Modular architecture for energy sources

Abstract

Apparatus, system, and methods for managing power transmission between an array of DC components or energy sources and one or more loads or an AC grid. One system includes a plurality of energy sources, a plurality of DC-DC converters coupled to the plurality of energy sources, a DC bus coupled to the plurality of DC-DC converters, an inverter coupled to the DC bus and configured to transfer electrical power between the DC bus and an AC output, and a control system configured to control operation of the plurality of DC-DC converters and the inverter.

Description

MODULAR ARCHITECTURE FOR ENERGY SOURCESCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 615,987 specification filed on December 29, 2023, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] This specification generally relates to a system for flexibly managing cunent flow into and out of multiple direct current (DC) devices.BACKGROUND

[0003] Modem power electronics can include diverse sources and storage devices. These sources can provide and store energy in the form of direct current (DC) power. However, during transmission and usage of the power, it is often desirable for it to be in an alternating current (AC) form. Further, multiple disparate DC components may be used to work in tandem to achieve a desired AC output.SUMMARY

[0004] This specification describes systems, methods, and apparatus for managing alternating current (AC) power between a load or power grid and an array of direct current (DC) components, e.g., batteries, solar panels, fuel cells, DC generators, or DC motors, that are connected to a DC bus using a dedicated DC-DC converter. The DC-DC converter can control the output voltage and current flow for each DC component. One or more inverters convert power on the DC bus into AC for consumption or integration into further system components. The described systems enable modular addition or removal of different DC components and dynamic load balancing based on various parameters, e.g., state of charge, temperature, component type, or other parameters.

[0005] The details of one or more implementations of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the subject matter will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a block diagram illustrating an example modular architecture for DC components.

[0007] FIG. 2 is a block diagram illustrating an example modular architecture with a split DC bus for DC components.

[0008] FIG. 3A is a partial schematic diagram for an example DC-DC converters and inverters.

[0009] FIG. 3B is a partial schematic diagram for an example DC-DC converter and inverter with a split DC bus.

[0010] FIG. 4 is a flowchart of an example process for controlling a set of DC-DC converters.DETAILED DESCRIPTION

[0011] This specification describes a system for managing alternating current (AC) power between a load or power grid and an array of direct current (DC) components, e.g., batteries, solar panels, fuel cells, DC generators, DC motors, among other types of DC components that are each connected to a DC bus using a dedicated DC-DC converter. The DC- DC converter can control the output voltage and current flow for the DC component. One or more inverters convert power on the DC bus into AC for consumption or integration into further system components. The system enables modular addition or removal of different DC components or energy sources and dynamic load balancing based on various parameters, e.g., state of charge, temperature, component t pe, and / or other parameters.

[0012] Some example applications are as follows:

[0013] Stationary applications are those in which the modular energy system is located in a fixed location during use. although it may be capable of being transported to alternative locations when not in use. The module-based or modular energy system resides in a static location while providing electrical energy for consumption by one or more other entities, or storing or buffering energy' for later consumption. Examples of stationary' applications in which the technologies described herein can be used include, but are not limited to: energy systems for use by or within one or more residential structures or locales, energy systems for use by or within one or more industrial structures or locales, energy systems for use by or within one or more commercial structures or locales, energy' systems for use by or within one or more governmental structures or locales, including both military and non-military uses, energy systems for charging the mobile applications described below, e.g., a charge source or a charging station, and systems that convert solar, wind, geothermal energy, fossil fuel, or nuclear power into electricity' for storage. Stationary' applications often supply loads, e.g., gridsand microgrids, motors, and data centers. A stationary energy system can be used in either a storage or non-storage role.

[0014] Mobile applications, sometimes referred to as traction applications, are generally ones where a module-based energy system is located on or within an entity, and stores and provides electrical energy7for conversion into motive force by a motor to move or assist in moving that entity. Examples of mobile entities with which the technologies described herein can be used include, but are not limited to. electric and / or hybrid entities that move over or under land, over or undersea, above and out of contact with land or sea, e.g., flying or hovering in the air, or through outer space. Examples of mobile entities with which the technologies described herein can be used include, but are not limited to, vehicles, trains, trams, ships, vessels, aircraft, and spacecraft. Examples of mobile vehicles with which the technologies described herein can be used include, but are not limited to, those having only one wheel or track, those having only two wheels or tracks, those having only three wheels or tracks, those having only four wheels or tracks, and those having five or more wheels or tracks. Examples of mobile entities with which the technologies described herein can be used include, but are not limited to. a car. a bus. a truck, a motorcycle, a scooter, an industrial vehicle, a mining vehicle, a flying vehicle, e.g., a plane, a helicopter, or a drone, a maritime vessel, e.g., commercial shipping vessels, ships, yachts, boats or other watercraft, a submarine, a locomotive or rail-based vehicle, e.g., a train, or a tram, a military vehicle, a spacecraft, and a satellite.

[0015] In describing implementations, reference may be made to a particular stationary application, e.g., grid, micro-grid, data centers, cloud computing environments or mobile application, e.g., an electric car. Such references are made for ease of explanation and do not mean that a particular implementation is limited for use to only that particular mobile or stationary application. Implementations of systems providing power to a motor can be used in both mobile and stationary applications. While certain configurations may be more suitable to some applications over others, all example implementations described herein are capable of use in both mobile and stationary7applications unless otherwise noted.

[0016] The described technologies are advantageous in that they can work flexibly with a variety of sources and components. For example, batteries or energy^ storage units at different states of charge, based on different chemistry, or of different capacities can be connected to the DC bus and used to supply or receive power. Further, DC components can be added or removed during operation of the system, in other words the modular DC components are “hot- swappable.” Additionally, the system is scalable, and can operate in a wide range ofimplementations including large scale commercial / stationary installations or small-scale electronic devices. Further, the described technologies can be used with DC components of varying age or integrity, e.g., used batteries or degraded solar panels.

[0017] By utilizing a DC bus, additional components can be couple to, or removed from the DC bus with minimal additional hardware. This can include separate devices (with or without their own DC-DC converters), or additional DC components and DC-DC converters as described below.

[0018] FIG. 1 is a block diagram illustrating an example modular system 100 for an energy storage system or a conversion system. The system 100 includes a set of DC components 102A-D, a set of DC-DC converters 104A-D which can be controlled by local electronic control units (LECUs) 116A-D which supply or receive pow er from a DC bus 106. The DC bus 106 receives power from, or supplies pow er to, an inverter 108, which receives or supplies AC power 1 12 from or to loads or a power grid using a coupler 110. A main electronic control unit (MECU) 114 in operation provides control signals to each of the LECUs 116A-D controlling DC-DC converters 104A-D and to the inverter 108 to coordinate operation of the system 100.

[0019] DC components 102A-D can be, for example, energy' sources, e.g., batteries, battery packs, solar arrays, DC generators / motors, fuel cell generators, capacitors, thermoelectric generators, hydroelectric generators, or wind generators. Each DC component 102A-D can produce electrical power to be supplied to the DC bus 106 using the component’s associated DC-DC converter 104. Some DC components, e.g., batteries, capacitors, or other energy' storage devices, can also store energy.

[0020] The DC components 102 are connected in parallel to the DC bus 106 by the DC-DC converters 104, respectively. The DC-DC converters 104A-D can be bi-directional DC to DC converters that step up or boost the voltage received from their associated DC components 102 to a bus voltage of the DC bus 106. Such converters are also referred to as “boost converters.” Alternatively, the DC-DC converters 104 can be buck converters, boostbuck converters, flyback converters, or other types of converter. A DC-DC converter 104 can be any suitable switch ty pe, e.g., power semiconductors like the metal-oxide-semiconductor field-effect transistors (MOSFETs) shown here, insulated gate bipolar transistors (IGBTs), wide band transistors, e.g., gallium nitride (GaN) or silicon carbide (SiC) transistors, or other electronic switching mechanism, in addition to other components, e.g., capacitors andinductors, in order to raise or lower the voltage provided by the DC components 102. Semiconductor switches can operate at relatively high switching frequencies, thereby permitting a DC-DC converter 104 to respond to control commands within a relatively short interval of time. This can provide a high tolerance of output voltage and fast dynamic behavior in transient modes. In some implementations, the DC-DC converter 104 operates in a voltage control mode and regulates the output voltage by adjusting the duty cycle of the switches. In some implementations, the DC-DC converter 104 operates in a current control mode and regulates the output current by adjusting the duty cycle of the switching element. The output voltage may be indirectly controlled according to the output current.

[0021] Each of the DC-DC converters 104A-D includes, or is coupled to. a LECU 116A-D. The LECUs 116A-D can receive current-controlling commands from the MECU 114, the commands directing an amount of current to supply to the DC bus 106 based on demands downstream. In some implementations, the MECU 114 or LECUs 1 16A-D measure status information associated with each DC component 102 and / or DC-DC converter 104. Measured status information can include state of charge (SOC), e.g., the level of charge of an energy source 102 relative to its capacity, state of health (SOH), e.g., a figure of merit of the condition of an energy source compared to its ideal conditions, internal and / or external temperature of the one or more energy sources 102 and / or the DC-DC converters 104, voltage of the one or more energy sources 102 and / or of components of the DC-DC converters 104, capacity of the one or more energy sources 102, current of the one or more energy sources 102 and / or of components of the DC-DC converters 104, state of power (SOP), e.g., the available power limitation of the energy source during discharge and / or charge, state of energy (SOE), e.g., the present level of available energy of an energy source relative to the maximum available energy of the source, and / or the presence of absence of a fault in any one or more of the components of the energy sources 102 and / or the DC-DC converters 104, component impedance, and mode of operations, e.g., charge, generate, or idle, among other parameters. In some implementations, the LECUs 116A-D and MECU 114 each include one or more microcontrollers, that are configured to process input signals and provide output signals. Various control algorithms can be implemented with the microcontrollers including proportional and integral (PI), proportional-integral-derivative (PID), or other feedback control systems. These control algorithms can control system 100 by assigning a target DC bus 106 voltage and instructingthe LECU's 116 to control the output voltages to meet that target DC bus 106 voltage. The control algorithms can also regulate the output of inverter 108. In some implementations. MECU 114 can instruct (e.g., sending an instruction to LECU’s 116) the isolation, disconnection, or connection of individual DCDC converters 104A-D according to the demands on the AC bus 112 or the status of the DC components 102A-D.

[0022] It should be noted that, while system 100 is illustrated with four DC components 102 and DC-DC converters 104. fewer or more components can readily be added or removed. That is, the system 100 could include 6, 10, or more DC components 102, or one, two, or three DC components 102.

[0023] Inverter 108 converts power between the DC bus 106 and the AC bus 112. The inverter 108 includes a set of high frequency switching components controlled by a microcontroller unit, or alternatively the MECU 114. The switching components of the inverter 108 can be any suitable switch type, e.g., power semiconductors like the metal-oxide- semi conductor field-effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), wide band transistors, e g., gallium nitride (GaN) or silicon carbide (SiC) transistors, or other electronic switching mechanism. Semiconductor switches can operate at relatively high switching frequencies, e.g., thereby permitting the inverter 108 to respond to control commands within a relatively short interval of time. This can provide a high tolerance of output voltage regulation and fast dynamic behavior in transient modes compared to lower frequency switching. The switching components of the inverter 108 can be arranged in an H-bridge configuration. When DC power is supplied to the input of the inverter, e.g., from the DC bus 106, the MECU 114 modulates the switching of these components, rapidly switching the polarity’ of the current to generate a sinusoidal AC output waveform. Inverter 108 can operate bi-directionally. That is, in addition to converting DC power to supply the AC bus 1 12, inverter 108 can convert AC power to supply the DC bus 106. The inverter 108 can be a single phase, three phase, or other multi -phase inverter configuration. Additionally, inverter 108 can be a multi-stage inverter, or other inverter topology. Further, multiple inverters can be connected to the DC bus 106 in parallel and supply the same, or different loads. The inverter 108 can be or include any suitable arrangement of switches (e.g., power transistors) such as a half bridge or full bridge (H-bridge). In some embodiments inverter 108 includes only switches and the converter (and the module as a whole) does not include a transformer.

[0024] Inverter 108 can be also (or alternatively) be configured to perform AC to DC conversion (e.g., a rectifier) such as to charge a DC component 102A-D from an AC source.

[0025] In some implementations, the system 100 also includes coupler 110. Coupler 110 can be a mechanical safety system that selectively isolates the inverter 108 from the AC bus 112 and efficiently conducts current between the inverter 108 and the AC bus 112. Coupler 112 can include one or more breakers, fuses, disconnects, contacts and other mechanical components for coupling the output of the inverter 108 to the AC bus 1 12. In some implementations, coupler 110 includes one or more sensors for measuring the AC bus 112 or inverter 108 including, but not limited to, temperature sensors, current sensors, voltage sensors, among other types of sensors. In some implementations, the coupler 110 includes one or more passive or active filters designed to condition AC power as it leaves or enters inverter 108.

[0026] MECU 114 controls operation of both inverter 108 and the LECUs 116A-D of the DC-DC converters 104A-D. MECU can receive signals from sensors or control system 101, e.g., sensors in or on inverter 108, coupler 110, and / or DC-DC converters 104A-D. Additional sensors can measure line voltages and currents, for example, the voltage of the DC bus 106, or current / voltage at AC Bus 112. These sensed signals can be relayed to a control system 101, which can perform pre-processing or signal conditioning before sending control communications to MECU 114. In some implementations, MECU 114 receives signals from sensors external to sy stem 100, e.g., solar irradiance, ambient temperature, humidity, predicted weather, etc. In some implementations, the MECU 114 is configured to determine a mode of operation for the systems 100 including, e.g., a load share for each DC component 102A-D based on the signals received from one or more sensors. Modes of operation can include MECU regulation, LECU regulation, grid regulation, external regulation, or others.

[0027] In some implementations, the MECU 114 regulates voltage at the DC bus 106 using the inverter 108. For example, the DC-DC converters 104A-D operate in a cunent regulation mode, and receive a current reference from the MECU 114. The MECU 114 receives status information, as described herein, from the LECUs 116A-D, as well as external commands, e.g.. a centralized grid controller, to determine how much power each DC component 102 is to supply. The MECU 114 can select or determine a load amount for each DC component 102 in order to balance current, SOC, temperature, or other parameters.

[0028] The MECU 1 14 can be configured to control one or more DC components 102 based on status information received from the same or different one or more of DC components 102. Control can also be based on one or more other factors, e.g., energy' requirements of load. Controllable aspects include, but are not limited to, one or more of the voltage, current, and / oroutput power of each DC component 102. In some implementations, control can be implemented using a classical controller, e.g., a PI, PID, or other control scheme. In some implementations, control is implemented using modem controls e.g., state space control. Linear quadradic regulation (LQR) or linear quadradic gaussian (LQG) control, fuzzy logic, or nonlinear control schemes.

[0029] Status information of every DC component 102 in system 100 can be communicated to the MECU 114, which can independently control every DC component 102A-D and its corresponding DC-DC converter 104A-D. Other variations are possible. For example, a particular DC component 102, or subset of DC components 102 can be controlled based on status information of that particular component 102 or subset, based on status information of a different DC component 102 that is not that particular DC component 102 or subset, based on status information of all components 102 other than that particular component 102 or subset.

[0030] The status information can be information about one or more aspects, characteristics, or parameters of each DC component 102. Types of status information include, but are not limited to. the following aspects of a DC component 102 or one or more components thereof, e.g., energy source, energy buffer, converter, monitor circuitry, SOC, e.g., the level of charge of an energy7source relative to its capacity, of the one or more energy' sources of the module, SOH, e.g., a figure of merit of the condition of an energy source compared to its ideal conditions, of the one or more energy sources of the module, temperature of the one or more energy sources or other components of the module, capacity of the one or more energy sources of the module, voltage of the one or more energy' sources and / or other components of the module, current of the one or more energy sources and / or other components of the module, State of Power (SOP), e.g., the available power limitation of the energy’ source during discharge and / or charge. State of Energy (SOE), e.g., the present level of available energy of an energy source relative to the maximum available energy of the source, and / or the presence of absence of a fault in any one or more of the components of the module.

[0031] The MECU 114 can control the DC components 102 by setting a target output current or voltage for the component 102, or disconnecting / connecting the component. In some implementations additional control is possible. For example, where the DC component 102 is a tracking solar panel, the MECU 114 can command track angles. In another example, where the DC component 102 is a DC generator, the MECU 114 can specify a target RPM or speed for the generator.

[0032] The DC-DC converters 104 can include LECU's 116A-D which can be configured to receive the status information from corresponding DC components 102. or determine the status information from monitored signals or data received from or within each DC component 102, and communicate that information to the MECU 114. In some implementations, each LECU 116A-D can communicate raw collected data to the MECU 114, which then algorithmically determines the status information on the basis of that raw data. The MECU 114 can then use the status information of DC component 102 to make control determinations. The determinations may take the form of instructions, commands, or other information, e.g. , a modulation index, that can be utilized by LECUs 116A-D to either maintain or adjust the operation of each DC component 102.

[0033] For example, the MECU 114 may receive status information and assess that information to determine a difference between at least one DC component 102, e.g., a component thereof, and at least one or more other DC components 102, e.g., comparable components thereof. For example, the MECU 114 may determine that a particular DC component 102 is operating with one of the following conditions as compared to one or more other DC component 102: with a relatively lower or higher SOC, SOH. capacity, voltage, current, or temperature, or with or without a fault. In such cases, the MECU 114 can output control information that causes the relevant aspect, e.g., output voltage, current, power, or temperature, of that particular DC component 102 to be reduced or increased, depending on the condition. In this manner, the utilization of an outlier DC component 102. e.g., operating with a relatively lower SOC or higher temperature, can be reduced to cause the relevant aspect of that DC component 102, e.g., SOC or temperature, to converge towards that of one or more other DC component 102.

[0034] The determination of whether to adjust the operation of a particular DC component 102 can be made by comparison of the status information to predetermined thresholds, limits, or conditions, and not necessarily by comparison to statuses of other DC components 102. The predetermined thresholds, limits, or conditions can be state thresholds, limits, or conditions, e.g., those set by the manufacturer, that do not change during use. The predetermined thresholds, limits, or conditions can be dynamic thresholds, limits, or conditions, that are permitted to change, or that do change, during use. For example, the MECU 114 can adjust the operation of a DC component 102 if the status information for that DC component 102 indicates it to be operating in violation, e.g. , above or below, of a predetermined threshold or limit, or outside of a predetermined range of acceptable operating conditions. Similarly, the MECU 1 14 can adjust the operation of a DC component 102 if the statusinformation for that DC component 102 indicates the presence of an actual or potential fault, e.g., an alarm or warning, or indicates the absence or removal of an actual or potential fault. Examples of a fault include an actual failure of a component, a potential failure of a component, a short circuit or other excessive current condition, an open circuit, an excessive voltage condition, a failure to receive a communication, the receipt of corrupted data, and the like. Depending on the type and severity of the fault, the faulty component’s utilization can be decreased to avoid damaging the DC component 102, or the component’s utilization can be ceased altogether. For example, if a fault occurs in a given component 102, then the MECU 114 or the LECU 116A-D associated with that component 102 can cause that DC component 102 to enter a bypass state. This will isolate that DC component 102, enabling the system to continue operations despite the failed DC component 102.

[0035] The MECU 114 can control a DC component 102 within the system 100 to achieve or converge towards a desired operational target. The target can be, for example, operation of all DC components 102 at the same or similar levels with respect to each other, or within predetermined thresholds limits, or conditions. This process is also referred to as balancing or seeking to achieve balance in the operation or operating characteristics of the DC components 102. The term “balance” as used herein does not require absolute equality betw een DC components 102 or components thereof, but rather is used in a broad sense to convey that operation of the system 100 can be used to actively reduce disparities in operation or operative state between DC component 102 that would otherwise exist.

[0036] The MECU 1 14 can control operation, to the extent that, in some embodiments, it does not prevent achieving the powder output requirements of the system at any one time (e.g., such as during maximum acceleration of an EV), such that SOC of the energy source(s) in each DC component 102 remains balanced or converges to a balanced condition if they are unbalanced, and / or such that temperature of the energy source(s) or other component (e.g., energy buffer) in each module remains balanced or converges to a balanced condition if they are unbalanced. Pow er flow' in and out of the modules can be regulated such that a capacity difference between sources does not cause an SOC deviation. Balancing of SOC and temperature can indirectly cause some balancing of SOH. Voltage and current can be directly balanced if desired, but in many embodiments the main goal of the system is to balance SOC and temperature, and balancing of SOC can lead to balance of voltage and current in a highly symmetric systems where modules are of similar capacity and impedance.

[0037] Since balancing all parameters may not be possible at the same time (e.g., balancing of one parameter may further unbalance another parameter), a combination ofbalancing any two or more parameters (SOC, T, Q, SOH, V, I) may be applied with priority given to either one depending on the requirements of the application. Priority in balancing can be given to SOC over other parameters (T, Q, SOH, V, I), with exceptions made if one of the other parameters (T, Q, SOH, V, I) reaches a severe unbalanced condition outside a threshold.

[0038] Further, “balancing’' may not necessarily mean equalizing the balanced parameter. For example, the control system 101 could balance current supplied, but cause each DC component 102 to deliver current proportional to its SOH or component age, thereby normalizing the expected lifespan across the DC components 102. This may be referred to herein as “proportional balancing.'’

[0039] In some implementations, the DC-DC converters 104 regulate voltage at the DC bus 106. In these implementations, each DC-DC converter 104 implements a droop control of voltage at the DC bus 106 in order to proportionally load share with other DC-DC converters 104. Droop control is an operation mode where the output voltage of the DC-DC converters 104 decreases slightly as output current increases. This results in a naturally even load balancing across the DC-DC converters 104. In order to enable uneven or selected load balancing, a gain can be multiplied to the droop function of each individual DC-DC converter 104, the gain can be selected by, for example, the MECU 114 to result in the desired balancing state.

[0040] While illustrated as a separate component, control system 101 can include MECU 114 and the LECUs 116A-D, as well as additional circuitry or components. In some implementations, the control system 101 is remote from system 100. For example, control system 101 can be software executing in a cloud environment. In some implementations, control system 101 is integrated in a single unit with MECU 114.

[0041] Components within the system 100 can communicate using serial communications, ethemet communications, wireless communications, or other methods. For example, the MECU 114 and DC-DC converters 104 can be on a local area network (LAN) and send / receive data bidirectionally. Communication links or paths can each be wired, e.g., electrical, optical, or wireless communication paths that communicate data or information bidirectionally, in parallel or series fashion. Data can be communicated in a standardized, e.g., IEEE, ANSI, or custom, e.g., proprietary, format. In automotive applications, communication paths can be configured to communicate according to FlexRay or CAN protocols. Communication paths can also provide wired power to directly supply the operating power for throughout system 100 from one or more DC components 102. For example, the operatingpower for each DC-DC converter 104 can be supplied only by the one or more DC components 102 to which that DC-DC converter 104 is connected and the operating power for the MECU 114 can be supplied indirectly from one or more of DC components 102, e.g., through a car’s power network.

[0042] FIG. 2 is a block diagram illustrating an example modular system 100 with a split DC bus for DC components. System 100 includes DC components 102A-D, DC-DC converters 1045A-D, an inverter 108, a coupler 110, and an MECU 114. Each of these components can be similar to or different from their analogous components as illustrated and described with reference to FIG. 1. A primary difference between FIG. 1 and FIG. 2 is the split DC bus 206.

[0043] The split DC bus 206 includes a pair of matched capacitors 216 that isolate a voltage halfway between the positive leg 218 and negative leg 220 of the split DC bus 206, which can be used as a neutral voltage in the AC bus 112. To achieve a split DC bus 206, the positive outputs of DC-DC converters 104 A and 104B are connected to the positive leg of DC bus 206, while the negative output of DC-DC converters 104A and 104B, as well as the positive legs of DC-DC converters 104C and 104D, are connected to the neutral leg 222. Finally, the negative outputs of DC-DC converters 104C and 104D are connected to the negative leg of split DC bus 206. It should be noted that, in some implementations, the matched capacitors 216 do not have equal capacitance, and the split DC bus 206 is not split at half voltage. For example, a voltage between the positive leg 218 and the neutral 222 could be twice the voltage between the neutral 222 and the negative leg 220, depending on the relative capacitances between matched capacitors 216.

[0044] In this configuration, each DC-DC converter 104A-D need only generate half the total voltage of split DC bus 206. Because each DC-DC converter 104A-D is stepping up voltage less than in a single bus implementation, greater efficiency at the DC-DC converters 104A-D can be achieved for high voltage DC bus configurations. This system 100 can also be suited to applications where a neutral point is desired or required at the AC bus 112.

[0045] While illustrated as a single stage split DC bus 206, multiple stages are possible. For example, the array of DC-DC converters 104A-D could be effectively connected in series, enabling higher voltages for the same amount of boost at each individual DC-DC converter 104. Similarly to FIG. 1, FIG. 2 is not limited to four DC components 102A-D or DC-DC converters 104A-D. Greater, or fewer components can be used in the system of FIG. 2.

[0046] In the embodiments of FIGs. 1 and 2. the master control functionality' of system 100 is shared in a common control system 101. however, other divisions of shared control or permitted. For example, part of the master control functionality' can be distributed between control system 101 and a dedicated MECU 114. In another example, both the master control functionality and at least part of the local control functionality' can be implemented in control system 101 (e.g.. with remaining local control functionality implemented in LECUs 116A-D). In some embodiments, all of control system 101 is implemented in the MECU 114. In some embodiments, local control functionality is implemented within a device shared with another component of each DC component 102A-D, such as a Battery' Management System (BMS).

[0047] FIG. 3A is a partial schematic diagram for a DC-DC converter and inverter system 100 in some example implementations. System 100 includes an array of DC-DC converters 104A-N that are connected in parallel to a single inverter 108.

[0048] Each of DC-DC converters 104 in the illustrated system 100 includes a positive, negative, and neutral output. The illustrated DC-DC converters 104 perform like boost converters, stepping up voltage received from DC components 102 using an array of switches 302 and passive components, e.g., inductors and capacitors. Each switch 302 can be a MOSFET, an IGBT, wide band transistors, e.g., GaN or SiC transistors, or other switching device, and can be controlled locally, e.g., by a local controller at the DC-DC converter, or remotely, e.g., by a centralized controller, e.g., an MECU as illustrated above in FIGs. 1 or 2. In general each DC-DC converter 104A-N in the array can independently manage its associate DC component or components 102. The DC component or components 102 can provide a consistent output at a predetermined or remotely identified voltage which is provided to the inverter 108 by a DC bus.

[0049] The inverter 108 receives the DC voltage, as well as the neutral, and uses its own switches 308, e.g., IBGTs, MOSFETs, wide band transistors, e.g., GaN or SiC transistors, or other switching devices, to generate an AC waveform. In the illustrated implementation, the midpoint of the DC bus is fed through the inverter 108 to be used as a neutral between the B and A outputs. In some implementations, switches 302 and / or 308 are silicon carbide (SiC) devices, which provide enhanced efficiency and greater voltage differential capacity, as well as reduced switching losses.

[0050] FIG. 3B is a partial schematic diagram of an example sy stem 100 for a DC-DC converter and inverter with a split DC bus. e.g., for the system illustrated in FIG. 2. The system100 includes two DC-DC converter groups, group 352A and group 352B, connected in series to supply voltage to a two-stage inverter 356. Each group of DC-DC Converters 352A-B can include any number of individual LECUs 116A-D and associated DC components 360.

[0051] The inverter 356 generates AC voltage at output A. In order to generate 3-phase AC power, the system 100 could include three inverters 356, or a single inverter with three sets of switches 358, each set similar to the switches 358 illustrated in FIG 3B, each generating one phase of the three required phases. The switches 358 in the inverter 356 are arranged in a two- stage format, with each stage increasing the output voltage of an AC sinusoid. In this manner, no single switch needs to operate with a large voltage differential, enabling more efficient energy conversion.

[0052] FIG. 4 is a flowchart of an example process 400 for controlling a set of DC-DC converters. It will be understood that process 400 and related methods may be performed, for example, by any suitable system, environment, software, and hardware, or a combination of them. For example, a system comprising a communications module, memory7storing instructions and other required data, and at least one hardware processor operably coupled to the memory and the communications module can be used to execute the process 400. In some implementations, the process 400 and related methods are executed by one or more components of the system 100 described above with reference to FIG. 1 or FIG. 2 described above, e.g.. the control system 101, MECU 114, LECUs 116 associated with the DC-DC converters 104, or a combination thereof. Further, it should be noted that the process 400 does not necessarily proceed in a sequential manner, and elements of the process 400 can happen repeatedly, in parallel or out of order, as would be understood by one of ordinary7skill in the art.

[0053] Control system 101 receives or determines (402) a demand for power to be supplied to the AC bus. The demand can be a current, voltage, or other parameter that identifies how7much power the system needs to deliver or receive. In general, the demand can be determined based on sensed parameters, e.g.. AC bus voltage, or received from a centralized control system, e.g., control system 101.

[0054] Control system 101 determines (404) whether the MECU 114 or the LECUs 1 16 are regulating DC bus voltage. In some implementations, the MECU 114 determines whether to regulate DC bus voltage using the inverter 108, or whether to enable voltage regulation at the LECUs 116. This determination can be made based on a user input, e.g.,“Voltage Regulate” selected for the inverter 108, or based on external factors. For example, where there is a large differential in the SOC across multiple DC components 102, it may be beneficial to reduce the DC bus voltage, sacrificing efficiency at the inverter 108 for better performance in some of the LECUs 116. If the LECUs 116 are regulating DC bus voltage, the process 400 proceeds to 412, otherwise if the MECU 114 is regulating DC bus voltage, the process 400 proceeds to 406. In some implementations, step 404 is not necessary7. For example, some configurations can include hardware permanently configured to operate with the LECUs 116 regulating DC bus voltage. In some implementations the MECU 114 permanently regulates DC bus voltage. In these implementations, such a determination is not required.

[0055] Control system 101 sends (406) voltage signals to the inverter 108 to cause it to adjust its switching duty cycles in order to maintain DC bus voltage at a predetermined level. The inverter 108 supplies or receives AC power and regulates the DC voltage.

[0056] Alternatively, the MECU 114 determines (408) how to balance the connected DC components 102 via their LECUs 116. The MECU 114 receives parameters associated with each individual DC component 102 and LECU 116 including device temperatures, SOC, power history, e g., past 48 hours of voltages and currents. Based on this data, the MECU 114 determines a balancing profile for the array of LECUs 116 in order to satisly certain criteria. For example, in some implementations it may be desirable to minimize local hot spots, and so hotter DC-DC converters and / or energy sources or DC components 102 can be cooled by reducing, e.g., current, voltage, or power output, from those components. To balance the reduction in current at certain components, the current generated at other components can be increased. In another implementation, a current may be elected for each component so that they will each reach a minimum or maximum, during charging operations, SOC simultaneously. Other balancing functions are possible. For example, certain DC components 102 may be more efficient, and thus have a higher priority for discharge and charging, than the rest. In this example, the MECU 114 may select higher current flows for the more efficient DC components 102.

[0057] Control system 101 sends (410) current signals to the LECUs 116. which operate in a current regulation mode, and step up voltage according to the target output. In some implementations, these current signals are sent from MECU 114, which has previously determined a DC component 102 balance. Each LECU 116 can independently control its DCcomponent 102 and switching signals in order to achieve the target current based on the current signal output at the DC bus voltage that is regulated by the MECU 114 and inverter 108. This control can be achieved by altering the duty cycle of the switching components in the DC-DC converter 104 associated with the LECU 116.

[0058] If the LECUs 116 are regulating DC bus voltage, the MECU 114, instead of regulating DC bus voltage, sends (412) current signals to the inverter 108 to adjust the switching duty cycle and achieve a target output cunent, in order to supply the required AC load.

[0059] Control system 101 determines (414) a droop gain for each LECU 116 that controls a DC-DC converter. This is similar to the balancing (408) and can be performed with similar goals of achieving uniform thermal loading, simultaneous SOC depletion or other aspect, but occurs while the LECUs 116 are in a voltage regulate mode. The droop gain, or gain associated with the droop function, for each LECU 116 can be determined by the MECU 114 in order to achieve a desired balance. In some instances, the droop gain is a number that is multiplied by the current being supplied by the DC component 102. The droop function can follow the equation: Droop = kdroapx IComponent- This is used to determine an updated target output voltage for that DC component’s 102 respective DC-DC converter 104. The resulting target output function is one that decreases or “droops” as output current increases. This causes the DC component 102 to naturally shed load to other DC components 102 operating in parallel as it’s current increases (and voltage droops). In some implementations, droop gain is updated regularly, e.g., every minute, every second, every hour. That is, the DC component 102 balance is adapted on the fly by adapting droop gains for each LECU 116. Because each LECU 116 is maintaining a constant or nearly constant output voltage, a droop function is implemented to allow for controlled load sharing. The droop control causes an LECU’s 116 target output voltage to drop slightly as the output current increases. This ensures stable sharing amongst all of the parallel LECUs 116. Each LECU 116 can have an independent droop factor, which can include an adjustable gain. The MECU 114 can assign the gain for the droop function at each DC component 102 or LECU 116, to prioritize or deprioritize certain LECUs 116 and achieve a balancing effect. The LECUs 116 can be prioritized or deprioritized based on similar balancing parameters as discussed above. For example, droop gains can beselected based on DC component 102 SOC, SOH, temperature, power capacity, ambient conditions, or other parameters.

[0060] Control system 101 determines (416) a target DC bus voltage and each LECU 116 supplies current to achieve the target DC bus voltage. In some implementations, the target DC bus voltage can vary based on certain parameters. For example, the target DC bus voltage may be reduced when a DC component 102 SOC is low, in order to improve the efficiency of the LECUs 116. Similarly, if the desired AC output current is high, the target DC bus voltage can be raised to reduce switching losses across the inverter 108. The target DC bus voltage can be determined by the MECU 114, or by other control entities, e.g., an external system controller.

[0061] This specification describes systems, methods, and an apparatus for managing power transmission between an array of DC components 102 or energy sources and one or more loads or an AC grid. The system can include a plurality of energy sources, a plurality of DC-DC converters coupled to the plurality of energy sources, a DC bus coupled to the plurality of DC-DC converters, an inverter coupled to the DC bus and configured to transfer electrical power between the DC bus and an AC output, and a control system configured to control operation of the plurality of DC-DC converters and the inverter.

[0062] Implementations can optionally include one or more of the following features.

[0063] In some instances, the control system includes a plurality of local control devices, each local control device controlling a particular DC-DC converter of the plurality' of DC-DC converters.

[0064] In some instances, each local controller is configured to calculate a target voltage as a function of output current at the DC-DC converter.

[0065] In some instances, the function of output current is a droop function.

[0066] In some instances, the command signals are current signals, and each local controller is configured to cause each DC-DC converter to provide a current according to the current signal.

[0067] In some instances, the control system includes a main control device configured to observe operations of the inverter and send the command signals to the plurality of local control devices.

[0068] In some instances, the controller receives as input, a state of charge for each DC component 102, a temperature for each energy source, and a target output for the inverter.

[0069] In some instances, the energy sources are at least one of, a battery, a photovoltaic source, a DC generator, or a capacitor.

[0070] The preceding figures and accompanying description illustrate example processes and techniques. However, system 100 and its software or other components can be considered using, implementing, or executing any suitable technique for performing these and other tasks. Particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

Claims

CLAIMS1. A system comprising: a plurality of DC components; a plurality' of DC-DC converters coupled to the plurality of DC components; a DC bus coupled to the plurality' of DC-DC converters; an inverter coupled to the DC bus and configured to transfer electrical power between the DC bus and an AC output; and a control system configured to adjust outputs of the plurality- of DC-DC converters and the inverter.

2. The system of claim 1 , wherein the control system comprises a plurality of local control devices, wherein each DC-DC converter of the plurality of DC-DC converters is coupled to a respective local control device of the plurality of local control devices, and wherein each local control device is configured to provide one or more command signals to control operation of the DC-DC converter to which the local control device is coupled.

3. The system of claim 2, wherein each local control device is configured to calculate a target voltage as a function of output current at the DC-DC converter, wherein the target voltage is a target output voltage of the DC-DC converter.

4. The system of claim 3, wherein the function of output current is a droop function.

5. The system of any one of claims 2-3, wherein each command signal comprises a current signal, and wherein each local controller is configured to cause the respective DC-DC converter, to which the local controller is coupled, to provide a current according to the current signal.

6. The system of any one of claims 2-4, wherein the control system further comprises a main control device configured to monitor operations of the inverter and send target output signals to the plurality of local control devices.

7. The system of any one of claims 1-6, wherein the control system receives as input, a state of charge for at least one DC component of the plurality of DC components, a temperaturefor at least one DC component of the plurality of DC components, and a target output for the inverter, and determines a nominal output for the at least one DC component of the plurality of DC components.

8. The system of claim 1, wherein the plurality of DC components comprise at least one of a battery, a photovoltaic source, a DC generator, or capacitor.

9. A system comprising: an inverter configured to transfer electrical power between an AC bus and a split DC bus, wherein the inverter is configured to generate a first AC line voltage and a second AC line voltage, wherein the split DC bus comprises a positive bus, a neutral bus. and a negative bus, and wherein the neutral bus maintains a potential that is at a potential between the positive bus and the negative bus; two or more DC components coupled to the split DC bus, wherein the two or more DC components are each coupled to the split DC bus by a DC-DC converter; and a control system configured to send first switching signals to the inverter to maintain the AC bus at a predetermined AC voltage, the control system further configured to send a respective command signal to each DC-DC converter.

10. The system of claim 9, wherein the control system comprises a plurality of local control devices, wherein each local control device is coupled to a respective DC-DC converter, and wherein each local control device is configured to generate to a second switching signal in response to the command signal, the second switching signal configured to cause the respective DC-DC converter to provide a target output voltage to the DC bus.

11. The system of claim 10, wherein each local control device is configured to calculate the target output voltage as a function of output current at the DC-DC converter to which the local control device is coupled.

12. The system of claim 11, wherein the function of output current is a droop function.

13. The system of any one of claims 9-12, wherein each command signal is a current signal, and wherein each local control device is configured to cause each DC-DC converter to provide a cunent according to the current signal.

14. The system of any one of claims 9-13. wherein the control system is configured to receive, as input, a state of charge for each DC component, a temperature for each DC component, and a target output for the inverter and determine a nominal output for DC component of the plurality of DC components.

15. The system of any one of claims 9-14, wherein each DC components comprises at least one of: a battery, a photovoltaic source, a DC generator, or capacitor.

16. The system of any one of claims 9-15, wherein a first DC component of the two or more DC components is coupled across the positive and neutral busses and a second DC component of the two or more DC components is coupled across the neutral and negative busses17. A method comprising: receiving a demanded power to be supplied to an AC bus; sending first switching signals to an inverter to convert power between the AC bus and a DC bus; receiving sensed parameters associated with a plurality of DC components; and sending second switching signals to a plurality of DC-DC converters, each DC-DC converter coupled to a respective DC component of the plurality of DC components, wherein each second switching signal is configured to cause the DC-DC converter to convert power between the DC components and the DC bus.

18. The method of claim 17, wherein the first switching signals are configured to cause the inverter to regulate voltage on the DC bus.

19. The method of any one of claims 17-18, wherein the second switching signals are configured to cause the DC-DC converters to supply a target current to the DC bus.

20. The method of any one of claims 17-19, wherein each DC-DC converter of the plurality of DC-DC converters is configured to determine a portion of the target current to be supplied, based on at least one of:DC component state of charge;DC component temperature;DC-DC converter temperature; or DC component capacity.

21. The method of any one of claims 17-20, wherein the sensed parameters associated with the plurality of DC components comprise at least one of: component temperature; component state of charge; component capacity; or component power history.

22. The method of any one of claims 17-21, wherein each DC-DC converter regulates voltage on the DC bus.

23. The method of claim 22, wherein each DC-DC converter regulates voltage on the DC bus according to a predetermined droop function.

24. The method of claim 23, wherein the predetermined droop function is determined based on at least on of:DC component state of charge;DC component temperature;DC-DC converter temperature; orDC component capacity.

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