Parallel direct current architectures for power generation

Abstract

In some implementations, a system includes a plurality of photovoltaic panels that are each configured to generate a DC voltage. The system includes a plurality of converter modules that each include a DC-DC converter. The converter modules are electrically coupled together to provide DC output in parallel to a DC bus. Each of the converter modules is configured to receive input of a DC voltage from at least one of the photovoltaic panels and is also configured to convert the received DC voltage to an output DC voltage. The system includes a DC-AC converter configured to receive DC power from the DC bus and provide an AC output.

Description

[0001] PARALLEL DIRECT CURRENT ARCHITECTURES FOR POWER GENERATION

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 596,228, filed on November 3, 2023, the entire contents of which are incorporated herein by reference.

[0004] FIELD

[0005] The technology described in this specification relates generally to systems, devices, and methods for power generation using parallel direct current (DC) architectures.

[0006] BACKGROUND

[0007] Photovoltaic (PV) panels provide a valuable source of renewable energy that is increasingly being used in residential and commercial settings. Each PV panel provides a limited amount of power, so PV systems often use multiple PV panels together to provide the amount of power desired. However, the architectures used to couple PV panels together often limit scalability and reliability. Some architectures require a DC-AC converter for each PV panel, but this can significantly increase the size and cost of the electronics needed for each PV panel. PV systems would benefit from an architecture that can provide high efficiency and high reliability while limiting size and cost of the electronic components used.

[0008] SUMMARY

[0009] Examples of systems, devices, and methods for generating power using parallel DC architectures are described. For example, a system can include multiple PV panels, e.g., PV modules or collections of PV cells. The system can also include multiple converter modules that receive DC input from the PV panels and provide DC output coupled together in parallel. Each converter module can receive input from one or more PV panels. In some implementations, each of the PV panels provides a DC input to a different converter module. The converter modules provide DC outputs that are coupled together in parallel, for example, to a shared DC bus. For example, the converter modules can each include a DC-DC converter so that they separately boost the DC input voltage from their respective PV panels to the voltage of the shared DC bus. Through the parallel connection to the DC bus, each of the converter modules can supply current at the voltage of the DC bus. To provide alternating current (AC) power, the system powers a central DC-AC converter, e.g., an inverter, from the DC bus, with the converter modules each contributing to the overall power generated by the system.

[0010] By coupling the DC outputs of the converter modules in parallel, the system provides highly scalable and highly reliable power generation. For example, the system can supply power with as few as one PV panel and converter module or as many are appropriate for the application. Additional PV panels and converter modules can be easily added or removed to adjust the power capacity of the system. In addition, because the converter modules connect through the DC bus, a failure of PV panel or one converter module removes its power output but does not otherwise affect the system. The converter modules also improve resilience under varying conditions, such as different PV panels experiencing different light levels, shading, wear, and so on. When the PV panels supply different DC voltages, the converter modules can operate independently to apply the appropriate boost needed to bring the output voltage to the level of the DC bus voltage.

[0011] The parallel DC architecture can also provide significant benefits for the design and characteristics of the converter modules. For example, each converter module can include a boost converter that allows for a small and cost-efficient design. The system can be arranged so that the DC bus voltage is consistently greater than the maximum output of each individual PV panel, so that the converter modules operate consistently with a voltage step up. In addition, DC-DC conversion can generally be performed with smaller and fewer components than DC-AC conversion. For example, a DC- AC converter would typically require, among other components, large electrolytic capacitors for an energy buffer, a transformer for isolation, and several active switches for conversion. The DC-AC converters used in a parallel DC architecture do not need these components, which can allow significant cost savings and size reduction.

[0012] In one general aspect, a system includes: a plurality of photovoltaic panels, where each of the photovoltaic panels is configured to generate a DC voltage; a plurality of converter modules, where each of the converter modules includes a DC-DC converter, where each of the converter modules has an input and an output, and where each of the converter modules is configured to (i) receive, at the input, a DC voltage from at least one of the photovoltaic panels and (ii) convert the received DC voltage to an output DC voltage at the output, where the outputs of the converter modules are electrically coupled together to provide DC output in parallel to a DC bus; and a DC-AC converter configured to receive DC power from the DC bus and provide an AC output. In some implementations, for each of the converter modules, the DC-DC converter is a boost converter.

[0013] In some implementations, for each of the converter modules, the boost converter includes a gallium nitride (GaN) transistor as a switching element of the boost converter.

[0014] In some implementations, the boost converter includes one or more Schottky diodes coupled to the GaN transistor.

[0015] In some implementations, the one or more Schottky diodes are one or more silicon Schottky diodes, and where the DC bus has a voltage between 100 V and 300 V.

[0016] In some implementations, the one or more Schottky diodes are one or more silicon carbide Schottky diodes, and where the DC bus has a voltage between 600 V and 1000 V.

[0017] In some implementations, the GaN transistor has a gate, a source, and a drain, and the boost converter includes at least one of: a first Schottky diode having a first anode and a first cathode, the first anode being electrically coupled to the drain of the GaN transistor; and a second Schottky diode having a second anode and a second cathode, the second cathode being electrically coupled to the source of the GaN transistor.

[0018] In some implementations, the DC-DC converter is a switch-mode power supply having a switching frequency in a range from 500 kHz to 1.5 MHz.

[0019] In some implementations, the DC-DC converter is a switch-mode power supply having a switching frequency in a range from 750 kHz to 1.25 MHz.

[0020] In some implementations, the DC-DC converter is a switch-mode power supply having a switching frequency in a range from 800 kHz to 1.00 MHz.

[0021] In some implementations, the photovoltaic panels each have a maximum output voltage, and the converter modules are configured to convert the DC voltages from the photovoltaic panels to a voltage of the DC bus that is more than twice the maximum output voltage of the photovoltaic panels.

[0022] In some implementations, the converter modules are configured to provide a variable gain and are configured to generate DC outputs at a same voltage level.

[0023] In some implementations, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain from 5 to 10.

[0024] In some implementations, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain at least from 3 to 12. In some implementations, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain at least from 3 to 15.

[0025] In some implementations, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain at least from 2 to 20.

[0026] In some implementations, each of the converter modules includes short-circuit protection circuitry configured to terminate output of the converter module in response to a short circuit at the output of the converter module.

[0027] In some implementations, the photovoltaic panels each have a negative terminal or ground terminal, and the negative terminal or ground terminal is AC-coupled to a positive rail of the DC bus.

[0028] In some implementations, each of the converter modules includes a common-mode choke electrically coupled in series with the output of the converter module.

[0029] In some implementations, the system includes one or more batteries and an additional DC-DC converter; and the additional DC-DC converter is configured to receive DC input from the DC bus and to charge the one or more batteries using output of the additional DC- DC converter.

[0030] In some implementations, the system includes (i) a first group of converter modules having outputs coupled in parallel and (ii) a second group of converter module having outputs coupled in parallel, and a negative rail for output of the first group of converter modules is coupled to a positive rail for output of the second group of converter modules.

[0031] In some implementations, the first group of converter modules and the second group of converter modules each provide DC input to the DC-AC converter; and the DC-AC converter is configured to generate split-phase AC output including two AC outputs having opposite phase.

[0032] In some implementations, each of the converter modules comprise a control device that is configured to control output of the converter module based on a sensed voltage at the DC bus.

[0033] In some implementations, the system includes a controller that is configured to adjust a level of load on the DC bus based on a sensed voltage at the DC bus.

[0034] In some implementations, the controller is configured to initiate supply of power to the DC bus by establishing a voltage at the DC bus in a predetermined operating range, and each of the converter modules is configured to sense the voltage at the DC bus and initiate supply of power to the DC bus in response to sensing the voltage at the DC bus in the predetermined operating range.

[0035] In some implementations, the controller is configured to terminate supply of power to the DC bus by causing a short circuit on the DC bus, and each of the converter modules includes short circuit protection circuitry that is configured to detect a short circuit on the DC bus and terminate supply of power to the DC bus in response to detecting a short circuit on the DC bus.

[0036] In another general aspect, a system includes: a plurality of converter modules, where each of the converter modules includes a DC-DC converter, where each of the converter modules has an input and an output, and where each of the converter modules is configured to (i) receive, at the input, a DC voltage from at least one photovoltaic panel and (ii) convert the received DC voltage to an output DC voltage at the output, where the outputs of the converter modules are electrically coupled together to provide DC output in parallel to a DC bus; and a DC-AC converter configured to receive DC power from the DC bus and provide an AC output.

[0037] In another general aspect, a method includes: receiving DC input voltages generated from photovoltaic panels; converting the DC input voltages to DC output voltages using a plurality of converter modules, where the converter modules are configured to boost the DC input voltages to the DC output voltages, and where the converter modules are each are configured to provide the DC output voltages in parallel to a DC bus; and controlling the converter modules to provide an amount of power output to the DC bus that is based on a voltage at the DC bus.

[0038] In some implementations, controlling the converter modules includes, for each of the converter modules: sensing the voltage at the DC bus; and using a control device of the converter module to adjust power output of the converter module based on the sensed voltage at the DC bus.

[0039] In some implementations, controlling the converter modules includes controlling the converter modules to provide power at a maximum power point of the photovoltaic panels when the voltage at the DC bus is less than a target DC bus voltage.

[0040] In some implementations, controlling the converter modules includes controlling the converter modules to reduce or limit power output to the DC bus when the voltage at the DC bus is greater than a target DC bus voltage.

[0041] In some implementations, the method includes adjusting an amount of power demand on the DC bus based on the voltage at the DC bus. In some implementations, adjusting the amount of power demand on the DC bus includes adjusting an amount of power from the DC bus that is used to inject AC power to an AC power grid.

[0042] In some implementations, adjusting the amount of power demand on the DC bus includes adjusting an amount of power from the DC bus that is used to charge one or more batteries.

[0043] In some implementations, adjusting an amount of power demand on the DC bus includes increasing an amount of power demand on the DC bus when the voltage at the DC bus is above a target DC bus voltage.

[0044] In some implementations, adjusting an amount of power demand on the DC bus includes decreasing an amount of power demand on the DC bus when the voltage at the DC bus is below a target DC bus voltage.

[0045] In some implementations, each of the converter modules is controlled by a separate control device that adjusts power output of the converter module based on the voltage at the DC bus; and an additional controller adjusts load demand on the DC bus based on the voltage at the DC bus.

[0046] In another general aspect, a method includes: monitoring, by a converter module, a DC bus to determine a DC bus voltage; detecting, by the converter module, that the DC bus voltage is in a predetermined operating range; and in response to detecting that the DC bus voltage is in the predetermined operating range, supplying, by the converter module, power to the DC bus, where the converter module is configured to supply power to the DC bus in parallel with one or more other converter modules, and where the converter module boosts a DC input voltage from one or more photovoltaic panels to a DC output voltage that the converter module provides to the DC bus.

[0047] In some implementations, the method includes: monitoring the DC bus voltage while the converter module supplies power from the converter module to the DC bus; determining that the DC bus voltage is between a lower threshold and a target DC bus voltage; and in response to determining that the DC bus voltage is between the lower threshold and the target DC bus voltage, controlling the converter module to provide power to the DC bus without limiting the amount of power from the one or more photovoltaic panels that is provided to the DC bus.

[0048] In some implementations, controlling the converter module includes: monitoring input current and input voltage from the one or more photovoltaic panels; and controlling the converter module to maximize an amount of power generated from the one or more photovoltaic panels.

[0049] In some implementations, the method includes: monitoring the DC bus voltage while the converter module supplies power from the converter module to the DC bus; determining that the DC bus voltage is between the target DC bus voltage and an upper threshold; and in response to determining that the DC bus voltage is between the target DC bus voltage and the upper threshold, controlling the converter module to limit an amount of power from the one or more photovoltaic panels that is provided to the DC bus.

[0050] In some implementations, controlling the converter module includes: in response to determining that the DC bus voltage is greater than the target DC bus voltage, limiting input current from the one or more photovoltaic panels.

[0051] In some implementations, limiting input current from the one or more photovoltaic panels includes applying an input current limit that is based on a magnitude by which the DC bus voltage exceeds the target DC bus voltage.

[0052] In some implementations, the method includes: while the converter module supplies power to the DC bus, determining, by the converter module, that the DC bus voltage is outside the predetermined operating range; and in response determining that the DC bus voltage is outside the predetermined operating range, terminating, by the converter module, supply of power from the converter module to the DC bus.

[0053] In some implementations, the method includes: while the converter module supplies power to the DC bus, detecting, by the converter module, a short circuit at the DC bus; and in response detecting the short circuit at the DC bus, terminating, by the converter module, supply of power from the converter module to the DC bus.

[0054] In some implementations, the method includes: after terminating supply of power from the converter module to the DC bus: monitoring, by the converter module, the DC bus voltage while the converter module does not supply power to the DC bus; detecting, by the converter module, that the DC bus voltage is in the predetermined operating range; and in response to detecting that the DC bus voltage is in the predetermined operating range, resuming, by the converter module, supply of power from the converter module to the DC bus.

[0055] In another general aspect, a method includes: controlling, by a controller, one or more devices to establish a voltage in a predetermined operating range on a DC bus, where the multiple converter modules are coupled to the DC bus in parallel, and each of the converter modules is configured to provide power to the DC bus from one or more photovoltaic panels when the voltage on the DC bus is in the predetermined operating range; after establishing the voltage in the predetermined operating range on the DC bus, and after one or more of the converter modules begin supplying power to the DC bus, monitoring, by the controller, the voltage on the DC bus; and adjusting an amount of power demand on the DC bus based on the voltage on the DC bus.

[0056] In some implementations, after establishing the voltage in the predetermined operating range on the DC bus and after one or more of the converter modules begin supplying power to the DC bus, causing the one or more devices to discontinue providing power to the DC bus, such that the converter modules set the voltage on the DC bus.

[0057] In some implementations, controlling the one or more devices to establish the voltage in the predetermined operating range on the DC bus includes controlling the one or more devices to establish the voltage in the predetermined operating range using energy stored in one or more batteries.

[0058] In some implementations, controlling the one or more devices to establish the voltage in the predetermined operating range on the DC bus includes controlling an AC / DC converter that receives power from an AC power grid to provide the voltage in the predetermined operating range.

[0059] In some implementations, adjusting the amount of power demand on the DC bus based on the voltage of the DC bus includes: determining that the voltage on the DC bus is greater than a target voltage for the DC bus; in response to determining that the voltage on the DC bus is greater than the target voltage for the DC bus, increasing an amount of power drawn from the DC bus to (i) charge one or more batteries and / or (ii) supply power to an AC power grid.

[0060] In some implementations, adjusting the amount of power demand on the DC bus based on the voltage of the DC bus includes: determining that the voltage on the DC bus is less than a target voltage for the DC bus; in response to determining that the voltage on the DC bus is less than the target voltage for the DC bus, decreasing an amount of power drawn from the DC bus to (i) charge one or more batteries and / or (ii) supply power to an AC power grid.

[0061] Other implementations of these aspects include systems, apparatus, and circuitry configured to perform the actions of the methods, as well as computer programs, configured to perform the actions of the methods, encoded on computer-readable storage devices. A system can be so configured by virtue of software, firmware, hardware, or a combination of them installed on the system that in operation cause the system to perform the actions. One or more computer programs can be so configured by virtue having instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions.

[0062] Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

[0063] BRIEF DESCRIPTION OF FIGURES

[0064] FIG. l is a block diagram that illustrates an example system that generates power using a parallel DC architecture.

[0065] FIG. 2A is a block diagram that illustrates an example parallel DC architecture.

[0066] FIG. 2B is a block diagram that illustrates an example series DC architecture.

[0067] FIG. 2C is a block diagram that illustrates an example parallel AC architecture.

[0068] FIG. 3 is a block diagram that illustrates a split-phase arrangement using a parallel DC architecture.

[0069] FIG. 4A is a block diagram that illustrates an example converter module for a parallel DC architecture.

[0070] FIG. 4B is a circuit schematic diagram that illustrates an implementation of the example converter module of FIG. 4A.

[0071] FIG. 5 is a flow diagram that illustrates an example process for controlling a converter module in a parallel DC architecture.

[0072] FIG. 6 is a flow diagram that illustrates an example process for a managing output of a system that includes converter modules in a parallel DC architecture.

[0073] Like reference numbers and designations in the various drawings indicate like elements.

[0074] DETAILED DESCRIPTION

[0075] FIG. 1 is a block diagram that illustrates an example application 10 of power generation using a parallel DC architecture. The application 10 includes a power generation system (“system”) 100 that can provide power for various different uses, including electric vehicle charging, powering residential and / or commercial loads, supplying power to a power grid, and so on.

[0076] The system 100 includes multiple PV panels 112-1 through 112-N and multiple converter modules 110-1 through 110-M, where N and M can each be any number two or greater. In the example of FIG. 1, the quantity of PV panels 112-1 through 112-N is the same as the quantity of converter modules 110-1 through 110-M, but this is not required. For example, there may be more or fewer PV panels 112-1 through 112-N than converter modules 110-1 through 110-M.

[0077] In the example of FIG. 1, each of the PV panels 112-1 through 112-N provides generated DC voltage to a single one of the converter modules 110-1 through 110-M. For example, each of the PV panels 112-1 through 112-N can be coupled to a different one of the converter modules 110-1 through 110-Mand DC voltage generated by each PV panel 112-1 through 112-N serves as input to the corresponding converter module 110-1 through 110-M. As an alternative, the system 100 may not use converter modules 110-1 through 110-M and PV panels 112-1 through 112-N in a one-to-one relationship. For example, one or more of the converter modules 110-1 through 110-M can be coupled to receive input from two or more of the PV panels 112-1 through 112-N.

[0078] The converter modules 110-1 through 110-M each provide DC output in parallel to an inverter 114, which performs DC-AC conversion to supply AC power to an AC bus 115 from which power is provided to other components in the system 100. In the example of FIG. 1, a single inverter 114 is used as a central inverter for the system 100. In other implementations, multiple inverters may be used. The parallel DC output of the converter modules 110-1 through 110-M can also supply DC power to a battery buffer system 122, optionally through another DC-DC converter 120, and / or to an electric vehicle (EV) charger 124, without intermediate conversion to AC and back to DC.

[0079] Each of the PV panels 112-1 through 112-N represents one or more PV cells. For example, each of the PV panels 112-1 through 112-N can include one or more PV modules, where each PV module can include multiple PV cells, and the PV cells in the PV module can be optionally sealed in an environmentally protective laminate. Each of the collections of PV cells shown as one of the PV panels 112-1 through 112-N can be assembled as a pre-wired, field-installable unit, but is not required to be.

[0080] The system 100 can include a main controller 118 that monitors and manages power generation in the system 100. One function of the main controller 118 can be to receive and aggregate system status information. For example, the converter modules 110-1 through 110- M can each generate status information such as output characteristics (e.g., output voltage, output current, output power, etc.) for output to the DC bus 116, whether an output is being provided to the DC bus 116, input characteristics (e.g., input voltage, input current, input power, etc.) for input from its respective PV panel(s) 112-1 through 112-N, temperature of the converter module 110, an indication of the operating mode or control mode used, whether the converter module 110-1 through 110-M is powered on, whether errors have occurred or protection circuitry has been triggered, and so on. The converter modules 110-1 through 110- M can provide the status information to the main controller 118 periodically, in response to changes in status, in response to requests from the main controller 118, and so on. In some implementations, status information for the PV panels 112-1 through 112-N is determined by or provided through local control devices of the respective converter modules 110-1 through 110-M. In other implementations, the main controller 118 interfaces directly with the PV panels 112-1 through 112-N to obtain status information for the PV panels 112-1 through 112-N.

[0081] The main controller 118 may communicate with the converter modules 110-1 through 110-M and / or the inverter 114 through a wired communication link and / or a wireless communication link (e.g., Wi-Fi, Bluetooth, etc.). In some implementations, the main controller 118 communicates with the converter modules 110-1 through 110-M and / or the inverter 114 over a communication network 104, which can include public and / or private networks and may include the Internet.

[0082] The main controller 118 can aggregate the status information it receives. The main controller 118 can provide the status information for the converter modules 110-1 through 110-M and / or PV panels 112-1 through 112-N to a client device 102, with information being provided for the converter modules 110-1 through 110-M and / or PV panels 112-1 through 112-N individually and / or for the overall set of converter modules 110-1 through 110-M and / or PV panels 112-1 through 112-N collectively (e.g., for the system 100 as a whole). The main controller 118 can provide status information over the communication network 104, for delivery to the client device 102. For example, status information may be provided to a server system or cloud computing platform that supports presentation of the status information in a web page, web application, mobile device application, and so on.

[0083] In some implementations, the main controller 118 adjusts the load demand from various elements in the application 10 to balance or adjust the load level to the power level that the system 100 is currently capable of producing. This can be performed as discussed further below in FIG. 6. In addition, or as an alternative, the main controller 118 can coordinate operation of the converter modules 110-1 through 110-M and the inverter 114 more directly. For example, the main controller 118 may be configured to set parameter values that specify settings such as the target voltage for the DC bus 116, operating ranges for the DC bus 116, power output levels, and so on. The main controller 118 may take into account the circumstances of each converter module 110-1 through 110-M and its associated PV panel(s) 112-1 through 112-N, as well as the power demands of loads, to set the output for each of the different converter modules 110-1 through 110-M, as discussed further below.

[0084] In further detail, the converter modules 110-1 through 110-M are coupled in parallel to a DC bus 116, which in turn is connected to the inverter 114. Each converter module 110- 1 through 110-M includes a DC-DC converter (see FIG. 4 A) to convert the input DC voltage from the corresponding PV panel 112-1 through 112-N to the voltage of the DC bus 116. The system 100 can be designed so that the voltage of the DC bus 116, in a predetermined operating range for the system 100, is consistently higher than the maximum voltage generated by any single one of the PV panels 112-1 through 112-N. This enables the DC-DC converters in the converter modules 110-1 through 110-M to be boost converters, e.g., strictly stepping up voltage, without the need to also have the capability to step down voltage (e.g., buck conversion). As described further below, a boost topology can assist in reducing the size and cost of the converter modules.

[0085] The converter modules 110-1 through 110-M can provide a wide-range, high-gain boost to the input DC voltages from the PV panels 112-1 through 112-N. The DC-DC converter (discussed in more detail with respect to FIG. 4A) in each converter module 110-1 through 110-M can be a boost converter with a variable gain, and the gain can vary over a range of, for example, 2 to 20, or from 3 to 15, etc. As an example, the PV panels 112-1 through 112-N may be configured to supply DC voltages in the range of roughly 16 V to 60 V, and the voltage of the DC bus 116 can have a target level or nominal value of 200 V, although the system 100 can be designed for variation of the DC bus voltage within a range, such as from 190 V to 210 V. In this example, the boost converter in each converter module 110-1 through 110-M is configured to step up any of the DC inputs in the range of 16 V to 60 V to the DC bus voltage of 200V, and so can provide a gain over at least a range from 3.33 to 12.5.

[0086] The conversion modules 110 are configured so that as conditions change and the output voltages of the PV panels vary, the conversion modules 110 each separately adjust their DC-DC conversion gain to output the DC bus voltage. Each of the conversion modules 110 can independently contribute DC output to the DC bus 116, at an appropriate voltage, in parallel with the other conversion modules 110. The conversion modules 110 can also be configured to monitor the input DC voltage from a PV panel 112 and to terminate output if the input DC voltage is outside the range that the converter can properly convert to the DC bus voltage. For example, if the DC input voltage is detected to be below a minimum threshold or above a maximum threshold (e.g., outside the range the DC-DC converter can convert with its gain range), the converter module 110 can shut down output until the input DC voltage returns to the proper range. When the input voltage to a conversion module 110 from a PV module 112 is too low, the converter module 110 can simply stop operating, but this is not considered a protection function, meaning that the converter module 110 does not need to disconnect itself from the DC bus 116 in this condition.

[0087] By coupling the converter modules 110-1 through 110-M together to provide DC output in parallel, the system 100 has a high degree of scalability. The power capacity of the system 100 can be easily adjusted by adding additional PV panels 112 and associated converter modules 110-1 through 110-M in parallel. Similarly, removing one or more PV panels 112-1 through 112-N and associated converter modules 110-1 through 110-M reduces the power capacity without disrupting supply capabilities of the other PV panels 112-1 through 112-N and converter modules 110-1 through 110-M.

[0088] The parallel DC connection of the converter modules 110-1 through 110-M also provides the system 100 a high degree of reliability and fault tolerance at the system level. The parallel connection allows the converter modules 110-1 through 110-M supply power independently of each other. A failure or power reduction in one of the PV panels 112-1 through 112-N or its converter module 110-1 through 110-M does not interfere with the ability of any of the other PV panels 112-1 through 112-N or converter modules 110-1 through 110-M to continue supplying power.

[0089] Further, because the converter modules are coupled in parallel, each converter module handles only a portion of the overall current in the system. The components in each converter module can be rated for the current that the converter module supplies, which reduces the size and cost compared to arrangements that would require a higher amount. For example, a 2000 watt (W) system may include 10 PV panels and 10 converter modules, and may use a DC bus of 200 volts (V). In the system, if the total system current on the DC bus is 10 amps (A), each of the ten converter modules can be rated for one amp.

[0090] The system 100 draws power from the DC bus 116 and can provide power to a variety of other components. The inverter 114 converts the DC voltage at the DC bus 116 to an AC output. The AC output can be connected to AC loads through an automatic transfer switch (ATS) 130, which can be configured to switch between providing AC power from the inverter 130 or another source, such as a power grid 152. In general, the ATS 130 can be configured to provide continuous delivery of electrical power from one of two power sources to a load circuit, such as critical loads 132 that do not tolerate interruption. The system 100 can also route AC power from the inverter 114 to the main panel 140 of a building, to supply power to regular loads 142 (that may tolerate disruption more than the critical loads 132). The AC power from the inverter 114 can also be provided through the energy meter 150 to the power grid 152.

[0091] In many cases, performing DC-AC conversion in a centralized manner, such as at the inverter 114, can increase efficiency and decrease cost compared to distributed or decentralized DC-AC conversion. When generating AC power, the DC-AC converter often needs to synchronize output with the power grid 152 and / or other DC-AC converters in the system. Many DC-AC converters also are required to provide isolation, which often involves a high-frequency transformer. In addition, DC-AC conversion also requires a significant energy buffer, which usually takes the form of large electrolytic capacitors. To provide distributed DC-AC converters, e.g., separate DC-AC converters for each PV panel 112-1 through 112-N, would increase the size, weight, and cost of the conversion electronics for each PV panel 112-1 through 112-N. On the other hand, parallel DC connection of power from the PV panels 112-1 through 112-N avoids multiplying these components for each PV panel 112-1 through 112-N. In other words, the converter modules 110 each include a DC- DC converter and can omit the high-frequency transformer, electrolytic capacitors for energy buffering, and synchronization control systems that would be needed for DC-AC conversion.

[0092] Although a single inverter 114 in the system 100 might present a possible point of failure, the system 100 can be designed with this in mind to provide a inverter 114 with high reliability, or can include a redundant backup DC-AC converter to address this possibility. In addition, the inverter 114 is typically be mounted on a wall where it can be easily serviced or replaced if needed. In the event of a failure, gaining access to the inverter 114 would often be easier than gaining access to one of many distributed DC-AC converters that may be mounted on a roof near PV panels or other hard to reach locations.

[0093] The DC power on the DC bus 116 can be used to power DC loads, such as a battery buffer 122 or an EV charger 124 for an electric vehicle 126. This can allow greater efficiency than systems that have a greater number of intermediate conversions, such as conversion of PV panel DC output to AC power, then from AC power back to DC power. DC-DC conversion can be performed very efficiently, often with significantly higher efficiency than when an intermediate conversion to the AC power of a power grid is performed.

[0094] The battery buffer 122 can be an energy storage system for a building. The battery buffer 122 may receive DC power for charging, and supply DC power as output, at a different DC voltage than the DC bus 116. Accordingly, a DC-DC converter 120 can be placed between the DC bus 116 and the battery buffer 122 to convert from the DC bus voltage to the voltage needed for charging the battery buffer 122 and to convert output from the battery buffer 122 to the DC bus voltage. This provides the additional advantage of allowing the same inverter 114 to be used to generate AC power from energy provided by the PV panels 112-1 through 112-N or stored in the battery buffer 122. The EV charger 124 can also receive DC power from the DC bus 116 and perform DC-DC conversion to convert to the appropriate DC voltages needed to charge the batteries of the electric vehicle 126.

[0095] In many residential and commercial settings, many components are natively DC rather than AC. For example, PV panels provide DC output and batteries are charged and discharged with DC power. Many loads are or can be driven using DC power, such as televisions, heating, lighting, electric vehicle charging, and so on. There is a potential for buildings to be operated using a DC microgrid, which can provide significant efficiency improvements compared to traditional AC power. The system 100 facilitates a DC microgrid approach by maintaining access to DC power, without AC conversion, through the DC bus 116, allowing for the high efficiency for DC loads.

[0096] FIGS. 2A-2C illustrate examples of different architectures for combining power output of PV panels. FIG. 2A is a block diagram that illustrates an example of a parallel DC architecture 210, which is the arrangement shown and described for the system 100 of FIG. 1. Coupling the outputs of the converter modules 110-1 through 110-M to the DC bus 116 in parallel provides high reliability and scalability with low cost and small size for each converter module 110. Each converter module 110-1 through 110-M provides the same DC bus voltage, allowing converter modules 110 and PV panels 112 to be added or removed without disrupting the operation of the system 100. In addition, coupling the outputs of the converter modules 110-1 through 110-M in parallel limits the amount of current that needs to pass through each converter module 110-1 through 110-M, allowing smaller and less- expensive components to be used in each converter module 110-1 through 110-M while together providing a high current to the DC bus 116. The converter modules 110-1 through 110-M and the main controller 118 can also use the DC bus voltage to coordinate the total power output of to the DC bus 116, as discussed further with respect to FIGS. 5 and 6. Other advantages of the parallel DC architecture 210 are discussed below.

[0097] FIG. 2B is a block diagram that illustrates an example of a series DC architecture 220. In this arrangement, each PV panel 112-1 through 112-N has an associated converter module 222-1 through 222-M that provides DC output, but the converter modules 222-1 through 222- M are coupled together in series to the DC bus 116. As a result, the DC bus voltage provided to the inverter 114 is the sum of voltages output by the set of converter modules 222-1 through 222-M coupled together. Depending on the number of converter modules 222-1 through 222-M used, the output voltage needed from the converter modules 222-1 through 222-M can vary. Due to varying numbers of PV panels 112-1 through 112-N and converter modules 222-1 through 222-M and changing conditions, the output voltages from the converter modules 222-1 through 222-M may be higher or lower than the input voltage from the PV panels 112-1 through 112-N. As a result, the converter modules 222-1 through 222- M would generally need a buck-boost topology or similar capability, which increases complexity and cost compared to the boost-only topology for the converter modules 110-1 through 110-M in the parallel DC architecture 210.

[0098] Because output voltages from the converter modules 222-1 through 222-M are summed in the series DC architecture 220, the output voltages of the converter modules 222- 1 through 222-M need to be coordinated to achieve a stable DC bus voltage. For example, if one of the PV panels 112-1 through 112-N becomes shaded and its converter module 222-1 through 222-M does not supply the expected voltage, the other PV panels 112-1 through 112- N and converter modules 222-1 through 222-M need to quickly adjust their output to supply additional voltage to make up the difference.

[0099] By contrast, in the parallel DC architecture 210, the converter modules 110-1 through 110-M do not need to include components to negotiate or communicate in order to determine and provide their output voltages. For example, in some implementations, the converter modules 110-1 through 110-M can independently control themselves and adjust their output in an attempt to provide the same target DC bus voltage. The converter modules 110-1 through 110-M can each adjust their own output power levels based on the input power from the associated PV panels 112-1 through 112-N and the DC bus voltage, as discussed further below with respect to FIG. 5. This allows the system 100 to adjust for changes in load demand and changes in the power output of the PV panels 112-1 through 112-N, even without receiving commands from a main controller 118. The main controller 118 can also monitor the DC bus 116 and assist in control of the system 100 as discussed below with respect to FIG. 6. This can include adjusting the overall load on the DC bus 116 to maximize utilization of the available power from the PV panels 112-1 through 112-N, for example, adjusting the amount of power that is injected to the AC power grid 152, used to charge the electric vehicle 126, and / or used to charge the battery buffer 122. In other implementations of the parallel DC architecture 210, the main controller 118 can communicate with the converter modules 110. For example, the converter modules 110- 1 through 110-M can provide information about their status, the input received from the PV panels, outputs provided, and the sensed condition of the DC bus 116. The main controller 118 can provide this information to the client device 102 or other devices to indicate the status of the system 100. In some cases, the main controller 118 can also set the output characteristics (e.g., output voltage, output current, output power, etc.) for each of the converter modules 110. For example, through a communication link with the converter modules 110, the main controller 118 can specify the target voltage for the DC bus 116 for the converter modules 110. The main controller 118 can also set different amounts of output power or output current to be supplied by the respective converter modules 110, based on factors such as the amount of power from the different PV panels 112-1 through 112-N, temperature of the converter modules 110, load demand, and so on.

[0100] In the series DC architecture 220, the current at the DC bus 116 flows through all of the converter modules 222-1 through 222-M, so the components of all of the modules 222-1 through 222-M need to be sized to handle the full DC current. For example, if ten converter modules 222-1 through 222-M are used to provide 10 A at the DC bus 116, all of the modules 222-1 through 222-M would need to handle the full 10A of current. By contrast, in the parallel DC architecture 210, each converter module 110-1 through 110-M only handles the current that it contributes, so if ten converter modules 110-1 through 110-M provide 10 A and contribute equally, each converter module 110-1 through 110-M only needs to be rated to handle one amp.

[0101] In the series DC architecture 220, several factors limit scalability. For example, increasing current capacity may require replacing the converter modules 222-1 through 222- M with versions having higher current handling capability, or else using components that are rated for the highest current across many configurations, which would increase cost and size and provide components rated far above typical usage configurations. In addition, the number of converter modules 222-1 through 222-M that can be used is limited by the minimum and maximum voltages that the converter modules 222-1 through 222-M can provide. The maximum gain of the converter modules 222-1 through 222-M limits the minimum number of converter modules 222-1 through 222-M that can be used to achieve a desired DC bus voltage. Similarly, the minimum gain of the converter modules 222-1 through 222-M limits the maximum number of converter modules 222-1 through 222-M that can be used to achieve the DC bus voltage. By contrast, with the parallel DC architecture 210, each converter module 110-1 through 110-M provides the full DC bus voltage, so even a single converter module 110-1 through 110-M can supply the DC bus voltage. Also, with parallel connections, converter modules 110-1 through 110-M can be added or removed without the need to change the voltage output of the other converter modules 110. Although the converter modules 110-1 through 110-M also have limits to the range of gain they can provide, these limits do not affect the number of converter modules 110-1 through 110-M that can be used together in a parallel DC architecture 210. In addition, in some implementations, multiple PV panels 112 may be connected in series to provide a higher input voltage that is in the range that is appropriate for the converter modules 110-1 through 110-M to convert to the target DC bus voltage.

[0102] In addition, the series DC architecture 220 does not provide the fault tolerance of the parallel DC architecture 210. For example, if any of the converter modules 222-1 through 222-M is disconnected or fails and causes an open circuit, the entire string of converter modules 222-1 through 222-M stops supplying power. By contrast, in the parallel DC architecture 210, if any of the converter modules 110-1 through 110-M is disconnected or is unable to transmit power, the parallel connection allows the remaining converter modules 110-1 through 110-M to continue supplying power.

[0103] FIG. 2C is a block diagram that illustrates an example of a parallel AC architecture 230. In this arrangement, each PV panel 112-1 through 112-N has an associated converter module 232-1 through 232-M that includes a DC-AC converter to provide AC output. The converter modules 232-1 through 232-M are coupled together to provide their AC outputs in parallel to an AC bus 115.

[0104] The parallel connection of the converter modules 232-1 through 232-M provides scalability, but performing DC-AC conversion separately at each converter module 232-1 through 232-M increases the cost, size, and weight of the converter modules 232-1 through 232-M. For example, the DC-AC converters often need to be isolated, which requires additional components (such as a high-frequency transformer) that increase the size, cost, and weight of the converter modules 232-1 through 232-M compared to the converter modules 110-1 through 110-M that perform DC-DC conversion. In addition, electrolytic capacitors are typically needed as an energy buffer for DC-AC conversion, which increases cost and reduces reliability. DC-AC converters typically require a larger number of transistors and an overall greater complexity than DC-DC converters. As another example, the converter module 232-1 through 232-M need processing capability to synchronize their AC outputs with each other or with a power grid, which is not needed for a parallel DC architecture 210. Although DC-AC conversion in each of the converter modules 232-1 through 232-M can provide redundancy, it also lowers efficiency for some applications. For example, to charge an electric vehicle or battery system, power needs to be converted from the AC bus 115 back to DC. The intermediate conversion to AC often results in lower efficiency than DC-DC conversion as can be performed from the DC bus 116 in the parallel DC architecture 210.

[0105] FIG. 3 is a block diagram that illustrates a split-phase arrangement 300 using a parallel DC architecture. In the example of FIG. 1, the inverter 114 provides a single phase of AC output, and the converter modules 110-1 through 110-M are coupled together in the same way to DC bus 116. The example of FIG. 3 shows one way that converter modules 110 can be grouped together in different groups 302, 304 to provide split-phase output, e.g., two AC phases that are out of phase by 180 degrees from each other.

[0106] In the example, a first group 302 includes PV panels 112-1 through 112-N and converter modules 110-1 through 110-M that have outputs coupled together in parallel. The converter modules 110-1 through 110-M are each configured to provide a same DC bus voltage, such as 200 V in the illustrated example. The positive terminals of each of the converter modules 110-1 through 110-M in the first group 302 are coupled to a first positive rail PR1, and the negative terminals of each of the converter modules 110-1 through 110-M in the first group 302 are coupled to a first negative rail NR1.

[0107] A second group 304 includes another set of PV panels 112- la through 112-Na and converter modules 110- la through 110-Ma that have outputs coupled together in parallel. The converter modules 110- la through 110-Ma are each configured to provide the same DC bus voltage, such as 200 V. In this case, the converter modules 110-1 through 110-M of the first group 302 are each configured to provide the same DC bus voltage (or operate in the same range of DC bus voltages) as the converter modules 110- la through 110-Ma. The positive terminals of each of the converter modules 110- la through 110-Ma in the second group 304 are coupled to a second positive rail PR2, and the negative terminals of each of the converter modules 110- la through 110-Ma in the second group 304 are coupled to a second negative rail NR2.

[0108] As a result, the two groups 302, 304 provide separate pairs of voltage rails, e.g., rails PR1, NR1 for the group 302 and rails PR2, NR2 for the group 304, with a potential of 200 V across each pair. The split-phase arrangement 300 couples together the first negative rail NR1 and the second positive rail PR2. As a result, the voltage across the other two rails, e.g., the first positive rail PR1 and the second negative rail NR2 is 400 V, or twice the voltage developed by the individual groups 302, 304.

[0109] An split-phase inverter 314 can receive the DC outputs and generate split-phase output based on it. For example, the split-phase inverter 314 has three inputs: a first input for the first positive rail PR1 supplying +200 V, a second input for the neutral or zero potential resulting from coupling the rails NR1 and PR2, and a third input for the second negative rail NR2 supplying -200V. The split-phase inverter 314 has three outputs on the AC side: a first output LI providing a first phase of AC power, a second output that is neutral, and a third output L2 providing a second phase of AC power. The AC output for LI and L2 can be equal in magnitude and 180 degrees out of phase. The difference in phase of the LI and L2 AC outputs is indicated in the drawing as a symbol with two out-of-phase sinusoids. For example, the LI and L2 can each provide 110 V AC output, that if used together can provide 220 V AC output due to the difference in phase. In many cases, split-phase systems need to handle unbalanced loads, and so the split-phase inverter 314 can include an integrated balancer, which can help with balancing the difference in power generation between different sets of parallel PV strings.

[0110] Other arrangements of PV panels 112-1 through 112-N and converter modules 110-1 through 110-M coupled in parallel can be used to achieve other outputs. To generate singlephase 220 V AC output, an additional boost stage can be used. For example, converter modules 110-1 through 110-M can each provide 200 V output to a DC bus, and an additional DC-DC boost stage can double the voltage to 400 V for conversion into 220 V AC output. As another example, single-phase 220 V AC output can be obtained using two DC input lines of +200 V and -200 V as shown in FIG. 3, but with an added balancer.

[0111] As another example, the converter modules 110-1 through 110-M and the converter modules 110- la through 110-Ma, may be configured to output different DC bus voltages than are illustrated. For example, each converter module 110-1 through 110-M and converter module 110- la through 110-Ma can be configured to output a DC output voltage of, for example, 400 V, 600 V, 800 V, etc. For example, if the converter modules 110-1 through 110-M and the converter modules 110- la through 110-Ma are each configured to output 400 V, then the input to the split-phase inverter 314 can be +400 V and -400 V, which facilitates 220 V AC output.

[0112] FIG. 4A is a block diagram that illustrates an example converter module 110. Each of the converter modules 110-1 through 110-M and 110- la through 110-Ma can have features as shown and described for FIG. 4A. The converter module 110 includes input terminals, DC PV+ and DC PV-, to receive an input DC voltage from a PV panel 112. The input DC voltage is provided to an input filter 402, and then provided to a DC-DC converter 404, which boosts the voltage to generate an output DC voltage of the DC bus 116. The output DC voltage is provided to an output filter 406 and then provided at output terminals DC OUT+ and DC OUT-.

[0113] In some implementations, the converter module 110 provides information to the main controller 118 through a communication link 409. For example, as discussed further below, the converter module 110 can provide status information about the operation of the converter module 110, sensed conditions (e.g., temperature, input characteristics for input to the converter module 110, output characteristics of output from the converter module 110, sensed voltage of the DC bus 116, etc.), tracking data (e.g., power generation statistics which may be automatically provided periodically or may be provided on-demand in response to a request from the main controller 118), etc. The converter module 110 can also receive information from the main controller 118, such as configuration data, target voltages, thresholds, commands, instructions, updates to software or firmware, requests for information, etc.

[0114] The DC-DC converter 404 can be a switch-mode power supply, such as a boost converter. The DC-DC converter 404 can be configured to provide a wide range of high-gain boost. For example, the DC-DC converter 404 can be configured to provide a variable gain over a range from 5 to 10, 3 to 12, from 3 to 15, from 3 to 18, from 2 to 20, or another appropriate range. For example, the variable gain range can be a range in which the DC-DC converter can provide conversion efficiency of at least a minimum level across the range (e.g., a minimum level of efficiency of at least 90%, 95%, 98%, 99%, etc.). In some implementations, the DC-DC converter 404 is configured to provide levels of gain that are continuous or substantially continuous over the variable gain range specified. In other implementations, the DC-DC converter 404 is configured to provide multiple levels of gain along the variable gain range, but may do so through discrete or discontinuous gain settings across the range.

[0115] As an example, the DC-DC converter 404 can be configured to receive input in a range from 16 V to 60 V and to have the capability to set the gain to provide a DC bus voltage of 200 V. The gain of the DC-DC converter 404 can be adjusted by adjusting the switching duty cycle. As an example, a boost converter can provide a gain, M, that is based on the duty cycle, D, based on the relationship M = (1+D) / (1-D). As a result, the DC-DC converter 404 can provide a gain, M, over the range from 3 to 19 using a duty cycle, D, over the range from 55% to 90%, while achieving an efficiency of at least a minimum level (e.g., at least 95%, at least 98%, etc.) over these ranges. The DC-DC converter 404 can also be configured with step-down (or buck) capability to regulate the input voltage to a lower voltage. Thus, in some embodiments, the DC-DC converter 404 is a transformer-less boost- only converter having only the capability to regulate the input voltage up to a higher voltage, and in other embodiments the DC-DC converter can be a transformer-less boost and buck converter having both step up and step down voltage regulation capability. Of course, other DC-DC converter topologies, such as solid-state transformers, can alternatively be used depending on the needs of the individual application.

[0116] The converter module 110 can include a control device 408 that automatically adjusts the switching duty cycle of the DC-DC converter 404 based on sensed conditions and stored information. For example, the control device 408 can store or retrieve information indicating the target DC bus voltage to be provided, e.g., 200 V, 400 V, 800 V, etc., and data indicating the relationship between duty cycle and gain, e.g., as a lookup table, equation, algorithm, executable code, etc. In some implementations, the target DC bus voltage to be provided is set during manufacturing or installation of the converter module 110. For example, the DC bus voltage may be programmed into a memory of the converter module 110 or a selector switch or jumper can be used to select one of several predetermined options. As another example, the main controller 118 can set the target DC bus voltage through a command or parameter value that the main controller 118 provides to the converter module 110 through a wired or wireless communication link.

[0117] The control device 408 can communicate with a memory 403 of the converter module 110 to store and / or retrieve information. For example, the values for operating parameters, such as the target DC bus voltage setting, can be stored in the memory 403 and can be retrieved by the control device 408. Similarly, the memory 403 can store other items such as the relationship between duty cycle and gain and software and / or other executable instructions for execution by the control device 408. The memory 403 can include other information, such as calibration data, characterization data indicating characteristics of the connected PV panel(s), and so on. The control device 408 can use the memory 403 to store status information, including to accumulate status information over time so the converter module 110 can provide it to the main controller 118 periodically or in response to a request.

[0118] The converter module 110 can include sensing circuitry 407 that includes, for example, one or more voltage sensors, current sensors, temperature sensors, and so on. The sensing circuitry 407 can provide measured values for, for example, the DC bus voltage, input characteristics for input to the converter module 110 (e.g., input voltage, input current, and input power from the connected PV panel(s) 112), output characteristics for output from the converter module 110 (e.g., output voltage, output current, output power, etc.), temperature of the converter module 110, and so on. The control device 408 receives the measured values from the sensing circuitry 407, so the control device 408 can control operation of the DC-DC converter 404 based on the DC bus voltage and potentially other sensed conditions (e.g., voltages at the input terminals and / or other locations within the converter module 110). Based on the DC bus voltage and potentially other sensed conditions, the control device 408 can calculate the duty cycle needed to achieve the DC bus voltage and can send control signals to adjust the duty cycle. In some implementations, the control device 408 or the DC-DC converter 404 can use a feedback control loop to adjust the duty cycle to maintain the output within a reasonable tolerance of the nominal or target DC bus voltage. For example, the control device 408 or a control loop can adjust the duty cycle as the input voltage from the associated PV panel(s) 112 changes or as other conditions change. The control device 408 can implement control of the converter module using the techniques of FIG. 5 discussed below. As another example, the control device 408 can control the converter module 110 in response to instructions or commands given by the main controller 118.

[0119] The converter module 110 can include an input current limiter 401 that can selectively apply a current limit to the input from the connected PV panel(s) 112. As discussed below, in some cases, more power may be available from PV panels 112 than can be effectively drawn and used from the DC bus 116. As a result, to align the level of power provided at the DC bus 116 with the load demand, and to maintain the voltage at the DC bus 116 in an appropriate range (e.g., within a predetermined magnitude or range with respect to the nominal target DC bus voltage), the converter module 110 can selectively limit input power from the connected PV panel(s) 112 when needed. This limit can be applied by engaging the input current limiter 401 when the control device 408 determines that generated or available power exceeds the desired output power for the converter module 110, given the conditions sensed by the sensing circuitry 407. The input current limiter 401 can be configured to provide a variable current limit, as instructed by the control device 408. Thus, the control device 408 can set the level of input current limit to be applied by the input current limiter 401, and the control device 408 can alter the level of current limit to be applied, if any, as conditions change (e.g., as the DC bus voltage changes, the load on the DC bus voltage changes, the power available from the PV panel(s) changes, and so on). The control device 408 of the converter module 110 can be configured so that as conditions change and the output voltages of the PV panel(s) vary, the converter module 110 adjusts its output. For example, the converter modules 110-1 through 110-M can each separately and independently adjust their DC-DC conversion gain to provide output to the DC bus 116. For example, the converter module 110 can use sensing circuitry 407, such as a voltage sensor, to sense the voltage at the input and / or output of the converter module 110 and can use one or more feedback loops to automatically regulate (e.g., by adjusting the duty cycle of its boost converter) the output voltage to be in a predetermined operating range (e.g., 190 V to 210 V) and to maintain the DC bus voltage at or near a target DC bus voltage (e.g., 200 V). Each of the converter modules 110-1 through 110-M can operate in this way, so that they each independently contribute DC output to the DC bus 116 at the appropriate voltage or in the appropriate range of voltages, in parallel with the other converter modules 110-1 through 110-M, even though the converter modules 110-1 through 110-M may each receive different levels of input voltage and / or input power from their respective PV panels 112-1 through 112-N. In some implementations, the voltage at the DC bus 116 is set through a form of collective control loop with multiple converter modules 110 and the inverter 114 all sharing responsibility. For example, as discussed further below with respect to FIGS. 5 and 6, the converter modules 110 can each independently adjust their output to provide a DC bus voltage in a predetermined range around the target DC bus voltage. The inverter 114, which may be directed by the main controller 118, adjusts the amount of load on the DC bus 116 (e.g., amount of current or power drawn from the DC bus 116), which can operate to raise or lower the DC bus voltage. The changes in the DC bus voltage, in turn, can signal the converter modules 110 to adjust their output, e.g., to increase power output as voltage falls below the target DC bus voltage or decrease power output as voltage rises above the target DC bus voltage. In this way, the converter modules 110 and the inverter 114 (and / or main controller 118) can communicate indirectly through the DC bus voltage, even if other communication links are not implemented or are unavailable.

[0120] The converter module 110 can be configured to monitor conditions such as the voltage on the DC bus 116 and adjust their output in response. Each of the converter modules 110-1 through 110-M can controlled by its control device 408 to provide power output when the DC bus voltage is detected to be in a particular range, e.g., a predetermined operating range that the converter modules 110 have been configured to use. For example, a target DC bus voltage of 200 V can be set for the DC bus 116, and the converter module 110 can be configured to provide output when the DC bus voltage is in a predetermined operating range such as from 190 V to 210 V. The converter module 110 can be configured to terminate their output if the DC bus voltage is outside the predetermined operating range (e.g., above 210 V or below 190 V). When the DC bus voltage is within the predetermined operating range, the converter module 110 can increase its power output, if possible, when it detects the DC bus voltage is below the target voltage of 200 V, which indicates that the power demand of the load exceeds the collective output of the converter modules 110. Similarly, the converter module 110 can decrease its power output when it detects power output above the target voltage of 200 V, which indicates the power supplied by to the DC bus 116 (e.g., by the converter modules 110-1 through 110-M) exceeds the amount needed by the load. Control techniques are described in greater detail below with respect to FIGS. 5 and 6.

[0121] In some implementations, the converter module 110 can also monitor the input DC voltage from a PV panel 112 and to terminate output if the input DC voltage is outside the range that the converter module 110 can properly convert to the target DC bus voltage or the predetermined operating range for the DC bus voltage. For example, if the DC input voltage is detected to be below a minimum threshold or above a maximum threshold, e.g., outside the range the DC-DC converter can convert with its gain range, the converter module 110 can discontinue power output to the DC bus 116 until the input DC voltage returns to the proper range. Each converter module 110 can respond to a low input voltage from its PV panel(s) 112 (e.g., a voltage too low to provide an output in the predetermined operating range of the DC bus 116 or at the current voltage level of the DC bus 116) by stopping operation temporarily, but it is not necessary to disengage from the DC bus 116 in this condition.

[0122] The DC bus voltage or output voltage of the converter modules 110 is established to a large extent by the inverter 114 (which may be controlled by the main controller 118) which adjusts the load at the DC bus 116, and the converter modules 110 then inject energy in the form of current at the established voltage. Nevertheless, there is a collective loop of voltage control where the converter modules 110 also react to the DC bus voltage changes, and therefore contribute to the inverter’s 114 function of keeping the DC bus voltage within the predetermined operating range. If a converter module 110 receives an input voltage from a PV panel 112 that is too low (e.g., an input voltage too low for the converter module 110 to provide an output in the predetermined operating range of the DC bus 116 or at the current DC bus voltage), but the DC bus voltage is within the predetermined operating range, the converter module 110 simply stops injecting power to the DC bus 116 but does not need to disconnect from the DC bus 116. The converter module 110 experiencing the low input voltage simply stands by until the input voltage from the PV panel 112 rises to the appropriate input operating voltage range (e.g., an input voltage range at which the DC-DC converter in the converter module 110 can provide current at an appropriate output voltage for the DC bus 116).

[0123] The converter module 110 can include various types of protection circuitry 410. For example, the converter module 110 can include short circuit protection 411 that is configured to terminate output of the converter module 110 in response to detecting a short circuit across the output terminals of the converter module 110. As another example, the converter module 412 can include overcurrent protection 412, such as a fuse, to prevent damage if excessive currents occur. The converter module 110 can also include voltage surge protection 413 for the output terminals.

[0124] FIG. 4B is a circuit schematic diagram that illustrates an example of the converter module 110 of FIG. 4A. As illustrated, the input filter 402 can be provided by a resistor R1 and a capacitor Cl coupled across the input terminals of the converter module 110. In general, low pass filters and other input filters are advantageous to limit noise and voltage surges.

[0125] The DC-DC converter 404 includes a transistor QI, inductors LI, L2, diodes DI, D2, and capacitors C2, C3.

[0126] The transistor QI can be a gallium nitride (GaN) field effect transistor (FET). For example, the transistor QI in the illustrated example is an n-channel enhancement-mode GaN metal-oxide semiconductor FET (MOSFET). GaN FETs can provide a number of advantages over silicon-based transistors, including reduced switching loss and reduced conduction loss. These advantages allow for increased efficiency.

[0127] GaN FETs can allow significantly higher switching frequencies. For example, while silicon FETs are often used in DC-DC switching converters with a switching frequency in the ranges of 50 kHz to 150 kHz, GaN FETs can be used at switching frequencies of 800 kHz, 1 MHz, and higher. Higher switching frequencies often provide higher conversion efficiency in DC-DC converters. In addition, using a higher switching frequency often decreases the current ripple experienced by the passive components in the DC-DC converter by a significant amount, sometimes by roughly the magnitude that the switching frequency is increased. For example, compared to using a silicon FET at a switching frequency of 100 kHz, using a GaN FET at a switching frequency of 800 kHz can provide roughly 8 times lower current ripple, allowing smaller and less expensive passive components to be used while maintaining high efficiency. In many cases, the level of inductor ripple current affects the amount of inductance needed in a switching converter, and so the ripple current significantly affects the size and cost of the converter. For example, a higher switching frequency reduces inductor current ripple and allows the use of a lower inductance, which can be provided by a smaller and less expensive inductor. Similarly, the ripple current sets the amount of ripple voltage developed across an output capacitor, if one is used. Lowering the ripple current and ripple voltage allows for a reduced amount of capacitance, which can be provided by a smaller and less expensive capacitor.

[0128] GAN FETs are typically more expensive than silicon FETs. However, a boost converter can be implemented with only a single active switching transistor QI and Schottky diodes DI, D2. This allows the benefits of a high switching frequency to be achieved with only a single GaN transistor. The parallel DC architecture for connecting the converter modules 110-1 through 110-M enables the converter module 110 to employ a boost converter with few switching transistors. By contrast, a series DC architecture and a parallel AC architecture would each typically need more of the relatively expensive GaN transistors to operate at higher switching frequencies for their respective buck-boost converters and DC- AC converters.

[0129] The design of the converter modules can be enhanced using a gallium nitride (GaN) based semiconductor or similar material for the transistor or switch in the DC-DC converter. GaN transistors can provide a lower switching loss and lower conduction loss than silicon transistors, which supports high efficiency. In addition, these characteristics allow a significantly higher switching frequency to be used in the DC-DC converter, and higher switching frequencies allow for lower current requirements for many passive components (e.g., capacitors, inductors, diodes, etc.) in the DC-DC converter. Using a GaN transistor as the main switch in the DC-DC converter, e.g., boost converter, thus allows many other components of the DC-DC converter to be smaller and less expensive.

[0130] GaN transistors are often more expensive than silicon transistors, but using a boost converter topology limits the number of active transistors needed and thus the cost of the converter module. For example, with the parallel DC architecture, a boost converter having as few as one GaN transistor can be used, together with Schottky diodes, to achieve high efficiency at a high switching frequency and a relatively low cost. By contrast, many architectures that do not couple DC outputs in parallel require converter designs that use more active switching transistors than a boost topology. Thus, to achieve the higher switching frequencies GaN transistors can provide, these other architectures would often require higher costs due to a greater number of GaN transistors. The high-frequency operation of the DC-DC converter 404 is enhanced by using Schottky diodes DI, D2 with the GaN FET transistor QI. As illustrated, the diode DI is coupled with the cathode coupled to the drain D of the transistor QI . The diode D2 is coupled with the anode coupled to the source S of the transistor QI . Schottky diodes provide high switching frequency and low voltage drop. When the diodes DI, D2 will be subjected to reverse voltage (e.g., a maximum repetitive reverse voltage (VRRM)) of 200V or less, silicon Schottky diodes can be used. For example, silicon Schottky diodes can be used in a design when the drain voltage, VD, of the transistor QI reaches a maximum of less than or equal to 150V. In the converter module 110, this is typically sufficient to output a DC bus voltage of 200 V and potentially higher.

[0131] When the diodes DI, D2 will be subjected to reverse voltage that is higher, a silicon carbide (SiC) Schottky diode can be used. Although a SiC Schottky diodes may have a higher forward drop than a silicon Schottky diode, many SiC Schottky diodes can withstand repeated reverse voltage of 650 V or more. As a result, using SiC Schottky diodes, a converter module 110 can be made to boost voltage up to a DC bus voltage of 800 V or more, even when the design involves a drain voltage, VD, of 650 V or more. At higher DC bus voltages, the increased voltage drop of SiC Schottky diodes has a smaller impact on efficiency and allows overall high efficiency of the DC-DC conversion. In some implementations, a DC bus voltage of 800 V or higher can be desirable as input to a DC-AC converter for generating three-phase AC output.

[0132] In further detail, the DC-DC converter 404 places the inductor LI between the DC PV+ input and the drain, D, of the transistor QI . The transistor QI is placed between the diodes DI, D2. The capacitors Cl, C2 provide passive ground that is AC-coupled to the positive rail of the DC bus, e.g., the DC OUT+ terminal. For example, the capacitor C3 couples the anode of the diode D3 with the source S of the transistor QI. The capacitor C2 couples the cathode of the diode D2 with the drain D of the transistor QI . In the DC-DC converter 404, the transistor is source cooled, and the diodes are cathode cooled. The DC-DC converter 404 also includes another inductor L2 that couples the anode of the diode D2 with other components in the circuit.

[0133] Control of the DC-DC converter 404 can be performed by a processor 405, such as a microcontroller that serves as the control device 408. The processor 405 can be configured to adjust the duty cycle of switching of the transistor QI to achieve the desired DC bus voltage at the output of the converter module 110. To do this, the processor 405 can receive input of various voltage and / or current measurements sensed at different parts of the converter module 110, such as a the input ports, the output ports, or other locations. In addition, or as an alternative, the DC-DC converter 404 or the control device 408 can include an oscillator configured to generate the switching frequency and a feedback control loop to control output of the DC-DC converter 404 to achieve or maintain output of the DC bus voltage. The processor 405 can generate status information and provide the information over a communication link to the main controller 118. In some implementations, the processor 405 also receives commands or settings from the main controller 118 over a communication link, for example, to set the target DC bus voltage, to set the operating range in which the DC bus voltage is permitted to vary, to set output power or output current of the converter module 110 to the DC bus 116, and so on.

[0134] The DC-DC converter 404 includes short circuit protection circuitry 411, which includes a transistor Q2, a diode D3, and a driver circuit 420. The transistor Q2 is not an active switching transistor, and so can be a silicon transistor rather than a GaN transistor even when high switching frequencies are used, e.g., 500 kHz and higher. Similarly, the diode D3 can be a standard silicon diode. The driver circuit 420 is coupled to the gate of the transistor Q2 to control whether the transistor Q2 is on or off. In normal operation, current flows through the transistor Q2 in an on state in the path to the output DC OUT+. If the driver circuit 420 detects a short circuit at the output terminals, the driver circuit 420 turns the transistor Q2 off to block further output by the converter module 110. This feature can provide safety and control features in systems that use the converter modules 110. For example, if a short circuit is detected in the DC bus 116 of the system 100, each of the converter modules 110-1 through 110-M coupled in parallel can activate their short circuit protection circuitry 411 to stop output to the DC bus 116.

[0135] The output of the DC-DC converter 404 is also provided through the output filter 406, which can include several components. For example, the output filter 406 includes a resistor R2 and a capacitor C4 that provide low pass filtering. An additional diode D4 is placed to block reverse currents coupled to the DC OUT- output line. The output filter 406 also includes a common mode choke CMC that DC output passes through to reach the output terminals. In some cases, common mode noise can be a factor that limits the quality and stability of the voltage on the DC bus 116, and thus presents a practical limitation to the number of converter modules 110-1 through 110-M that can be coupled in parallel to the DC bus 116. Including a common mode choke CMC in each converter module 110-1 through 110-M lessens this issue, and the common mode choke CMC can be sized to meet the DC bus requirements for the number of converter modules 110-1 through 110-M anticipated to be coupled together in parallel. In some implementations, an active common-mode filter can be included to further reduce common-mode noise.

[0136] The DC-DC converter 404 optionally includes a fuse F as overcurrent protection 412. The fuse 412 can be coupled in series with one of the output terminals. The DC-DC converter 404 also optionally includes a varistor V as voltage surge protection. The varistor V can be coupled across the output terminals to limit the effects of voltage surges at the output terminals.

[0137] FIG. 5 is a flow diagram that illustrates an example process 500 for controlling the converter module 110. In the system 100 of FIG. 1, any or all of the converter modules 110- 1 through 110-M can be controlled as described in the process 500. The determinations and actions of the process 500 can be performed by the converter module 110 itself, such as by the control device 408 and / or other circuitry of the converter module 110. The converter module 110 can be additionally or alternatively controlled by another component of the system 100, such as the main controller 118 and / or the inverter 116. For example, in some implementations, at least some of the operations of the process 500 can be performed by the main controller 118, which can send control signals or commands to the converter module 110.

[0138] In FIG. 5, various blocks are illustrated to represent determinations and actions of the converter module 110. The operations represented by the blocks can be performed in a sequential or ordered manner, but are not required to be. For example, the converter module 110 can concurrently monitor for and respond to multiple different conditions (e.g., blocks 508, 510, 514, 518) rather than making determinations sequentially. As another example, the converter module 110 continues to provide output to the DC bus 116 and monitor the DC bus voltage while determining whether to adjust the level of output. The converter module 110 can be configured to be perform the operations shown in FIG. 5 using analog circuitry, digital circuitry, programmable logic, software, firmware, or any combination thereof.

[0139] Various different control schemes can be used to control the converter modules 110-1 through 110-M. In some implementations, the converter modules 110-1 through 110-M operate independently and each converter module 110-1 through 110-M separately adjusts its operation based on sensed conditions of the shared DC bus 116. In each converter module 110-1 through 110-M, the control device 408 can adjust power output to adapt to changing conditions, without relying on control signals or other communication from an external controller. This increases the robustness of the system 100, because the converter modules 110-1 through 110-M do not depend on a communication link to an external controller. Independent control of the converter modules 110-1 through 110-M also reduces costs, because an external communication link is optional and can be omitted, or a low-cost external communication link can be used because high latency or low throughput would not impact power generation. Independent control of the converter modules 110-1 through 110-M also improves scalability and the ease of installation. Additional converter modules 110 can be added to the system 100 simply by connecting their outputs to the DC bus 116. Similarly, some existing converter modules 110-1 through 110-M can be removed from the system 100 without the need to adjust or re-configure the converter modules 110-1 through 110-M that remain.

[0140] In the process 500, the converter module 110 monitors the DC bus 116 and adjusts its output to bring the voltage on the DC bus 116 (the “DC bus voltage”) toward a target voltage. As an example, the target voltage may be 200 V, 400 V, 800 V, etc., and each of the converter modules 110-1 through 110-M connected to the DC bus 116 is configured to use the same target voltage. The converter module 110 provides power to the DC bus 116 while the DC bus voltage is in a predetermined operating range, such as a range that extends a predetermined amount (e.g., 2.5%, 5%, 10%, 15%, etc.) above and below the target voltage. If the DC bus voltage is in the operating range and is below the target voltage, the converter module 110 supplies as much power as possible based on the DC input from the connected PV panel(s) 112. If the DC bus voltage is in the operating range and is above the target voltage, the converter module 110 reduces the amount of power it injects into the DC bus 116.

[0141] The control device 408 is primarily responsible for the control of the converter module 110 and thus the actions of the process 500, but other circuitry of the converter module 110 can additionally or alternatively be used to carry out the operations of the process 500. For example, the detection of a short circuit (block 508) and terminating power output (block 512) can be performed by analog circuitry (e.g., short circuit protection 411) in cooperation with or independently of the control device 408.

[0142] In further detail, in block 502, the converter module 110 monitors the DC bus voltage on the DC bus 116. At this stage, the converter module 110 is not yet providing output to the DC bus 116, and the converter module 110 is configured to not begin providing power to the DC bus until the DC bus voltage reaches the predetermined operating range.

[0143] In block 504, the converter module 110 determines whether the DC bus voltage is in the predetermined operating range. For example, the converter module 110 uses the sensing circuitry 407 to determine the DC bus voltage. The control device 408 of the converter module 110 compares the DC bus voltage with thresholds representing the predetermined operating range to determine whether the DC bus voltage is currently in the predetermined operating range. The predetermined operating range can be defined in any appropriate manner, using analog or digital elements. As an example, the converter module 110 can store parameter values indicating the target voltage for the DC bus 116 and the predetermined operating range for the converter module 110. The parameter values for the converter module 110 can be set during manufacture or installation of the converter module 110, or may be specified at a later time or adjusted dynamically, such as through a setting or command later received from the main controller 118.

[0144] The target voltage and operating range can be set according to the needs of the application. As an example, the converter module 110 can be configured to operate with a target voltage of 200 V, and the operating range can be 190 V to 210 V (e.g., 5% above and below the target voltage). The converter module 100 can be configured to alternatively use a different target voltage, e.g., 150V, 400 V, 800 V, etc. The operating range may be smaller or larger than 5% above and below the target voltage, e.g., 1%, 2.5%, 10%, 15%, etc.

[0145] If the DC bus voltage is determined to be outside the operating range, the control device 408 maintains the converter module 110 in a standby mode in which the converter device 110 does not output power to the DC bus 116. As a result, the converter module 110 continues to monitor the DC bus voltage and to assess whether the DC bus voltage reaches the operating range.

[0146] Once the DC bus voltage is determined to be in the operating range, the control device 408 controls the converter module 110 to provide output to the DC bus 116 in block 506 (e.g., to initiate or resume providing power to the DC bus 116). The converter module 110 continues to monitor the DC bus voltage, and the control device 408 uses the DC bus voltage to make additional control adjustments.

[0147] As represented by block 508, the converter module 110 includes short circuit protection 411 that is configured to detect a short circuit at the output of the converter module 110 (e.g., the DC bus 116). When a short circuit is detected, the converter module 110 enters a short circuit protection mode and the converter module 110 discontinues output to the DC bus (block 512). The converter module 110 then returns to the standby mode represented by block 502 and will not resume providing output to the DC bus 116 until the DC bus voltage is reestablished in the operating range.

[0148] Short circuit protection can be active throughout the entire process 500 and the full range of operating states of the converter module 110. The representation of block 508 is included to illustrate that a short circuit condition triggers the termination of power output and a return to the standby mode, and this does not signify that short circuit protection is merely a periodic or occasional action.

[0149] In block 510, if the DC bus is determined to be outside the operating range, the control device 408 can discontinue output to the DC bus (block 512) or otherwise reduce or limit power output. If the DC bus voltage is above the operating range, no further power from the converter module 110 is needed reach the target voltage. Power output is terminated, or at least reduced, and the converter module 110 returns to the standby mode represented by block 502 to allow the DC bus voltage to fall back to the operating range. Once the DC bus voltage returns to the operating range, the converter module 110 resumes providing power output (block 506).

[0150] While the DC bus voltage is in the operating range, the converter module 110 can use different control strategies depending on whether the DC bus voltage is above or below the target voltage. For example, the converter module 110 can apply a first control strategy when the DC bus voltage is in a range from a lower threshold up to the target voltage, and the converter module 110 can apply a second control strategy when the DC bus voltage is in a range from the target voltage up to an upper threshold. The lower threshold and the upper threshold can be the lower and upper bounds of the operating range. For example, if the target voltage is 200 V and the operating range is from 190 V to 210 V, the lower threshold can be 190 V and the upper threshold can be 210 V. In other implementations, the lower threshold and upper threshold may be different from the operating range boundaries.

[0151] Blocks 514 and 516 show that if the DC output voltage is between the lower threshold and the target voltage, the converter module 110 sets its output to maximize power output to the DC bus 116. For example, if the converter module 110 determines that the DC bus voltage is between the lower threshold and the target voltage, the converter module 110 operates in maximum power point tracking (MPPT) mode, in which the converter module 110 monitors input voltage and input current from the PV panel(s) 112 providing input to the converter module 110. The control device 408 and / or other circuitry controls the converter module so that the PV panel(s) 112 are operated at the maximum power point (MPP), which is the point at which the product of input voltage and input current is maximized. As discussed above, the converter module 110 provides a variable gain and so allows a variable boost or voltage step-up from the DC input to the DC output. The control device 408 can adjust the duty cycle of the DC-DC converter 404 to maximize the power received from the PV panel(s) 112 while also providing an output that is within the operating range, e.g., at or near the target voltage for the DC bus 116.

[0152] Blocks 518 and 520 show that if the DC bus voltage is between the target voltage and the upper threshold, the converter module 110 reduces or limits the power output to the DC bus 116. For example, if the control device 408 determines that the DC bus voltage is between the target voltage and the upper threshold, the control device 408 controls the converter module 110 to reduce power output. A DC bus voltage above the target voltage indicates that the total power provided to the DC bus 116 (from all converter modules 110-1 through 110-M or power sources) exceeds the amount of power needed, and so the converter module 110 can decreases the amount of generated power it provides. The converter module 110 can reduce its power output based on or in proportion to the magnitude of overvoltage (e.g., the amount that the DC bus value exceeds the target voltage).

[0153] One way the converter module 110 can reduce power output is to limit (e.g., throttle) the input current from the connected PV panel(s) 112. For example, the converter module 110 can be connected to a PV panel 112 that provides a current of 10 A at the maximum power point. The target voltage can be 200 V, and the upper threshold (e.g., upper boundary of the operating range) can be 210 V. The converter module 110 can be configured vary the input current received from the PV panel 112 according to the level of the DC bus voltage. The converter module 110 can use the maximum input current (e.g., 10 A) when the DC bus voltage is at the target voltage (e.g., 200 V), and progressively restrict the input current as the DC bus voltage exceeds the target voltage, until at the upper threshold and above no input current is drawn from the PV panel 112. Thus, the converter module 110 can use the input current limiter 401 to scale the input current according to the amount that the DC bus voltage exceeds the target voltage, e.g., limiting input current to 90% of the maximum input current at a DC bus voltage of 201 V, limiting input current to 80% of the maximum input current at a DC bus voltage of 202 V, limiting input current to 70% of the maximum input current at a DC bus voltage of 203 V, and so on. In this case, the input current limit, h im, can be set based on the equation below:

[0154] Ilam Imax * (V DCBus—V Target) / V Target , where Imax represents the maximum input current at the maximum power point, VDCBUS represents the DC bus voltage, and Vrarget represents the target voltage for the DC bus 116. This example shows a linear scaling or a linear relationship between the current limit and the overvoltage, but other relationships can be used, such as a quadratic, polynomial, or exponential relationship. When one or more converter modules 110-1 through 110-M each operate as shown in FIG. 5, the control approach allows maximum power generation from the PV panels 112-1 through 112-N and allows the DC bus voltage to be brought as close to the target DC bus voltage as the PV panel outputs permit (e.g., if the PV panels 112-1 through 112-N generate sufficient power). In addition, by scaling back power when overvoltage is detected, the converter modules 110-1 through 110-M avoid injecting more energy into to the DC bus than can be used, e.g., by a combination of the loads 132, 142, charging the battery buffer 122, charging an electric vehicle 126, and power injection to the AC power grid 152.

[0155] Allowing the DC bus voltage to exceed the nominal target by a limited amount can be useful as a signal to other components in the system 100. For example, a DC bus voltage above the target (but still below the upper threshold) can indicate to the main controller 118 and / or the inverter 114 that the power available from the PV panels 112-1 through 112-N exceeds the amount needed by the current loads, indicating that further power is available. In response to detecting a DC bus overvoltage, the main controller 118 and / or the inverter 114 can increase the load or power drawn from the DC bus 116, such as by initiating charging, or increasing the charging rate, for the battery buffer 122 and / or the electric vehicle 126. Similarly, in response to detecting an overvoltage, the main controller 118 and / or the inverter 114 can initiate or increase power injection to the AC power grid 152.

[0156] As the electrical load on the DC bus 116 is increased, the DC bus voltage will fall toward the target voltage. Even before the DC bus voltage reaches to the target voltage, the converter module 110 will detect the decrease in the DC bus voltage and begin supplying a greater proportion of the available power from the connected PV panel(s) 112, e.g., by reducing the input current limitation and operating closer to the maximum power point of the PV panel(s) 112. The increased power output, in turn, maintains a overvoltage on the DC bus 116, which indicates that there is still available power generation capacity to be tapped, so the main controller 118 and / or the inverter 114 can further increase the load on the DC bus 116. The increase in DC bus 116 load and increase in power output to the DC bus 116 can continue until the converter module 110 and any other converter modules 110-1 through 110- M connected in parallel to the DC bus 116 are operating at the maximum power point for their connected PV panels 112-1 through 112-N. In other words, as the main controller 118 and / or the inverter 114 continue to increase the loading on the DC bus 116, the converter modules 110-1 through 110-M increase power output to the DC bus 116 until the maximum power generation levels are reached. The main controller 118 and / or the inverter 114 can then increase the loading on the DC bus 116 further until the DC bus voltage decreases to the target voltage.

[0157] In the steady state, when there are loads sufficient power to accept the full power output from the converter modules, the converter modules 110-1 through 110-M that are connected to the DC bus 116 can each produce power at the maximum power points of their associated PV panels 112-1 through 112-N, and the main controller 118 and / or the inverter 114 adjust the power draw so that the DC bus voltage is at or very near the target voltage. Over time, as load demands vary, the main controller 118 and / or the inverter 114 can dynamically adjust the amount of power drawn by discretionary loads (e.g., battery charging, injection to the AC power grid, etc.) to adjust the DC bus voltage 116 toward the target voltage. For example, if the power demand of the loads 132, 142 increases, the DC bus voltage will decrease below the target voltage, and so the main controller 118 and / or the inverter 114 can respond by decreasing the power drawn from the DC bus 116 for charging the battery 122, charging the electric vehicle 126, and / or injecting energy to the AC power grid 152 until the DC bus voltage increases to the target voltage. Similarly, if the power demand of the loads 132, 142 decreases, the DC bus voltage will increase above the target voltage, and so the main controller 118 and / or the inverter 114 can respond by increasing the power drawn from the DC bus 116 for charging the battery 122, charging the electric vehicle 126, and / or injecting energy to the AC power grid 152 until the DC bus voltage decreases to the target voltage. In this manner, the converter modules 110-1 through 110-M and the main controller 118 and / or the inverter 114 can cooperate to control the DC bus voltage and efficiently use the full amount of power available from a set of PV panels 112-1 through 112- N, without the need for a separate communication link between the converter modules 110-1 through 110-M and the main controller 118 and / or the inverter 114.

[0158] When multiple converter modules 110-1 through 110-M are connected in parallel to the DC bus 116, the short circuit protection functionality can be used to terminate power generation to the DC bus 116. For example, the main controller 118 and / or the inverter 114 can cause a short circuit across the DC bus 116, such as by activating a crowbar circuit, which will activate the short circuit protection circuitry 411 of each of the converter modules 110-1 through 110-M (blocks 508 and 512) which will return them to the standby mode (block 502) in which no output is provided to the DC bus 116. The converter modules 110-1 through 110-M will remain in the standby mode until the main controller 118 and / or the inverter 114 bring the DC bus voltage back into the operating range, at which point the converter modules 110-1 through 110-M will resume power output (block 506). In FIG. 5, the various blocks illustrate the functionality of the converter module 110 but are not required to be evaluated in sequentially or in order. Instead, the control device 408 or other control circuitry can be implemented to concurrently monitor for various conditions and to automatically respond to the conditions without making the decisions as separate or sequential operations. For example, short circuit protection can be active concurrent with other assessments of the DC bus voltage. Similarly, the assessment of the DC bus voltage as shown in blocks 510, 514, 518 can be performed as a combined analysis to select an operating mode (e.g., standby mode (no output), maximum power point tracking mode, and a power limited mode) and set the output level, rather than as three separate determinations. The control device 408 or other control circuitry can perform the operations by using comparisons of the DC voltage to corresponding thresholds, or may detect the conditions represented through other means.

[0159] FIG. 6 is a flow diagram that illustrates an example process 600 that the main controller 118 and / or the inverter 114 can perform to control power generation using one or more converter modules 110. In FIG. 6, various blocks are illustrated to represent determinations and actions of the main controller 118 and / or the inverter 114. The operations represented by the blocks can be performed in a sequential or ordered manner, but are not required to be. For example, the converter module 110 can concurrently monitor for and respond to multiple different conditions (e.g., blocks 608, 612) rather than making determinations sequentially. As another example, the converter module 110 can continue to monitor the DC bus voltage while determining whether to adjust loading on the DC bus 116. The main controller 118 and / or the inverter 114 can be configured to be perform the operations shown in FIG. 5 using analog circuitry, digital circuitry, programmable logic, software, firmware, or any combination thereof.

[0160] In general, the main controller 118 and / or the inverter 114 can initiate the supply of power by the converter modules 110-1 through 110-M to the DC bus 116 by setting the DC bus voltage to a level in the predetermined operating range discussed with respect to FIG. 5. The main controller 118 and / or the inverter 114 can also terminate the supply of power by the converter modules 110-1 through 110-M to the DC bus 116 by causing a short circuit at the DC bus 116 (e.g., by activating a crowbar circuit), which causes the converter modules 110-1 through 110-M to activate short circuit protection and enter the standby mode in which power is not output to the DC bus 116. While the converter modules 110-1 through 110-M are providing power to the DC bus 116, the main controller 118 and / or the inverter 114 monitors the DC bus voltage and dynamically adjusts the loading on the DC bus 116 by varying the amount of power drawn for charging the battery buffer 122, charging the electric vehicle 126, and / or injecting power to the AC power grid 152.

[0161] In further detail, in block 602, the main controller 118 and / or the inverter 114 determines that power supply to the DC bus 116 should be initiated using the converter modules 110-1 through 110-M and their associated PV panels 112-1 through 112-N. For example, the main controller 118 may receive a command or instruction from a user to begin power generation, or may detect that one or more predetermined conditions for initiating power generation have occurred (e.g., the time of day permits solar power generation, status information from the converter modules 110-1 through 110-M indicates sufficient input voltage from the PV panels 112-1 through 112-N is being generated, etc.).

[0162] In block 604, having determined to begin supplying power using the PV panels 112-1 through 112-N and converter modules 110-1 through 110-M, the main controller 118 and / or the inverter 114 establish a voltage on the DC bus 116 that is in the predetermined operating range for the converter modules 110. For systems that are connected to the AC power grid 152, power from the AC power grid 152 can be used to generate a DC output voltage in the operating range. For example, the main controller 118 and / or the inverter 114 can cause an AC -DC converter to temporarily provide a voltage to the DC bus 116 that is in the operating range, until one or more converter modules 110-1 through 110-M detect the DC bus voltage and begin supplying power to sustain a DC bus voltage in the operating range. As another example, the main controller 118 and / or the inverter 114 can control the battery buffer 122 and DC-DC converter 120 to temporarily provide a voltage to the DC bus 116 that is in the operating range.

[0163] After establishing the DC bus voltage in the operating range, the main controller 118 and / or the inverter 114 can evaluate conditions to determine whether the converter modules 110-1 through 110-M are supplying power to the DC bus 116 and have the input power sufficient to meet minimum load demands. For example, the main controller 118 and / or the inverter 114 can determine whether the combined power output from the converter modules 110-1 through 110-M is sufficient to reach or exceed the target voltage for the DC bus 116, or to at least maintain the DC bus voltage in the operating range. When the output of the converter modules 110-1 through 110-M is determined to be sufficient, the main controller 118 and / or the inverter 114 may cause the supply of power to the DC bus 116 based on power from the battery buffer 122 or AC power grid 152 to be discontinued.

[0164] In block 606, the main controller 118 and / or the inverter 114 monitor the DC bus voltage while the converter modules 110-1 through 110-M provide power to the DC bus 116. The level of the DC bus voltage signals if there is additional power supply capacity currently available from the PV panels 112-1 through 112-N (e.g., when the DC bus voltage exceeds the target DC bus voltage), or if the current load on the DC bus 116 exceeds the combined maximum power output currently available from the PV panels 112-1 through 112-N (e.g., when the DC bus voltage is below the target DC bus voltage).

[0165] When the DC bus voltage is above the target voltage and below an upper threshold (block 608), the main controller 118 and / or the inverter 114 increases loading on the DC bus 116 (block 610). For example, the amount of power that is injected into the AC power grid 152, used to charge the battery buffer 122, or used to charge the electric vehicle 126 can be increased to use more of the power available from the PV panels 112-1 through 112-N. The increase in loading can be gradual or incremental, so that converter modules 110-1 through 110-M can respond to increases in power drawn from the DC bus 116 with increases gradual or incremental increases in power supplied to the DC bus 116. In general, gradual or incremental changes in loading and output can help promote stability of the DC bus voltage as the load levels and power supply levels are both changing. Once the load on the DC bus 116 has increased to make use of full power available from the PV panels 112-1 through 112- N, the DC bus voltage will decrease to the target voltage, at which point the main controller 118 and / or the inverter 114 does maintains the amount of power drawn.

[0166] When the DC bus voltage is below the target voltage and above a lower threshold (block 612), the main controller 118 and / or the inverter 114 decreases loading on the DC bus 116 (block 614). For example, the amount of power that is injected into the AC power grid 152, used to charge the battery buffer 122, or used to charge the electric vehicle 126 can be decreased to draw less power from the PV panels 112-1 through 112-N and the converter modules 110-1 through 110-M. The decrease in loading can be gradual or incremental, so that the DC bus voltage can gradually or incrementally rise toward or to the target voltage, as the total amount of power drawn decrease toward or to the amount of power available from the PV panels 112-1 through 112-N through the converter modules 110. The converter modules 110-1 through 110-M control themselves to operate in maximum power point tracking mode when the DC bus voltage is between the lower threshold and the target voltage. As a result, decreasing the load on the DC bus 116 to the point that the DC bus voltage reaches the target voltage aligns the total load on the DC bus 116 to the current total power supply capability of the PV panels 112-1 through 112-N and the converter modules 110-1 through 110-M. In the system 100, some loads, such as loads 142, 132, are not controlled or adjusted by the main controller 118 and / or the inverter 114. These loads may vary the amount of power they draw over time, resulting in changes in the DC bus voltage. Similarly, the amount of incident light on the PV panels 112-1 through 112-N can change over time, which changes the amount of power the PV panels 112-1 through 112-N can supply and also changes the DC bus voltage. The main controller 118 and / or the inverter 114 use the techniques shown in FIG. 6 to respond to the changes in the DC bus voltage by adjusting the load on the DC bus 116 from loads that the main controller 118 and / or the inverter 114 can adjust (e.g., battery charging and power grid injection).

[0167] The main controller 118 and / or the inverter 114 can use various techniques to adjust the load at the DC bus 116. For example, the main controller 118 and / or the inverter 114 may be configured to send commands or control signals that adjust the settings or operation of the EV charger 124, the DC-DC converter 120 acting as a battery charger for the battery buffer 122, or other components. In some implementations, the main controller 118 and / or the inverter 114 can control or override operating settings of these components, or may be able to disconnect or reconnect components to the DC bus 116. In other implementations, the main controller 118 and / or the inverter 114 can send requests to various devices coordinate or negotiate the power draw of those devices, which may not be directly controlled by the main controller 118 and / or the inverter 114. For example, the main controller 118 and / or the inverter 114 can receive information indicating the minimum or desired amount of power currently requested by each of various devices. Devices may send requests for power or indicate a priority level for receiving power. The main controller 118 and / or the inverter 114 can then allocate the amount of excess power available (e.g., beyond what is currently needed by the other loads 132, 142) among the different devices based on the information received.

[0168] The main controller 118 and / or the inverter 114 can prioritize power delivery among different devices based on various factors, such as the state of charge of different battery systems (e.g., providing more power to battery systems with lower states of charge or levels below a threshold state of charge), historical or projected usage of battery systems (e.g., prioritizing EV charging before an upcoming time of typical usage), power reimbursement rates for AC grid injection at the current time (e.g., prioritizing AC power grid injection at times that reimbursement rates are higher), user preferences, current or recent user interactions with devices, and so on. Similarly, whether adjustments increase or decrease amount of discretionary power supplied, the main controller 118 and / or the inverter 114 can attempt to balance power distribution among the components, such as to allow the electric vehicle 126 and the battery buffer 122 to charge concurrently at charging rates appropriate for their typical usage patterns and operating conditions (e.g., state of charge, temperature, etc.).

[0169] The adjustments to the load at the DC bus 116 the main controller 118 and / or the inverter 114, which can be performed in a repeated and ongoing manner, can adjust and calibrate the total load on the DC bus 116 to approximate or match, to the extent possible, the current power supply capability of the PV panels 112-1 through 112-N and the converter modules 110-1 through 110-M. The load adjustments, together with the power output adjustments made by the controller modules 110-1 through 110-M as discussed with respect to FIG. 5, can allow the system 100 to operate efficiently, such as by operating at or near the maximum power point of the various PV panels 112-1 through 112-N while achieving the target voltage or other operating characteristics desired for the DC bus 116.

[0170] Although not illustrated in FIG. 6, the main controller 118 and / or the inverter 114 can also cause the converter modules 110-1 through 110-M to terminate supplying power to the DC bus 116. For example, the main controller 118 can determine that power generation should be terminated, and in response the main controller 118 can cause a short circuit across the DC bus 116 (e.g., by activating a crowbar circuit) to cause the converter modules 110-1 through 110-M to stop supplying power to the DC bus 116.

[0171] In some implementations, converter modules 110-1 through 110-M can communicate with the main controller 118 and / or the inverter 114 through a communication link, in addition to or instead of the interactions that set the DC bus voltage. For example, the control device 408 in each converter module 110-1 through 110-M can provide information about the operation of the converter module 110-1 through 110-M and its associated PV panel(s) 112-1 through 112-N. In many cases, users are interested in tracking or viewing status information such as the amount of power generated by each PV panel 112-1 through 112-N. As discussed above, communication of this information is not needed to control the power output of the converter module 110, and so a relatively slow (e.g., high latency and / or low throughput) and low-cost communication link can be used without reducing the efficiency and responsiveness of power generation. For example, to provide status information, a simplex (e.g., unidirectional) communication channel can be provided so each converter module 110 transmits status information that is then received by the main controller 118 and / or the inverter 114. The status information from the various converter modules 110-1 through 110- M can then be aggregated by the main controller 118 and / or the inverter 114, which then transmits the aggregated status information to the users. Generating and transmitting status information in this way can be used to troubleshoot or diagnose errors in case one of the converter modules 110-1 through 110-M or one of the PV panels 112-1 through 112-N does not operate normally.

[0172] In general, the control device 408 in each converter module 110-1 through 110-M can monitor operating conditions to determine status information and then provide it to the main controller 118 and / or the inverter 114 through a wired communication link or a wireless communication link (e.g., Wi-Fi, Bluetooth, etc.). The status information from a converter module 110 can include, for example, input characteristics of input from a PV panel 112 (e.g., input current, input voltage, input power, etc.), a maximum power point for the PV panel 112, an input current limit or input power limit being applied by the converter module 112, output characteristics of DC output of the converter module 110 (e.g., output voltage, output current, output power, etc.), a current operating mode for the converter module 110 (e.g., standby mode, power-producing mode, maximum power point control, etc.), a level of current a measured DC bus voltage, a temperature of the converter module 110, a gain of the DC-DC converter 404, whether any error conditions have been detected, whether each of the various types of protection circuitry 410 have been triggered, and so on. Each converter module 110-1 through 110-M and / or PV panel 112-1 through 112-N can have a unique identifier, and the status information reported can include the corresponding identified s) to specify which devices the status information describes.

[0173] The control device 408 can provide instantaneous measures (e.g., real-time or near- real-time values) and / or averaged measures (e.g., for periods of one minute, five minutes, fifteen minutes, one hour, etc.) for the various types of status information provided. The converter module 110 can be configured to provide status information periodically (e.g., every minute, every five minutes, every fifteen minutes, etc.) and / or on-demand in response to receiving a request for status information from the main controller 118 and / or the inverter 114.

[0174] In some implementations, the converter modules 110-1 through 110-M each have a duplex (e.g., bidirectional) communication link to the main controller 118 and / or the inverter 114. The main controller 118 and / or the inverter 114 can use the communication link to change operating settings of the converter modules 110, such as to dynamically adjust the power output of individual converter modules 110. Thus, operations to determine and adjust output characteristics of a converter module can be performed in whole or in part by the main controller 118 and / or the inverter 114.

[0175] As an example, the converter modules 110-1 through 110-M can each report the status information that they generate, as discussed above. The main controller 118 can then assess the DC bus voltage in the manner discussed for FIG. 5 and instruct the respective converter modules 110-1 through 110-M to set their power output accordingly. In this example, the main controller 118 determine the operating settings for the converter modules 110-1 through 110-M when power is provided to the DC bus 116, rather than converter modules 110-1 through 110-M locally determining the operating settings. The main controller 118 can determine operating parameter values for each converter module 110 individually, and then send commands or instructions to specify the operating parameter values, such as by setting the DC-DC conversion gain, DC-DC converter duty cycle, input current limit setting, input or output power limit, and so on.

[0176] As another example, the main controller 118 can perform analysis of conditions at the various converter modules 110-1 through 110-M in order to set operating conditions for the converter modules 110-1 through 110-M individually, using factors in addition to or instead of those discussed with respect to FIG. 5. The main controller 118 may adaptively change the amount or proportion of power supplied by different converter modules 110-1 through 110-M according to the circumstances of each converter module 110 and its associated PV panel(s). Due to factors such as locations of the PV panels 112-1 through 112-N, wear of the PV panels 112-1 through 112-N over time, and different locations of the PV panels 112-1 through 112-N, different PV panels 112-1 through 112-N may generate different amounts of power at different times. Similarly, different converter modules 110-1 through 110-M may experience different conditions, such as different temperatures, or may be best operated in different modes due to the differing levels of input power available from their respective PV panels 112-1 through 112-N. As a result, the main controller 118 can assess the power generating capability of each converter module 110 individually and select the operating parameters that are most appropriate for each converter module 110 and that, across the set of converter modules 110, will provide the total amount of power needed at the DC bus 116.

[0177] To determine the power output for individual converter modules 110, the main controller 118 determine the amount of power required by the primary loads on the DC bus 116, such as the loads 132, 142. The main controller 118 can also use the status information to determine the amount of power available from each of the individual converter modules 110, and can add the amounts to determine the total amount of power collectively available from the set of converter modules 110. The main controller 118 can then use this information to determine the amount of excess power available (e.g., beyond the amount requested by the loads 132, 142) that is available for other discretionary loads, such as charging the battery buffer 122, charging the electric vehicle 126, and injecting power into the AC electric grid 152. The main controller 118 can then calculate the amount of available excess power, if any, to allocate to the various discretionary loads, to use as much as possible of the available power from the PV panels 112-1 through 112-N.

[0178] In general, calculating the amount of power to draw and allocate to various loads can allow the main controller 118 to set the output power from the converter modules 110-1 through 110-M and adjust load demands more directly than the interactions through the DC bus voltage. For example, the main controller 118 can set the output levels for the converter modules 110-1 through 110-M and set the amounts or power to provide for battery charging and supply to the AC power grid 152 without the need for the DC bus voltage to exceed the target voltage to signal that additional unused power generation capacity is available or for the DC bus voltage. This can help achieve a more stable voltage on the DC bus 116, although it involves additional communication in the system 110 and processing by the main controller 118 compared to other approaches.

[0179] The main controller 118 can set power generation levels for each of the converter modules 110-1 through 110-M so that the total amount of power output to the DC bus 116 provides the total amount of power needed (e.g., for the primary loads 132, 142 and discretionary loads such as battery charging and injection to the AC power grid 152). In many cases, this may involve each converter module 110-1 through 110-M providing output at the maximum power point of the associated PV panel(s) 112-1 through 112-N. In other cases, such as if there is more available power than the discretionary loads can absorb, the main controller 118 can then instruct lower power generation levels for the converter modules 110-1 through 110-M. For example, the power generation capacity of each converter module 110-1 through 110-M can be scaled in proportion to the amount of available power to be used. If only 90% of the total available power supply can be used, then the main controller 118 can instruct each converter module 110-1 through 110-M to operate at 90% of the maximum power point of its associated PV panels 112-1 through 112-N.

[0180] As another example, the main controller 118 can operate the converter modules 110-1 through 110-M to reduce wear and maximize longevity. For example, the main controller 118 can limit the output of converter modules 110-1 through 110-M to avoid high temperatures in the converter modules 110. For example, when less than the total power capacity of the system is currently needed, the main controller 118 can control the converter modules 110-1 through 110-M to operate at different proportions of the maximum power points of their respective PV panels 112-1 through 112-N. This can include operating some converter modules 110-1 through 110-M (e.g., those with the highest input power or that currently experience high temperatures) at lower proportions of maximum available output power than other converter modules 110-1 through 110-M (e.g., those with lower maximum input power or lower temperatures).

[0181] For example, three converter modules 110 may respectively receive maximum input power of 300 W, 250 W, and 200 W, due to differences in their PV panel characteristics, levels of incident light, PV panel locations or orientations, etc. If a total of 600 W is needed for the loads 132, 142, the main controller 118 may allocate an additional 100 W for battery charging, even though this leaves an additional 50 W of available power unused. The main controller 118 can then instruct the converter modules 110-1 through 110-M to output 250 W, 250 W, and 200 W, respectively. In this case, the converter module 110 with the highest available power is controlled to not utilize the full available power, in order to reduce temperature of and stress on the converter module 110. Depending on the conditions, the main controller 118 may alternatively allocate the power generation in a different manner, such as 300 W, 200 W, and 200 W if the second converter module 110 is currently experiencing higher temperatures than the others.

[0182] In general, using a duplex communication link and with the main controller 118 providing commands to the converter modules 110-1 through 110-M, the main controller 118 may set or adjust the power output for individual converter modules 110-1 through 110-M based on their respective circumstances, as the main controller 118 determines them from any or all of the status information from the converter modules 110-1 through 110-M. The main controller 118 can set any of various parameters such as an input current limit for input from a PV panel 112, output characteristics of DC output of the converter module 110-1 through 110-M (e.g., output voltage, output current, output power, etc.), an operating mode for the converter module 110-1 through 110-M (e.g., standby mode, power-producing mode, maximum power point control, etc.), a gain or duty cycle of the DC-DC converter 404, and so on.

[0183] The term “module” as used herein refers to one of two or more devices or subsystems within a larger system. The module can be configured to work in conjunction with other modules of similar size, function, and physical arrangement (e.g., location of electrical terminals, connectors, etc.). Modules having the same function and energy source(s) can be configured identical (e.g., size and physical arrangement) to all other modules within the same system, while modules having different functions or energy source(s) may vary in size and physical arrangement. While each module may be independently removable and replaceable with respect to the other modules of the system, such is not required. For example, a system may be packaged in a common housing that does not permit removal and replacement any one module, without disassembly of the system as a whole. However, any and all implementations herein can be configured such that each module is removable and replaceable with respect to the other modules in a convenient fashion, such as without disassembly of the system.

[0184] The term “output” is used herein in a broad sense, and does not preclude functioning in a bidirectional manner as both an output and an input. Similarly, the term “input” is used herein in a broad sense, and does not preclude functioning in a bidirectional manner as both an input and an output.

[0185] The terms “terminal” and “port” are used herein in a broad sense, can be either unidirectional or bidirectional, can be an input or an output, and do not require a specific physical or mechanical structure, such as a female or male configuration.

[0186] Processing circuitry can include one or more processors, microprocessors, controllers, and / or microcontrollers, each of which can be a discrete or stand-alone chip or distributed amongst (and a portion of) a number of different chips. Any type of processing circuitry can be implemented, such as, but not limited to, personal computing architectures (e.g., such as used in desktop PC’s, laptops, tablets, etc.), programmable gate array architectures, proprietary architectures, custom architectures, and others. Processing circuitry can include a digital signal processor, which can be implemented in hardware and / or software. Processing circuitry can execute software instructions stored on memory that cause processing circuitry to take a host of different actions and control other components.

[0187] Processing circuitry can also perform other software and / or hardware routines. For example, processing circuitry can interface with communication circuitry and perform analog-to-digital conversions, encoding and decoding, other digital signal processing, multimedia functions, conversion of data into a format (e.g., in-phase and quadrature) suitable for provision to communication circuitry, and / or can cause communication circuitry to transmit the data (wired or wirelessly).

[0188] Processing circuitry can also be adapted to execute the operating system and any software applications, and perform those other functions not related to the processing of communications transmitted and received.

[0189] Computer program instructions for carrying out operations in accordance with the described subject matter may be written in any combination of one or more programming languages, including computer and programming languages. Memory, storage, and / or computer readable media can be shared by one or more of the various functional units present, or can be distributed amongst two or more of them (e.g., as separate memories present within different chips). Memory can also reside in a separate chip of its own.

[0190] To the extent the implementations disclosed herein include or operate in association with memory, storage, and / or computer readable media, then that memory, storage, and / or computer readable media are non-transitory. Accordingly, to the extent that memory, storage, and / or computer readable media are covered by one or more claims, then that memory, storage, and / or computer readable media is only non-transitory. The terms “non-transitory” and “tangible” as used herein, are intended to describe memory, storage, and / or computer readable media excluding propagating electromagnetic signals, but are not intended to limit the type of memory, storage, and / or computer readable media in terms of the persistency of storage or otherwise. For example, “non-transitory” and / or “tangible” memory, storage, and / or computer readable media encompasses volatile and non-volatile media such as random access media (e.g., RAM, SRAM, DRAM, FRAM, etc.), read-only media (e.g., ROM, PROM, EPROM, EEPROM, flash, etc.) and combinations thereof (e.g., hybrid RAM and ROM, NVRAM, etc.) and variants thereof.

[0191] In addition to the embodiments of the attached claims and the embodiments described above, the following numbered embodiments are also innovative.

Claims

CLAIMS1. A system comprising: a plurality of photovoltaic panels, wherein each of the photovoltaic panels is configured to generate a DC voltage; a plurality of converter modules, wherein each of the converter modules comprises a DC-DC converter, wherein each of the converter modules has an input and an output, and wherein each of the converter modules is configured to (i) receive, at the input, a DC voltage from at least one of the photovoltaic panels and (ii) convert the received DC voltage to an output DC voltage at the output, wherein the outputs of the converter modules are electrically coupled together to provide DC output in parallel to a DC bus; and a DC-AC converter configured to receive DC power from the DC bus and provide an AC output.

2. The system of claim 1, wherein, for each of the converter modules, the DC-DC converter is a boost converter.

3. The system of claim 2, wherein, for each of the converter modules, the boost converter comprises a gallium nitride (GaN) transistor as a switching element of the boost converter.

4. The system of claim 3, wherein the boost converter comprises one or more Schottky diodes coupled to the GaN transistor.

5. The system of claim 4, wherein the one or more Schottky diodes are one or more silicon Schottky diodes, and wherein the DC bus has a voltage between 100 V and 300 V.

6. The system of claim 4, wherein the one or more Schottky diodes are one or more silicon carbide Schottky diodes, and wherein the DC bus has a voltage between 600 V and 1000 V.

7. The system of any of claims 4 to 6, wherein the GaN transistor has a gate, a source, and a drain, and wherein the boost converter comprises at least one of: a first Schottky diode having a first anode and a first cathode, the first anode being electrically coupled to the drain of the GaN transistor; and a second Schottky diode having a second anode and a second cathode, the second cathode being electrically coupled to the source of the GaN transistor.

8. The system of any preceding claim, wherein the DC-DC converter is a switch-mode power supply having a switching frequency in a range from 500 kHz to 1.5 MHz.

9. The system of any preceding claim, wherein the DC-DC converter is a switch-mode power supply having a switching frequency in a range from 750 kHz to 1.25 MHz.

10. The system of any preceding claim, wherein the DC-DC converter is a switch-mode power supply having a switching frequency in a range from 800 kHz to 1.00 MHz.

11. The system of any preceding claim, wherein the photovoltaic panels each have a maximum output voltage, and the converter modules are configured to convert the DC voltages from the photovoltaic panels to a voltage of the DC bus that is more than twice the maximum output voltage of the photovoltaic panels.

12. The system of any preceding claim, wherein the converter modules are configured to provide a variable gain and are configured to generate DC outputs at a same voltage level.

13. The system of any preceding claim, wherein, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain from 5 to 10.

14. The system of any preceding claim, wherein, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain at least from 3 to 12.

15. The system of any preceding claim, wherein, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain at least from 3 to 15.

16. The system of any preceding claim, wherein, for each of the converter modules, the DC-DC converter is configured to step up voltage with a variable gain, including over a range of gain at least from 2 to 20.

17. The system of any preceding claim, wherein each of the converter modules comprises short-circuit protection circuitry configured to terminate output of the converter module in response to a short circuit at the output of the converter module.

18. The system of any preceding claim, wherein the photovoltaic panels each have a negative terminal or ground terminal, and wherein the negative terminal or ground terminal is AC-coupled to a positive rail of the DC bus.

19. The system of any preceding claim, wherein each of the converter modules comprises a common-mode choke electrically coupled in series with the output of the converter module.

20. The system of any preceding claim, further comprising one or more batteries and an additional DC-DC converter; wherein the additional DC-DC converter is configured to receive DC input from the DC bus and to charge the one or more batteries using output of the additional DC-DC converter.

21. The system of any preceding claim, comprising (i) a first group of converter modules having outputs coupled in parallel and (ii) a second group of converter module having outputs coupled in parallel, wherein a negative rail for output of the first group of converter modules is coupled to a positive rail for output of the second group of converter modules.

22. The system of claim 21, wherein the first group of converter modules and the second group of converter modules each provide DC input to the DC-AC converter; and wherein the DC-AC converter is configured to generate split-phase AC output comprising two AC outputs having opposite phase.

23. The system of any preceding claim, wherein each of the converter modules comprise a control device that is configured to control output of the converter module based on a sensed voltage at the DC bus.

24. The system of any preceding claim, further comprising a controller that is configured to adjust a level of load on the DC bus based on a sensed voltage at the DC bus.

25. The system of claim 24, wherein the controller is configured to initiate supply of power to the DC bus by establishing a voltage at the DC bus in a predetermined operating range, and wherein each of the converter modules is configured to sense the voltage at the DC bus and initiate supply of power to the DC bus in response to sensing the voltage at the DC bus in the predetermined operating range.

26. The system of claim 24 or 25, wherein the controller is configured to terminate supply of power to the DC bus by causing a short circuit on the DC bus, and wherein each of the converter modules comprises short circuit protection circuitry that is configured to detect a short circuit on the DC bus and terminate supply of power to the DC bus in response to detecting a short circuit on the DC bus.

27. A system comprising: a plurality of converter modules, wherein each of the converter modules comprises a DC-DC converter, wherein each of the converter modules has an input and an output, and wherein each of the converter modules is configured to (i) receive, at the input, a DC voltage from at least one photovoltaic panel and (ii) convert the received DC voltage to an output DC voltage at the output, wherein the outputs of the converter modules are electrically coupled together to provide DC output in parallel to a DC bus; and a DC-AC converter configured to receive DC power from the DC bus and provide an AC output.

28. A method comprising: receiving DC input voltages generated from photovoltaic panels; converting the DC input voltages to DC output voltages using a plurality of converter modules, wherein the converter modules are configured to boost the DC input voltages to theDC output voltages, and wherein the converter modules are each are configured to provide the DC output voltages in parallel to a DC bus; and controlling the converter modules to provide an amount of power output to the DC bus that is based on a voltage at the DC bus.

29. The method of claim 28, wherein controlling the converter modules comprises, for each of the converter modules: sensing the voltage at the DC bus; and using a control device of the converter module to adjust power output of the converter module based on the sensed voltage at the DC bus.

30. The method of claim 28 or 29, wherein controlling the converter modules comprises controlling the converter modules to provide power at a maximum power point of the photovoltaic panels when the voltage at the DC bus is less than a target DC bus voltage.

31. The method of any of claims 28 to 30, wherein controlling the converter modules comprises controlling the converter modules to reduce or limit power output to the DC bus when the voltage at the DC bus is greater than a target DC bus voltage.

32. The method of any of claims 28 to 31, further comprising adjusting an amount of power demand on the DC bus based on the voltage at the DC bus.

33. The method of claim 32, wherein adjusting the amount of power demand on the DC bus comprises adjusting an amount of power from the DC bus that is used to inject AC power to an AC power grid.

34. The method of any of claims 32 or 33, wherein adjusting the amount of power demand on the DC bus comprises adjusting an amount of power from the DC bus that is used to charge one or more batteries.

35. The method of any of claims 32 to 34, wherein adjusting an amount of power demand on the DC bus comprises increasing an amount of power demand on the DC bus when the voltage at the DC bus is above a target DC bus voltage.

36. The method of any of claims 32 to 35, wherein adjusting an amount of power demand on the DC bus comprises decreasing an amount of power demand on the DC bus when the voltage at the DC bus is below a target DC bus voltage.

37. The method of any of claims 28 to 36, wherein each of the converter modules is controlled by a separate control device that adjusts power output of the converter module based on the voltage at the DC bus; and wherein an additional controller adjusts load demand on the DC bus based on the voltage at the DC bus.

38. A method compri sing : monitoring, by a converter module, a DC bus to determine a DC bus voltage; detecting, by the converter module, that the DC bus voltage is in a predetermined operating range; and in response to detecting that the DC bus voltage is in the predetermined operating range, supplying, by the converter module, power to the DC bus, wherein the converter module is configured to supply power to the DC bus in parallel with one or more other converter modules, and wherein the converter module boosts a DC input voltage from one or more photovoltaic panels to a DC output voltage that the converter module provides to the DC bus.

39. The method of claim 38, further comprising: monitoring the DC bus voltage while the converter module supplies power from the converter module to the DC bus; determining that the DC bus voltage is between a lower threshold and a target DC bus voltage; and in response to determining that the DC bus voltage is between the lower threshold and the target DC bus voltage, controlling the converter module to provide power to the DC bus without limiting the amount of power from the one or more photovoltaic panels that is provided to the DC bus.

40. The method of claim 39, wherein controlling the converter module comprises: monitoring input current and input voltage from the one or more photovoltaic panels; andcontrolling the converter module to maximize an amount of power generated from the one or more photovoltaic panels.

41. The method of any of claims 38 to 40, further comprising: monitoring the DC bus voltage while the converter module supplies power from the converter module to the DC bus; determining that the DC bus voltage is between the target DC bus voltage and an upper threshold; and in response to determining that the DC bus voltage is between the target DC bus voltage and the upper threshold, controlling the converter module to limit an amount of power from the one or more photovoltaic panels that is provided to the DC bus.

42. The method of claim 41, wherein controlling the converter module comprises: in response to determining that the DC bus voltage is greater than the target DC bus voltage, limiting input current from the one or more photovoltaic panels.

43. The method of claim 42, wherein limiting input current from the one or more photovoltaic panels comprises applying an input current limit that is based on a magnitude by which the DC bus voltage exceeds the target DC bus voltage.

44. The method of any of claims 38 to 43, further comprising: while the converter module supplies power to the DC bus, determining, by the converter module, that the DC bus voltage is outside the predetermined operating range; and in response determining that the DC bus voltage is outside the predetermined operating range, terminating, by the converter module, supply of power from the converter module to the DC bus.

45. The method of any of claims 38 to 44, further comprising: while the converter module supplies power to the DC bus, detecting, by the converter module, a short circuit at the DC bus; and in response detecting the short circuit at the DC bus, terminating, by the converter module, supply of power from the converter module to the DC bus.

46. The method of claim 44 or 45, further comprising: after terminating supply of power from the converter module to the DC bus: monitoring, by the converter module, the DC bus voltage while the converter module does not supply power to the DC bus; detecting, by the converter module, that the DC bus voltage is in the predetermined operating range; and in response to detecting that the DC bus voltage is in the predetermined operating range, resuming, by the converter module, supply of power from the converter module to the DC bus.

47. A method comprising: controlling, by a controller, one or more devices to establish a voltage in a predetermined operating range on a DC bus, wherein the multiple converter modules are coupled to the DC bus in parallel, and each of the converter modules is configured to provide power to the DC bus from one or more photovoltaic panels when the voltage on the DC bus is in the predetermined operating range; after establishing the voltage in the predetermined operating range on the DC bus, and after one or more of the converter modules begin supplying power to the DC bus, monitoring, by the controller, the voltage on the DC bus; and adjusting an amount of power demand on the DC bus based on the voltage on the DC bus.

48. The method of claim 47, after establishing the voltage in the predetermined operating range on the DC bus and after one or more of the converter modules begin supplying power to the DC bus, causing the one or more devices to discontinue providing power to the DC bus, such that the converter modules set the voltage on the DC bus.

49. The method of claim 47 or 48, wherein controlling the one or more devices to establish the voltage in the predetermined operating range on the DC bus comprises controlling the one or more devices to establish the voltage in the predetermined operating range using energy stored in one or more batteries.

50. The method of claim 47 or 49, wherein controlling the one or more devices to establish the voltage in the predetermined operating range on the DC bus comprisescontrolling an AC / DC converter that receives power from an AC power grid to provide the voltage in the predetermined operating range.

51. The method of any of claims 47 to 50, wherein adjusting the amount of power demand on the DC bus based on the voltage of the DC bus comprises: determining that the voltage on the DC bus is greater than a target voltage for the DC bus; in response to determining that the voltage on the DC bus is greater than the target voltage for the DC bus, increasing an amount of power drawn from the DC bus to (i) charge one or more batteries and / or (ii) supply power to an AC power grid.

52. The method of any of claims 47 to 51, wherein adjusting the amount of power demand on the DC bus based on the voltage of the DC bus comprises: determining that the voltage on the DC bus is less than a target voltage for the DC bus; in response to determining that the voltage on the DC bus is less than the target voltage for the DC bus, decreasing an amount of power drawn from the DC bus to (i) charge one or more batteries and / or (ii) supply power to an AC power grid.

53. A system configured to perform the operations of the method of any of claims 28 to 52.

54. A converter module configured to perform the operations of the method of any of claims 38 to 46.

55. A controller configured to perform the operations of the method of any of claims 47 to 52.

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