Mi, and this modulated reference signal (Vrnm) can be used as Vref (or -Vref) according to the PWM techniques described with respect to FIGS. 8C-8F or 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 to S6 or S1 to S6) and thus regulate the operation of each module 108. For example, a module 108 controlled to maintain normal or full operation may receive a Mi of one, while a module 108 controlled to operate less than normal or full may receive a Mi of less than one, and a module 108 controlled to cease power output may receive a Mi of zero. This operation can be performed in a variety of ways by the control system 102, such as by the MCD 112 outputting Vrn and Mi to the appropriate LCD 114 for modulation and switch signal generation, by the MCD 112 performing the modulation and outputting the modulated Vrnm to the appropriate LCD 114 for switch signal generation, or by the MCD 112 performing the modulation and switch signal generation and outputting the switch signal directly to the LCD or converter 202 of each module 108. Vrn can be transmitted continuously, with Mi being transmitted at regular intervals, such as once per period of Vrn or once per minute.

[0121] The controller 906 can generate Mi for each module 108 using any type or combination of types of status information described herein (e.g., SOC, temperature (T), Q, SOH, voltage, current). For example, when using SOC and T, a module 108 can have a relatively high Mi if its SOC is relatively high and its temperature is relatively low compared to other modules 108 in the array 700. If either of the SOCs is relatively low or T is relatively high, that module 108 can have a relatively low Mi and result in less utilization than other modules 108 in the array 700. The controller 906 can determine Mi such that the sum of the module voltages does not exceed Vpk. For example, Vpk is the sum of the products of the voltages of each module's sources 206 and the Mi for that module (e.g., Vpk=M1V1+M2V2+M3V3...+M N V N etc. Different combinations of modulation indexes, and therefore individual voltage contributions by the modules, may be used, but the total generated voltage should remain the same.

[0122] The controller 900 can control operation so that the SOC of the energy sources within each module 108 remains balanced or, if unbalanced, converges to a balanced condition, and / or the temperature of the energy sources or other components (e.g., energy buffers) within each module remains balanced or, if unbalanced, converges to a balanced condition, as long as it does not prevent the system from achieving its power output requirements at any time (e.g., during maximum acceleration of an EV). Power flow into and out of modules can be adjusted so that capacitance differences between sources do not cause SOC deviations. SOC and temperature balancing can indirectly cause some balancing of the SOH. While voltage and current can be balanced directly if desired, in many implementations, the primary goal of the system is SOC and temperature balancing, and SOC balancing can lead to voltage and current balancing in a highly symmetrical system where modules are of similar capacitance and impedance.

[0123] Since balancing all parameters may not be possible simultaneously (e.g., balancing one parameter may further unbalance another), a combination of balancing any two or more parameters (SOC, T, Q, SOH, V, I) may be applied, with priority given to one or the other, depending on the requirements of the application. Priority in balancing may be given to SOC over the other parameters (T, Q, SOH, V, I), with exceptions being allowed if one of the other parameters (T, Q, SOH, V, I) reaches a critical unbalance condition outside the threshold.

[0124] Balancing between arrays 700 of different phases (or arrays of the same phase, e.g., if parallel arrays are used) can be performed in parallel with intra-phase balancing. FIG. 9B depicts an example of an Ω-phase (or Ω-array) controller 950 configured for operation in an Ω-phase system 100 having at least Ω arrays 700, where Ω is any integer greater than 1. The controller 950 may include one inter-phase (or inter-array) controller 910 and Ω intra-phase balance controllers 906-PA...906-PΩ for phases PA to PΩ, as well as peak detectors 902 and dividers 904 ( FIG. 9A ) for generating normalized references VrnPA to VrnPΩ from each phase-specific reference VrPA to VrPΩ. The intra-phase controller 906 may generate Mi for each module 108 of each array 700, as described with respect to FIG. 9A . The phase-to-phase balance controller 910 is configured or programmed to balance the sides of the modules 108 across the entire multidimensional system, for example, between arrays of different phases. This may be achieved through injecting common mode into the phases (e.g., neutral terminal point shift), or through the use of interconnection modules (described herein), or both. Common mode injection involves introducing phase and amplitude shifts into reference signals VrPA to VrPΩ to generate normalized waveforms VrnPA to VrnPΩ to compensate for imbalances within one or more arrays, and is further described in International Application No. PCT / US20 / 25366, incorporated herein.

[0125] Controllers 900 and 950 (and 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, partially or completely distributed among LCD 114, or may be implemented as discrete controllers independent of MCD 112 and LCD 114.

[0126] (Interconnect (IC) module example) Modules 108 can be wired between modules of different arrays 700 to exchange energy between arrays, act as sources for auxiliary loads, or both. Such modules are referred to herein as interconnect (IC) modules 108. The IC modules 108 can be implemented in any of the module configurations already described (108A, 108B, 108C) and others to be described herein. The IC modules 108 can include any number of one or more energy sources, optional energy buffers, switch circuitry for supplying energy to one or more arrays and / or power to one or more auxiliary loads, control circuitry (e.g., local control devices), and monitor circuitry for collecting status information about the IC module itself or its various loads (e.g., SOC of the energy source, temperature of the energy source or energy buffer, capacity of the energy source, SOH of the energy source, voltage and / or current measurements for the IC module, voltage and / or current measurements for the auxiliary loads, etc.).

[0127] 10A is a block diagram depicting an example embodiment of system 100 capable of producing Ω-phase power using Ω arrays 700-PA to 700-PΩ, where Ω can be any integer greater than 1. In this and other implementations, IC module 108IC can be located on the rail side of array 700 such that the array 700 to which module 108IC is wired (in this implementation, array 700-PA to 700-PΩ) is electrically wired between module 108IC and the output to the load (e.g., SIO1 to SIOΩ). Here, module 108IC has Ω IO ports for wiring from array 700-PA to IO port 2 of each 700-PΩ module 108-N. In the configuration depicted here, module 108IC can perform phase balancing by selectively wiring one or more energy sources of module 108IC to one or more of the 700-PΩ from array 700-PA (or to none or equally to all outputs if phase balancing is not required). System 100 can be controlled by control system 102 (not shown, see FIG. 1A).

[0128] FIG. 10B is a schematic diagram depicting an example of module 108IC. In this implementation, module 108IC includes energy source 206 wired to energy buffer 204, which in turn is wired to switch network 603. Switch network 603 can include switch network units 604-PA to 604-PΩ to independently wire energy source 206 to each of arrays 700-PA to 700-PΩ. Various switch configurations can be used for each unit 604, which in this implementation is configured as a half-bridge with two semiconductor switches S7 and S8. Each half-bridge is controlled by control line 118-3 from LCD 114. This configuration is similar to module 108A described with reference to FIG. 3A. As described with reference to converter 202, switch network 603 can be configured with any switch type (e.g., MOSFET, IGBT, silicon, GaN, etc.) in any arrangement suitable for the application requirements.

[0129] The switch network unit 604 has an output coupled between the positive and negative terminals of the energy source 206 and wired to an IO port of the module 108 IC. The units 604-PA through 604-PΩ are connected by the control system 102 to a voltage +V IC or -V ICto individual module I / O ports 1 through Ω. The control system 102 can control the switch network 603 according to any desired control technique, including the PWM and hysteresis techniques described herein. Here, the control circuitry 102 is implemented as an LCD 114 and an MCD 112 (not shown). The LCD 114 can receive monitoring data or status information from the monitor circuitry of the module 108 IC. This monitoring data and / or other status information derived from this monitoring data can be output to the MCD 112 for use in system control, as described herein. The LCD 114 can also receive timing information (not shown) for purposes of synchronization of the modules 108 of the system 100 and one or more carrier signals (not shown), such as sawtooth signals ( FIGS. 8C-8D ) used in PWM.

[0130] Due to phase-to-phase balance, proportionally more energy from source 206 can be delivered to any one or more of arrays 700-PA through 700-PΩ that are at a relatively low state of charge compared to other arrays 700. This complementary energy delivery to a particular array 700 allows the energy output of those cascaded modules 108-1 through 108-N within that array 700 to be reduced relative to the undelivered phase array.

[0131] For example, in some exemplary implementations applying PWM, the LCD 114 can be configured to receive (from the MCD 112) a normalized voltage reference signal (Vrn) for each of the one or more arrays 700 to which its module 108 IC is coupled, e.g., VrnPA to VrnPΩ. The LCD 114 can also receive modulation indexes MiPA to MiPΩ for switch units 604-PA to 604-PΩ from the MCD 112, respectively, for each array 700. The LCD 114 can modulate (e.g., multiply) each individual Vrn with the modulation index (e.g., VrnA is multiplied by MiA) for the switch section directly coupled to its array and then generate a control signal for each switch unit 604 using a carrier signal. In other implementations, the MCD 112 can perform the modulation and output the modulated voltage reference waveform for each unit 604 directly to the LCD 114 of the module 108 IC. In yet other implementations, all processing and modulation may occur by a single control entity, which may output control signals directly to each unit 604 .

[0132] This switching can be modulated so that power from the energy source 206 is supplied to the array 700 at appropriate intervals and durations. Such a methodology can be implemented in a variety of ways.

[0133] Based on collected status information about the system 100, such as the current capacity (Q) and SOC of each energy source in each array, the MCD 112 can determine a total charge for each array 700 (e.g., the total charge for an array can be determined as the sum of the capacities times the SOCs for each module in that array). The 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 indices MiPA to MiPΩ for each switch unit 604-PA to 604-PΩ, as appropriate.

[0134] During balanced operation, Mi per switch unit 604 can be set to a value that causes the same or similar amount of net energy to be supplied by the energy source 206 and / or energy buffer 204 to each array 700 over time. For example, Mi per switch unit 604 can be the same or similar and can be set to a level or value that causes the module 108IC to perform a net or time-averaged discharge of energy from one or more arrays 700-PA to 700-PΩ during balanced operation, such that the module 108IC drains at the same rate as the other modules 108 in the system 100. In some implementations, Mi per unit 604 can be set to a level or value that causes no net or time-averaged discharge of energy (causing a net energy discharge of zero) during balanced operation. This can be useful if the module 108IC has a lower total charge than the other modules in the system.

[0135] If an unbalanced condition occurs between arrays 700, the modulation index of system 100 can be adjusted to cause convergence toward a balanced condition or minimize further divergence. For example, control system 102 can cause module 108 to discharge more into an array 700 with a lower charge than others and cause modules 108-1 to 108-N of that lower array 700 to discharge relatively less (e.g., on a time-averaged basis). The relative net energy contributed by module 108 increases compared to modules 108-1 to 108-N of the array 700 it is assisting, and compared to the amount of net energy that module 108 contributes to other arrays. This can be accomplished by increasing Mi for the switch unit 604 feeding that low array 700, and by decreasing the modulation indexes of the modules 108-1 through 108-N of the low array 700 in a manner that maintains Vout for that low array at an appropriate or required level and keeps the modulation indexes for the other switch units 604 feeding other higher arrays relatively unchanged (or decreases them).

[0136] 10A-10B can be used alone to provide phase-to-phase or array-to-array 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 sections 604 coupled to one or more arrays. For example, a module 108IC with Ω switch sections 604 coupled to Ω different arrays 700 can be combined with a second module 108IC having one switch section 604 coupled to one array 700, such that the two modules are combined to power a system 100 having Ω+1 arrays 700. Any number of modules 108IC can be combined in this manner, each coupled to one or more arrays 700 of the system 100.

[0137] Additionally, the IC module can be configured to exchange energy between two or more subsystems of system 100. FIG. 10C is a block diagram depicting an example of system 100 with a first subsystem 1000-1 and a second subsystem 1000-2 interconnected by an IC module. Specifically, subsystem 1000-1 is configured to supply three-phase power PA, PB, and PC to a first load (not shown) using system I / O ports SIO1, SIO2, and SIO3, respectively, while subsystem 1000-2 is configured to supply three-phase power PD, PE, and PF to a second load (not shown) using system I / O ports SIO4, SIO5, and SIO6, 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.

[0138] In this implementation, each module 108IC is coupled to the first array of subsystem 1000-1 (via IO port 1) and the first array of subsystem 1000-2 (via IO port 2), and each module 108IC can be electrically wired to each other module 108IC using I / O ports 3 and 4, which are coupled to the energy source 206 of each module 108IC, as described with respect to module 108C in FIG. 3C. This wiring places the sources 206 of modules 108IC-1, 108IC-2, and 108IC-3 in parallel; thus, the energy stored and supplied by the modules 108IC is pooled together by this parallel arrangement. Other arrangements, such as serial wiring, can also be used. The modules 108IC are housed within the common enclosure of subsystem 1000-1; however, the interconnection module can be external to the common enclosure and physically located as an independent entity between the common enclosures of both subsystems 1000-1.

[0139] Each module 108IC has a switch unit 604-1 coupled to IO port 1 and a switch unit 604-2 coupled to I / O port 2, as described with respect to FIG. 10B . Thus, for balancing between subsystems 1000 (e.g., pack-to-pack or rack-to-rack balancing), a particular module 108IC can supply relatively more energy to one or both of the two arrays to which it is wired (e.g., module 108IC-1 can supply array 700-PA and / or array 700-PD). Control circuitry can monitor relative parameters (e.g., SOC and temperature) of the arrays of different subsystems and adjust the energy output of the IC modules to compensate for imbalances between arrays or phases of different subsystems, in a manner similar to compensating for imbalances between two arrays of the same rack or pack as described herein. Because all three modules 108IC are in parallel, energy can be efficiently exchanged between every array of system 100. In this implementation, each module 108 IC supplies two arrays 700, although other configurations can be used, including a single IC module for all arrays in system 100 and a configuration with one dedicated IC module per array 700 (e.g., six IC modules for six arrays, each IC module having one switch unit 604). In all cases, with multiple IC modules, energy sources can be coupled together in parallel to share energy as described herein.

[0140] In systems with IC modules between the phases, phase-to-phase balancing can also be performed by neutral terminal 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 appropriate situations under which phase-to-phase balancing should be performed using neutral terminal point shifting alone, phase-to-phase energy injection alone, or a combination of both simultaneously.

[0141] The 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 a stepped-down voltage from source 302). FIG. 10D is a block diagram depicting an example of a three-phase system 100A with two modules 108IC wired to perform phase balancing and supply auxiliary loads 301 and 302. FIG. 10E is a schematic diagram depicting this example of system 100, with emphasis on modules 108IC-1 and 108IC-2. Here, control circuitry 102 is again implemented as an LCD 114 and an MCD 112 (not shown). The LCD 114 can receive monitoring data (e.g., SOC of ES1, temperature of ES1, Q of ES1, voltage of auxiliary loads 301 and 302, etc.) from module 108IC and 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, as described with respect to FIG. 6C ) for each load 302 being supplied by that module, and each switch portion 602 can be controlled by the LCD 114, either independently or based on a control input from MCD 112, to maintain the required voltage level for the load 302. In this implementation, each module 108IC includes switch portions 602A wired together and supplying one load 302, although that is not required.

[0142] FIG. 10F is a block diagram depicting another example of a three-phase system configured to supply power to one or more auxiliary loads 301 and 302 using modules 108IC-1, 108IC-2, and 108IC-3. In this implementation, 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 simple auxiliary role and does not actively inject voltage or current into any array 700 of system 100. In this implementation, module 108IC-3 may have converters 202B, C (FIGS. 6B-6C) configured like module 108C of FIG. 3B with one or more auxiliary switch portions 602A but omitting switch portion 601. Thus, 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 implementation of system 100 is configured with additional energy to supply auxiliary loads 301 and 302 and to maintain charge on sources 206A of modules 108IC-1 and 108IC-2 through parallel wiring with sources 206 of module 108IC-3.

[0143] 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 in the system, but that is not required. For example, a relatively high capacitance may be desirable in implementations where one module 108 applies energy to multiple arrays 700 (FIG. 10A), allowing the IC module to discharge at the same rate as the modules in the phased array itself. If the module 108 also supplies an auxiliary load, even more capacitance may be desired to allow the IC module to both supply the auxiliary load and discharge at relatively the same rate as the other modules.

[0144] (Example of secondary energy source) The energy sources 206 described herein can be used in the system 100 described herein in both primary and secondary use applications. The primary use of the source 206 is the original use in which the source 206 is used. For example, a primary use application is the first implementation of the source 206 after their original manufacture (and unrefurbished) as it will be used by the original customer of the source 206. Users of the source 206 in their primary use will typically receive the source 206 from a manufacturer, distributor, or original equipment manufacturer (OEM). Batteries 206 used in primary use applications will typically have the same electrochemistry (e.g., the same variant of lithium-ion electrochemistry (e.g., LFP, NMC)), the same nominal voltage, and minimal (e.g., 5% or less) capacity variation across the pack or system. The use of an energy storage system with batteries 206 in their primary use applications will result in batteries 206 having a longer life in their primary use applications, and upon removal from their primary use applications, the batteries 206 will be similar in terms of capacity degradation to batteries from primary use applications that do not use an energy storage system.

[0145] As used herein, a "secondary use" application is any use or implementation (e.g., secondary implementation, tertiary implementation, quaternary implementation, etc.) of source 206 after the primary use application. A secondary use energy source refers to any energy source (e.g., a battery or HED capacitor) that is implemented in a secondary use application of that source.

[0146] An example of a primary use application for battery 206 is in an energy storage system for an EV. Then, at the end of its life (e.g., after 100,000 miles of driving or after a threshold amount of degradation of the batteries in the battery pack), battery 206 can be removed from the battery pack, optionally refurbished and tested, and then implemented in a secondary use application, where it may be used, for example, in a stationary energy storage system (e.g., residential, commercial, or industrial energy buffer, EV charging station energy buffer, renewable source (e.g., wind, solar, hydroelectric), energy buffer, and the like) or another mobile energy storage system (e.g., a battery pack for an electric vehicle, bus, train, or truck). Similarly, the primary use application can initially be a stationary application, and the secondary use application can be a stationary or mobile application.

[0147] For secondary use applications, sources 206 can be selected and / or utilized by system 100 to minimize (or at least reduce) any differences in initial capacity and nominal voltage. For example, sources 206 having a capacity difference of 5% or more can be included in system 100 and operated to provide energy for a load. In another example, an operator or automated system can select sources 206 for system 100 that have capacities that differ within a threshold amount, e.g., to reduce the initial capacity difference between the sources of system 206. If a module 108 is compatible with both primary and secondary use applications (e.g., with or without reconfiguration), the module 108 can be selected for secondary use applications based on the capacity difference of the sources 206 of the module 108.

[0148] System 100 can individually adjust the utilization of each source 206 so that the sources 206 in system 100 or a pack of system 100 are relatively balanced in terms of SOC or total charge (SOC x capacity) as the pack or system 100 is discharged, even though the sources 206 within system 100 may have widely varying capacities. Similarly, system 100 can maintain balance as the pack or system 100 is charged. Sources 206 can vary not only in terms of capacity, but also in terms of nominal voltage, power rating, electrochemistry type (e.g., a combination of LFP and NMC batteries), and the like. Thus, system 100 can be used such that all modules 206 in system 100 or each pack of system 100 are secondary energy sources (or a combination of primary and secondary energy sources is used) with various combinations of different characteristics.

[0149] In one example, system 100 may include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) that has an energy capacity variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0150] In another example, system 100 can include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) having an energy capacity / mass density variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0151] In another example, the system 100 may include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) that has a peak power / mass density variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0152] In another example, system 100 may include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) that has a nominal voltage variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0153] In another example, system 100 may include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) that has an operating voltage range variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0154] In another example, the system 100 may include a secondary utilization energy source 206 (and optionally one or more primary utilization energy sources 206) that has a maximum specified current rise time variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0155] In another example, the system 100 may include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) that has a specified peak current variation of 2% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more, 30% or more, 5-30%, 10-30%, and / or 20-30%.

[0156] A variation of X% (e.g., 5% or more, or 5-30%) can be satisfied by the variation between the module 108 with the highest value for that parameter and the module 108 with the lowest value for that parameter within the system 100. For example, a variation of 5% or more in capacity can be satisfied by the system 100, with the module 108 with the lowest capacity source 206 having 95% or less of the capacity of the module 108 with the highest capacity source 206. For any embodiment and parameter disclosed herein, the time at which a system 100 having one or more secondary utilization sources satisfies the X% variation condition in that parameter may be upon installation of the system 100, upon start-up of the system 100, after replacing one source 206 with another, after 10 or more hours of operation of the system 100, after 100 or more hours of operation of the system 100, after 1,000 or more hours of operation of the system 100, and / or after 10,000 or more hours of operation of the system 100. For example, a 5% or greater capacity variation may occur after the system 100 has been operated for 1,000 hours, even if no capacity variation was present at the start-up. This reflects the ability of an embodiment of the system 100 to continue operating and account for capacity differences between sources 206 that increase over time of operation.

[0157] In another example, system 100 may include secondary use energy source 206 (and optionally one or more primary use energy sources 206) with a variety of electrochemical types (e.g., non-lithium ion batteries or lithium ion batteries with different lithium ion batteries (e.g., NMC, LFP, LTO, or any combination of other lithium ion battery types)).

[0158] System 100 can include a secondary use energy source 206 (and optionally one or more primary use energy sources 206) having any combination of the characteristics provided in the preceding examples.

[0159] (Example of islanding state detection) 11A is a block diagram depicting an example of a grid-connected system 1100 in which an energy system 100 is connected to a load 101, such as auxiliary load 301 or 302 in FIG. 10E, and a grid 1130. System 100 may include MCD 112 and modules 108, which may be arranged in one or more arrays 700, as described above in connection with FIGS. 10A-10F. Any of the implementations of system 100 described herein may be used in grid-connected system 1100.

[0160] The system 100 is connected to the load 101 and the grid 1130 using circuit contacts 1115. The system 100 is configured to provide power to the load 101 and / or the grid 1130. The system 100 can also receive power from the grid 1130. In this example, the system 100 and the load 101 can be referred to as a microgrid that is connected to the grid 1130. The grid 1130 can be a utility power grid that also provides power to the microgrid load 101.

[0161] System 100 can be configured to operate in multiple modes. One example mode is a grid-tied mode, which may also be referred to as a grid-following mode. When system 100 is connected to grid 1130 and grid 1130 is operating normally, e.g., without an error or other condition that would cause system 100 to disconnect from grid 1130, system 100 can operate in the grid-tied mode, where system 100 follows the voltage, frequency, and phase of the power grid 1130 while regulating the amount of current provided to load 101. In other words, system 100 can provide AC power (e.g., a single-phase AC signal or a poly-phase AC signal) to load 101 with regulated current at the same voltage, frequency, and phase as one or more AC signals provided by grid 1130.

[0162] Another example mode is a standalone mode, in which the system 100 supplies the load 101 with a voltage whose frequency, amplitude, and / or phase may differ from that of the grid 1130. When the system 100 detects an error or other condition that causes the system 100 to be configured to disconnect from the grid 1130, such as an islanding or islanding condition, the system 100 can disconnect from the grid 1130 and operate in a standalone mode. An example of an islanding condition is a power outage or other short- or long-term loss of power from the grid 1130. During an islanding condition, the system 100 may still provide power to the grid 1130, which is unsafe, until it disconnects from the grid 1130. The system 100 can disconnect from the grid 1130 and continue to provide power to the load 101 in a standalone mode. In the standalone mode, the system 100 can act as a voltage controller and regulate the voltage provided to the load 101. The system 100 can adjust the voltage provided to the load 101 so that the voltage, frequency, and phase of the AC power provided to the load 101 matches the last known voltage, frequency, and phase of the grid 1130 before the system 100 was disconnected from the grid 1130.

[0163] The system 100 can also be configured to operate in other modes. For example, the system 100 can be configured to operate in a grid-tied rectifier mode or a grid-tied charger / discharger mode. The grid-tied rectifier mode is a mode in which the system 100 is connected to the grid 1130 and the modules 108 of the system 100 regulate the DC bus voltage and provide power to the DC loads 101. The grid-tied charger / discharger mode is a mode in which the system 100 is connected to the grid 1130 and the modules 108 of the system 100 regulate the charge or discharge current to charge or discharge the energy source 206.

[0164] 11B is an electrical equivalent diagram depicting an example of a grid-connected system 1100 in which the energy system 100 is connected to a microgrid load 101 and a grid 1130. The system 100 includes an output filter 1112 configured to filter the voltage output by all of the modules 108 of the system 100 and provide a precise and accurate output voltage. The filtered output voltage is connected to the load 101 and the grid 1130 at nodes 1113-1 and 1113-2, which may include terminals. To measure the output impedance of the system 100, and therefore the output impedance of the modules 108 of the system 100, the voltage across points 1113-1 and 1113-2 can be measured, along with the current flowing between points 1113-1 and 1113-2. The ratio of the voltage across points 1113-1 and 1113-2 to the current flowing between points 1113-1 and 1113-2 provides the impedance of load 101 when contact 1115 is closed. As described herein, this output impedance of system 100 can be used to detect an islanding condition for system 100.

[0165] The contacts 1115 can be switched between a closed state, which allows current flow, and an open state, which blocks current flow. The contacts 1115 include a main contact 1115-1 configured to connect and disconnect the system 100 to both the load 101 and the grid 1130 (depending on the states of contacts 1115-2 and 1115-3). Contact 1115-2 is configured to connect and disconnect the load 101 to the system 100 and the grid 1130 (depending on the states of contacts 1115-1 and 1115-3). Contact 1115-3 is configured to connect and disconnect the grid 1130 to the system 100 and the load 101 (depending on the states of contacts 1115-1 and 1115-2).

[0166] The MCD 112 of the system 100 is communicatively coupled to the contactor 1115 and can control the operation of the contactor 1115. The MCD 112 can issue control signals that cause the contactor 1115 to selectively open or close in any combination depending on the operating mode of the system 100 and / or the status of the system 100, the load 101, or the grid 1130. For example, if the system 100 detects an islanding condition, the MCD 112 can open the contactor 1115-3, disconnecting the system 100 and the load 101 from the grid 1130. The MCD 112 can also transition to a standalone operating mode in response to detecting the islanding condition.

[0167] The load 101 has an impedance that may be represented by a resistor, a capacitor, and / or an inductor, depending on the type of load connected to the system 100. Similarly, the grid 1130 has an impedance that may be represented by a resistor and an inductor. The impedance of the grid 1130 may vary based on the quality of the grid 1130 and the current state of the grid 1130, for example, whether power is present on the grid 1130.

[0168] 12A is a block diagram depicting an example of the MCD 112. The MCD 112 includes a primary controller 1210, an islanding detector 1220, a fundamental frequency reference signal generator 1225-1, several harmonic frequency reference signal generators 1225-2 through 1225-N, and a signal combiner 1250. In some implementations, the islanding detector 1220 can be distributed throughout the LCD 114. Additionally or alternatively, a single adjustable generator can generate multiple harmonic frequencies. The MCD 112 can include other components described herein. The primary controller 1210 and each reference signal generator 1225 can be implemented in hardware, e.g., by processing circuitry described herein, in software, e.g., using software modules and / or routines in conjunction with specific functions, or in a combination of hardware and software.

[0169] In general, the MCD 112 generates and transmits control information to the modules 108 of the system 100. The control information may include a normalized reference signal Vrn for each module 108 of the system 100 and a modulation index Mi for each module 108. The normalized reference signal may be the same for each module 108 in the array 700, while the modulation index Mi may be different for different modules 108 in each array 700. In some implementations, the control information includes a modulated reference signal. For example, the MCD 112 may use the modulation index Mi to scale or modulate the normalized reference signal Vrn for each module 108.

[0170] The normalized reference signal can be a normalized reference voltage waveform (Vrn) or a normalized reference current waveform (Irn). For a particular module 108, the normalized reference signal Vrn can be modulated or scaled by Mi, and this modulated reference signal Vrnm can be used as Vref (or −Vref) according to the PWM techniques described with reference to Figures 8C-8F or other techniques. Similarly, for a particular module 108, the normalized reference current waveform Irn can be modulated or scaled by Mi, and this modulated reference signal Irnm can be used as Vref (or −Vref) according to the PWM techniques described with reference to Figures 8C-8F or other techniques.

[0171] The MCD 112 can transmit control information to the modules 108 of the system 100 on an ongoing basis, e.g., permanently or periodically, and the control information can change over time based on any changing status of the modules 108 or requirements of the load 101. To detect when the system 100 is under an islanding condition, the MCD 112 can insert a disturbance signal into the control information, e.g., into the normalized reference signal Vrn or Irn, that causes the modules 108 of the system 100 to inject disturbance currents at harmonic frequencies onto the output of the system 100. For example, the modulated reference signal can be in the form of an AC voltage or current waveform having a component at a fundamental frequency and a component at a harmonic frequency. Generally, the fundamental frequency reference signal generator 1225-1 generates the fundamental frequency component of the normalized reference signal, and one or more harmonic frequency signal generators 1225-2 through 1225-N generate the harmonic frequency components of the normalized reference signal. In some implementations, a single reference signal generator can generate both fundamental and harmonic frequency components of the normalized reference signal. The fundamental frequency component can include an AC waveform at the fundamental frequency, and the harmonic frequency component can include one or more AC waveforms at various harmonic frequencies. As described in further detail herein, the islanding detector 1220 can determine the output impedance of a module 108 of the system 100 at one or more harmonic frequencies and use this impedance to determine whether the system 100 is experiencing an islanding condition.

[0172] The primary controller 1210 may generate a reference signal for the fundamental frequency reference signal generator 1225-1 based on, for example, the power requirements of the load 101. Depending on the operating mode, this reference signal may be a voltage reference signal or a current reference signal. The modes may include, for example, a grid-tied mode and a standalone mode.

[0173] The primary controller 1210 may include one or more balance controllers. In a single-array implementation, the primary controller 1210 may include a controller similar to the controller 900 of FIG. 9A. However, the primary controller 1210 may be configured to output a reference signal rather than a normalized reference signal, for example, by not dividing the reference signal by its peak prior to outputting the reference signal. The primary controller 1210 may include an in-phase balance controller 906, which is configured to generate modulation indexes Mi for the modules 108 of the array 700 based on status information, as described herein.

[0174] In a multi-phase implementation including multiple arrays 700, the primary controller 1210 may include a controller similar to the controller 950 of FIG. 9B . However, the primary controller 1210 may be configured to output a reference signal for each array 700 rather than a normalized reference signal for each array, for example, by not dividing the reference signal for each array 700 by the peak for the array 700. The primary controller 1210 may include inter-phase balance controllers 910 and individual intra-phase balance controllers 906 for the multiple arrays 700 to generate a modulation index for each module 108 of each array 700 based on status information, as described herein. The primary controller 1210 may generate the modulation index Mi in any of the modes of the system 100. In some implementations, the various controllers of FIGS. 9A and 9B , e.g., the controller 900, the inter-phase balance controller 910, the intra-phase balance controller 906, and the controller 950, may be combined into a single controller.

[0175] In the grid-tied mode, the MCD 112 controls the modules 108 to output AC waveforms having voltages, frequencies, and phases that match those of the grid 1130. The MCD 112 also adjusts the current of the AC waveforms output by the modules 108 based on the power requirements of the loads 101. In some implementations, the system 100 includes a phase-locked loop (PLL) (not shown) coupled to the grid 1130, the phase-locked loop having a phase detector and outputting a voltage reference signal to the MCD 112. The voltage reference signal can have a voltage, frequency, and phase that is based on the voltage, frequency, and phase of the grid 1130. The primary controller 1210 can receive the voltage reference signal from the PLL. In some implementations, the MCD 112 can include a PLL.

[0176] The system 100 may also receive voltage and current measurements from voltage and current sensors (not shown) electrically coupled to the grid. These sensors may report voltage and current measurements to corresponding inputs of the system 100 that indicate the current voltage and current of the grid 1130. The MCD 112 or another suitable component of the system 100 may generate a voltage reference signal having a voltage, frequency, and phase that is based on the voltage, frequency, and phase of the grid 1130. For example, the MCD 112 may generate the voltage reference signal using frequency and phase measurements received from a phase detector of the PLL and voltage and current measurements received from the voltage and current sensors.

[0177] To regulate the current, the primary controller 1210 can generate a current reference signal based on the power requirements of the load 101 and provide the current reference signal to the fundamental frequency reference signal generator 1225-1. The current reference signal can be in the form of an AC current waveform. The fundamental frequency reference signal generator 1225-1 can be configured to generate a voltage reference signal Vrf at a fundamental frequency for the system 100 to regulate the output current of the system 100. The fundamental frequency voltage reference signal Vrf can be in the form of an AC voltage waveform. Generally, the fundamental frequency reference signal generator 1225-1 can use a closed-loop control technique, e.g., one or more controllers, to generate the fundamental frequency voltage reference signal Vrf based on the current reference signal and an actual measurement of the output current of the system 100. An exemplary closed-loop control technique is described with reference to FIG. 12B . The fundamental frequency reference signal generator 1225 outputs the fundamental frequency voltage reference signal Vrf to the signal combiner 1250. The operation of harmonic frequency signal generators 1225-2 through 1225-N may be similar to that of fundamental frequency reference signal generator 1225-1, except that the frequencies are different.

[0178] Signal combiner 1250 is configured to combine fundamental frequency voltage reference signal Vrf and any harmonic frequency voltage reference signals output by harmonic frequency signal generators 1225-2 through 1225-N. For example, signal combiner 1250 can generate combined voltage reference signal Vrc by summing the individual voltage reference signals.

[0179] The signal combiner 1250 may normalize the combined voltage reference signal Vrc, for example, by dividing it by the peak voltage of the fundamental frequency voltage reference signal Vrf to generate a normalized voltage reference signal Vrn. The signal combiner 1250 transmits control information to each module 108 in the system 100. The control information for a module 108 may include the normalized reference signal for the module 108 and a modulation index. The signal combiner 1250 may transmit the control information for the module 108 to the LCD 114. As described herein, the LCD 114 may control the switches of the module 108 based on the reference signal and the modulation index.

[0180] In some implementations, the signal combiner 1250 generates, for each module 108, a modulated reference signal by scaling or modulating the normalized reference signal Vrn for the module 108 using the modulation index Mi for the module 108. In this example, the control information for the module 108 may include the modulated reference signal for the module 108.

[0181] In standalone mode, the MCD 112 controls the modules 108 of the system 100, each outputting an AC waveform having a voltage, frequency, and phase that matches the final, e.g., normal, voltage, frequency, and phase, of the grid 1130. In standalone mode, the MCD 112 can operate, for example, as a voltage regulator rather than a current regulator as in grid-tied mode. The primary controller 1210 or other portions of the MCD 112 can monitor and record the voltage, frequency, and phase of the AC signal received from the grid 1130. As described in more detail below, in response to detecting an islanding condition and disconnecting from the grid 1130, the primary controller 1210 can determine final measurements of the grid 1130's last normal voltage, frequency, and phase, e.g., before the grid 1130 lost power, compared to operating range requirements to determine the last normal condition, if necessary, and control the modules 108 of the system 100 to output AC waveforms having voltages, frequencies, and phases that match the last normal voltage, frequency, and phase of the grid 1130. In some implementations, the controller 1210 can consider voltage, frequency, and phase measurements over a short period of time, e.g., 10 seconds or 30 seconds, prior to the islanding condition using a moving central tendency value, e.g., the mean or median. For simplicity, the last normal voltage, frequency, and phase may also be referred to as the last normal values ​​of the grid 1130.

[0182] To regulate the voltage, the primary controller 1210 can generate a voltage reference signal based on the last normal value of the grid 1130 and provide the voltage reference signal to the fundamental frequency reference signal generator 1225-1. The voltage reference signal can be in the form of an AC voltage waveform. The fundamental frequency reference signal generator 1225-1 can be configured to generate a voltage reference signal Vrf at a fundamental frequency for the system 100 to regulate the output voltage of the system 100. Generally, the fundamental frequency reference signal generator 1225-1 can generate the fundamental frequency voltage reference signal Vrf based on the voltage reference signal and an actual measurement of the output voltage of the system 100 using a closed-loop control technique. An exemplary closed-loop control technique is described with reference to FIG. 12B . The fundamental frequency reference signal generator 1225 outputs the fundamental frequency voltage reference signal Vrf to the signal combiner 1250.

[0183] Signal combiner 1250 can operate in either mode, such as a grid-tied mode or a standalone mode, which may also be referred to as an islanding mode or a grid-forming mode. Islanding mode refers to when system 100, e.g., a battery energy storage system (BESS) and load 101, are disconnected from grid 1130, but system 100 and load 101 may still be connected to each other. In either mode, signal combiner 1250 can combine fundamental frequency voltage reference signal Vrf and any harmonic frequency voltage reference signals output by harmonic frequency signal generators 1225-2 through 1225-N, as described above.

[0184] The presence of switching dead times within modules 108 of the system 100 can cause the appearance of harmonics that distort the output waveform. For example, switching dead times can result in the appearance of third and fifth harmonics on the output waveform of a module 108. In some implementations, switching dead times can vary between modules 108. Due to the cascaded nature of the modules 108, these harmonics can accumulate and should be compensated for, if applicable. If a particular harmonic, e.g., the fifth harmonic, is not fully compensated for, it is possible to identify its effect on the output waveform. When switching dead times vary between modules 108, various switching dead times can be used to determine how to compensate for each harmonic. The effect of compensating for accumulated harmonics can be used to calculate an approximation of the output impedance of the system 100, which can be used to detect islanding conditions. For example, accumulated harmonics can introduce harmonic currents into the output of a module 108. The output impedance at the fifth harmonic frequency can be calculated as the ratio of the output voltage of system 100 at the fifth harmonic frequency to the output current of system 100 at the fifth harmonic frequency. When system 100 is connected to an electric utility utility via grid 1130, the fifth harmonic output impedance is very low. In contrast, the fifth harmonic output impedance is very high when the electric utility utility is not providing AC power to system 100 and load 101 using grid 1130. In some implementations, higher harmonic frequencies (e.g., fifth, seventh, ninth, etc.) enable faster detection of islanding conditions.

[0185] Islanding detector 1220 is configured to cause some or all of the modules 108 in system 100 to generate a disturbance signal and then measure the impedance at the output of the modules 108 while the disturbance signal is present. To do so, islanding detector 1220 is configured to cause one or more harmonic frequency reference signal generators 1225-2 through 1225-N to generate and output harmonic frequency voltage reference signals to signal combiner 1250.

[0186] The islanding detector 1220 can be configured to cause the module 108 of the system 100 to periodically generate a disturbance signal based on a defined islanding detection period. In other words, the module 108 of the system 100 does not have to continuously generate a disturbance signal. Instead, the module 108 can periodically generate a disturbance signal so that the islanding detector 1220 can evaluate whether an islanding condition exists during each period in which the disturbance signal is generated. For example, the module 108 can generate a disturbance signal at a frequency of 5 Hz with an amplitude of 0 to 1 A. Because harmonic currents can increase THD, generating a disturbance signal periodically rather than continuously can reduce the THD of the module 108 output compared to a continuous disturbance signal, e.g., by 10%. Additionally, generating the disturbance signal periodically allows the disturbance signal to have a higher amplitude, which improves the accuracy of islanding detection while still dissipating the same average power.

[0187] The islanding detector 1220 can transmit a disturbance reference signal to one or more harmonic frequency reference signal generators 1225-2 to 1225-N using a specified islanding detection period and using a specified disturbance duty cycle. For example, the islanding detector 1220 can use the specified islanding detection period to determine an upper limit on the duration of the disturbance reference signal. For example, determining the upper limit can include setting the upper limit to 75%, 90%, or some other value of the specified islanding detection period. Setting an upper limit on the duration of the disturbance reference signal can ensure that enough disturbance reference signal can be detected for correct recognition. As another example, the islanding detector 1220 can use a specified disturbance duty cycle to determine an upper limit on the frequency at which to inject the disturbance reference signal. In some implementations, the duty cycle is 50%. The islanding detection period can represent the amount of dead time between injections of disturbance current. For example, assume that islanding detector 1220 is configured to cause harmonic frequency reference signal generator 1225-2 to output a harmonic frequency voltage reference signal to signal combiner 1250. In a 50% duty cycle embodiment, islanding detector 1220 transmits a disturbance reference signal to harmonic frequency reference signal generator 1225-2 for a periodic time that coincides with a defined islanding detection period. In a particular embodiment, the defined islanding detection period may be 25 milliseconds (ms). In this embodiment, for every recurring 50 ms period, islanding detector 1220 transmits the disturbance reference signal to harmonic frequency reference signal generator 1225-2 for a sustained 25 ms period and does not transmit the disturbance reference signal to harmonic frequency reference signal generator 1225-2 for a sustained 25 ms period. Thus, for each 50 ms period, module 108 generates a disturbance signal at the harmonic frequency of harmonic frequency reference signal generator 1225-2 for 25 ms and does not generate a disturbance signal for 25 ms.

[0188] Other suitable islanding detection periods and duty cycles can also be used. For example, a shorter duty cycle can be used to further reduce THD. In another example, in implementations where faster islanding detection is required or desired, a longer duty cycle can be used and / or multiple impedance measurements can be generated per injection of disturbance current.

[0189] In some implementations, all modules 108 in the system 100 generate a portion of the disturbance signal output by the system 100 and used for islanding detection. In some implementations, a suitable subset of all modules 108 in the system 100 generate individual portions of the disturbance signal. For example, the signal combiner 1250 can be configured to combine the harmonic frequency voltage reference signal and the fundamental frequency voltage reference signal Vrf only for the modules 108 in the appropriate subset. For other modules 108, the signal combiner 1250 can normalize the fundamental frequency voltage reference signal Vrf and include this normalized reference signal Vrn in the control information for the other modules 108. The subset can be selected based on module efficiency, temperature, or status, for example, to select more efficient modules, cooler modules, or not select modules in bypass mode.

[0190] In one example, the islanding detector 1220 may be configured to evaluate whether an islanding condition exists based on the output impedance of the module 108 of the system 100 at the fifth harmonic frequency when the disturbance signal is output by the module 108. Other suitable harmonic frequencies may alternatively be used. The islanding detector 1220 may receive data indicative of the output impedance for each islanding detection period and compare the output impedance to an impedance threshold. If the output impedance meets the impedance threshold, for example, by equalizing or exceeding the impedance threshold, the islanding detector 1220 may determine that an islanding condition exists and notify the primary controller 1210. If the output impedance does not meet the impedance threshold, the islanding detector 1220 may determine that an islanding condition does not exist. If an islanding condition exists, the primary controller 1210 may transition from the grid-tied mode to the standalone mode.

[0191] To improve the accuracy of islanding detection, the islanding detector 1220 can obtain baseline impedance measurements at frequencies that are harmonic frequencies of the disturbance signal. In some implementations, the disturbance signal includes two or more harmonic frequencies, for example, both the third and fifth harmonic frequencies. The baseline impedance measurements are measurements of the impedance of the output of the module 108 of the system 100 when the disturbance signal is not being output by the module 108. The islanding detector 1220 can use the baseline impedance measurements when determining whether an islanding condition exists. For example, the islanding detector 1220 can compare the output impedance of the module 108 when the disturbance signal is present to the sum of the baseline impedance measurement and an impedance threshold. In this manner, the islanding detector 1220 can determine that an islanding condition exists when the output impedance is at least a threshold amount above the baseline impedance measurement.

[0192] The MCD 112 can cause the modules 108 to output disturbance signals, e.g., disturbance voltages and / or disturbance currents, at a specified harmonic frequency, e.g., the fifth harmonic frequency. The islanding detector 1220 can receive data indicating the output impedance of the system 100, e.g., the output impedance of the modules 108 of the system 100, at the specified harmonic frequency. In some implementations, the specified harmonic frequency can be selected in real time by a user. If the measured impedance exceeds an impedance threshold, the MCD 112 can determine that an islanding condition exists. In some implementations, the system 100 includes an integrator that integrates the total impedance across all modules (see FIG. 11B) corresponding to one or more harmonic frequency reference signals over a predetermined period of time.

[0193] In some implementations, measurements of the impedance of individual modules 108 are used to determine that an islanding condition has occurred. For example, the LCD 114, rather than the MCD 112, may use measurements of the impedance of one or more modules 108 compared to a particular impedance threshold for the one or more modules 108 to detect an islanding condition in one or more modules 108. In these cases, only a subset of the modules 108 may receive the disturbance reference signal.

[0194] In some implementations, distributed impedance measurements can improve system reliability. For example, instead of shutting down a current or voltage sensor in system 100 that communicates with MCD 112 if it is not working properly, system 100 can rely on the sensor that communicates with each LCD 114. As another example, when impedance measurements for one or more modules 108 disagree, MCD 114 can invoke an algorithm to determine an impedance measurement based on the differing impedance measurements.

[0195] In this example, the MCD 112 includes several harmonic frequency reference signal generators 1225-2 through 1225-N for N-1 harmonic frequencies. In some implementations, the MCD 112 may include a harmonic frequency reference signal generator 1225 for a single harmonic frequency used for islanding detection. In some implementations, the MCD 112 includes multiple harmonic frequency reference signal generators 1225-2 through 1225-N to provide flexibility in using harmonic frequencies where multiple harmonic frequencies operate to best detect islanding conditions for a particular grid 1130. Any suitable harmonic frequencies can be used. For example, the MCD 112 may allow the system 100, a user, or an external system 104 communicatively coupled to the MCD 112 to select harmonic frequencies to use in detecting islanding conditions. In response, the MCD 112 can adjust the command from the islanding detector 1220 to cause the harmonic frequency reference signal generator 1225 to generate a reference signal for the selected harmonic frequency.

[0196] Each harmonic frequency reference signal generator 1225-2 through 1225-N is configured to generate a harmonic frequency voltage reference signal based on the disturbance reference signal received from the islanding detector 1220. The disturbance reference signal can be in the form of an AC waveform at the harmonic frequency having a target amplitude. The primary controller 1210 can receive the target amplitude from a user or from the external system 104. In another example, the system 100, e.g., the islanding detector 1210, can determine the target amplitude based on the characteristics of the grid 1130 at the harmonic frequencies and / or the output impedance of the system 100, e.g., when the grid 1130 is healthy.

[0197] Each harmonic frequency voltage reference signal can be an AC voltage waveform having a particular harmonic frequency. For example, fifth harmonic frequency reference signal generator 1225-3 can be configured to generate and output an AC voltage waveform at a fifth harmonic frequency of the fundamental frequency of system 100 as the harmonic frequency voltage reference signal. Each harmonic frequency reference signal generator 1225-2 through 1225-N can be configured to generate and output a harmonic frequency voltage reference signal having a different harmonic frequency from each other harmonic frequency reference signal generator 1225-2 through 1225-N.

[0198] Generally, the amplitude of the harmonic frequency voltage reference signal may be significantly less than the amplitude of the fundamental frequency voltage reference signal Vrf for islanding detection when utility power is present on the grid 1130 because the impedance of the grid 1130 at harmonic frequencies is very low. For example, the amplitude of the harmonic frequency voltage reference signal may be less than 5%, e.g., 2% or less, of the amplitude of the fundamental frequency voltage reference signal. Other suitable ratios or percentages may also be used. Thus, a slight increase in impedance at harmonic frequencies may indicate when utility power is no longer present on the grid 1130.

[0199] The islanding detector 1220 may initially obtain a baseline impedance measurement prior to applying the disturbance signal. The islanding detector 1220 may also obtain baseline impedance measurements periodically, for example, between successive injections of the disturbance signal. In this manner, the islanding detector 1220 may use the most recent baseline impedance measurement to dynamically account for any changes to the state of the grid 1130 that affect the baseline impedance at harmonic frequencies.

[0200] The islanding detector 1220 can also dynamically adjust the harmonic frequency at which the disturbance signal is generated. The output of the islanding detector 1220 can be communicatively coupled to the input of each of the harmonic frequency reference signal generators 1225-2 through 1225-N. The islanding detector 1220 can selectively provide the disturbance reference signal to one or more of the harmonic frequency reference signal generators 1225-2 through 1225-N, causing the one or more of the harmonic frequency reference signal generators 1225-2 through 1225-N to generate their respective harmonic frequency voltage reference signals.

[0201] Dynamically adjusting the harmonic frequency allows the islanding detector 1220 to adjust for changing grid conditions and / or obtain more accurate impedance measurements for more accurate islanding detection. For example, if the baseline impedance at a particular harmonic frequency is high, e.g., above a threshold, or unstable, e.g., changing by at least a threshold amount within a period of time, the islanding detector 1220 can switch to a different harmonic frequency for islanding detection. In another example, if faster islanding detection is required or desired, a higher harmonic frequency can be used.

[0202] If an islanding condition is detected, the islanding detector 1220 can notify the primary controller 1210 that an islanding condition exists. In response, the primary controller 1210 can transition the system 100 from the grid-tied mode to the stand-alone mode. For example, the primary controller 1210 can issue a control signal to the contactor 1115 to disconnect the system 100 from the grid 1130, as described with reference to FIGS. 11A-11B . Additionally, the primary controller 1210 can determine the last normal voltage, frequency, and phase of the grid 1130 and control the modules 108 of the system 100 to output AC waveforms having voltages, frequencies, and phases that match the last normal voltage, frequency, and phase of the grid 1130.

[0203] The primary controller 1210 can also transition the system 100 from standalone mode to grid-tied mode when the grid 1130 returns to normal, e.g., when utility power is restored to the grid 1130. For example, the primary controller 1210 can issue a control signal to the contactor 1115 to reconnect the system to the grid 1130, as described with reference to FIGS. 11A-11B . Additionally, the primary controller 1210 can obtain data indicative of the voltage, frequency, and phase of the grid 1130, e.g., using a PLL, as described above, and control the module 108 to output an AC waveform having a voltage, frequency, and phase that match the current voltage, frequency, and phase of the grid 1130, respectively. The primary controller 1210 can also control the module 108 to regulate the current to the load 101, as described herein.

[0204] The primary controller 1210 can receive data from the external system 104 indicating that the grid 1130 has returned to normal. The islanding detector 1220 can also be configured to determine when the grid 1130 has returned to normal. For example, when the grid 1130 and the system 100 are reconnected, the islanding detector 1220 can receive data indicating the impedance of the grid 1130 at one or more harmonic frequencies and compare the impedance to an impedance threshold. If the impedance of the grid 1130 at the harmonic frequencies is less than the impedance threshold, the islanding detector 1220 can determine that the grid 1130 has returned to normal and notify the primary controller 1210. The use of an impedance threshold reflects that the grid 1130 ideally has a low impedance, allowing the grid 1130 to supply power to a wide area without voltage collapse. Thus, exceeding the impedance threshold generally indicates that there is some kind of fault in the grid 1130.

[0205] The MCD 112 or the external control device 104 may provide a user interface, e.g., a graphical user interface (GUI), that allows a user to adjust various parameters of the MCD 112. For example, the MCD 112 may provide a user interface that allows a user to specify one or more harmonic frequencies at which a disturbance signal is generated, an impedance threshold, an islanding detection period, and / or a disturbance reference signal amplitude.

[0206] In a multi-phase implementation, the MCD 112 can be configured to output a disturbance signal on any of the arrays 700, e.g., one array 700, some but not all arrays 700, or all arrays 700. For example, the fundamental frequency reference signal generator 1225-1 can be configured to generate a separate fundamental frequency voltage reference signal Vrf for each array 700. The signal combiner 1250 can be configured to combine the harmonic frequency voltage reference signal and the fundamental frequency voltage reference signal Vrf for one array 700 or the fundamental frequency voltage reference signal Vrf for multiple arrays 700. The islanding detector 1220 can output a disturbance signal and receive impedance measurements for each array 700, compare the impedance measurements to an impedance threshold, and detect when an islanding condition exists.

[0207] In some implementations, each module 108 that outputs a portion of the disturbance signal may output the disturbance signal at the same amplitude as each other module 108 that outputs a portion of the disturbance signal. In other words, balance may not be applied to the disturbance signal in this case. For example, the signal combiner 1250 may be configured to generate a modulated reference signal for each module 108 based on the normalized reference signal Vrn and a modulation index for the module 108. The signal combiner 1250 may then combine the modulated reference signal and the harmonic frequency voltage reference signal such that the modulation index is not applied to the harmonic frequency voltage reference signal.

[0208] FIG. 12B is a block diagram depicting an example MCD 112. Compared to FIG. 12A, FIG. 12B depicts a more integrated control structure, which can, for example, result in more dynamic voltage control and provide current limiting capabilities. MCD 112 includes harmonic frequency reference signal generators 1225-2 through 1225-N. Each harmonic frequency reference signal generator 1225-2 through 1225-N includes both a harmonic voltage controller and a harmonic current controller, collectively referred to as a harmonic controller. The harmonic frequency reference signal generator 1225-2 includes a third harmonic frequency reference signal generator 1230-2 configured to generate a harmonic frequency voltage reference signal at the third harmonic of the fundamental frequency, and the fifth harmonic frequency reference signal generator 1225-3 includes a fifth harmonic frequency reference signal generator 1230-3 configured to generate a harmonic frequency voltage reference signal at the fifth harmonic of the fundamental frequency.

[0209] In this embodiment, MCD 112 includes harmonic frequency reference signal generators 1225-2 through 1225-N for odd harmonics, e.g., from the third harmonic through the fifth harmonic up to the Mth harmonic. However, MCD 112 can also include harmonic frequency reference signal generators for even harmonics or a combination of odd and even harmonics. For which harmonic frequency reference signal generators are included, harmonics may be relied upon to perform well for harmonic noise suppression and / or islanding detection.

[0210] In this exemplary implementation, each reference signal generator 1225 includes, for example, an outer voltage controller 1230 and an inner current controller 1240, and includes a multi-loop controller that controls the various closed-circuit loops in FIG. 12A , e.g., where a signal passes from the outer voltage controller 1230 to the inner current controller 1240. For example, the fundamental frequency reference signal generator 1225-1 includes an outer fundamental voltage controller 1230-1 and an inner fundamental current controller 1240-1. Similarly, the fifth harmonic frequency reference signal generator 1230-3 includes an outer fifth harmonic voltage controller 1230-3 and an inner fifth harmonic current controller 1240-3. Each multi-loop controller can be implemented in hardware (e.g., by processing circuitry described herein), software (e.g., using software modules and / or routines in conjunction with specific functions), or a combination of hardware and software.

[0211] In general, the multi-loop controller of each reference signal generator 1225 can be operated in current control mode or voltage control mode. In current control mode, the voltage loop controller 1230 can be disabled such that the current controller 1240 generates an output AC voltage waveform having a particular frequency, e.g., at a fundamental frequency for current controller 1240-1, based on an error representing the difference between a reference current, e.g., an error set point, and an actual current, e.g., a feedback, at the output of the system 100 at a particular frequency.

[0212] In some implementations, the voltage controller 1230 generates an output AC voltage waveform based on an error instead of the current controller 1240. In these implementations, the output of the current controller 1240 is induced by the voltage error. In voltage control mode, the voltage controller 1230 is enabled and generates an output AC voltage waveform having a specific frequency based on an error representing the difference between a reference voltage and the actual voltage at the output of the system 100 at a specific frequency. This output AC waveform is provided as an input to the corresponding current controller 1240. For example, the voltage controller 1230-1 can generate an output AC voltage waveform at a fundamental frequency based on the difference between the reference voltage waveform and the actual voltage at the fundamental frequency. The current controller 1240-1 receives this output AC voltage waveform as a reference signal. The current controller 1240-1 generates an output AC voltage waveform based on an error representing the difference between the reference AC voltage waveform received from the voltage controller 1230-1 and the actual current waveform measured at the output of the system 100 at the fundamental frequency, which can be scaled to match the scale of the reference AC voltage waveform.

[0213] The primary controller 1210 can also be configured to generate and provide as input a reference signal to the fundamental voltage controller 1230-1 and / or the fundamental current controller 1240-1 depending on the mode, for example, whether the system 100 is in a grid-tied mode or a standalone mode. The fundamental voltage controller 1230-1 and / or the fundamental current controller 1240-1 can use the reference signal to generate a target AC voltage waveform at the fundamental frequency.

[0214] In the grid-tied mode, the MCD 112 controls the modules 108 to output AC waveforms having voltages, frequencies, and phases that match those of the grid 1130. The primary controller 1210 can disable the fundamental voltage controller 1230-1 such that the fundamental current controller 1240-1 generates a fundamental frequency voltage reference signal Vrf based on the difference between a target current set point and the output current of the system 100 at the fundamental frequency for the system 100. The target current set point can be a current reference signal received from the primary controller 1210. The primary controller 1210 can be configured to determine the current reference signal based on the power requirements of the load 101. In some implementations, the primary controller 1210 determines the current reference signal based on a power reference received, for example, from a user or the external system 104. In one example, the primary controller 1210 can determine the current reference signal based on a measured grid voltage and a power reference, for example, a true power reference (P) and / or a reactive power reference (Q).

[0215] In some implementations, the voltage and current controllers 1230 and 1240 are configured to cause the energy system 100 to track low voltage and current set points, respectively. In some implementations, the voltage and current controllers 1230 and 1240 can be an FPGA, a CPU, a microcontroller, or a biological cell, respectively. In the grid-forming mode, the voltage controller 1230 controls the voltage, and in the grid-following mode, the current controller 1240 controls the voltage. In either the grid-following or grid-forming mode, the control signal is normalized with a reference signal and passed to the LCD 114.

[0216] The fundamental current controller 1240-1 may generate a fundamental frequency voltage reference signal Vrf based, at least in part, on an error indicating the difference between a target current set point and the actual output current of the system 100 at the fundamental frequency. For example, the fundamental current controller 1240-1 may include other suitable closed-loop controllers, such as a proportional-resonant (PR) controller, a proportional-integral-derivative (PID) controller, or a proportional-integral (PI) controller. The fundamental current controller 1240-1 may include a model predictive control (MPC) controller that uses a process model to generate the fundamental frequency voltage reference signal Vrf.

[0217] In standalone mode, the primary controller 1210 can enable both the fundamental voltage controller 1230-1 and the fundamental current controller 1240-1 for more dynamic control. As explained above, the primary controller 1210 can determine the last normal (specification) voltage, frequency, and phase of the grid 1130, e.g., the last measured values ​​of these values ​​before the grid 1130 lost power, and control the modules 108 of the control system 100 to output AC waveforms having voltages, frequencies, and phases that match the last normal voltage, frequency, and phase of the grid 1130, respectively.

[0218] The basic voltage controller 1230-1 can adjust the output of the module 108 to match the last known value of the grid 1130. In some implementations, the primary controller 1210 can receive a reference voltage from a user or the external system 104, and the basic voltage controller 1230-1 can adjust the output of the module 108 to match the reference voltage.

[0219] In some implementations, the fundamental voltage controller 1230-1 generates an output AC voltage waveform based on a voltage error indicating the difference between a voltage reference, e.g., a last good voltage or a received voltage reference, and the actual output voltage of the module 108 of the system 100 at the fundamental frequency. Similar to the fundamental current controller 1240-1, the fundamental voltage controller 1230-1 can include a closed-loop controller, e.g., a PI, PR, or PID controller, that generates the output AC voltage waveform based on the error. In another example, the fundamental voltage controller 1230-1 can include an MPC controller.

[0220] The AC voltage waveform output by the fundamental voltage controller 1230-1 is provided as a reference signal input to the fundamental current controller 1240-1, thereby generating a reference current. The fundamental current controller 1240-1 is configured to determine an error based on the difference between the reference current and the actual output current (e.g., output AC current waveform) of the module 108 of the system 100 at the fundamental frequency.

[0221] The multi-loop controller of each harmonic frequency reference signal generator 1225-2 through 1225-N operates in a similar manner to the multi-loop controller of fundamental frequency reference signal generator 1225-1. As described above, islanding detector 1220 can generate and provide disturbance reference signals to one or more harmonic frequency reference signal generators 1225-2 through 1225-N. Individual disturbance reference signals can be provided to voltage controllers 1230 of one or more harmonic frequency reference signal generators 1225-2 through 1225-N and to respective combiner modules 1235 of one or more harmonic frequency reference signal generators 1225-2 through 1225-N. Because the harmonic frequencies are different for the harmonic frequency reference signal generators 1225-2 to 1225-N, the frequencies of the disturbance reference signals for each of the harmonic frequency reference signal generators 1225-2 to 1225-N are also different so that the frequencies of the disturbance signals for the harmonic frequency reference signal generators 1225 match the harmonic frequencies of the harmonic frequency reference signal generators 1225.

[0222] For simplicity, the operation of the multi-loop controller of the harmonic frequency reference signal generator 1225-2 will be described. However, each harmonic frequency reference signal generator 1225-2 can operate in the same or similar manner.

[0223] In either mode, the harmonic frequency reference signal generator 1225-2 generates and outputs a harmonic frequency voltage reference signal based on the disturbance reference signal received from the islanding detector 1220. In the grid-tied mode, the primary controller 1210 can disable the voltage controller 1230-2 such that the current controller 1240-2 generates a harmonic frequency voltage reference signal based on the difference between the reference current received from the combiner module 1235-2 and the output current of the system 100 at the third harmonic frequency. The combiner module 1235-2 is configured to combine the output signal from the voltage controller 1230-2 and the disturbance reference signal. For example, the combiner module 1235-2 can be configured to sum the output signal from the voltage controller 1230-2 and the disturbance reference signal. Because the voltage controller 1230-2 is disabled and has a zero output, this combination results in a disturbance reference signal.

[0224] The current controller 1240-2 may generate a harmonic frequency voltage reference signal based, at least in part, on an error indicative of a difference between the disturbance reference signal and the actual output current of the system 100 at the third harmonic frequency. For example, the current controller 1240-2 may include a PR controller, a PID controller, a PI controller, or other suitable closed-loop controller. The current controller 1240-2 may include an MPC controller that uses a process model to generate the harmonic frequency voltage reference signal.

[0225] In standalone mode, the primary controller 1210 can enable both the voltage controller 1230-2 and the current controller 1240-2. Rather than providing a disturbance reference signal to the combiner module 1235-2, the islanding detector 1220 provides the disturbance reference signal to the voltage controller 1230-2. An algorithmic switch can provide control of the destination of the disturbance reference signal. The fundamental voltage controller 1230-1 generates an output AC voltage waveform based on a voltage error indicating the difference between the disturbance reference signal and the actual output voltage of the module 108 of the system 100 at the third harmonic frequency. Similar to the fundamental voltage controller 1230-1, the third harmonic voltage controller 1230-2 can include a closed-loop controller, such as a PI, PR, or PID controller, that generates the output AC voltage waveform based on the error. In another example, the voltage controller 1230-2 can include an MPC controller.

[0226] The AC voltage waveform output by the fundamental voltage controller 1230-2 is provided as a reference signal input to the current controller 1240-2. The current controller 1240-2 is configured to determine an error based on the difference between the reference current and the actual output current, such as the output AC current waveform of the module 108 of the system 100 at the third harmonic frequency. The current controller 1240-2 can generate a harmonic frequency voltage reference signal based, at least in part, on the error. In some implementations, the current controller 1240-2 uses instructions from the islanding detector to calculate the harmonic frequency voltage reference signal, which can use a proportional-resonant controller for each harmonic.

[0227] FIG. 13 is a block diagram of an example of an islanding detector 1220, such as the islanding detector 1220 in FIGS. 12A and 12B. The islanding detector 1220 is configured to generate a disturbance reference signal and detect an islanding condition. The islanding detector 1220 includes an impedance comparator 1222 and a disturbance generator 1224, which receive a disturbance reference signal from one or more integrators 1232. The integrator 1232 may include a hardware component that integrates a total output impedance 1234 of the system 100, corresponding to one or more harmonic frequency reference signals, over a predetermined period of time, for example. Generally, impedance is frequency dependent, and thus the integrator 1232 can calculate the total impedance 1234 as a function of frequency. The integrator 1232 may be included as part of the master control device or not. The integrator 1232 may include a field-programmable gate array (FPGA) processor on the MCD 112.

[0228] The impedance comparators 1222 are configured to receive data indicative of impedance measurements, each representing a measurement of the output impedance of a module 108 of the system 100. The impedance comparators 1222 can compare each impedance measurement, e.g., the impedance for each harmonic signal injected onto the output of at least one module of the array of modules, to an impedance threshold. If the impedance measurement satisfies the impedance threshold, e.g., by equalizing or exceeding the impedance threshold, the islanding detector 1222 can determine that an islanding condition exists, e.g., that the system 100 is experiencing an islanding condition.

[0229] In some implementations, the impedance comparator 1222 can determine that an islanding condition exists if a particular higher-order harmonic signal, e.g., the fifth harmonic, meets the impedance threshold for the particular higher-order harmonic, even if the lower-order harmonic signals do not meet their respective impedance thresholds.

[0230] In some implementations, the impedance threshold is an adjustable value. For example, a user may be able to adjust the impedance threshold using a GUI or other interface of a terminal communicatively coupled to system 100 and / or a user interface of system 100. Because some grids 1130 have different characteristics, e.g., different normal operating impedance values, than others, allowing impedance threshold adjustment allows system 100 with islanding detector 1220 to be used on grids with different characteristics. In some implementations, machine learning techniques can be used to determine the impedance threshold. For example, a machine learning module can learn from historical data the impedance threshold that is best suited for a certain time period or season. If a common impedance threshold is used on all grids 1130, islanding detector 1220 may always detect an islanding condition when connected to a grid 1130 that has a normal operating impedance that exceeds the common impedance threshold.

[0231] In some implementations, the impedance comparator 1222 includes a filter 1226, such as a digital filter for filtering feedback signals, e.g., noise from loads in the grid, that would cause a non-zero impedance measurement for a disconnected module 108 that should have a zero impedance measurement. For example, an overload occurring in the grid can lead to high-order harmonic signals external to the module 108. Alternatively, or in addition, a power supply connected to the grid can cause high-order harmonic signals to be generated external to the module 108. The term "order" in high-order harmonic signals refers to orders of the fundamental frequency greater than 1; for example, for n=5, a fifth-order harmonic signal has a frequency five times the fundamental frequency. External high-order harmonic signals can cause the impedance comparator 1222 to malfunction and detect an islanding condition when none exists. Thus, the filter 1226 can reduce external high-order harmonic signals processed by the impedance comparator 1222. For example, using a defined harmonic frequency, the digital filter 1226 can adjust its bandwidth in real time to pass only the defined harmonic frequency and filter out other frequencies. In some implementations, the digital filter 1226 is based on an infinite impulse response (IIR) or finite impulse response (FIR) mechanism. The digital filter 1226 can be a band-pass filter. In some implementations, the digital filter 1226 is a low-pass filter that approximates a band-pass filter as a first-order approximation.

[0232] The disturbance generator 1224 transmits a disturbance reference signal to one or more harmonic frequency reference signal generators 1225-2 to 1225-N. The disturbance generator 1224 can be configured to periodically transmit the disturbance reference signal based on a defined islanding detection period. In some implementations, the defined islanding detection period is stored in a memory of the master control device 112. In some implementations, the islanding detection period is defined by a user, for example, through a GUI or other interface of a terminal communicatively coupled to the system 100 and / or a user interface of the system 100, as described herein. Similarly, the impedance comparator 1222 can be configured to compare each impedance measurement received between successive islanding detection periods to an impedance threshold to determine whether an islanding condition exists.

[0233] The disturbance generator 1224 can calculate the waveform of the disturbance. For example, to calculate the waveform of the disturbance, the disturbance generator 1224 receives as inputs from the primary controller 1210 the fundamental frequency and angular frequency of the signal, i.e., the phase angle t of the fundamental frequency, and receives as outputs the fifth harmonic frequency and the phase angle ω associated with the fifth harmonic frequency. T ,for example, [ka] where n=5 can be calculated. Additionally, the primary controller 1210 provides the amplitude of the disturbance for reference, e.g., to compare with the amplitude of a fundamental frequency voltage reference signal. The higher the frequency of the disturbance signal, the shorter the pulse duration, e.g., the period of the signal. Thus, in some implementations, using higher harmonic frequencies can reduce the total pulse length of the disturbance and therefore reduce THD.

[0234] In some implementations, the disturbance generator 1224 periodically receives inputs, such as fundamental / angular frequencies, from the primary controller 1210. For example, in some implementations, the primary controller 1210 sends inputs to the disturbance generator 1224 in response to receiving instructions from the MCU 112.

[0235] The state decoder machine 1228 will be discussed later with reference to the processes performed by the islanding detector 1220 .

[0236] 14 is a flow diagram depicting an example method 1400 of detecting an islanding condition and operating an energy system based on whether an islanding condition is detected. Method 1400 can be performed by any one of systems 100 described herein.

[0237] As a starting point, the system 100 operates in a grid-tied mode 1410. The system 100 can operate in the grid-tied mode when the grid 1130 is operating normally, e.g., without errors or other conditions that would cause the system 100 to disconnect from the grid 1130.

[0238] The system 100 periodically injects (1420) a disturbance signal, e.g., a disturbance voltage or current, onto the output of one or more modules 108 of the system 100. The system 100 can inject the disturbance signal onto the output of a module 108 by adjusting control information sent to the one or more modules 108 of the system 100. For example, the system 100 can adjust the normalized reference signal (Vrn or Irn) for one or more modules 108 to include increased current amplitudes at specified harmonic frequencies, as described with reference to FIG.

[0239] The system 100 measures (1430) the output impedance of the module 108 of the system 100 over a period of time during which the disturbance current is output by the module 108. The measured impedance can be the impedance at one or more specified harmonic frequencies. For example, the impedance can be determined based on the output voltage of the module 108 at the specified harmonic frequency and the output current of the module 108 at the specified harmonic frequency.

[0240] Measuring the output impedance of the module 108 can include measuring the current of the module 108 and determining the output impedance from the derivative of the output voltage of the module 108 with respect to the output current. In some implementations, measuring the current of the module 108 includes performing a direct-to-quadrature-to-zero transformation, e.g., a Park transformation, on the ABC format (three-phase coordinate system) measurements of the current and converting them to a DQ0 format (rotating vector coordinate system with one variable vector projection) measurement, rotating the frame of reference for AC signals to that for DC signals. In some implementations, an intermediate format exists, e.g., an AB0 (stationary vector coordinate system with two variable vector projections). Performing a direct-to-quadrature-to-zero transformation can simplify analysis, for example, resulting in a single vector for voltage and current for a single phase rather than two vectors.

[0241] In some implementations, the system 100 stores the impedance magnitude for each harmonic signal corresponding to each module for later use in debugging, for example, determining the cause of an islanding condition.

[0242] The system 100 compares 1440 the measured impedance to a threshold impedance to determine whether the measured impedance meets the impedance threshold, for example, by equaling or exceeding the impedance threshold. If the measured impedance meets the impedance threshold, the system 100 can determine that an islanding condition exists. If not, the system 100 can determine that an islanding condition does not exist and continue to periodically inject a disturbance current, measure the impedance, and check whether an islanding condition exists.

[0243] In some implementations, the system 100 compares the measured impedance of the system's 100 modules 108 for each harmonic injected with a signal to a separate threshold impedance for each harmonic. Impedance measurements corresponding to higher harmonics may be weighted more heavily in determining whether an islanding condition exists. For example, if the impedance for the fifth harmonic meets the fifth threshold impedance while the impedance for the second harmonic does not meet the second threshold impedance, the system 100 may determine that an islanding condition exists. In some implementations, impedance measurements corresponding to the fundamental frequency are more likely not to be associated with disturbances generated by the islanding detector 1220 because the fundamental frequency is closer to the operating frequency of other components on the grid. As a result, impedance measurements for higher frequencies may be more likely to have been generated by the islanding detector 1220 and are weighted more heavily.

[0244] If the system 100 determines (1440 "YES") that an islanding condition exists, the system 100 may disconnect (1450) from the grid 1130. For example, the system 100 may open contactor 1115-3, which selectively connects the system 100 and the load 101 to the grid 1130.

[0245] System 100 can also transition to standalone mode. During grid-tied mode, system 100 can measure the voltage, frequency, and phase of the power on grid 1130, for example, using a phase-locked loop (PLL) of system 100. For example, system 100 can use the PLL to track the phase of grid 1130 in grid-tied mode. System 100 can store these measurements so that system 100 can identify the last normal voltage, frequency, and phase of grid 1130 before an islanding condition was detected. As part of the transition to standalone mode, system 100 can enable the outer voltage control loop, for example, by enabling fundamental voltage controller 1230-1 and disabling PLL tracking.

[0246] The system 100 operates 1460 in a standalone mode. In the standalone mode, the system 100 adjusts the output voltage of the modules 108 to match the last known good voltage, frequency, and phase of the grid 1130. The system 100 can operate in the standalone mode, providing power to the load 101, until, for example, the grid 1130 returns to normal operation.

[0247] In some implementations, the system 100 can use a state machine decoder 1228 to inject digital signals, for example, to switch from current mode to voltage mode, and continue to monitor the impedance of the module 108 even when the module 108 is disconnected from the grid 1130. In some implementations, the state machine decoder 1228 varies the filter coefficients of the frequencies enabled within the bandwidth of the digital filter 1226.

[0248] The system 100 determines 1470 whether the grid has returned to normal operation. The system 100 can be configured to monitor the grid 1130 and determine whether power has returned to the grid 1130. If not, the system 100 continues to operate in standalone mode.

[0249] If the grid 1130 returns to normal operation, the system 100 may return to the grid-tied mode (1480). For example, the system 100 may enable PLL tracking to track the phase of the grid 1130. The PLL detects that the phase and voltage mode output are synchronized with the grid 1130. In some implementations, the system 100 may remain in the voltage control mode until the contactor 1115-3 is closed. In this example, the system 100 may disable the fundamental voltage controller 1230-1 and enable the fundamental current controller 1240-1 after the contactor 1115-3 is closed. The system 100 may also enable the islanding detector 1220 while in the grid-tied mode.

[0250] In some implementations, system 100 can reset all used integrators that may have accumulated errors between steps 1450 and 1480. For example, while system 100 is in idle mode, system 100 can detect noise signals arising from external loads connected to the grid. These noise signals can erroneously lead to incorrect impedance values ​​because the impedance of a disconnected module should be zero. Therefore, impedance comparator 1222 can use causal control to reset any non-zero impedance and current values ​​determined by the system while the system is in idle mode. For example, impedance comparator 1222 can have in-memory instructions to set the impedance measurement for a particular module to zero when the particular module is disconnected from the grid.

[0251] 15 is a flow diagram depicting an example method 1500 in which one or more modules 108 adjust control information for injecting disturbance signals onto the output of one or more modules 108. Method 1500 can be performed by any one of systems 100 described herein.

[0252] The system 100 determines 1510 to inject a disturbance signal onto the output of the module 108. As described herein, the system 100 may cause the module 108 to periodically inject the disturbance signal based on a defined islanding detection period. Each time the islanding detection period elapses, the system 100 may determine to inject a disturbance signal onto the output of the module 108. The disturbance signal may have a defined amplitude and be at a defined harmonic frequency.

[0253] The system 100 adjusts 1520 the control information for the module 108 based on the disturbance signal. As described herein, the system 100 can adjust the normalized reference signal (Vrn or Irn) for the module 108 to include increased amplitude at defined harmonic frequencies, as described with reference to FIG.

[0254] The system 100 transmits 1530 the adjusted control information to the modules 108. As described herein, each module 108 can use the control information to operate a switch and generate an output AC waveform.

[0255] The system 100 determines 1540 to remove the disturbance signal. For example, the system 100 can be configured to inject the disturbance signal and measure the output impedance of the system 100 at a specified harmonic frequency every islanding detection period for a short disturbance period (e.g., in milliseconds). Once this disturbance period has elapsed, the system 100 can determine to remove the disturbance signal from the output of the module 108.

[0256] The system transmits 1550 unadjusted control information to the modules 108. For example, the system 100 can transmit a normalized reference signal (Vrn or Irn) for the modules 108, along with a modulation index Mi for each module 108, without adjustment for the disturbance signal. Method 1500 can be performed iteratively, for example, to detect islanding conditions while in a grid-tied mode.

[0257] Various aspects of the present subject matter are described below as elaborations and / or complements of previously described implementations, with emphasis placed on the interrelationships and interchangeability of the following implementations. In other words, emphasis is placed on the fact that each feature of the implementations can be combined with any other feature unless expressly stated or taught otherwise.

[0258] In many embodiments, an energy system configured to connect to a power grid includes an array of cascaded modules, each outputting an individual voltage waveform, each module including a local control device; and a master control device including one or more harmonic controllers communicatively coupled to each local control device via a communication interface and configured to periodically cause one or more of the modules to output increased voltages at specified harmonic frequencies by adjusting control information sent to the local control device of each of the one or more modules periodically in accordance with a specified islanding detection period; and an islanding detector configured to detect when the array of cascaded modules is under an islanding condition based on the output impedance of the modules.

[0259] In many embodiments, an energy system configured to connect to a power grid includes one or more modules, each outputting a respective voltage waveform to a load, a controller configured to periodically cause at least a portion of the one or more modules to output an increased voltage at a specified harmonic frequency, and an islanding detector configured to detect when one or more modules are under an islanding condition based on grid impedance.

[0260] In many embodiments, an energy system configured to connect to a power grid includes an array of cascaded modules, each configured to output a respective voltage waveform to a load, each module including a local control device, and a master control device communicatively coupled to each local control device via a communication interface. The master control device is configured to cause one or more of the modules to generate output signals with disturbance components, measure or produce measurements of impedance of the power grid during application of the output signals with disturbance components to the grid, and determine whether an islanding condition exists based on the impedance measurements and the disturbance component.

[0261] In many embodiments, a method for detecting an islanding condition includes: controlling, by a master control device, an array of cascaded modules to output individual voltage waveforms to a load, each module including a local control device; controlling, by one or more harmonic controllers of the master control device, one or more of the modules to periodically output increased voltages at specified harmonic frequencies by adjusting control information sent to the local control devices of each of the one or more modules periodically according to a specified islanding detection period; and detecting, by an islanding detector of the master control device, when the cascaded array of modules is under an islanding condition based on the output impedances of the modules.

[0262] In many embodiments, a method for detecting an islanding condition includes controlling one or more modules to each output a respective voltage waveform to a load, periodically causing at least a portion of the one or more modules to output an increased voltage at a specified harmonic frequency, and detecting when the one or more modules are under an islanding condition based on grid impedance.

[0263] In many embodiments, a method for detecting an islanding condition includes controlling an array of cascaded modules to each output an individual voltage waveform to a load, each module including a local control device; causing one or more of the modules to generate an output signal with a disturbance component by a master control device communicatively coupled to each local control device via a communication interface; measuring or producing a measurement of the impedance of the power grid during application of the output signal to the grid; and determining whether an islanding condition exists based on the impedance measurement.

[0264] In some embodiments, the energy system further includes an impedance measurement circuit configured to measure the output impedance of the module at the specified harmonic frequency and to periodically provide data to the islanding detector indicative of the output impedance of the module based on the specified islanding detection period.

[0265] In some embodiments, the output impedance of the module at the specified harmonic frequency is the sum of the output impedances of each module in the energy system at the specified harmonic frequency.

[0266] In some embodiments, the output impedance of a module at a specified harmonic frequency is the sum of the output impedances of a subset of the modules in the energy system at the specified harmonic frequency.

[0267] In some embodiments, the master control device is configured, in response to the islanding detector detecting that the array of cascaded modules is under an islanding condition, to disconnect the array of cascaded modules from the grid, obtain data indicative of the last normal voltage frequency and voltage phase of the grid, and send instructions to the harmonic controllers of the one or more harmonic controllers to control individual voltage waveforms output by each module to the load based on the last normal voltage phase and the last normal voltage frequency.

[0268] In some embodiments, the master control device is configured to receive data indicating that the grid has returned to normal operation, and in response, retrieve data indicating the current voltage phase and current voltage frequency of the grid, reconnect the array of cascaded modules to the grid, and send instructions to one or more harmonic controllers to control the individual voltage waveforms provided to the loads by the array of cascaded modules.

[0269] In some embodiments, the master control device is configured to send control information to each local control device via the communication interface instructing the local control device to operate the switch network and output a respective voltage waveform.

[0270] In some embodiments, the control information transmitted to each local control device includes a normalized reference signal for each module of the array of cascaded modules and, for at least one module, a modulation index used to scale the normalized reference signal by the at least one module.

[0271] In some embodiments, the normalized reference signal represents (i) the fundamental frequency and (ii) the voltage at a defined harmonic frequency.

[0272] In some embodiments, (i) the fundamental frequency and (ii) the voltage at the specified harmonic frequency are measured in parallel.

[0273] In some embodiments, the master control device is configured to periodically transmit control information to each local control device such that the control information is transmitted to each local control device multiple times during each defined islanding detection period. Periodically adjusting the control information transmitted to each local control device of the one or more modules in accordance with the defined islanding detection period includes transmitting, over a first subperiod of each repetitive period, control information including a normalized reference signal with harmonic voltages at a first magnitude to each local control device, and transmitting, over a second subperiod of each repetitive period, adjusted control information including the adjusted harmonic voltages at a second magnitude greater than the first magnitude to each local control device.

[0274] In some embodiments, the one or more harmonic controllers include a fundamental frequency reference signal generator configured to generate a voltage reference signal at a fundamental frequency.

[0275] In some embodiments, the one or more harmonic controllers include one or more harmonic frequency reference signal generators configured to generate harmonic frequency voltage reference signals at individual harmonic frequencies relative to the fundamental frequency.

[0276] In some embodiments, the master controller includes a signal combiner that generates the control information by combining the fundamental frequency voltage reference signal with at least one harmonic frequency voltage reference signal of the one or more harmonic frequency reference signal generators.

[0277] In some embodiments, the one or more harmonic frequency reference signal generators include a plurality of harmonic frequency reference signal generators, and the master controller further includes a primary controller configured to select between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

[0278] In some embodiments, each harmonic controller of the one or more harmonic controllers comprises a multi-loop controller including an outer voltage control loop and an inner current control loop.

[0279] In some embodiments, the islanding detector is configured to obtain one or more baseline impedance measurements of the energy system at defined harmonic frequencies.

[0280] In some embodiments, the islanding detector is configured to detect when the array of cascaded modules is under an islanding condition based on the output impedance of the modules, one or more baseline impedance measurements, and an impedance threshold.

[0281] In some embodiments, the islanding detector includes a filter configured to remove parasitic signals from the output impedance of the module, the parasitic signals originating from sources external to the module.

[0282] In some embodiments, the islanding detector includes a state machine decoder configured to determine filter coefficients for removing frequencies in the output impedance of the module.

[0283] In some embodiments, the energy system further includes a master control device including the controller and the islanding detector, and each of the one or more modules includes a local control device configured to operate the switch network based on control information received from the master control device.

[0284] In some embodiments, the control information received by each local control device includes a normalized reference signal for the module and a modulation index used by the local control device to scale the normalized reference signal.

[0285] In some embodiments, the normalized reference signal represents the voltage at the fundamental frequency and the voltage at a defined harmonic frequency.

[0286] In some embodiments, the controller includes a fundamental frequency voltage reference signal generator configured to generate a voltage reference signal at the fundamental frequency.

[0287] In some embodiments, the controller includes one or more harmonic frequency reference signal generators each configured to generate a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

[0288] In some embodiments, the energy system further includes a signal combiner that (i) generates control information for the one or more modules by combining the fundamental frequency voltage reference signal and at least one harmonic frequency voltage reference signal of the one or more harmonic frequency reference signal generators, and (ii) transmits the control information for the one or more modules to one or more local control devices.

[0289] In some embodiments, the one or more harmonic frequency reference signal generators include a plurality of harmonic frequency reference signal generators, and the energy system further includes a primary controller configured to select between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

[0290] In some embodiments, the energy system further includes an impedance measurement circuit configured to measure the output impedance of the module at a specified harmonic frequency and to periodically provide data to the islanding detector indicative of the impedance of the grid.

[0291] In some embodiments, the islanding detector is configured to obtain one or more baseline impedance measurements at defined harmonic frequencies.

[0292] In some embodiments, the islanding detector is configured to detect when one or more modules are under an islanding condition based on the grid impedance, one or more baseline impedance measurements, and an impedance threshold.

[0293] In some embodiments, the master control device is configured to cause one or more modules to generate an output signal with a disturbance component by sending control information to each local control device, the control information including a normalized reference signal and a modulation index used by the local control device to scale the normalized reference signal.

[0294] In some embodiments, the normalized reference signal represents the voltage at the fundamental frequency and the voltage at a defined harmonic frequency.

[0295] In some embodiments, the master control device includes a fundamental frequency voltage reference signal generator configured to generate a voltage reference signal at a fundamental frequency.

[0296] In some embodiments, the master control device includes one or more harmonic frequency reference signal generators each configured to generate a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

[0297] In some embodiments, the master controller includes a signal combiner that (i) generates control information for the one or more modules by combining the fundamental frequency voltage reference signal and at least one harmonic frequency voltage reference signal of the one or more harmonic frequency reference signal generators, and (ii) transmits the control information for the one or more modules to one or more local control devices.

[0298] In some embodiments, the one or more harmonic frequency reference signal generators include a plurality of harmonic frequency reference signal generators, and the master control device further includes a primary controller configured to select between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

[0299] In some embodiments, the master control device is configured to obtain one or more baseline impedance measurements of the energy system at defined harmonic frequencies.

[0300] In some embodiments, the master control device is configured to detect that an islanding condition exists based on the impedance of the power grid, one or more baseline impedance measurements, and an impedance threshold value.

[0301] In some embodiments, the output signal comprises an AC waveform having a fundamental frequency, and the disturbance component comprises an increased voltage or current at a particular harmonic frequency of the fundamental frequency.

[0302] In some embodiments, the method further includes controlling the impedance measurement circuit to measure the output impedance to the module at the specified harmonic frequency, and controlling the impedance measurement circuit to periodically provide data to the islanding detector indicative of the output impedance of the module based on the specified islanding detection period.

[0303] In some embodiments, the method further includes, in response to detecting that the array of cascaded modules is under an islanding condition, disconnecting the array of cascaded modules from the grid; obtaining data indicative of a last normal phase of the voltage of the grid and a last normal frequency of the voltage of the grid; and enabling a voltage controller to control, by each module, an individual voltage waveform output to the load based on the last normal phase and the last normal frequency.

[0304] In some embodiments, the method further includes receiving data indicating that the grid has returned to normal operation; obtaining data indicating a current phase of the grid voltage and a current frequency of the grid voltage; reconnecting the array of cascaded modules to the grid and disabling the voltage controller; and enabling the one or more harmonic controllers to control the current provided to the grid by the array of cascaded modules.

[0305] In some embodiments, the method further includes transmitting, by the master control device, control information to each local control device via the communication interface instructing the local control device to operate the switch network and cause the array to output a respective voltage waveform.

[0306] In some embodiments, the control information transmitted to each local control device includes a normalized reference signal for each module of the array of cascaded modules and, for at least one module, a modulation index used to scale the normalized reference signal by the at least one module.

[0307] In some embodiments, the normalized reference signal represents the fundamental frequency and the voltage at a defined harmonic frequency.

[0308] In some embodiments, the normalized reference signal represents a current at a defined harmonic frequency.

[0309] In some embodiments, the master control device periodically transmits control information to each local control device such that the control information is transmitted to each local control device multiple times during each defined islanding detection period, and adjusting the control information transmitted to each local control device of one or more modules periodically in accordance with the defined islanding detection period includes transmitting, for a first sub-period of each repetitive period, control information including a normalized reference signal with harmonic voltage and / or current levels at a first magnitude to each local control device, and transmitting, for a second sub-period of each repetitive period, adjusted control information including adjusted harmonic voltage and / or current levels at a second magnitude greater than the first magnitude to each local control device.

[0310] In some embodiments, the method further includes generating, by a fundamental frequency reference signal generator of the one or more harmonic controllers, a fundamental frequency voltage reference signal at the fundamental frequency.

[0311] In some embodiments, the method further includes generating, by each of one or more harmonic frequency reference signal generators of the one or more harmonic controllers, harmonic frequency voltage reference signals at distinct harmonic frequencies relative to the fundamental frequency.

[0312] In some embodiments, the method further includes generating the control information by combining, by a signal combiner, the fundamental frequency voltage reference signal and at least one harmonic frequency voltage reference signal of the one or more harmonic frequency reference signal generators.

[0313] In some embodiments, the one or more harmonic frequency reference signal generators include a plurality of harmonic frequency reference signal generators, and the method further includes selecting between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

[0314] In some embodiments, each harmonic controller of the one or more harmonic controllers comprises a multi-loop controller including an outer voltage control loop and an inner current control loop.

[0315] In some embodiments, the method further includes obtaining, by the islanding detector, one or more baseline impedance measurements at the defined harmonic frequencies.

[0316] In some embodiments, the method further includes detecting, by an islanding detector, when the array of cascaded modules is under an islanding condition based on the output impedance of the module, the one or more baseline impedance measurements, and an impedance threshold value.

[0317] In some embodiments, the method further includes controlling, by a master control device, one or more modules to cause a portion of the one or more modules to output increased voltages at defined harmonic frequencies, and detecting, by an islanding detector, that the one or more modules are under an islanding condition. Each module of the one or more modules includes a local control device configured to operate a switch network based on control information received from the master control device.

[0318] In some embodiments, the control information received by each local control device includes a normalized reference signal for the module and a modulation index used by the local control device to scale the normalized reference signal.

[0319] In some embodiments, the normalized reference signal represents a fundamental voltage about a fundamental frequency and a harmonic voltage about a defined harmonic frequency.

[0320] In some embodiments, the method further includes generating, by a fundamental frequency voltage reference signal generator, a fundamental frequency voltage reference signal at the fundamental frequency.

[0321] In some embodiments, the method further includes generating harmonic frequency voltage reference signals at distinct harmonic frequencies relative to the fundamental frequency with one or more harmonic frequency reference signal generators.

[0322] In some embodiments, the method further includes generating control information for the one or more modules by combining the fundamental frequency voltage reference signal with at least one harmonic frequency voltage reference signal of the one or more harmonic frequency reference signal generators.

[0323] In some embodiments, the one or more harmonic frequency reference signal generators include a plurality of harmonic frequency reference signal generators, and the method further includes selecting between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

[0324] In some embodiments, the method further includes measuring, by the impedance measurement circuitry, the output impedance to the module at the specified harmonic frequency as the impedance of the grid, and periodically providing data indicative of the impedance of the grid to the islanding detector.

[0325] In some embodiments, the method further includes obtaining baseline impedance measurements of one or more of the array of cascaded modules at the defined harmonic frequency.

[0326] In some embodiments, detecting when one or more modules are in an islanding condition based on the impedance of the grid includes detecting when one or more modules are in an islanding condition based on the impedance of the grid, one or more baseline impedance measurements, and an impedance threshold.

[0327] In some embodiments, causing one or more modules to generate an output signal with a disturbance component includes transmitting control information to a local control device of each module, the control information including a normalized reference signal for the module and a modulation index used by the local control device to scale the normalized reference signal.

[0328] In some embodiments, the normalized reference signal represents a fundamental voltage about a fundamental frequency and a harmonic voltage about a defined harmonic frequency.

[0329] In some embodiments, the method further includes generating, by a fundamental frequency voltage reference signal generator, a voltage reference signal at the fundamental frequency.

[0330] In some embodiments, the method further includes generating, by each of the one or more harmonic frequency reference signal generators, a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

[0331] In some embodiments, the method further includes generating control information for the one or more modules by combining the voltage reference signal with at least one harmonic frequency voltage reference signal of the one or more harmonic frequency reference signal generators.

[0332] In some embodiments, the one or more harmonic frequency reference signal generators include a plurality of harmonic frequency reference signal generators, and the method further includes selecting between the plurality of harmonic frequency reference signal generators to generate a harmonic frequency voltage reference signal to be combined with the voltage reference signal.

[0333] In some embodiments, the method further includes obtaining baseline impedance measurements of one or more of the array of cascaded modules at the defined harmonic frequency.

[0334] In some embodiments, determining whether an islanding condition exists includes detecting that an islanding condition exists based on an impedance of the power grid, one or more baseline impedance measurements, and an impedance threshold.

[0335] In some embodiments, the output signal comprises an AC waveform having a fundamental frequency, and the disturbance component comprises an increased voltage or current at a particular harmonic frequency of the fundamental frequency.

[0336] In some embodiments, the method further includes resetting an integrator used in measuring the impedance of the power grid after determining whether an islanding condition exists based on the impedance measurement.

[0337] The term "module," as used herein, refers to one of two or more devices or subsystems within a larger system. A module can be configured to cooperate with other modules of similar size, function, and physical arrangement (e.g., location of electrical terminals, connectors, etc.). Modules with the same function and energy source can be configured the same (e.g., size and physical arrangement) as all other modules in the same system (e.g., rack or pack), while modules with different functions or energy sources may vary in size and physical arrangement. Each module may be physically removable and interchangeable with other modules in the system (e.g., like wheels on a car or blades in an information technology (IT) blade server), but this is not required. For example, a system may be packaged in a common enclosure that does not allow removal and replacement of any one module without disassembly of the system as a whole. However, any implementation herein can be configured so that each module is removable and replaceable with other modules in a convenient manner without disassembly of the system, etc.

[0338] The term "master control device" is used broadly herein and does not require the implementation of any particular protocol, such as a master and slave relationship with any other device, such as a local control device.

[0339] The term "output" is used broadly herein and does not exclude functioning in a bidirectional manner as both an output and an input. Similarly, the term "input" is used broadly herein and does not exclude functioning in a bidirectional manner as both an input and an output.

[0340] The terms "terminal" and "port" are used broadly herein and can be either unidirectional or bidirectional, can be input or output, and do not require a particular physical or mechanical structure such as a female or male configuration.

[0341] The processing circuitry can include one or more processors, microprocessors, hardware controllers, and / or microcontrollers, each of which can be a discrete or standalone chip or distributed among several different chips (or portions thereof). Any type of processing circuitry can be implemented, such as, but not limited to, personal computing architectures (e.g., as used in desktop PCs, laptops, tablets, etc.), programmable gate array architectures, dedicated architectures, custom architectures, and others. The processing circuitry can include digital signal processors, which can be implemented in hardware and / or software. The processing circuitry can execute software instructions stored on memory, which cause the processing circuitry to perform many different actions and control other components.

[0342] The processing circuitry may also implement other software and / or hardware routines. For example, the processing circuitry may interface with communications circuitry and perform analog-to-digital conversion, encoding and decoding, other digital signal processing, multimedia functions, conversion of data to a form suitable for presentation to the communications network (e.g., in-phase and quadrature), and / or cause the communications network to transmit data (wired or wirelessly).

[0343] The processing circuitry may also be adapted to run an operating system and any software applications and to perform their other functions not related to processing transmitted and received communications.

[0344] Computer program instructions for performing 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 Language (HDL), SystemC, C, C++, C#, Objective-C, Matlab®, SimulInk, SystemVerilog, SystemVHDL, Handel-C, Python, Java®, JavaScript®, Ruby, HTML, Smalltalk, Transact-SQL, XML, PHP, Golang (Go), the "R" language, and Swift, to name a few.

[0345] The memory, storage, and / or computer-readable medium may be shared by one or more of the various functional units present, or may be distributed among two or more of them (e.g., as separate memories present in different chips). A memory may also reside in its own separate chip.

[0346] To the extent that embodiments disclosed herein include or operate in conjunction with memory, storage, and / or computer-readable medium, that memory, storage, and / or computer-readable medium is non-transitory. Thus, to the extent that that memory, storage, and / or computer-readable medium is covered by one or more claims, that memory, storage, and / or computer-readable medium is only non-transitory. The terms "non-transitory" and "tangible" as used herein are intended to describe memory, storage, and / or computer-readable medium that exclude propagating electromagnetic signals, but are not intended to limit the type of memory, storage, and / or computer-readable medium in terms of persistence of storage or otherwise. For example, "non-transitory" and / or "tangible" memory, storage, and / or computer-readable media encompass 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.

[0347] 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 substituted with those from any other embodiment. If a feature, element, component, function, or step is described with respect to only one embodiment, it should be understood that that feature, element, component, function, or step can be used in conjunction with any other embodiment described herein, unless explicitly stated otherwise. This paragraph therefore serves as preamble and descriptive support for the introduction of claims that, where appropriate, combine features, elements, components, functions, and steps from different embodiments or substitute features, elements, components, functions, and steps from one embodiment for another, even if the following description does not explicitly state that such combinations or substitutions are possible in a particular instance. It is expressly acknowledged that an explicit enumeration of all possible combinations and substitutions would be overly burdensome, particularly given that the permissibility of all such combinations and substitutions would be readily recognized by those skilled in the art.

[0348] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0349] While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are described in detail herein. It should be understood, however, that these embodiments are not limited to the particular forms disclosed; on the contrary, these embodiments are intended to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, any feature, function, step, or element of the embodiments may be recited in or added to the claims, as well as any negative limit that defines the scope of the claimed invention by any feature, function, step, or element not falling within its scope.

Claims

1. 1. An energy system configured to connect to a power grid, the energy system comprising: an array of cascaded modules, each of the cascaded modules outputting a respective voltage waveform, each module including a local control device; a master control device communicatively coupled to each local control device via a communication interface, said master control device comprising: one or more harmonic controllers configured to periodically cause one or more of the modules to output increased voltages at defined harmonic frequencies by adjusting control information sent to the local control devices of each of the one or more modules periodically in accordance with a defined islanding detection period; an islanding detector configured to detect when the array of cascaded modules is under an islanding condition based on the output impedance of the module; and a master control device comprising: An energy system comprising:

2. measuring the output impedance of the module at the defined harmonic frequency; periodically providing to the islanding detector data indicative of an output impedance of the module based on the defined islanding detection period; an impedance measurement circuit configured to The energy system of claim 1 further comprising:

3. The master control device in response to the islanding detector detecting that the array of cascaded modules is under the islanding condition, disconnecting the array of cascaded modules from the grid; obtaining data indicative of a last normal voltage frequency and voltage phase of the grid; sending instructions to a harmonic controller of the one or more harmonic controllers by each module to control the individual voltage waveform output to the load based on the last normal voltage phase and the last normal voltage frequency; 10. An energy system according to any preceding claim, configured to:

4. The master control device receiving data indicating that the grid has returned to normal operation, and in response thereto; obtaining data indicative of a current voltage phase and a current voltage frequency of the grid; reconnecting the array of cascaded modules to the grid; sending instructions to the one or more harmonic controllers to control the individual voltage waveforms provided to the load by the array of cascaded modules; The energy system of claim 3 configured to:

5. 10. An energy system as described in any preceding claim, wherein the master control device is configured to send the control information to each local control device via the communication interface, the control information instructing the local control device to operate a switch network and output the individual voltage waveform.

6. 10. An energy system as described in any preceding claim, wherein the control information transmitted to each local control device comprises a normalized reference signal for each module of the array of cascaded modules and, for at least one module, a modulation index used to scale the normalized reference signal by the at least one module.

7. 7. The energy system of claim 6, wherein the normalized reference signal represents (i) a fundamental frequency and (ii) a voltage at a defined harmonic frequency.

8. 8. The energy system of claim 7, wherein (i) the fundamental frequency and (ii) the voltage at the specified harmonic frequency are measured in parallel.

9. the master control device is configured to periodically transmit the control information to each local control device such that the control information is transmitted to each local control device multiple times during each defined islanding detection period; adjusting the control information transmitted to the local control device of each of the one or more modules periodically according to a defined islanding detection period; transmitting, over a first subperiod of each repeating period, control information to each local control device, the control information including a normalized reference signal with a harmonic voltage at a first magnitude; transmitting, over a second subperiod of each repeating period, to each local control device, adjusted control information including an adjusted harmonic voltage at a second magnitude greater than the first magnitude; The energy system of claim 8 , comprising:

10. 10. The energy system of any preceding claim, wherein the one or more harmonic controllers comprise a fundamental frequency reference signal generator configured to generate a voltage reference signal at a fundamental frequency.

11. 11. The energy system of claim 10, wherein the one or more harmonic controllers comprise one or more harmonic frequency reference signal generators, each configured to generate a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

12. 12. The energy system of claim 11 , wherein the master controller comprises a signal combiner that generates the control information by combining the fundamental frequency voltage reference signal with the harmonic frequency voltage reference signal of at least one of the one or more harmonic frequency reference signal generators.

13. 13. The energy system of claim 12, wherein the one or more harmonic frequency reference signal generators comprise a plurality of harmonic frequency reference signal generators, and the master controller further comprises a primary controller configured to select between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

14. 10. An energy system according to any preceding claim, wherein each harmonic controller of the one or more harmonic controllers comprises a multi-loop controller comprising an outer voltage control loop and an inner current control loop.

15. 10. The energy system of any preceding claim, wherein the islanding detector is configured to obtain one or more baseline impedance measurements of the energy system at the defined harmonic frequencies.

16. 16. The energy system of claim 15, wherein the islanding detector is configured to detect when the array of cascaded modules is under the islanding condition based on the output impedance of the module, the one or more baseline impedance measurements, and an impedance threshold.

17. 10. The energy system of any preceding claim, wherein the islanding detector comprises a filter configured to remove signals from output impedances of the modules that do not correspond to the module.

18. 18. The energy system of claim 17, wherein the islanding detector comprises a state machine decoder configured to determine filter coefficients of the filter in relation to allowed frequencies within the output impedance of the module.

19. 1. An energy system configured to connect to a power grid, the energy system comprising: one or more modules, each of which outputs a respective voltage waveform to a load; a controller configured to periodically cause at least a portion of the one or more modules to output increased voltages at defined harmonic frequencies; an islanding detector configured to detect when the one or more modules are under an islanding condition based on an impedance of the grid; and An energy system comprising:

20. 20. The energy system of claim 19, further comprising a master control device including the controller and the islanding detector, each module of the one or more modules comprising a local control device configured to operate a switch network based on control information received from the master control device.

21. 21. The energy system of claim 20, wherein the control information received by each local control device comprises a normalized reference signal for the module and a modulation index used by the local control device to scale the normalized reference signal.

22. 22. The energy system of claim 20 or claim 21, wherein the normalized reference signal represents a voltage at a fundamental frequency and a voltage at a defined harmonic frequency.

23. 23. The energy system of any one of claims 19-22, wherein the controller comprises a fundamental frequency voltage reference signal generator configured to generate a voltage reference signal at a fundamental frequency.

24. 24. The energy system of claim 23, wherein the controller comprises one or more harmonic frequency reference signal generators, each configured to generate a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

25. 25. The energy system of claim 24, further comprising a signal combiner that (i) generates the control information for each of the one or more modules by combining the fundamental frequency voltage reference signal and the harmonic frequency voltage reference signal of at least one of the one or more harmonic frequency reference signal generators, and (ii) transmits the control information for each of the one or more modules to the one or more local control devices.

26. 26. The energy system of claim 25, wherein the one or more harmonic frequency reference signal generators comprise a plurality of harmonic frequency reference signal generators, the energy system further comprising a primary controller configured to select between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

27. measuring the output impedance of the module at the defined harmonic frequency; periodically providing data indicative of the grid impedance to said islanding detector; an impedance measurement circuit configured to 27. The energy system of any one of claims 19-26, further comprising:

28. 28. The energy system of any one of claims 19-27, wherein the islanding detector is configured to obtain one or more baseline impedance measurements at the defined harmonic frequencies.

29. 30. The energy system of claim 28, wherein the islanding detector is configured to detect when one or more modules are under the islanding condition based on an impedance of the grid, the one or more baseline impedance measurements, and an impedance threshold.

30. 1. An energy system configured to connect to a power grid, the energy system comprising: an array of cascaded modules, each configured to output a respective voltage waveform to a load, each module including a local control device; a master control device communicatively coupled to each local control device via a communication interface, said master control device comprising: causing one or more of said modules to generate an output signal with a disturbance component; measuring or producing a measurement of the impedance of the power grid during application of the output signal with the disturbance component to the grid; determining whether an islanding condition exists based on the impedance measurements and the disturbance components; a master control device configured to: An energy system comprising:

31. 31. The energy system of claim 30, wherein the master control device is configured to cause the one or more modules to generate an output signal with the disturbance component, and wherein generating the output signal with the disturbance component is performed by sending control information to each local control device comprising a normalized reference signal and a modulation index used by the local control device to scale the normalized reference signal.

32. 32. The energy system of claim 31 , wherein the normalized reference signal represents a voltage at a fundamental frequency and a voltage at the defined harmonic frequency.

33. 33. The energy system of any one of claims 30-32, wherein the master control device comprises a fundamental frequency voltage reference signal generator configured to generate a voltage reference signal at a fundamental frequency.

34. 34. The energy system of claim 33, wherein the master control device comprises one or more harmonic frequency reference signal generators, the one or more harmonic frequency reference signal generators each configured to generate a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

35. 35. The energy system of claim 34, wherein the master controller comprises a signal combiner that (i) generates control information for the one or more modules by combining the fundamental frequency voltage reference signal and the harmonic frequency voltage reference signal of at least one of the one or more harmonic frequency reference signal generators, and (ii) transmits the control information for the one or more modules to the one or more local control devices.

36. 36. The energy system of claim 35, wherein the one or more harmonic frequency reference signal generators comprise a plurality of harmonic frequency reference signal generators, and the master control device further comprises a primary controller configured to select between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

37. 37. The energy system of any one of claims 30-36, wherein the master control device is configured to obtain one or more baseline impedance measurements of the energy system at the defined harmonic frequencies.

38. 38. The energy system of claim 37, wherein the master control device is configured to detect that the islanding condition exists based on an impedance of the power grid, the one or more baseline impedance measurements, and an impedance threshold.

39. 39. An energy system as described in any of claims 30-38, wherein the output signal comprises an AC waveform having a fundamental frequency and the disturbance component comprises an increased voltage or current at a particular harmonic frequency of the fundamental frequency.

40. 1. A method for detecting an islanding condition, the method comprising: controlling an array of cascaded modules by a master control device to output individual voltage waveforms to a load, each module having a local control device; controlling one or more of the modules to periodically output increased voltages at specified harmonic frequencies by adjusting control information sent by one or more harmonic controllers of the master control device to the local control devices of each of the one or more modules periodically in accordance with a specified islanding detection period; detecting, by an islanding detector of the master control device, when the array of cascaded modules is under an islanding condition based on the output impedance of the modules; A method comprising:

41. controlling an impedance measurement circuit to measure an output impedance to the module at the specified harmonic frequency; controlling the impedance measurement circuit to periodically provide data indicative of the output impedance of the module to the islanding detector based on the defined islanding detection period; 41. The method of claim 40, further comprising:

42. in response to detecting that the array of cascaded modules is under the islanding condition; disconnecting the array of cascaded modules from the grid; obtaining data indicative of a last normal phase of the voltage of the grid and a last normal frequency of the voltage of the grid; a voltage controller enabling each module to control a respective voltage waveform output to the load based on the last normal phase and the last normal frequency; 42. The method of claim 40 or 41, further comprising:

43. receiving data indicating that the grid has returned to normal operation; obtaining data indicative of a current phase of the grid voltage and a current frequency of the grid voltage; reconnecting the array of cascaded modules to the grid; Disabling the voltage controller; enabling the one or more harmonic controllers to control current provided to the grid by the array of cascaded modules; 43. The method of claim 42, further comprising:

44. 44. The method of any one of claims 40-43, further comprising transmitting, by the master control device, to each local control device via the communication interface, the control information instructing the local control device to operate a switch network to cause the array to output the individual voltage waveforms.

45. 45. A method according to any one of claims 40-44, wherein the control information transmitted to each local control device comprises a normalized reference signal for each module of the array of cascaded modules and, for at least one module, a modulation index used by the at least one module to scale the normalized reference signal.

46. 46. ​​The method of claim 45, wherein the normalized reference signal represents a fundamental frequency and a voltage at a defined harmonic frequency.

47. 47. The method of claim 46, wherein the normalized reference signal represents a current at the defined harmonic frequency.

48. the master control device periodically transmits the control information to each local control device such that the control information is transmitted to each local control device multiple times during each defined islanding detection period; adjusting the control information transmitted to the local control device of each of the one or more modules periodically according to a defined islanding detection period; transmitting, over a first subperiod of each repeating period, to each local control device, control information including a normalized reference signal with harmonic voltage and / or current levels at a first magnitude; transmitting, over a second subperiod of each repeating period, to each local control device, adjusted control information including adjusted harmonic voltage and / or current levels at a second magnitude greater than the first magnitude; 48. The method of claim 47, comprising:

49. 49. The method of any one of claims 40-48, further comprising generating, by a fundamental frequency reference signal generator of the one or more harmonic controllers, a fundamental frequency voltage reference signal at the fundamental frequency.

50. 50. The method of claim 49, further comprising generating, by each of one or more harmonic frequency reference signal generators of the one or more harmonic controllers, a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

51. 51. The method of claim 50, further comprising generating the control information by combining, with a signal combiner, the fundamental frequency voltage reference signal and the harmonic frequency voltage reference signal of at least one of the one or more harmonic frequency reference signal generators.

52. 52. The method of claim 51 , wherein the one or more harmonic frequency reference signal generators comprise a plurality of harmonic frequency reference signal generators, the method further comprising selecting between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

53. A method according to any one of claims 40-52, wherein each harmonic controller of the one or more harmonic controllers comprises a multi-loop controller comprising an outer voltage control loop and an inner current control loop.

54. 53. The method of any one of claims 40-52, further comprising obtaining, by the islanding detector, one or more baseline impedance measurements at the defined harmonic frequencies.

55. 55. The method of claim 54, further comprising detecting, by the islanding detector, when the array of cascaded modules is under the islanding condition based on the output impedance of the module, the one or more baseline impedance measurements, and an impedance threshold.

56. 1. A method for detecting an islanding condition, the method comprising: controlling one or more modules so that each outputs a respective voltage waveform to a load; periodically causing at least a portion of the one or more modules to output increased voltages at defined harmonic frequencies; detecting when the one or more modules are under an islanding condition based on an impedance of the grid; A method comprising:

57. controlling, by a master control device, the one or more modules to cause some of the one or more modules to output the increased voltage at the defined harmonic frequency; detecting, with an islanding detector, that the one or more modules are in the islanding condition, each module of the one or more modules comprising a local control device configured to operate a switch network based on control information received from the master control device; 57. The method of claim 56, further comprising:

58. 58. The method of claim 57, wherein the control information received by each local control device comprises a normalized reference signal for the module and a modulation index used by the local control device to scale the normalized reference signal.

59. 59. A method according to claim 57 or claim 58, wherein the normalised reference signal represents a fundamental voltage for a fundamental frequency and a harmonic voltage for the defined harmonic frequency.

60. 60. The method of any one of claims 56-59, further comprising generating, by a fundamental frequency voltage reference signal generator, a fundamental frequency voltage reference signal at the fundamental frequency.

61. 61. The method of claim 60, further comprising generating harmonic frequency voltage reference signals at distinct harmonic frequencies relative to the fundamental frequency with one or more harmonic frequency reference signal generators.

62. 62. The method of claim 61 , further comprising generating control information for the one or more modules by combining the fundamental frequency voltage reference signal and the harmonic frequency voltage reference signal of at least one of the one or more harmonic frequency reference signal generators.

63. 63. The method of claim 62, wherein the one or more harmonic frequency reference signal generators comprise a plurality of harmonic frequency reference signal generators, the method further comprising selecting between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the fundamental frequency voltage reference signal.

64. measuring an output impedance to the module at the specified harmonic frequency as the impedance of the grid by an impedance measurement circuit; periodically providing data indicative of the grid impedance to said islanding detector; 64. The method of any one of claims 56-63, further comprising:

65. 65. The method of any one of claims 56-64, further comprising obtaining baseline impedance measurements of one or more of the array of cascaded modules at the defined harmonic frequency.

66. 66. The method of claim 65, wherein detecting when the one or more modules are in an islanding condition based on the impedance of the grid comprises detecting when one or more modules are in the islanding condition based on the impedance of the grid, the one or more baseline impedance measurements, and an impedance threshold.

67. 1. A method for detecting an islanding condition, the method comprising: controlling an array of cascaded modules, each of which outputs a respective voltage waveform to a load, each module including a local control device; generating, by a master control device communicatively coupled to each local control device via a communication interface, an output signal with a disturbance component to one or more of the modules; measuring or producing a measurement of the impedance of the power grid during application of an output signal to the grid; determining whether an islanding condition exists based on the impedance measurements; A method comprising:

68. 68. The method of claim 67, wherein causing the one or more modules to generate an output signal with the disturbance component comprises transmitting control information to the local control device of each module comprising a normalized reference signal for the module and a modulation index used by the local control device to scale the normalized reference signal.

69. 69. The method of claim 68, wherein the normalized reference signal represents a fundamental voltage about a fundamental frequency and a harmonic voltage about the defined harmonic frequency.

70. 70. The method of any one of claims 67-69, further comprising generating a voltage reference signal at the fundamental frequency by a fundamental frequency voltage reference signal generator.

71. 71. The method of claim 70, further comprising generating, by each of one or more harmonic frequency reference signal generators, a harmonic frequency voltage reference signal at a distinct harmonic frequency relative to the fundamental frequency.

72. 72. The method of claim 71, further comprising generating control information for the one or more modules by combining the voltage reference signal and the harmonic frequency voltage reference signal of at least one of the one or more harmonic frequency reference signal generators.

73. 73. The method of claim 72, wherein the one or more harmonic frequency reference signal generators comprise a plurality of harmonic frequency reference signal generators, the method further comprising selecting between the plurality of harmonic frequency reference signal generators to generate the harmonic frequency voltage reference signal to be combined with the voltage reference signal.

74. 74. The method of any one of claims 67-73, further comprising obtaining baseline impedance measurements of one or more of the array of cascaded modules at the defined harmonic frequency.

75. 75. The method of claim 74, wherein determining whether an islanding condition exists comprises detecting that the islanding condition exists based on an impedance of the power grid, the one or more baseline impedance measurements, and an impedance threshold.

76. A method according to any of claims 67-75, wherein the output signal comprises an AC waveform having a fundamental frequency, and the disturbance component comprises an increased voltage or current at a particular harmonic frequency of the fundamental frequency.

77. 68. The method of claim 67, comprising resetting an integrator used in measuring the impedance of the power grid after determining whether the islanding condition exists based on the impedance measurements.

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