Cascaded multi-level power supply for electrochemical processes and systems

Abstract

An electrolyzer system includes a plurality of power management units, each power management unit in the plurality of power management units includes a first converter coupled to a first terminal of the power management unit, a second converter coupled to a second terminal of the power management unit, and an energy buffer coupled between the first converter and the second converter. The electrolyzer system includes a plurality of electrolyzer modules, in which the second terminal of each power management unit is coupled to at least one respective electrolyzer module of the plurality of electrolyzer modules. The electrolyzer system includes a control system configured to control operation of the power management units. The control system includes a master control device and a plurality of local control devices communicatively coupled to the master control device, each local control device being configured to provide control information to a respective power management unit.

Description

[0001] CASCADED MULTI-LEVEL POWER SUPPLY FOR ELECTROCHEMICAL PROCESSES AND SYSTEMS

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application is an International Application which claims priority to U.S. Provisional Patent Application No. 63 / 615,611, filed December 28, 2023. The disclosure of the foregoing application is hereby incorporated by reference in its entirety.

[0004] BACKGROUND

[0005] Electrolyzers are devices that are capable of performing electrochemical processes such as electrolysis and reverse-electrolysis. These processes rely on electrochemical reactions, in which the flow of electricity through a substance cause electrical energy to be converted into chemical energy or vice-versa. In particular, electrolysis is the application of electric current to naturally occurring sources, e.g., water, that are made up of multiple elements. By applying electric current, the components that make up the source can be obtained, e.g., the hydrogen and oxygen elements of a water molecule.

[0006] The chemical constituents resulting from electrolysis can be used for energy production, provisioning, and storage. In reverse electrolysis, chemical components, such as hydrogen and oxygen, can be combined to generate electricity.

[0007] The predominant types of water electrolysis are: Alkaline Water Electrolysis (“AWE”); Proton Exchange Membrane (“PEM”); Anion Exchange Membrane (“AEM”); and Solid Oxide Electrolytic Cell (“SOEC”). Alkaline electrolyzers are unidirectional in that they can only convert water and electricity to hydrogen and oxygen (also referred to as “electrolysis” or “storage mode”), while PEM, AEM, and SOEC may be either unidirectional or bidirectional in that they can convert water and electricity to hydrogen and oxygen (electrolysis or storage mode) or convert hydrogen and oxygen back into water and electricity (also referred to as “fuel cell” or “generation mode”). Bidirectional systems reverse direction by operating at a voltage lower than a thermoneutral voltage for water electrolysis. Typically, this thermoneutral voltage level is around 1.3 V across each cell of an electrolyzer.

[0008] The cells of an electrolyzer are typically assembled in cell “stacks,” similar to electrochemical battery cells that are connected in series. The low-voltages of each cell may be summed to provide a high voltage “stack.” The high voltage stack can, in certain implementations, allow for greater power ratings (e.g., greater hydrogen production) with lower losses, by keeping current low. The overall stack voltages typically may be in the 100-250 VDC range, but may alternatively be substantially higher or lower. In some cases, the current densities of the stacks are in the range of 200-600 mA / cm2(e.g., for AWE) and in some cases up to 3 A / cm2(e.g., for PEM, AEM, and SOEC). The area referenced is the cross sectional area of the each cell. In general, the cross-sectional area of the stack is may be the same as that of an individual cell within the stack.

[0009] Electrolyzers may be used in various applications, such as providing a clean energy power source to a load, as a means for storing electrical energy (e.g., from a solar cell array, power grid, or other power source), producing feedstock for various industries, producing hydrogen for transportation fuel cells in transportation or for heating and power in buildings, among other uses. Different applications may have different power generation and / or storage requirements. Thus, electrolyzers may include control systems to set currents, voltages, and to maintain production outputs across different industries.

[0010] SUMMARY

[0011] This specification relates to power systems and devices for delivering power to or receiving power from electrolyzers. Electrolyzers perform electrochemical processes such as electrolysis and / or reverse-electrolysis.

[0012] In some implementations, such as in large scale industrial operations, large electrolyzer stacks having hundreds or more cells are employed. The inductance and thermal mass of such large electrolyzer stacks system can be high, such that the electrolyzers are slow “ramping” up and down (e.g., in response to a variable power input from a solar array) or switching directions from storage to generation mode on-demand. Moreover, imprecise electrical control of the electrolyzer cells can risk triggering side reactions, which may damage the cells (e.g., the ion-conducting membranes) and require an electrolyzer stack be taken offline and / or replaced.

[0013] The present disclosure is directed to electrolyzer systems that can, in various implementations, provide improved electrolyzer responsiveness and control. For instance, in some implementations, the electrolyzer systems disclosed herein can include control systems that adjust electrolyzer operation across portions (e.g., across individual electrolyzer cells or groups of cells) of the stack to improve operating uniformity across the stack as a whole. The control systems disclosed herein can account for variations in factors such as cell temperature, electrolyte concentration, cell operating capacity, among other factors to improve the precise control of, ramping capability of, and uniformity across electrolyzer stacks.

[0014] In general, in some aspects, the electrolyzers of the present disclosure are implemented using a cascaded multilevel converter (e.g., microinverter or microconverter) topology. For the present disclosure, the microinverters or microconverters are also referred to as power management units (PMUs). Each PMU may be coupled to one or more cells of the electrolyzer. The one or more cells to which a PMU is coupled may be referred to as a “module.” Each PMU may be configured to provide power to the respective module to which it is attached (e.g., power from a solar cell array or a single or multi-phase power source such as an electric grid) or receive power from the module and provide the power to a load (e.g., by providing power collectively to the load from the electrolyzer stack). A system with multiple PMUs can include a main (or master) control device that is configured to coordinate operation of the PMUs. In some implementations, the system also includes a coupling module (“CM”) through which the PMUs are coupled to an input power source.

[0015] Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. For example, by delivering power through the use of PMUs, the input to individual modules and / or individual electrolyzer cells may, in some implementations, be tailored to the needs of each module and / or cell, respectively, to improve rampability and efficiency of the electrolyzer stack.

[0016] In some implementations, coordinating control activity through a master control device allows for an electrolyzer stack to be responsive to changes in grid-connected configurations and that can reduce operating errors. Moreover, in some implementations, by arranging groups of electrolyzer cells in modules, in which each module is controlled by a respective PMU, the electrolyzer stack can be scaled, e.g., by increasing or decreasing a number of connected modules, depending on the needs of the application to which the electrolyzer stack is applied. For example, in some implementations, one or more modules of the electrolyzer system can be can be turned off or removed from the stack, while other modules in the stack remain in operation, so that repairs on modules can be performed or replacement modules can be provided, without the need to take the entire stack offline.

[0017] In some implementations, the disclosed technology provides customized power delivery to electrolyzer cells in an electrolyzer system (e.g., an electrolyzer stack) or other type of electrochemical system. Customized power delivery at target voltage levels and target current densities improves efficiency of the electrolyzer system without wasting electric power or inadvertently changing operational modes of the electrolyzer cells of the system. In some implementations, cascaded multi-level inverter or converter topologies can provide precise control the electrolyzer cells through the application of pulse-width modulated signals.

[0018] In some implementations, the electrolyzer systems of the present disclosure exhibit improved reliability despite variations in power sources, loads, and individual electrolyzer cell conditions.

[0019] In some implementations, the improved control of the disclosed electrolyzer systems facilitates execution of electrochemical processes at higher current densities with a lower risk of overheating. In some implementations, the improved efficiency and operability of the presently disclosed systems can result in more efficient hydrogen production, increasing its usefulness as an alternative and clean energy source.

[0020] In some implementations, the electrolyzer system includes a control system that improves power conditioning for the electrolyzer system. The control system may provide precise current control for the modules by determining and generating switching signals to operate the PMUs of the electrolyzer system. In some implementations, the control system may determine switching signals that reduce distortive effects, such as the distortion generated from impedance between electrical sources, e.g., an electric grid, and loads.

[0021] Other advantages of the disclosed technology include utilization of high voltage input without including step-down transformers in the circuitry between the electrolyzer stack and an input power source. For example, the disclosed technology may allow high voltage input to the electrolyzer system for a transformer-less connection to the electrical grid. In some implementations, the disclosed technology allows high voltage input to the electrolyzer system without inefficient voltage transformation, e.g., due to eddy currents or hysteresis from transformers. In some implementations, the omission of transformers can reduce the amount of space needed for electrical connections between the electrolyzer system and the electric grid.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGS. 1 A through 1C are diagrams depicting example embodiments of electrolyzer modules and stacks.

[0024] FIG. ID is a block diagram depicting an example arrangement of electrolyzer stacks. FIG. IE is a block diagram depicting an example arrangement of electrolyzer modules.

[0025] FIG. 2A is a schematic view depicting an example embodiment of a power management unit coupled to an electrolyzer module.

[0026] FIGS. 2B through 2D are schematic views depicting example embodiments of converters of a power management unit.

[0027] FIGS. 2E and 2F are schematic views depicting control devices for a power management unit.

[0028] FIG. 3 A is a schematic view depicting an example embodiment of an electrical system connected to a power management system for a cascaded electrolyzer system.

[0029] FIG. 3B is a schematic view depicting an example embodiment of an electrolyzer system that couples an electrolyzer modules to power management units of FIG. 3 A.

[0030] FIGS. 3C and 3D are schematic views depicting example embodiments of power management units of FIG. 3A.

[0031] FIG. 4 is a schematic view depicting an example embodiment of a power management unit coupled to a pair of electrolyzer modules.

[0032] FIG. 5 is a schematic view depicting an example embodiment of an electrolyzer system that couples pairs of electrolyzer modules to power management units of FIG. 4.

[0033] FIG. 6 is a schematic view depicting an example embodiment of a power management unit coupled to a pair of electrolyzer modules and a photovoltaic system.

[0034] FIG. 7 is a schematic view depicting an example environment of an electrolyzer system that couples a pair of electrolyzer modules and a photovoltaic system to each to power management unit of FIG. 6.

[0035] FIG. 8 is a schematic view depicting an example embodiment of a power management unit coupled to an electrolyzer stack.

[0036] FIG. 9 is a schematic view depicting an example embodiment of an electrolyzer system that couples an electrolyzer stack to the power management units of FIG. 8.

[0037] FIG. 10 is a schematic view depicting an example embodiment of an electrolyzer system that couples an electrolyzer module to power management units of FIG. 3 A.

[0038] FIG. 11 is a schematic view depicting an example embodiment of a power management unit coupled to an electrolyzer stack and an electrolyzer module.

[0039] FIG. 12 is a schematic view depicting an example embodiment of an electrolyzer system that couples an electrolyzer module and an electrolyzer stack to power management units of FIG. 11. FIG. 13 is a schematic view depicting an example embodiment of an electrolyzer system that couples an electrolyzer module and a photovoltaic system to power management units of FIG. 11.

[0040] FIG. 14 is a flowchart diagram depicting an example process for controlling voltage levels of an electrolyzer system.

[0041] FIGS. 15A and 15B are block diagrams depicting example embodiments of a module and control system within an energy system.

[0042] FIG. 15C is a block diagram depicting an example embodiment of a physical configuration of a module.

[0043] FIG. 15D is block diagram depicting example embodiments of modules having various electrical configurations.

[0044] FIGS. 16A through 16C are schematic views depicting example embodiments of energy buffers.

[0045] FIG. 17A is a plot depicting an example output voltage of a module.

[0046] FIG. 17B is a plot depicting an example multilevel output voltage of an array of power management units.

[0047] FIG. 17C is a plot depicting an example reference signal and carrier signals usable in a pulse width modulation control technique.

[0048] FIG. 17D is a plot depicting example reference signals and carrier signals usable in a pulse width modulation control technique.

[0049] FIG. 17E is a plot depicting example switch signals generated according to a pulse width modulation control technique.

[0050] FIG. 17F as a plot depicting an example multilevel output voltage generated by superposition of output voltages from an array of power management units under a pulse width modulation control technique.

[0051] FIGS. 18A and 18B are block diagrams depicting example embodiments of controllers for a power management system of FIG. 3 A.

[0052] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0053] Electrochemical systems such as electrolyzers can perform electrolysis to generate hydrogen. Depending on the source for electricity used in electrolysis, the generated hydrogen can be a form of clean energy, e.g., very little to zero carbon emissions. The generation of hydrogen through electrochemical processes can be coupled to renewable energy sources such as wind, solar, hydro, and geothermal, as well as nuclear energy options. However, some approaches for electrochemical systems to improve grid reliability and power supply through the generation of hydrogen or operation of electrolyzer cells in a fuel cell mode is limited due to imprecise control of electrical current provided to the electrolyzer cells. This can hamper the ability of an electrochemical system to adjust hydrogen or electrical energy production, thereby limiting the ability of the electrochemical system to be a viable alternative to carbonbased energy sources, e.g., ones that emit carbon into the atmosphere and exacerbate climate change.

[0054] Examples of Electrolyzer Modules and Stacks

[0055] FIG. 1A illustrates an example implementation of an electrolyzer 100 in the form of an electrolyzer cylindrical stack 102. Although shown and referred to here as “cylindrical,” the stack can have other shapes. The electrolyzer cylindrical stack 102 includes N electrolyzer cells 104-1 through 104-N (collectively referred to as “electrolyzer cells 104”) arranged along an axis 105. As illustrated, the axis 105 extends from a front portion of the electrolyzer cylindrical stack 102 to a rear portion of the electrolyzer cylindrical stack 102. The electrolyzer cells 104 are arranged such that the first electrolyzer cell 104-1 is located closest to the front portion of the electrolyzer cylindrical stack 102 and the last electrolyzer cell 104-N is located furthest from the front portion, e.g., at the rear portion of electrolyzer cylindrical stack 102. The electrolyzer cylindrical stack 102 can be configured to perform a type of electrolysis. Examples of different types of electrolysis include alkaline water electrolysis (“AWE”), proton exchange membrane (“PEM”), anion exchange membrane (“AEM”), and solid oxide electrolytic cell (“SOEC”).

[0056] Other types of electrolysis such as PEM, AEM, and SOEC electrolysis can demand higher current densities, e.g., up to 3 A / cm2(amps per square centimeter) in cross-sectional area. In some implementations, some electrolyzer systems (e.g., configured to perform AWE) are unidirectional, e.g., limited to only performing electrolysis using water and electricity to generate hydrogen and oxygen. In some implementations, some electrolyzer systems (e.g., PEM, AEM, SOEC) can be operated bidirectionally, e.g., able to perform electrolysis or reverse-electrolysis. Bidirectional electrolyzer systems can reverse direction of operation (e.g., the electrochemical process being performed) by operating at a voltage lower than a threshold voltage, e.g. , -1.3V (volts) thermoneutral voltage for water electrolysis.

[0057] Each electrolyzer cell 104 can include components for an electrolyzer, including an electrode, a diaphragm, among other electrolyzer components, and can be configured to perform a type of electrolysis. The type of electrolysis and ability to perform reverseelectrolysis for an electrolyzer may be determined by the type of components included the electrolyzer stack 102. Components such as galvanic cells (e.g., voltaic cells) indicate that an electrolyzer device can be configured to operate in fuel cell mode to generate electricity.

[0058] The electrolyzer cylindrical stack 102 includes at least one inlet to receive input for electrolysis, e.g., water, and at least two outlets to provide output resulting from electrolysis, e.g., hydrogen and oxygen. For example, the electrolyzer cylindrical stack 102 can be configured to perform PEM electrolysis, by including solid polymer electrolytes in the electrolyzer cells 104 to attract protons from an anode portion to a cathode portion of the electrolyzer cylindrical stack 102, e.g., by operating the electrolyzer cylindrical stack 102 and applying DC current. As another example, the electrolyzer cylindrical stack 102 can be configured to perform AEM electrolysis, by including semi-permeable membranes in the electrolyzer cells 104 to conduct hydroxide ions in the electrolysis process.

[0059] One or more electrolyzer cells of a stack of cells can be grouped together into an electrolyzer module, thereby allowing for a greater voltage capacity than a single cell. Grouping in modular fashion permits a large quantity of electrolyzers to be located in a central space, where power for the electrolyzers can be sourced from a central point and distributed to each electrolyzer efficiently and as needed. The modular arrangement permits ready contraction or expansion of the system as a whole by removing or adding cells within a module and by removing or adding other modules, which provides flexibility for the size of the system to meet changing demands. Modular arrangement further permits individual modules to be removed or brought off-line (no power) for purposes of repair or replacement with a functioning module, or upgrade to a newer model.

[0060] FIG. IB illustrates a perspective view 122 of an electrolyzer module 108. The electrolyzer module 108 has a number of electrolyzer cells 110-1 - 110-N that can be configured to perform electrolysis. The electrolyzer module 108 also includes a number inlets 114-1 through 114-N (collectively referred to as “inlets 114”), a number of outlets 116-1 through 116-N (collectively referred to as “outlets 116”), and a number of ports 118- 1 through 118-N (collectively referred to as “ports 118”). Depending on the type of electrolyzer cells included within the module 108 (e.g., whether the cells are AWE cells or are AEM, PEM or SOEC cells), the electrolyzer module 108 may be configured to operate unidirectionally or bidirectionally. In bidirectional operation, the electrolyzer cells of the electrolyzer module 108 can switch between two modes: an electrolysis mode to perform electrolysis using electrolyzer cells 110-1 - 110-N, or a fuel cell mode to perform reverse electrolysis using voltaic cells 112-1 - 112-N. In unidirectional operation (e.g., in the case of AWE cells), the electrolyzer module 108 operates in electrolysis mode only.

[0061] The electrolyzer module 108 is configured to be a load of an electrical power system by receiving electrical power through the ports 118, which serve as an interface between the electrolyzer module 108 and the electrical power system. For example, a system for storing and outputting electrical energy can be configured to output electrical power at a target voltage level and current density. The electrical power provided to the electrolyzer module 108 through ports 118 can configure the operational mode of the electrolyzer module 108, e.g., electrolysis mode or fuel cell mode. The electrical power provided to the electrolyzer module 108 can be distributed among the electrolyzer cells 110, which can cause the electrolyzer cells 110 to transition between operational modes (e.g., from electrolysis mode to fuel mode or vice-versa) and / or maintain operation of the cells in electrolysis or fuel cell mode. In some implementations, voltage levels of the electrolyzer module can be configured by control signals provided from a control system (e.g., control system 205) described in reference to FIG. 2B below. For example, a master control device (e.g., MCD 212) and / or local control device (e.g., LCD 214) can determine voltage levels and generate control signals to control the voltage level of the electrolyzer module 108.

[0062] In some cases, maintaining cell operations in a particular mode can include increasing or decreasing voltages applied to the cells, while still maintaining the voltage level above or below a threshold voltage (e.g., thermoneutral voltage) to maintain the particular mode. For example, the voltage level applied to the cells 110 can be decreased to reduce temperature (e.g., to prevent overheating), but still maintain a voltage above a threshold level for the cells 110 to continue operating in electrolysis mode. As another example, the voltage level applied to the cells 110 can be increased to draw more power from the electrolyzer module 108 while maintaining a voltage below a threshold voltage for the cells 110 to continue operating in fuel cell mode.

[0063] The electrolyzer module 108 can be configured to perform electrolysis based on received power at the ports 118. The electrolyzer 108 operating in fuel cell mode can be configured to provide power to the electrical power system at the ports 118. Additional power characteristics such as current, current density, or some combination thereof, can affect the efficiency of performing electrochemical processes.

[0064] In electrolysis mode, the electrolyzer module 108 receives water through an inlet 114 and provides hydrogen and oxygen resulting from electrolysis separately through outlets 116. In some implementations, the electrolyzer module 108 can be configured to receive electrical power through ports 118 to power electrolysis in the electrolyzer module 108. In some implementations, the inlets 114 and outlets 116 are bi-directional, e.g., the direction or flow of materials being provided to and received from the electrolyzer module 108 can be adjusted according to the operational mode of the electrolyzer module 108. For example, inputs for performing electrolysis can be provided through inlets 114, e.g., from storage tanks, vessels, and other systems configured to store and provide input materials. Any generated electrical output (e.g., an output obtained by performing reverseelectrolysis) is provided through one or more of the ports 118.

[0065] In fuel cell mode, the electrolyzer module 108 is configured to receive and combine hydrogen and oxygen, e.g., stored as a gas through one or more connecting chemical storage systems, and provide an output of water and electricity. In some cases, by-products, e.g., water vapor, sodium or hydrogen ions, can be generated based on reaction rates and completeness of reduction and / or oxidation performed during reverse-electrolysis. The resulting electricity generated by performing reverse-electrolysis, e.g., combining hydrogen and oxygen provided through the inlets 114, is provided from ports 118 to a connected system from the electrolyzer cell, e.g., to the a power management unit described in reference to FIG 2A.

[0066] The components of the electrolyzer module 108 assist operation of the electrolyzer module 108 in a number of ways. The electrolyzer cells 110 can include electrodes, halfcells, conductors, electrolytes, membranes, catalysts, and other related components for performing electrolysis and reverse-electrolysis. For example, the electrolyzer cell 110 includes an anode, i.e., a positively charged electrode, and a cathode, i.e., a negatively charged electrode, at which respective chemical processes such as oxidation and reduction can occur. The electrolyzer module 108 can include additional ports, cables, wiring, etc. to facilitate the connection of the electrolyzer module 108 to other electrochemical devices and systems.

[0067] As illustrated, in some implementations, the electrolyzer module 108 includes sensors 120 to capture measurements of electrolytic conductivity, water vapor, current, voltage, temperature, gas flow rates (e.g., flow rates of oxygen and / or hydrogen), liquid flow rates (e.g., water flow rate) or any parameter describing state (e.g., electrical, chemical) information or processes of the electrolyzer module 108. The gas flow rate (GFR) describes a flow rate of hydrogen gas and / or oxygen output from the electrolyzer module by performing electrolysis.

[0068] The sensors 120 can provide status information to a control system that can configure and control the electrochemical system. In some implementations, signals including sensor data from the electrolyzer module 108 is transmitted to one or both of a local control device 214 and / or a master control device 212, of a control system 205 (see, e.g., FIG. 2A). For example, sensor data can be transmitted by Wi-Fi, Bluetooth, Modbus TCP over Ethernet. Data transfer between electrolyzer module 108 and the control system 205 can follow standardized or customized communication protocols, e.g., I2C.

[0069] As illustrated in FIG. 1C, multiple electrolyzer modules 108 can be arranged into a electrochemical device array, e.g., the example electrolyzer rack-mounted stack 130 of the electrochemical system 128. As illustrated, N electrolyzer modules 140-1 through 140-N (collectively referred to as “electrolyzer modules 140”) are arranged along an axis or direction 132. Each module in the set of electrolyzer modules 140 can include, e.g., the electrolyzer module 108 described in reference to FIG. IB above. A front view of the example electrolyzer device array 130, sometimes also called a “stack,” is illustrated in FIG. 1C. In some implementations, each successive electrolyzer module 140 is positioned directly above and connects to a previous electrolyzer module 140 in the stack so as to provide efficient connections between the electrolyzer modules 140 to readily exchange inputs, outputs, by-products, or some combination thereof, in electrochemical processes between two or more connected electrochemical modules. The electrolyzer modules 140 can be connected in series such that the voltages of each module 140 are combined to create a high-voltage stack.

[0070] In some implementations, the stack 130 can include an additional set of inlets, outlets, ports, and sensors for the overall electrochemical system. The stack 130 can operate some or all of the electrolyzer modules 140 to jointly perform the same electrochemical process, e.g., electrolysis or reverse-electrolysis. The stack 130 can also operate as an electrochemical system with the electrolyzer modules 140 operating as electrochemical subsystems, in which the stack configures some or all of the electrolyzer modules 140 to operate independently, e.g., some electrolyzer modules perform electrolysis while other electrolyzer modules perform reverse-electrolysis.

[0071] FIG. ID depicts an example implementation of multiple electrolyzer rack-mounted stacks 160-1 through 160-N (collectively referred to as “stacks 160”) having electrolyzer modules 162-1 through 162-MN (collectively referred to as “modules 162”) arranged in an example framework 150. The maximum number of stacks 160 is limited only by the practical limits of space for framework 150 and the operating parameters of the particular application. Each stack 160 includes M electrolyzer modules 162 that can be connected as a single electrochemical system, and / or multiple electrochemical subsystems.

[0072] Each stack can have a housing with panels on any number of the sides, with further openings between electrolyzer modules and / or electrolyzer stacks to facilitate connections between ports, inlets, outlets, and other components. Furthermore, a subset of electrolyzer modules can be referred to as an electrochemical subsystem of a respective stack. By arranging the modules 162 in the framework 150, subsystems of multiple electrochemical modules in a stack, multiple electrochemical modules across multiple stacks, and multiple electrochemical stacks in general, can be configured to receive or supply respective amounts of electrical power from a power management system.

[0073] FIG. IE is a block diagram illustrating a front perspective view 170 and a rear perspective view 180 of an example arrangement of electrochemical modules. In this example arrangement, pairs of electrolyzer modules are be coupled together in a “back-to- back” configuration, and N successive pairs 176-1 through 176-N of electrolyzer modules may be coupled together in a stack that is oriented parallel to a horizontal axis 178 (in a horizontal stack of electrolyzer modules). Each electrolyzer module in the successive pairs 176-1 through 176-N of electrolyzer modules can be an example of the electrolyzer module 108, described in reference to FIG. 1 A above. For example, a first pair 176-1 of electrolyzer modules includes a first electrolyzer module 172a-l and a second electrolyzer module 172b-l. The first electrolyzer module 172a-l is illustrated in an orientation facing out of the page and the second electrolyzer module 172b- 1 is illustrated in an orientation facing into the page in the front view 170. Although FIGS. 1A through IE illustrate examples of electrolyzer module arrangements, any arrangement can be utilized based on the desired application and physical space constraints. A subset having some or all of the electrolyzer modules of the electrolyzer systems disclosed herein can be configured in operate in fuel cell mode while remaining modules operate in electrolysis mode. In some implementations, subsets of electrolyzer modules can be turned off (e.g., for maintenance, repair, or replacement) and the remaining subsets of electrolyzer modules can be configured to continue performing electrochemical processes, thereby maintaining the production of hydrogen and / or electricity from the electrolyzer modules. Additionally, the inclusion of sensors for electrolyzer modules across the electrolyzer systems can provide measurement data, in which a power management system can responsively process and determine feedback for the electrolyzer modules.

[0074] The implementation illustrated in FIG. IE can be desirable in circumstances in which electrolyzer modules operate in different modes, e.g., switching electrolyzer modes between two different electrolyzer modules. An electrolyzer module from a pair of electrolyzer modules, e.g., among the pairs 176-1 through 176-N, can only operate in a particular mode, such as fuel-cell mode, while the respective electrolyzer module from the same pair of electrolyzer modules operates in a different mode, such as electrolysis mode. Power can be supplied to a particular electrolyzer module among the pairs of electrolyzer modules 176-1 through 176-N to concurrently operate in a particular mode based on a configuration of electrochemical components in the electrolyzer module. Some electrolyzer modules can be limited to a particular mode, and therefore coupling two electrolyzer modules that are able to operate in different modes can be desirable. Referring to the rear view 180, the first pair 176-1 of electrolyzer modules is illustrated with first electrolyzer module 172a-l in an orientation facing into the page and the second electrolyzer module 172b-l in an orientation facing out of the page. Each pair in the successive pairs 176-1 through 176-N of electrolyzer modules is similarly illustrated in front view 170 and rear view 180. Each electrolyzer module in a pair of electrolyzer modules from the successive pairs 176-1 through 176-N also includes a respective electrolyzer cells, voltage cells, ports, inlets, and outlets. In some cases, some or all of the electrolyzer modules in some or all of the pairs of electrolyzer modules can also include sensors, such as sensors 120 described in reference to FIG. IB above.

[0075] Electrolyzer efficiency while performing electrochemical processes (such as electrolysis or reverse-electrolysis) can be directly affected by the control of electrical signals supplied to the electrolyzers, e.g., electrolyzers described in reference to FIGS. 1 A through IE. Some approaches for controlling electrolyzer systems in general can be limited by the inductance and thermal mass of electrochemical cells in electrolyzer systems. Due to the inductance of chemical reactants, electrolytes, and other materials utilized in electrochemical processes, electrochemical systems can be slow to adjust production and switch between operational modes. Other approaches for providing power to electrolyzer modules without converting, inverting, and / or regulating power flow based on conditions of electrolyzer cells in the electrolyzer modules can result in reduced lifecycles of components and devices for performing electrochemical processes. Without responsive conversion of electric power to the electrolyzer modules, the current provided to electrolyzer modules can damage current-sensitive components such as ion-conducting membranes in the electrochemical cells. In some cases, these approaches can also contaminate chemical components of electrochemical cells, such as electrolytes and electrodes.

[0076] Controlling electrolyzer systems without the use of converters to regulate electrochemical system power supply can result in inefficient operation. For example, the power from electric grids e.g., DC power from an AC grid input, may lead to large errors in target current density and voltage level. In turn, such errors result may result in an incorrect configuration and / or inefficient operation of the electrolyzer. For example, if an insufficient voltage is provided, an electrochemical system may operate in fuel cell mode instead of a electrolysis mode. Alternatively, if too much electrical current for an operational mode is provided, electrical power is wasted. Furthermore, existing approaches to control electrolyzer systems do not provide operation of electrochemical cells at high current densities without significant risk of overheating and can be limited by activation over-potential in the electrochemical cell.

[0077] Providing power to electrolyzer modules is a complex process as electrolyzer cells utilize solution with varying alkalinities based on the electrochemical process being performed. The alkalinity of solutions can affect membrane conductivity and availability of ionic pathways in electrochemical cells, resulting in varying utilization of catalysts in the electrochemical process. Changes in catalyst utilization can lead to changes in target voltages and current densities for operating electrolyzer cells in particular modes, e.g., a difference in a tenth of a volt can result in a different operational mode. Furthermore, different types of losses such as electrical losses (e.g., voltage drop, noise) and chemical losses (e.g., proton conductivity, mass transport) can cause the electrolyzer cell to operate inefficiently, thereby wasting electrical current and / or products such as hydrogen and oxygen. Electrolyzers include low-voltage cells (e.g., 3 V) connected, e.g. in series, to form a high-voltage stack of cells. The higher voltage (e.g., 100 to 250 VDC) provided by connecting multiple low-voltage cells allows for electrolyzer devices with greater power rating, e.g., to utilize larger amounts of current compared to supplying power to individual cells. Electrolyzer modules with increased power ratings can result in an increase in hydrogen generated by the electrolyzer, but can also result in damaging components. Therefore, maintaining currents close to thermoneutral voltage levels (e.g., 3 V) and current densities within an operable range, e.g., 200 to 600 mA / cm2(milliamps per square centimeter), can improve operability and the lifecycle of electrolyzer module components.

[0078] Furthermore, in some cases, an amount of current is provided to an electrolyzer system (e.g., current provided to electrolytic cells) that exceeds a current density and / or threshold voltage level that is sufficient for configuring the electrolyzer in electrolysis mode. This excess current may be due to, e.g., the complex nature of chemical reactions and reaction rates in electrolysis reactions. In some implementations, the voltage threshold for configured modes of the electrolyzer modules changes over time, based on changes in reactants, reactant efficiency, reaction duration, and / or other chemical characteristics related to the components of electrolyzer that are involved in performing electrochemical processes. Alternatively or in addition, electrical losses in power transmission between an energy source, e.g., an electrical grid for an electrochemical system and the electrochemical system itself may result in inadequate and / or undesired operating conditions for the electrochemical system.

[0079] Power Management and Control for Electrolyzer Modules

[0080] A power management unit (PMU) can include or be coupled to an electrolyzer module, e.g., electrolyzer module 108, to allow for precise control of the electrolyzer module, by providing power to the electrolyzer module at a target voltage levels and current densities. For example, the PMU converts voltage inputs (e.g., from a battery source, an electric grid) across the electrolyzer module in electrolysis mode. The PMU can also convert voltage outputs from the electrolyzer module in fuel cell mode to provide power to an electrical source or another type of load. The PMU can be configured to obtain measurements from sensors of the electrolyzer module, e.g., sensors 120, and adjust voltage control of the electrolyzer module based on the measurements. An example of voltage control can include the PMU converting input voltages to a lower or higher voltage level for input of the electrolyzer module in electrolysis mode. As another example, the PMU can be configured to draw and store excess electrical power, e.g., in battery storage, from the electrolyzer module in fuel cell mode.

[0081] The PMU provides voltage control to the connected electrolyzer module such that the electrolyzer modules can be connected or disconnected from a stack of electrolyzer modules. As an example, sensor measurements of the electrolyzer module can indicate operational failure or inefficiency (e.g., excess current density that can result in damage to electrolyzer components). The PMU can disconnect an electrolyzer module from the stack of electrolyzer modules by reducing voltage input and prevent damage to the electrolyzer module. As another example, the sensor measurements of the electrolyzer module can indicate undesired variations (e.g., due to wear and tear of electrolyzer components, signal noise) in the voltage thresholds that configure the operational mode of the electrolyzer module. The PMU adjusts voltage input to account for the variations and maintain operability of the electrolyzer in the desired mode. Multiple PMUs can be connected as a cascaded, module-based energy system for a stack of electrolyzer modules, each PMU connecting to a respective electrolyzer module. Each PMU from can include a microconverter or microinverter topology to provide electrical power at target parameters for the respective electrolyzer module, by controlling switches of PMU that adjust voltage levels of the electrolyzer module. Furthermore, control of power supply from the modulebased energy system by the respective PMU coupled to the electrolyzer module is performed by a control system that includes a master controller coupled to a local control device for each PMU. In some implementations, a PMU can be connected to an electrolyzer stack, e.g., electrolyzer modules connected in series. The electrolyzer stack connects to the PMU, in which the stack has a total voltage corresponding to the combined voltages across all of the electrolyzer modules, e.g., twelve volts to one kilovolt, based on the number of electrolyzer modules connected in series.

[0082] As an example, an electrolyzer module or electrolyzer stack is configurable at a threshold voltage level at which the electrochemical system switches between fuel cell and electrolysis modes. Power provided below a threshold voltage may not be sufficient to initiate or maintain the chemical reactions (e.g., oxidation, reduction) performed in a respective mode. Insufficient power provided to an electrolyzer module causes the electrolyzer module to operate in an undesired mode, e.g., configuring the electrolyzer module in fuel cell mode instead of electrolysis mode or vice versa. The control system includes the master control device and the local control devices of the PMUs to provide balancing for gas flow rate, temperature, capacity, voltage, current, current density, and / or voltage density across the electrolyzer modules. In other words, by electrically coupling electrolyzer modules (e.g., subsystems of the electrochemical system) to power management units of a cascaded, module-based energy system, the parameters across multiple electrolyzer modules can be balanced.

[0083] FIG. 2A is a schematic diagram of an example system 200 having an electrolyzer module 108 coupled to a power management unit 208 ("PMU 208”). The PMU 208 can be configured to utilize the electrolyzer module 108 as an energy source during fuel-cell mode. Alternatively, the electrolyzer module 108 can be configured as a load of the PMU 208 during electrolysis mode. The PMU 208 includes an energy subsystem 202 that connects to a power management circuit 206 that controls switching circuitry to convert or invert voltages between the electrolyzer module 108 and terminals 209-1 and 209-2 of the PMU 208.

[0084] The PMU 208 includes terminals 209-1 and 209-2 (collectively “terminals 209”), that can be connected to electrical systems (e.g., single-phase, multi -phase) that provide (e.g., as a source) or receive electrical power (e.g., as a load). The PMU 208 controls voltage levels between the terminals 209 and the electrolyzer module 108 to configure the voltage level provided to the electrolyzer module 108. By managing voltage levels between an electrical system and the electrolyzer module 108, the PMU 208 sets the operational mode for the electrolyzer module 108. Although illustrated with two terminals, additional terminals can be included for the PMU 208, e.g., ground and neutral. By connecting terminals 209-1 and 209-2 to a power supply such as a utility power grid, the power management unit 208 can be configured to convert, invert, regulate power to and from the electrolyzer module 108 with efficient current densities and / or voltage levels for the desired operational mode of the electrolyzer module 108.

[0085] The power management circuit 206 (also referred to as “circuit 206”) of the PMU 208 includes a first converter 210a and a second converter 210b (collectively referred to as “converters 210”), each of which can be configured to receive an input voltage and switch to generate pulses to achieve a target voltage signal for the electrolyzer module 108. A local control device 214 (“LCD 214”) of the PMU 208 is configured to independently control each switch.

[0086] The power management circuit 206 can include any number of DC-DC or AC -DC circuit topologies, including isolated and non-isolated converters. The power management circuit 206 utilizes switching circuits to perform AC -DC conversion, DC-DC conversion, DC-AC conversion, or AC-AC conversion to provide a target amount of power supply to the electrolyzer module. Examples of non-isolated topologies for circuit 206 can include buck, boost, flyback, Cuk, Sepic, and so on, while examples of isolated topologies for circuit 206 can include half-bridge, push-pull, full-bridge, and discontinuous conduction mode (DCM). A topology for the converter can be utilized based on a variety of factors for the electrolyzer module 108, e.g., driving desirable parameters for voltage, current, power, and switching frequency. Different combinations of circuit topologies using varying circuit components can be used to achieve desired voltage and circuit densities.

[0087] The switches for the converters 210 can be any suitable switch type, such as power semiconductors like the metal-oxide-semiconductor field-effect transistors (MOSFETs) shown here, insulated gate bipolar transistors (IGBTs), or gallium nitride (GaN) transistors. Semiconductor switches can operate at relatively high switching frequencies, thereby permitting the converters 210 to be operated in pulse-width modulated (PWM) mode if desired, and to respond to control commands within a relatively short interval of time. This can provide a high tolerance of output voltage regulation and fast dynamic behavior in transient modes. The utilization of high-speed switches in the converters 210 provides that the PMU 208 can dynamically respond to electrical operating conditions for the connected electrolyzer module 108. The PMU 208 dynamically responds to conditions of the electrolyzer module 108 when the electrolyzer module 108 is projected to fall outside of an operational range (e.g., threshold voltage, target current density, temperature, gas flow rate).

[0088] For example, the PMU 208 can reduce the amount of current provided to the electrolyzer module 108 in response to a sharp increase in temperature of the cells for the electrolyzer module 108, thereby preventing damage and other types of faults in the cells. As another example, low temperatures, gas flow rates, or some combination thereof, can indicate insufficient voltage levels for the electrolyzer module 108. The PMU can be configured to dynamically respond to the insufficient voltage level to maintain a voltage level sufficient for a particular mode of the electrolyzer module 108. As shown in FIG. 2 A, a control system 205 is provided to manage voltage levels throughout the PMU 208 by controlling operation of the converters 210 and other connected components of the circuit 206. The control system 205 is implemented as the LCD 214 that is communicatively coupled to a master control device 212 (“MCD 212”). The LCD 214 is communicatively coupled to the MCD 212 by communication paths or links. The communication paths or links can be wired (e.g., electrical, optical) or wireless communication paths that communicate data or information bidirectionally, in parallel or series fashion. Data can be communicated in a standardized (e.g., IEEE, ANSI) or custom (e.g., proprietary) format. Although FIG. 2A depicts the LCD 214 as an internal component of the PMU 208 (e.g., internal to a housing for the PMU 208), the LCD 214 can be external to the PMU 208, e.g., depicted in FIG. 15A and 15B.

[0089] The LCD 214 of the PMU 208 is configured to obtain status information from the electrolyzer module 108 (e.g., by sensors 120 of the electrolyzer module). The MCD 212 is configured to generate control information for the PMU 208 based on the status information of the electrolyzer module 108. The status information for the electrolyzer module 108 can include sensor measurements for gas flow rate, temperature, voltage level, and current density. For example, the sensor measurements can include flow rates of gases (e.g., hydrogen, oxygen) generated from electrolysis while the electrolyzer module 108 operates in electrolysis mode. The sensor measurements can also include flow rates of gases consumed in reverse-electrolysis while the electrolyzer module 108 operates in fuel cell mode. In some implementations, the LCD 214 includes additional sensors to measure temperature, current, voltage, and other characteristics of components in the PMU 208.

[0090] The status information can include information about one or more aspects, characteristics, or parameters the electrolyzer module 108 connected to the PMU 208. For example, the status information can include sensor measurements captured by sensors 120 of the electrolyzer module 108. The LCD 214 can be configured to receive the status information (e.g., measurement data from the sensors 120) of the electrolyzer module 108 by the communication paths of the control system and / or wireless communication with sensors 120. In some implementations, the sensors 120 can directly provide the status information to the MCD 212. In some cases, the LCD 214 can determine the status information from monitored signals or data received from or within the PMU 208, and communicate that information to the MCD 212. In some embodiments, the LCD 214 can communicate raw collected data to MCD 212, which then algorithmically determines the status information on the basis of that raw data.

[0091] The MCD 212 can then use the status information of the PMU 208 to make control determinations accordingly. The determinations may take the form of instructions, commands, or other information that can be utilized by the LCD 214 to either maintain or adjust the operation of the PMU 208 to convert or invert voltages for the electrolyzer module 108. The MCD 212 can communicate control information to the LCD 214 for the purpose of controlling the modules 208 associated with the LCD 214. The control information can be, e.g., a modulation index and a reference signal as described herein, a modulated reference signal, or otherwise. Each LCD 214 can use (e.g., receive and process) the control information to generate switch signals that control operation of one or more components (e.g., a converter) within the associated module(s) 208. In some embodiments, MCD 212 generates the switch signals directly and outputs them to LCD 214, which relays the switch signals to the intended converter of the PMU 208.

[0092] For example, MCD 212 may receive status information and assess that information to determine a difference between the electrolyzer module 108 (e.g., a component thereof) and at least one or more other electrolyzer modules 108 (e.g., comparable components thereof) and / or a target operating parameter. For example, MCD 212 may determine that a particular electrolyzer module 108 is operating with one of the following conditions as compared to one or more other electrolyzer modules 108: with a relatively lower or higher gas flow rate, with a relatively lower or higher electrolytic capacity, with a relatively lower or higher current density, with a relatively lower or higher voltage level, with a relatively lower or higher temperature, or with or without a fault. In such examples, the MCD 212 can output control information that causes the relevant aspect (e.g., voltage level, gas flow rate, current density, power, temperature) of that electrolyzer module 108 to be reduced or increased (depending on the condition) by adjusting operation of the respective PMU 208. In this manner, the utilization of an outlier electrolyzer module 108 (e.g., operating with a relatively lower gas flow rate or higher temperature), can be reduced so as to cause the relevant parameter of that electrolyzer module 108 (e.g., gas flow rate or temperature) to converge towards that of one or more other electrolyzer modules 108.

[0093] The determination of whether to adjust the operation of a particular electrolyzer module 108 can be made by comparison of the status information to predetermined target parameters, thresholds, limits, or conditions, and not necessarily by comparison to statuses of other electrolyzer modules 108. The predetermined thresholds, limits, or conditions can be static thresholds, limits, or conditions, such as those set by the manufacturer that do not change during use. The predetermined thresholds, limits, or conditions can be dynamic thresholds, limits, or conditions, that are permitted to change, or that do change, during use. For example, MCD 212 can adjust the operation of a electrolyzer module 108 if the status information for that module 208 indicates it to be operating in violation (e.g., above or below) of a predetermined threshold or limit, or outside of a predetermined range of acceptable operating conditions.

[0094] Similarly, the MCD 212 can adjust the operation of an electrolyzer module 108 if the status information for that electrolyzer module 108 indicates the presence of an actual or potential fault (e.g., an alarm, or warning) or indicates the absence or removal of an actual or potential fault. Examples of a fault include, but are not limited to, an actual failure of a component, a potential failure of a component, a short circuit or other excessive current condition such as current density, an open circuit, an excessive voltage condition, insufficient voltage, a failure to receive a communication, the receipt of corrupted data, and the like. Depending on the type and severity of the fault, the faulty electrolyzer module’s utilization can be decreased to avoid damaging the electrolyzer module 108, or the electrolyzer module’s utilization can be ceased altogether.

[0095] Control can also be based on one or more other factors, such as in response to detected voltage levels at various stages of the power management circuit 206. Controllable aspects include, but are not limited to, one or more of voltage, current, phase, and / or output power of the PMU 208. Control of the PMU 208 to provide power for an electrolyzer module can be based on status information from an LCD of a different PMU connected to a different electrolyzer module.

[0096] The LCD 214 can receive status information (or raw data) about the electrolyzer module 108 through sensors of the electrolyzer module. The LCD 214 can also transmit information to the PMU 208 components, which can include diagnostics, measurement, protection, and control signal lines. The transmitted information can be control signals for one or more PMU components. For example, the control signals can be switch signals for the power management circuit 206 and / or one or more signals that request the status information from the electrolyzer module 108. For example, the LCD 214 can cause the status information to be transmitted over communication by requesting the status information directly, or by applying a stimulus (e.g., voltage) to cause the status information from the sensors to be generated, in some cases in combination with switch signals that place converters of the power management circuit 206 in a particular state. In some implementations, the circuit 206 is combined with the LCD 214 as an integrated circuit that controls operation of the converters 210.

[0097] In some implementations, the LCD 214 is configured to perform maximum energy tracking (e.g., tracking a maximum amount of available power) for the electrolyzer module 108 connected to the PMU 208 when the electrolyzer module 108 operates in fuel cell mode. For example, the LCD 214 determines a maximum amount of power that can be obtained from the electrolyzer module 108 operating in fuel cell mode. By doing so, the LCD 214 can identify maximum electrical output of the electrolyzer module 108 to determine if power from PMU 208 should be supplemented from an additional source, e.g., energy storage 203.

[0098] The MCD 212 and LCD 214 provide controls to switches of the converters 210 to convert, invert, regulate, voltage levels. For example, the MCD 212 and LCD 214 receive a reference voltage waveform (Vr) and status information (e.g., gas flow rate, temperature, voltage level, current density) about electrolyzer module 108 from the connected PMU 208 as inputs. The MCD 212 generates a normalized reference voltage waveform (Vrn) and modulation indexes (Mi) as outputs for the converters 210 of the PMU 208. For example, the normalized reference voltage and modulation index is provided to the LCD 214 from the MCD 212 to adjust output voltage, current, current density, etc. for the electrolyzer module.

[0099] In particular, the modulation indexes and Vm can be used to generate the switching signals for each converter 210, which controls operation of electrolyzer devices based on the output power and power characteristics from the PMU 208. The modulation index can be a number between zero and one (inclusive of zero and one). For the PMU 208 and the respective connected electrolyzer module 108, the normalized reference Vrn can be modulated or scaled by Mi, and this modulated reference signal (Vmm) can be used as Vref (or -Vref) according to the PWM technique described with respect to FIGS. 17A through 17F, or according to other techniques. In this manner, the modulation index can be used to control the PWM switching signals provided to the converter switching circuitry regulate the operation of the electrolyzer module 108. In some implementations, a series of DC pulses at varying pulse frequencies are generated by the LCD based on the PWM switching signals. By modulating pulse frequency of DC pulses, the PMU 208 configures the electrolyzer module 108 (e.g., by the LCD 214) to perform pulsed electrolysis, e.g., thereby achieving target current densities and voltages, temperature of stack, and gas output flow e.g., of hydrogen and / or oxygen. Achieving target current densities and voltage levels to the electrolyzer module 108 provides efficient operations of the electrochemical processes.

[0100] A PMU 208 being controlled to maintain normal or full operation of the electrolyzer module 108 may receive an Mi of one, while a different PMU 208 being controlled to less than normal or full operation of a different electrolyzer module may receive an Mi less than one, and a PMU 208 controlled to cease power output for an electrolyzer module may receive an Mi of zero. This operation can be performed in various ways by the MCD 212 outputting Vm and Mi to the LCD 214 for modulation and switch signal generation, by MCD 212 performing modulation and outputting the modulated Vmm to the LCD 214 for switch signal generation, or by MCD 212 performing modulation and switch signal generation and outputting the switch signals to the LCD 214 or the converters 210 of the PMU 208 for the electrolyzer module 108 directly. Vrn can be sent continually with Mi sent at regular intervals, such as once for every period of the Vrn, or one per minute, etc.

[0101] In some implementations, the MCD 212 updates the Vrn and Mi for the LCD 214 of the PMU 208 for the electrolyzer module 108 based on sensor information from the electrolyzer module 108. For example, sensors 120 in the electrolyzer module 108 capture measurements describing temperature, gas flow, pressure, current, voltage, etc. and generate status information. Based on the status information of the electrochemical system, the MCD 212 generates updated signals for Vm and Mi for the LCD 214 of the module to adjust current and voltage characteristics of power provided to the electrochemical system of the respective module. For example, the resulting current provided to an electrochemical cell connected to the module can be adjusted to maintain the configured mode for the electrochemical cell (e.g., fuel cell mode, electrolysis mode) without generating excess power, e.g., which may not correspond to an increased efficiency in the electrochemical process.

[0102] Referring to FIG. 2A, the PMU 208 can connect to an electric power source or load at terminals 209-1 and 209-2, indicated by voltage VI. An electric power source can be a single phase of a common AC bus (e.g., a single-phase AC source, an AC bus with a singlephase of a three-phase source) or to a variable DC source (e.g., a solar panel, an array of solar panels). The circuit 206 can be configured to perform AC to DC conversion (e.g., operating as a rectifier), DC to DC conversion, and / or AC to AC conversion (e.g., in combination with an AC -DC converter). For example, the PMU 208 is configured to perform AC to DC conversion by the first converter 210a converting an AC voltage VI to a DC voltage V2. In the case of a DC source, the PMU 208 is configured to perform DC to DC conversion by the first converter 210a converting a first DC voltage VI to a second DC voltage V2, in which voltage V2 is different (typically lower but can be higher) than voltage VI. In either case, the second converter 210b is configured to convert the DC voltage V2 to a regulated DC voltage V3 for the electrolyzer module 108, e.g., DC-DC conversion. In some implementations, an electrolyzer module connected to a PMU (e.g., PMU 208) can be configured to operate with an AC signal. The PMU 208 can be configured to perform AC-AC conversion through the converters of the circuit 206, e.g., an AC-AC circuit topology. In some implementations, an electrolyzer module can be configured to receive an AC output voltage from multiple PMUs, e.g., multiple phases of multi-phase power supply.

[0103] In some implementations, e.g., to perform AC -DC conversion, the circuit 206 includes a transformer, either alone or in combination with one or more power semiconductors (e.g., switches, diodes, thyristors, and the like). In some implementations, such as those where weight and cost is a significant factor, the circuit 206 is configured to perform the conversions with only power switches, power diodes, or other semiconductor devices and without a transformer. Operation of the converters 210 of the circuit 206 is further described in reference to FIGS. 2B through 2D below.

[0104] For example, converters 210 of the circuit 206 include multiple switches arranged in a configuration such as half-bridge, full-bridge, etc. The switches of the converters 210 for the circuit 206 can be any suitable switch type. Furthermore, as described in reference to FIG. 3A below, one or both of the MCD 212 or LCD 214 (e.g., control system 205) can independently control each switch, e.g., via control input lines, to control voltage levels for electrolyzer modules at a target current density.

[0105] As illustrated, each of the first converter 210a and the second converter 210b for the circuit 206 includes an isolated half-bridge, in which a first converter 210a includes the terminals 209-1 through 209-2 for the power management unit 208 and connects in series to a second converter 210b. At least one capacitor 212 is included in the circuit 206 to stabilize voltage levels (e.g., filtering noise) between converters and to provide a more accurate frequency response (e.g., compared to directly coupling two converters together), as switching signals from the LCD or MCD cause the switches in the converters to open and close. The capacitor 212 provides a variable resistance based on a switching speed to provide a target voltage between converters that can be stabilized and modulated. Furthermore, the capacitor 212 provides an additional connection point for an energy subsystem to provide charge, e.g., to power electrolyzer modules operating in electrolysis mode, or to receive charge, e.g., generated by electrolyzer modules operating in fuel cell mode.

[0106] An input voltage is provided from an electric grid configured to supply power to the electrochemical system, e.g., the electrolyzer module 108, to operate the electrochemical system in electrolysis mode, e.g., to generate hydrogen. By separating the second converter 210b from the first converted 10a, the input voltage provided from an electric grid to the first converter 210a can be converted from the output voltage, current, current density, or some combination thereof, of the second converter 210b, which is provided to the connected electrolyzer module 108.

[0107] Advantages of separating portions of the circuit, such as the first converter 210a that connects to an electric grid from the second converter 210b by the capacitor 212 provides smoothing of the output voltage from the first converter 210a. By smoothing voltage levels (e.g., reducing noise) from the first converter 210a, the conversion to a different DC voltage level by the second converter 210b can be more efficiently with reduced overall noise in the voltage level V3 for the electrolyzer module 108. In other words, separating portions of circuits can help reduce the effects of noise from one portion of the circuit to another portion of the circuit. For example, high values of DC voltage from a power supply side of the circuit 206, e.g., an electric grid connecting to terminals 209-1 and 209-2 can include substantial amounts of noise that could drastically affect current quality and density at the load-side of the circuit 206, e.g., the electrolyzer module 108.

[0108] As illustrated, control (e.g., conversion, regulation, inversion) of voltage levels can be achieved throughout the PMU 208 by the converters 210a and 210b. For example, VI is a voltage level from an electrical source (e.g., AC or DC source) representing an input voltage for the PMU 208, while voltage level V2 is the voltage output from the first converter 210a (and an input voltage to the second converter 210b) and the voltage level V3 is an output voltage of the second converter 210b provided to the electrolyzer module 108. The voltage level V3 provided to an electrolyzer module 108 can be low, e.g., 48V, relative to the voltage of an electrical grid. In cases where the electrolyzer module 108 is part of a stack of electrolyzer modules, the voltage level provided to an electrolyzer module 108 is a portion of the voltage for the electrolyzer stack e.g., 600 V through 1.5 kV. By applying a target voltage level V3 to the electrolyzer module 108, the PMU 208 that is connected to the electrolyzer module can cause the electrolyzer cells of the module to generate target current density (e.g., 400 mA / cm2) to perform electrolysis. The applied target voltage causes the electrolyzer cells of the electrolyzer module 108 to generate a current for a cross-sectional area of the electrolyzer cells that corresponds to the target current density.

[0109] In addition to reducing noise, the voltage from the first converter 210a to the second converter 210b can be provided output by connecting the two converters with a capacitor 212 in parallel. For example, the portion of the circuit 206 that includes the first converter 210a can have a first voltage level VI obtained by connecting to a source (e.g., an electric grid) at terminals 209-1 and 209-2. In electrolysis mode, the output of electrical power provided a particular voltage level V3 (e.g., by converting voltage level VI to voltage level V2 by first converter 210a and regulating voltage level V2 to voltage level V3. The voltage level V3 at a particular current, current density, or some combination thereof, is provided to the electrolyzer module 108. In fuel cell mode, the electrolyzer module 108 generates an input voltage level V3 to the PMU 208 that can be converted (e.g., DC-DC, DC-AC) or regulated to voltage level V2 by the second converter 210b, then converted (e.g., DC-DC, DC-AC) as an output voltage level VI to a load, e.g., an electric grid, a solar panel. In some implementations, the converters 210a and 210b can operate in DC-AC mode.

[0110] In further detail, the output voltage V2 from the first converter 210a can be provided as an input to the switching circuity of the second converter 210b, e.g., at voltage nodes located where the capacitor 212 connects to the remainder of the circuit. Therefore, the voltage provided from the first converter 210a to the second converter 210b can be adjusted, e.g., shifted or inverted, by adjusting output voltage of the energy subsystem 202 connected in parallel. Additional power provided by the energy subsystem 202 can allow the input voltage at the second converter 210b to be a greater voltage level than the output voltage provided from the first converter 210a. The two portions of circuits under the control of switching signals from the control system 205, e.g., MCD 212 and LCD 214, the PMU can provide a voltage to a load from the second converter 210b that is at a target current, current density, and voltage for operating the electrolyzer module in a target configuration.

[0111] The energy subsystem 202 includes energy storage 203 to supply power to electrolyzer module 108 when electrolyzer module 108 is in electrolysis mode, or store electrical power from electrolyzer module 108 when electrolyzer module 108 is in fuel-cell mode, e.g., for later use. In some implementations, the energy subsystem 202 is configured to store, charge, or discharge power through a complementary energy storage 203 in support of electrolyzer module 208 operations, e.g., electrolysis and reverse-electrolysis. The electrolyzer module 108 operates as a primary load or energy source based on the configuration of the electrolyzer module 108, e.g., target parameters.

[0112] The management system 204 that can perform local control functions and the energy storage device 203 configured to store, charge, and discharge electrical power. The LCD 214 of the control system 205 can provide high-level control signals (e.g., target voltage, current, current density) to the management system 204, which converts the high- level control signal to low-level control instructions. As an example, the energy storage 203 can be a battery with the management system 204 being configured as a battery management system (BMS) that controls discharging and charging of the battery. The energy subsystem 202 can store and discharge additional power to facilitate efficient operation of the electrolyzer module 108 or stack connected to the PMU 208. For example, the electrolyzer module 108 operating in electrolysis mode can be provided additional power from the energy subsystem 202 to perform electrolysis at target voltage levels, current, and / or current densities. Furthermore, excess power from a connected voltage source at terminals 209-1 and 209-2 can be stored in the energy subsystem 202. When the electrolyzer module 108 is operating in fuel cell mode, the energy subsystem 202 can store some or all of the power generated from the electrolyzer module 108 performing reverse-electrolysis. In some implementations, the electrolyzer module 108 operating in fuel cell mode can generate electrical power that is supplemented by energy stored in the energy subsystem 202, e.g., to provide power to a load coupled to the electrolyzer system. In some implementations, the PMU 208 is configured to operate without the energy subsystem 202, energy storage 203, and management system 204.

[0113] As illustrated, the LCD 214 of the control system 205 is configured to communicate and control the energy subsystem 202 by providing controls and / or instructions to adjust operation of the energy storage 203. For example, controls can include low-level commands to charge or discharge the energy storage 203. In some implementations, the management system 204 may be optionally included and the local control device 214 of the power management unit 208 directly executes controls for the energy storage 203, e.g., providing responsive control to the energy subsystem 202 to charge / discharge. As illustrated, the energy subsystem 202 includes a single energy storage 203, although any number of energy storage devices may be utilized and connected, e.g., in series, in parallel, to the PMU 208.

[0114] FIG. 2B is a schematic diagram depicting an example embodiment of converters 210a and 210b configured as a DC-AC converter that can receive a DC voltage (corresponding to voltage VI in FIG. 2 A) at ports IO1 and IO2 (corresponding to terminals 209-1 and 209-2 in FIG. 2) and switch to generate pulses at ports IO3 and IO4. The converters 210a and 210b of FIG. 2A are depicted as converter 250A. The converter 250A can include multiple switches, and here converter 250A includes four switches S3, S4, S5, S6 arranged in a full bridge configuration. Control system 205 or LCD 214 can independently control each switch via control input lines 218-1 through 218-3 to each gate. In this embodiment, a DC line voltage VDCL can be applied to converter 250A between ports 101 and 102. By connecting VDCL to ports 103 and 104 by different combinations of switches S3, S4, S5, S6, converter 250A can generate three different voltage outputs at ports 103 and 104: +VDCL, 0, and -VDCL. A switch signal provided to each switch controls whether the switch is on (closed) or off (open). To obtain +VDCL, switches S3 and S6 are turned on while S4 and S5 are turned off, whereas -VDCL can be obtained by turning on switches S4 and S5 and turning off S3 and S6. The output voltage can be set to zero (including near zero) or a reference voltage by turning on S3 and S5 with S4 and S6 off, or by turning on S4 and S6 with S3 and S5 off. These voltages can be output from the PMU 208 over a power connection to the electrolyzer module 108. Ports 103 and 104 of converter 250A can be connected to (or form) module 10 ports 1 and 2 of the power connection, so as to generate the output voltage for use with output voltages from other PMUs 208 connected to other electrolyzer modules 108.

[0115] The control or switch signals for the embodiments of converter 250A described herein can be generated in different ways depending on the control technique utilized by MCD 212 to generate the output voltage of converter 250A. In some embodiments, the control technique is a PWM technique such as space vector pulse-width modulation (SVPWM) or sinusoidal pulse-width modulation (SPWM), or variations thereof, performed by the converters applying switching signals from determined the control system 205, e.g., described in reference to FIG. 2A above.

[0116] FIGS. 2C and 2D are schematic views depicting example embodiments of converters 250B and 250C, respectively. Converter 250B includes switch circuitry portions 251 and 252A. Portion 251 includes switches S3 through S6 configured as a full bridge in similar manner to converter 250A, and is configured to selectively couple 101 and 102 to either of 103 and 104, thereby changing the output voltages of the PMU 208. Portion 252 A includes switches SI and S2 configured as a half bridge and coupled between ports 101 and 102. A coupling inductor LC is connected between port 105 and a nodel present between switches SI and S2 such that switch portion 602A is a bidirectional converter that can regulate (boost or buck) voltage (or inversely current). Switch portion 252A can generate two different voltages at nodel, which are +VDCL2 and 0, referenced to port 102, which can be at virtual zero potential. The current drawn from an energy source connected to the PMU 208 to the electrolyzer module 108 can be controlled by regulating the voltage on coupling inductor LC, using, for example, a pulse-width modulation technique or a hysteresis control method for commutating switches SI and S2. Other techniques can also be used.

[0117] Converter 250C differs from that of 250B as switch portion 252B includes switches

[0118] 51 and S2 configured as a half bridge and coupled between ports 105 and 102. A coupling inductor LC is connected between port 101 and a nodel present between switches SI and

[0119] 52 such that switch portion 252B is configured to regulate voltage.

[0120] The control system 205 or the LCD 214 can independently control each switch of the converters 250B and 250C via control input lines 218-1 through 218-3 to each gate. In these embodiments and that of FIG. 2B, the LCD 214 (not the MCD 212) generates the switching signals for the converter switches. Alternatively, the MCD 212 can generate the switching signals, which can be communicated directly to the switches, or relayed by the LCD 214. Although illustrated as a single PMU 208 in FIG. 2A, a number of PMUs 208-1 through 208-N can be connected as a cascaded, module-based system connected to an electrochemical system with a number of electrolyzer modules 108. For example, the MCD 212 can control multiple PMUs within a system to achieve or converge towards a desired target gas flow rate, voltage level, current density, etc. for the electrolyzer modules. The target can be, for example, operation of all electrolyzer modules at the same or similar levels with respect to each other, or within predetermined thresholds limits, or conditions. This process is also referred to as balancing or seeking to achieve balance in the operation or operating characteristics of electrolyzer modules. The term “balance” as used herein does not require absolute equality between electrolyzer modules or components thereof, but rather is used in a broad sense to convey that operation of the system can be used to actively reduce disparities in operation (or operative state) between the electrolyzer modules that would otherwise exist.

[0121] Referring to FIG. 2A, the control system 205 can be configured as a single device for the entire system 200 or can be distributed across or implemented as multiple devices, e.g., MCD 212 and LCD 214. In some embodiments, control system 205 can be distributed between different LCDs 114 associated with multiple PMUs 208, such that no MCD 212 is necessary and can be omitted from system 200. Control system 205 can be configured to execute control using software (instructions stored in memory that are executable by processing circuitry), hardware, or a combination thereof. The one or more devices of control system 205 can each include processing circuitry 211 and memory 213 as shown here. The status information of a PMU 208 in system 200 can be communicated to control system 205, which can independently control every PMU 208-1 . . ,208-N. Other variations are possible. For example, a particular PMU 208 (or subset of PMUs 208) can be controlled based on status information of that particular module 208 (or subset), based on status information of a different PMU 208 that is not that particular PMU 208 (or subset), based on status information of all PMUs 208 other than that particular PMU 208 (or subset), based on status information of that particular PMU 208 (or subset) and status information of at least one other PMU 208 that is not that particular PMU 208 (or subset), or based on status information of all PMUs 208 in system 300.

[0122] All or a portion of control system 205 can be combined with a system external device 207 that monitors one or more other aspects of a stationary application, e.g., an electrolyzer stack. When integrated in this shared or common control device (or subsystem), control of system 200 can be implemented in any desired fashion, such as one or more software applications executed by processing circuitry of the shared device, with hardware of the shared device, or a combination thereof. For electrolyzer systems, examples of external devices 207 can include an electrolyzer monitoring system configured to provide sensor readings, e.g., temperature, pressure, voltage level, of the electrolyzer modules and / or electrolyzer modules in an electrolyzer stack. In some implementations, the electrolyzer monitoring system is configured to capture sensor measurements across multiple electrolyzer modules. The sensor measurement readings can be provided to the control system 205, e.g., to at least one or both of the LCD of a power management unit or the MCD for the electrolyzer system.

[0123] FIGS. 2E and 2F are block diagrams depicting example embodiments of a shared or common control device (or system) 232 in which control system 205 can be implemented. In FIG. 2E, common control device 232 includes master control device 212 and external control device 207. Master control device 212 includes an interface 241 for communication with LCDs 214 over path 215, as well as an interface 242 for communication with external control device 207 over internal communication bus 236. External control device 207 includes an interface 243 for communication with master control device 212 over bus 236, and an interface 244 for communication with other entities (e.g., components of an electrolyzer management system , an electric grid, a photovoltaic system) of the overall application over communication path 236. In some embodiments, common control device 232 can be integrated as a common housing or package with devices 212 and 207 implemented as discrete integrated circuit (IC) chips or packages contained therein.

[0124] In FIG. 2F, external control device 207 acts as common control device 232, with the master control functionality implemented as a component within device 207. This component 212 can be or include software or other program instructions stored and / or hardcoded within memory of device 207 and executed by processing circuitry thereof. The component can also contain dedicated hardware. The component can be a self-contained module or core, with one or more internal hardware and / or software interfaces (e.g., application program interface (API)) for communication with the operating software of external control device 207. External control device 207 can manage communication with LCDs 214 over interface 241 and other devices over interface 244. In various embodiments, device 207 / 232 can be integrated as a single IC chip, can be integrated into multiple IC chips in a single package, or integrated as multiple semiconductor packages within a common housing.

[0125] In the embodiments of FIGS. 2E and 2F, the master control functionality of system 200 is shared in common device 232, however, other divisions of shared control or permitted. For example, part of the master control functionality can be distributed between common device 232 and a dedicated MCD 212. In another example, both the master control functionality and at least part of the local control functionality can be implemented in common device 232 (e.g., with remaining local control functionality implemented in LCDs 214). In some embodiments, all of control system 200 is implemented in common device (or subsystem) 232. In some embodiments, local control functionality is implemented within a device shared with another component of each power management unit 208, such as energy subsystem 202, which includes energy storage 203 (e.g., a battery) and management system 204 (e.g., a battery management system).

[0126] FIG. 3A is a schematic diagram of an example grid connected system 300 that depicts an electrical system 302 connected to a cascaded, power management system 304. The power management system 304 includes an array of multiple PMUs 208 connected in series. In some implementations, the power management system also includes the MCD 212 to provide control signals for the PMUs 208, e.g., described in reference to FIG. 2A above. Each of the PMUs 208 is coupled to a respective electrolyzer module 108 of a cascaded module-based electrolyzer system 308. The electrolyzer modules 108-1 to 108-N may be arranged in a stack and connected in series. The grid connected system 300 includes the MCD 212 configured to control the LCDs of the respective PMUs 208-1 through 208- N.

[0127] The PMUs 208 of the power management system 304 are examples of the PMU described in reference to FIG. 2A above. Each PMU from the PMUs 208 include an LCD 214 coupled to the MCD 212 of for the power management system 304. The LCD 214 of the PMU 208 for a connected electrolyzer module collects status information of the electrolyzer module and provides the status information to the MCD 112. The MCD 212 is configured to receive status information of the electrolyzer modules 108-1 through 108-N, from one or more sensors, as explained herein. The MCD 212 determines the control information for each of the PMUs 208 based on conditions of their respective electrolyzer modules. As an example, the MCD 212 can determine the appropriate control signals so that each PMU causes the electrolyzer module to which the PMU is coupled to maintain a defined current. Due to electrochemical cell conditions in each electrolyzer module, the control signals (e.g., switching signals for converters of a PMU) can vary from one electrolyzer module to another electrolyzer module in the stack.

[0128] As depicted in FIG. 3 A, a terminal of a last PMU 208-N of the power management system 304 is connected to ground. In some implementations, a terminal of the last PMU 208-N of the power management system 304 can be connected to a bus of another AC- power electrical system, e.g., an AC bus described in reference to FIG. 3B below.

[0129] The electrical system 302 can be a single phase AC electrical system, a three-phase AC electrical system, or any type of multi-phase electrical system. In some implementations, the electrical system 302 is a DC electrical system and optionally, the last PMU 208-N of the power management 304 can be connected to a DC bus of another DC- power electrical system.

[0130] The system 300 also includes a coupling module 306 that couples the electrical system 302 to the power management system 301. The coupling module 306 may include filters such as an inductor 306a depicted in FIG. 3A, to filter noise associated with high frequency portions of AC signals from the electrical system 302. The coupling module 306 may further include sensor circuitry to capture measurements (e.g., current, voltage, and frequency) at connected nodes of the electrical system 302 and the power management system 301. The coupling module 306 can provide the sensor measurements from an output of the electrical system 302 to the MCD 212. The MCD 212 can be configured to generate the control information for the power management system 301 based on the sensor measurements of the electrical system 302, in addition to the status information of the electrolyzer modules 108-1 to 108-N from the electrolyzer system 308.

[0131] The implementation illustrated by the system 300 is an example of the power management system 301 adjusting voltage levels of the electrolyzer system 308, thereby configuring operational modes of the electrolyzer modules 108. Voltage levels for each of the electrolyzer modules 108 can be independently controlled by the respective PMU 208 to which the electrolyzer module 108 is connected. Each module can perform electrolysis by receiving converted power from the electrical system 302 through the respective PMU of the power management system 304. Alternatively, each electrolyzer module can operate in fuel cell mode to provide power to the electrical system of the grid connected system 300 by performing reverse electrolysis.

[0132] By connecting each electrolyzer module in the electrolyzer stack 108 to a respective PMU, the power management system 304 provides individual control to each of the electrolyzer modules in the electrolyzer system 308. In contrast to applying a target voltage to the electrolyzer system 308 as a whole to meet target gas flow rates and operational modes, the independent control of each electrolyzer module can account for variability among the electrolyzer modules 108-1 through 108-N of the electrolyzer system 308. For instance, the independent control of each electrolyzer module can account for variations in electrolyzer module conditions such as, e.g., module temperature, module gas flow rates, or module current sensitivity, among other conditions. In addition, independent control of electrolyzer modules can, in some implementations, result in improved efficiency of operation. For instance, in some cases, the PMUs allow each electrolyzer module to be supplied with a respective target voltage for that particular module, and thus avoid the application of a voltage that unnecessarily exceeds or falls below a module threshold voltage.

[0133] FIG. 3B is a schematic diagram of an example electrolyzer system 350. The electrolyzer system 350 includes a multi-phase power supply 352 coupled to a cascaded, power management system 351. The power management system 351 includes multiple arrays of PMUs 208. In the present example, the multi-phase power supply 352 is a three- phase power supply, although other multi-phase power supplies can be used instead. The multiple PMUs 208 are arranged in three arrays (300-PA, 300-PB, and 300-PC), with each array coupled to a different phase of the power supply 352. Each PMU 208 within an array 300 is coupled to a respective electrolyzer module 108. For example, each PMU 208a-l to 208a-N within array 300-PA is coupled to an electrolyzer module 108a-l to 108a-N, respectively. Each PMU 208b-l to 208b-N within array 300-PB is coupled to an electrolyzer module 108b-l to 108b-N, respectively. Each PMU 108c-l to 108c-N within array 300-PC is coupled to an electrolyzer module 108c-l to 108c-N, respectively. In this arrangement, the connected electrolyzer modules 108 of the PMUs are electrically isolated from each other. Thus, non-isolated converter circuit topologies, such as those described in FIG. 2A, may be desired.

[0134] Each power management unit 208 of the multiple PMUs 208 depicted in FIG. 3B has the same structure as shown in the example PMU 208 depicted in FIG. 2A above. The LCDs 214 of each PMU 208 are communicatively coupled to MCD 212. Each PMU is configured to convert AC power supplied by a respective phase of the grid 358 into regulated DC power, which can then be further provided to the load of the PMU, e.g., one or more electrolyzer modules. The respective PMU 208 for a connected electrolyzer module can also invert DC power from the connected electrolyzer module operating in fuelcell mode into supplying AC power for the grid 358. In some implementations, the respective PMU 208 for an electrolyzer module also inverts DC power stored in an energy storage device coupled to the PMU to supply power for the grid 358 or the connected electrolyzer module. Each power management unit can be configured by the MCD 212 to have a voltage rating and / or current rating at the input for the respective electrolyzer module that is based on a voltage rating and / or current rating of the electrolyzer modules 108.

[0135] The MCD 212 provides coordinated control activity through switching signals for the power management unit, e.g., to achieve a target current, current density, and / or voltage level for the respective electrolyzer module of the power management unit. Furthermore, the MCD 212 determines control activity that provides corresponding voltage and current densities to operate respective electrolyzer modules of the power management units 208. Although each power management unit in FIG. 3B is illustrated as being coupled to a single electrolyzer module, multiple electrolyzer modules can be connected to the power management unit, e.g., described in reference to FIGS. 4 and 5 below.

[0136] The MCD 212 can provide control signals to the PMUs that cause the PMUs to generate a current and output voltage (e.g., any appropriate voltage for input to an electrolyzer module and / or stack) for input to the terminals of the electrolyzer module 108. The connected electrolyzer module and / or stack of the PMU provides the applied voltage to the electrolyzer cells of the electrolyzer module to maintain the electrolyzer cells at a voltage threshold, e.g., ~1.6 volts in electrolysis mode. For example, an electrolyzer module can include 50 electrolyzer cells, each electrolyzer cell can be configured to receive a respective portion (e.g., 1.8 Volts) of the applied voltage (e.g., 1.8 Volts per cell, multiplied by 50 cells, for a total voltage of 90 Volts) to operate the electrolyzer cells in electrolysis mode. The electrolyzer cells can be configured to operate in fuel cell mode by adjusting a voltage level of the electrolyzer module, thereby operating the electrolyzer cells at the voltage threshold for fuel cell mode (e.g., below 1.6 Volts).

[0137] The MCD 212 can also provide signals to adjust voltage output from the electrolyzer module operating in fuel-cell mode, to provide electrical power to the grid 358. For example, the MCD 212 generates control signals causing the PMUs to generate a current below the threshold voltage for input to the terminals of electrolyzer module to operate in fuel cell mode. While the control signals generated by the MCD 212 may cause the PMU 208 to produce a voltage level that is below a threshold value to operate an electrolyzer module in fuel cell mode, the voltage level and current density is sufficient to improve electricity yielded in reverse-electrolysis, compared to voltage levels that are further from the voltage threshold. For example, a voltage level that is well below the threshold voltage for fuel cell mode can result in relatively low amounts of electricity generated from reverse-electrolysis, e.g., compared to operating at a voltage level that is below but closer to the threshold voltage.

[0138] In some implementations, the arrays 300 connect to the power management units 208 through a coupling module 356. For instance, each array 300 can be connected to a respective inductor 356a through 356c that in turn is connected to a different phase of the power supply 352 and provides high-frequency filtering for the respective phase. As shown in the example of FIG. 3B, a first inductor 356a is connected at a first end to a first terminal of power management unit 208a- 1 and at a second end to a first phase of the power supply 352 at node 1. The second inductor 356b is connected at a first end to a first terminal of power management unit 208b- 1 and at a second end to a second phase of the power supply 352 at node 2. The third inductor 356c is connected at a first end to a first terminal of power management unit 208c- 1 and at a second end to a third phase of the power supply 352 at node 3. In some implementations, the coupling module 356 also includes measurement and sensing circuits to capture parameters related to the grid 358, such as current, voltage, and frequency, at the connected nodes of the grid with input and output terminals to connect the electrolyzer modules 108 to the electric grid 358. The control system 205 can utilize measurements captured by the coupling module 356 to control operation of the PMUs 208, to optimize operation of the electrolyzer modules 108. For example, the measurements of the grid 358 can indicate a resulting change (e.g., an increase or decrease) of voltage levels from the power supply 358. The control system 205 can configure the converters of the PMUs 208 to maintain operability of the electrolyzer modules 108 at a particular voltage level. In some implementations, the coupling module 356 includes contactors and fuse breakers to disconnect the PMUs 208 from the grid 358. Each of the last PMUs in a respective array includes a pair of terminals (e.g., terminals 209-1 and 209-2, referring to FIG. 2A) and can be connected to each other by a respective second terminal from each of the last PMUs in the array, e.g., terminal 209-2.

[0139] The electrolyzer modules within each array can be connected in series (e.g., as a stack depicted in FIG. 3A). For instance, the electrolyzer modules 108a-l through 108a-N can be connected in series to form a first electrolyzer stack, the electrolyzer modules 108b- 1 through 108b-N can be connected in series to form a second electrolyzer stack, and the electrolyzer modules 108c-l through 108c-N can be connected in series to form a third electrolyzer stack. Alternatively, in some implementations, the electrolyzer modules from each of the different arrays can be combined together into a single stack. For example, electrolyzer modules 108a-l through 108a-N, 108b-l through 108b-N, and 108c-l through 108c-N can be connected in series to form a single electrolyzer stack. When connected in a stack, electrolyzer modules 108 can be controlled by their respective PMUs to operate in a same mode, e.g., such that all the electrolyzer modules in a stack operate in electrolysis mode or in fuel cell mode. In some implementations, one or more of the electrolyzer modules operate in a different mode from one or more other electrolyzer modules. For example, in some cases, one or more electrolyzer modules operate in a fuel cell mode, whereas one or more other electrolyzer modules operate in electrolysis mode, and vice versa. Through the LCDs 214 and MCD 212, the power management system 351 provides precise, responsive, and independent control to each of the electrolyzer modules 108.

[0140] Voltage applied to each electrolyzer module 108 can be independently controlled by a respective PMU 208 to which the electrolyzer module 108 is connected. For example, each PMU 208 converts a first voltage from the supply 352 to provide a second voltage to the respective electrolyzer module 108 to which the PMU 208 is connected, so that the electrolyzer module 108 operates in an electrolysis mode. Alternatively, each PMU can convert a first voltage from the supply 352 to provide a second voltage to the respective electrolyzer module 108 to which the PMU 208 is connected so that the electrolyzer module 108 operates in a fuel cell mode. As illustrated, the supply 352 is configured to provide three-phase power and optionally includes a grid transformer 354. For example, the electrical system 352 can be configured to provide three-phase power at medium voltage levels, for example, 2.4 kV, 4.16 kV, 12.4 kV, and 13.8 kV. As another example, the source 352 can be configured to provide three-phase power at higher voltage levels, for example, 22.9 kV, or 35 kV through 65 kV. In some implementations, the transformer 354 is configured to step down the input voltage from the supply 352 to provide low voltage levels, for example, 208V, 380V, 480V. Examples of the supply 352 include a power plant, wind turbine, wind farm, generators, and other types of electrical equipment configured to provide AC power.

[0141] The transformer 354 can be configured as a wye-connected transformer, delta- connected transformer, or delta-wye transformer, to the source 352. The transformer 354 can include multiple transformers, such as the case when connecting a single transformer for each phase provided by the source 352.

[0142] In some implementations, the output voltage from a PMU 208 is regulated using pulse-width modulation control. One or more sensors, e.g., sensors 120 of FIG. IB, can be included in one or more of the electrolyzer modules 108. The sensors can include, e.g., temperature sensors, current sensors, voltage sensors, gas flow rate sensors, among other types of sensors to measure one or more conditions of the electrolyzer cells within the electrolyzer modules. Based on the measurements from the one or more sensors, the control system (e.g., LCD 214 and / or MCD 212) for the PMUs 208 can determine a change in pulse-width modulated duty cycle to achieve a target average current density and / or target average voltage for operating one or more electrolyzer modules 108. In some implementations, the control system 205 can modify the pulse-width modulated duty cycle in instances where the voltage applied to the electrolyzer module 108 is departing from a target voltage. For example, the control system 205 may modify the pulse-width modulated duty cycle to increase or decrease the average voltage applied to an electrolyzer module 108.

[0143] In a particular example, the control system 205 can modify the pulse-width modulated duty cycle to compensate for variations in electrolyzer module performance caused by a change in operating temperature of the electrolyzer module 108. Operating temperatures for electrolyzer modules can impact reaction rates for performing electrolysis or reverse-electrolysis within the electrolyzer cells. The control system 205 (e.g., MCD 212 and / or LCDs 214) together with the PMUs can set upper and lower limit temperatures and perform temperature balancing across the electrolyzer modules 108, while maintaining target current, current density, voltage level, or some combination thereof. Temperature balancing may be desired to prevent damage to electrolyzer cells of electrolyzer modules, by sharing electrical loads or power supply across different PMUs.

[0144] For example, an electrolyzer module 108 can include one or more sensors (e.g., sensors 120 depicted and described in reference to FIG. IB) to measure a temperature of the electrolyzer module 108. The temperature data recorded by the one or more sensors can be provided to the MCD 212, the LCD 214 or both the MCD 212 and the LCD 214 , Based on the temperature data, the MCD 212 or the LCD 214 determines a pulse-width modulated duty cycle of the current or voltage to be applied to the electrolyzer module 108 to compensate for variations in the module temperature from a target temperature. The target temperature can include, e.g., a temperature at which the chemical reactions of the electrolyzer module occur at a target efficiency. For example, by increasing the voltage / current duty cycle, it may be possible to increase the temperature of the module. Alternatively, by decreasing the voltage / current duty cycle, it may be possible to decrease the temperature of the module. This is because of the correlation between dissipated heat associate with current, which is dependent on voltage. Thus, increasing current can result in an increase of dissipated heat in the electrolyzer cells of the electrolyzer module 108, thereby increasing the temperature of the electrolyzer module. Similarly, a decrease in current results in a decrease of dissipated heat in the electrolyzer cells of the electrolyzer module 108, thereby decreasing the temperature of the electrolyzer module.

[0145] In particular, the MCD 212 and / or LCD 214 can generate control signals that cause the PMU 208 to alter the pulse-width modulated duty cycle of the voltage / current applied to the electrolyzer module to which the PMU 208 is coupled

[0146] In some implementations, the control system performs gas flow rate (GFR) balancing to maintain or adjust voltage levels applied to the electrolyzers modules 108, thereby maintaining operational modes for some or all of the electrolyzer modules 108. For example, the MCD 212, the LCD 214, or the MCD 212 and LCD 214 can process GFR measurements from one or more sensors of an electrolyzer module 108 and determine a target GFR for the electrolyzer module 1208. In some cases, the MCD 212, the LCD 214, or the MCD 212 and LCD 214 cause one or more PMUs 208 to adjust the voltage levels of one or more electrolyzer modules 108, respectively, to accommodate a change in voltage levels in one or more other electrolyzer modules. For example, the MCD 212 can generate control signals that cause one or more PMUs 208 to increase voltage levels applied to electrolyzer modules with low GFR (e.g., relative to one or more other electrolyzer modules). The increased voltage can result in an increase in GFR for the subset of electrolyzer modules.

[0147] In some implementations, the output voltage from the power management unit is down-regulated using pulse-width modulation control. Sensors, e.g., sensors 120 of FIG. IB, can be included in some or all of the electrolyzer modules 108 to capture measurements for current at the electrolyzer module 108. By measuring current at the electrolyzer module 108, the control system (e.g., LCD 214 and / or MCD 212) for the power management units 208-1 through 208-N can determine a change in pulse-width modulated duty cycle to achieve a target current density for operating the electrolyzer module for the power management unit. For example, duty cycle can be reduced in instances where excess current and / or excess current density is being provided to the electrolyzer module based on the chemical conditions, temperature, gas flow rate, etc. of the electrolyzer cells, e.g., electrolyzer cells 110. The duty cycle can be increased in instances where insufficient current and / or current density is being provided to the electrolyzer module.

[0148] In some implementations, the power management units 208 operate in a reverse direction to convert DC power from the respective electrolyzer module of the power management unit to DC or AC power on a common bus, e.g., when operating an electrochemical system of electrolyzer modules in fuel cell mode.

[0149] In some implementations, the power management system 351 can be configured such that arrays 300 are interconnected at electrical nodes between PMUs 208 within each array. FIG. 3C is a block diagram depicting power management system 351 with three arrays 300-PA, 300-PB, and 300-PC coupled together in a combined series and delta arrangement. Each array 300 includes a first series connection of M PMUs 208, where M is two or greater, coupled with a second series connection of N PMUs 208, where N is two or greater. The delta configuration is formed by the interconnections between arrays, which can be placed in any desired location. In this implementation, the terminal 209-2 of PMU

[0150] 208-(M+N) of array 300-PC is coupled with terminal 209-2 of PMU 208-M and terminal

[0151] 209-1 of PMU 208-(M+l) of array 300-PA, terminal 209-2 of PMU 208-(M+N) of array 300-PB is coupled with terminal 209-2 of PMU 208-M and terminal 209-1 of PMU 208- (M+l) of array 300-PC, and terminal 209-2 of PMU 208-(M+N) of array 300-PA is coupled with terminal 209-2 of PMU 208-M and terminal 209-1 of PMU 208-(M+l) of array 300- PB.

[0152] FIG. 3D is a block diagram depicting power management system 351 with three arrays 300-PA, 300-PB, and 300-PC coupled together in a combined series and delta arrangement. This implementation is similar to that of FIG. 3C except with different cross connections. In this implementation, terminal 209-2 of PMU 208-M of array 300-PC is coupled with terminal 209-1 of PMU 208-1 of array 300-PA, terminal 209-2 of PMU 208- M of array 300-PB is coupled with terminal 209-1 of PMU 208-1 of array 300-PC, and terminal 209-2 of PMU 208-M of array 300-PA is coupled with terminal 209-1 of PMU 208-1 of array 300-PB. The arrangements of FIGS. 3C and 3D can be implemented with as little as two modules in each array 300. Combined delta and series configurations permit an effective exchange of energy between all PMUs 208 of the power management system 351 (interphase balancing) and phases of a power supply, and also allows reducing the total number of PMUs 208 in an array 300 to obtain the desired output voltages to apply to the connected electrolyzer modules of the PMUs 208.

[0153] Although it is advantageous for the number of PMUs 208 to be the same in each array 300 within power management system 351, such is not required and different arrays 300 can have differing numbers of modules 108. Further, each array 300 can have modules 108 that are all of the same configuration (e.g., all PMU are 208 A, all PMUs are 208B, all PMUs are 208C, or others) or different configurations (e.g., one or more PMUs are 208A, one or more are 208B, and one or more are 208C, or otherwise).

[0154] FIG. 4 is a schematic diagram depicting an example system 400 having more than one electrolyzer module, e.g., electrolyzer module 108-1 (also referred to as “a first electrolyzer module 108-1”) and 108-2 (also referred to as “a second electrolyzer module 108-2” from the pair), coupled to a single PMU 408. The PMU 408 can be configured to utilize the pair of electrolyzer modules 108-1 and 108-2 (collectively “electrolyzer modules 108”) as an energy source during fuel cell mode. Alternatively, the electrolyzer modules 108 can be configured as a load of the PMU 408 during electrolysis mode. In some implementations, both of the electrolyzer modules 108-1 and 108-2 can be coupled together in a back-to-back configuration as described in reference to FIG. IE above. Similar to the PMU 208 of FIG. 2A, the PMU 408 of FIG. 4 includes terminals 409-1 and 409-2 (collectively “terminals 409”) to connect to an electrical system, such as a multi-phase power supply. The PMU 408 also includes an energy subsystem 202 that connects to a power management circuit 406 ("circuit 406”). The circuit 406 controls converters ("collectively converters 410”) to convert or invert voltage levels of components in the PMU 408 between the terminals 409 and the electrolyzer modules 108.

[0155] FIG. 4 depicts the control system 205, e.g., the MCD 212 and the LCD 212, which provides control information to the circuit 406 to control voltage levels, such as voltage level VI at the terminals 409-1 to voltage levels V3 and V4 for the electrolyzers 108. In particular, the circuit 406 includes a first converter 410a that converts voltage level VI at the terminals 409 to voltage level V2 or vice-versa, e.g., AC -DC conversion (in electrolysis mode) or DC-AC conversion (in fuel cell mode). The circuit 406 also includes a capacitor 412 to filter noise resulting from the conversion of voltage level VI to voltage level V2.

[0156] The first converter 410a is connected in series to a second converter 410b, which can be configured to convert a voltage level V2 to a voltage level V3 that is applied to the first electrolyzer module 108-1. A third converter 410c can be configured to convert a voltage level V2 to a voltage level V4 that is applied to the second electrolyzer module 108-2.

[0157] The first converter 410a of the circuit 406 is configured to convert a voltage from a voltage level VI to a voltage level V2, from a connection of terminals 409 to an electrical system, e.g., an AC source. The first converter 410a is connected to the second converter 410b to configure a voltage level V3 for input to the first electrolyzer module 108-1. The first converter 410a is connected to the third converter 410c to configure a voltage level V4 for input to the second electrolyzer module 108-2. In electrolysis mode (e.g., for either of the first electrolyzer module 108-1 or the second electrolyzer module 108-2), the voltage level V3 or V4 for the respective electrolyzer module is an input for electrolysis. The voltage levels V3 or V4 in electrolysis mode can be efficiently maintained at a voltage level for the electrolyzer module that allows the electrolyzer cells of the electrolyzer module to be maintained at a thermoneutral voltage level (e.g., 1.6 V). Any converter from the converters 410 can be configured to output a target voltage level for input in electrolysis mode. In fuel cell mode, the voltage levels V3 or V4 for the respective electrolyzer module are output from the electrolyzer module, to be converted to voltage levels V2 (e.g., by converters 410b and / or 410c) and voltage level VI (e.g., by converter 410a) for output to an electrical system. The voltage levels can be attained by providing switching signals from the control system 105, by the MCD 212, the LCD 214 of the PMU 408, or both the MCD 212 and the LCD 214 of the PMU 408.

[0158] The MCD 212, the LCD 214, or both MCD 212 and LCD 214, can receive status information of the electrolyzer modules 108-1 and 108-2 (e.g., by wireless or wired communication by sensors 120 described in FIG. IB). The MCD 212 can generate and transmit (e.g., directly to the circuit 406 or through the LCD 214) control information for the converters 410 of the PMU 408. The control information allows for the PMU 408 to achieve a target current and / or target voltage levels throughout the circuit 406 of the PMU 408 (e.g., VI, V2, V3, and V4) and applied to the electrolyzer modules 108-1 and 108-2.

[0159] In contrast to the implementation described in reference to FIG. 2A above, the PMU 408 is coupled to an additional electrolyzer module, e.g., second electrolyzer module 108- 2. In some implementations, the first electrolyzer module 108-1 and the second electrolyzer module 108-2 are configured to operate in different modes. For example, the first electrolyzer module 108-1 can be configured to operate in fuel cell mode, e.g., performing reverse-electrolysis, while the second electrolyzer module 108-2 is configured to operate in electrolysis mode, e.g., performing electrolysis. In some cases, some types of electrolyzer modules (e.g., alkaline electrolyzers) are unidirectional and thus limited to one type of electrochemical process, e.g., electrolysis or reverse-electrolysis. The implementation depicted in FIG. 4 provides that multiple types of electrolyzer modules performing different electrochemical processes can be still be coupled to the same PMU 408 for independent, precise voltage control of each electrolyzer modules. For example, the LCD 214 can be configured to adjust voltage levels V3 and / or V4 to balance temperatures, gas flow rates, and other related conditions between the first electrolyzer module 108-1 and the second electrolyzer module 108-2.

[0160] In some implementations, the electrolyzer modules 108-1 and 108-2 can be configured to operate in the same mode. A system 400 with electrolyzer modules 108-1 and 108-2 operating in the same mode may be desirable to provide redundancy for an electrochemical process. For example, both the first electrolyzer module 108-1 and the second electrolyzer module 108-2 can be configured to operate in electrolysis mode until a fault is detected in either of the modules 108-1 or 108-2. The PMU 408 can be configured to halt or reduce operation of faulty electrolyzer module (e.g., the first electrolyzer module 108-1) and compensate for any losses in generated power, gas flow rate, temperature, etc., by adjusting operation of the operative electrolyzer module (e.g., the second electrolyzer module 108-2. From this example, the LCD 214 can also be configured to draw power from the energy storage 203 by the management system 204 to ramp up production (e.g., gas output, electrical output) of the operative electrolyzer module. As described in reference to FIG. 2 A above, the LCD 214 can be configured to draw or store power to energy storage 203 of the energy subsystem 202 to prevent interruptions in operating the connected electrolyzer modules of the PMU. By coupling more than one electrolyzer module to the same power management unit, fewer components for control circuitry can be utilized. Instead of a PMU 208 for each electrolyzer module 108-1 and 108-2, the PMU 408 can include a single LCD 214 and a different power management circuit, e.g., circuit 406, rather than circuit 206. The LCD 214 for the PMU 208 can be configured to obtain status information from both modules and manages controls for the converters 410 of the circuit 406. Although the system 400 depicts two electrolyzer modules connected to the PMU 408, any number of electrolyzer modules can be connected to the PMU 408, with a corresponding number of converters to independently control voltage levels between the PMU 408 and each electrolyzer module. The circuit 408 can include additional converters connected in series with the first connector 410a. The additional converters can be connected in series to the first connector 410 that is further connected to a power supply. The additional converters can be further coupled to an electrolyzer (e.g., stack, module).

[0161] FIG. 5 is a schematic diagram of an example electrolyzer system 500. The electrolyzer system 500 includes the power supply 352 (e.g., a multi-phase system) of FIG. 3 coupled to a cascaded, power management system 551. The power management system 551 includes multiple arrays of PMUs 408, e.g., described in reference to FIG. 4 above. In the present example, the multiple PMUs 408 are arranged in three arrays (500-PA, 500-PB, and 500-PC) and similar to the arrays 300 of FIG. 3B, each array 500 is coupled to a different phase of the power supply 352. The electrolyzer system 500 also optionally includes the transformer 354, e.g., described in reference to FIG. 3B above, to step down voltages at each phase of the power supply 352.

[0162] As an example, the array 500-PA includes N PMUs 408a- 1 to 408a-N connected in series. The first PMU 408a-l in the array 500-PA connects to the inductor 356a of the coupling module 356, which is further connected to phase A of the power supply 352 at “Node 1” of the grid 358. The first PMU 408b-l in the array 500-PB and the first PMU 408c-l in the array 500-PC are connected to the power supply 352. The PMUs of the arrays 500-PB and 500-PC are similarly connected, e.g., N PMUs connected in series. As described in reference to FIG. 3B above, the last PMU 408-N of each array (e.g., PMU 408a-N, PMU 408b-N, PMU 408c-N) connects the arrays together, e.g., at a common reference.

[0163] Each PMU 408 of the multiple PMUs 408 depicted in FIG. 5 has the same structure as shown in the example PMU 408 depicted in FIG. 4 above, e.g., each PMU being connected to a pair of electrolyzer modules. Each array 500 includes N connected PMUs in connected in series and N pairs of electrolyzer modules that are connected the N- connected PMUs. As an example, the first PMU 408a-l in the array 500-PA (e.g., corresponding to phase A of the power supply 352) connects to electrolyzer modules 108a- 1 and 108-2, while the last PMU 408a-N in the array 500-PA is connected to a pair of electrolyzer modules 108a-(2N-l) and 108-2N.

[0164] Each PMU 408 is configured to convert AC power supplied by a respective phase of the grid 358 into regulated DC power, which can then be further provided to the load of the PMU, e.g., the pair of electrolyzer modules connected to the PMU. Each PMU 408 for the electrolyzer stack can also invert DC power from the pair of electrolyzer modules operating in fuel-cell mode into supplying AC power for the grid 358. Similar to the implementations described in reference to FIG. 3B above, each PMU 408 can be configured to invert DC power stored in an energy storage device (e.g., energy subsystem 202 with energy storage 203) coupled to the PMU 408 to supply power for the grid 358 or the pair of electrolyzers. The PMU 408 can be configured by the MCD 212 to have a voltage rating and / or current rating as an input in a respective array for the PMU. The voltage and / or current rating from each array is provided for input to the connected pair of electrolyzer modules of the PMU. Similar to FIG. 3B, the MCD 212 provides coordinated control activity through switching signals for the PMUs 408to achieve a target current, current density, and / or voltage level for the pair of electrolyzer modules.

[0165] The pair of electrolyzers do not need to be coupled to each other, and the PMU 408a-l is configured to independently control voltage levels provided to each electrolyzer module. As discussed in reference to FIG. 4 above, electrolyzer modules sharing a PMU may be desirable for electrolyzer devices that perform solely perform different types (e.g., unidirectional) of electrochemical processes relative to each other. The electrolyzer system 500 can also be a desirable implementation to minimize the number of components, e.g., in contrast to the electrolyzer system 350 that couples each electrolyzer module to its own PMU. In this way, the LCDs 214 of each PMU 408 (which are communicatively coupled to the MCD 212) can be configured to independently control each electrolyzer module by the respective converter configured to adjust (e.g., convert, invert, regulate) the voltage level at the electrolyzer module.

[0166] An advantage of the electrolyzer system 500 that connects pairs of electrolyzer modules that are each limited to a unidirectional electrochemical process, is that electrolyzer modules of the electrolyzer system 500 can be grouped by electrochemical process. For example, a first electrolyzer in every pair of electrolyzers may solely operate in electrolysis mode, while a second electrolyzer in every pair of electrolyzers may solely operate in fuel cell mode. The first electrolyzer in every pair of electrolyzers can be connected to each other as a first subsystem (e.g., an electrolysis subsystem), while the second electrolyzer in every pair of electrolyzers can be connected to each other as a second subsystem (e.g., a fuel cell subsystem), of the electrolyzer system 500.

[0167] Separating the electrolyzer system 500 into two different subsystems based on respective electrochemical processes allows for the PMUs to perform a gradual transition between operating modes of the electrolyzer system 500 and improve rampability. For example, voltage levels for the first electrolyzer modules in the electrolysis subsystem can gradually transition (e.g., decrease) to reduce or halt operations of the electrolysis subsystem, while voltage levels for the second electrolyzer modules can gradually transition (e.g., increase) to initiate or maintain operations of the fuel cell subsystem. Thus, the pairs of electrolyzer modules in the electrolyzer system 500 provide a smooth transition between different operating modes (e.g., switching from electrolysis to fuel cell mode, or vice-versa), despite the unidirectionality of the electrolyzer modules.

[0168] In addition to the balancing described in reference to FIG. 4 above, the control system 205 can also balance parameters (e.g., temperature, GFR, voltage levels, current, current densities) across different pairs of electrolyzer modules connected to different PMUs in the electrolyzer system 500. For example, the MCD 212 can be configured to detect overheating in a pair of electrolyzer modules connected to a first PMU 408 in an array. The MCD 212 can generate and transmit control information to reduce or cease operation of one or both electrolyzers in the first PMU 408. Adjusting operation of the electrolyzer module can be performed by achieve a target voltage level, which can be implemented through switching signals indicated by the control information. The control information is implemented by one or both of the LCD 214 of the first PMU or the MCD 212 for the electrolyzer system 500 for the converters (e.g., converters 410) of the first PMU. The MCD 212 can identify a different PMU 408 with a different pair of connected electrolyzer modules and determine control information for the different PMU 408 to adjust voltage levels and ramp up operation of the different pair of connected electrolyzer modules.

[0169] In some implementations, the control system 205 can detect a fault condition or an indication of a possible fault condition based on the status information (e.g., from sensors 120 of either of the electrolyzer modules or by the respective LCD of the PMU). The MCD 212 can prevent the fault condition by halting or ceasing operation of the affected electrolyzer module (e.g., one or both of the electrolyzer modules in the pair).

[0170] FIG. 6 is a schematic diagram depicting an example system 600 having a photovoltaic system 614 ("PV system 614”) coupled to a PMU 608, in addition to the PMU 608 being coupled to a pair of electrolyzer modules 108-1 and 108-2. The pair of electrolyzer modules 108-1 and 108-2 operate similarly to the pair of electrolyzers connected to PMU 408 described in reference to FIG. 4 above. The PMU 608 also includes terminals 609-1 and 609-2, (collectively referred to as “terminals 609”), that connect to an electrical system, e.g., power supply 352. In contrast to the PMU 408 described in FIG. 4, the PMU 608 includes a power management circuit 606 (“circuit 606”) with four converters instead of the three converters 410 depicted in FIG. 4. The four converters of the circuit 606 include a first converter 610a a second converter 610b, a third converter 610c, and a fourth converter 610d, (collectively referred to as “converters 610”). Similar to the converters 410, the converters 610 are configured convert or invert voltage levels for the components of the circuit 606. For example, FIG. 6 depicts the control system 205, which can provide control information that includes switching signals to the converters 610 of the circuit 606.

[0171] The circuit 606 includes the first converter 410a that converts voltage level VI at the terminals 609 to voltage level V2 or vice-versa, e.g., AC -DC conversion (in electrolysis mode) or DC-AC conversion (in fuel cell mode). The circuit 606 also includes a capacitor 612 to filter noise resulting from the conversion of voltage level VI to voltage level V2. The first converter 610a is connected in series to a second converter 410b, which can be configured to convert a voltage level V2 to a voltage level V3 that is applied to the PV system 614. The third converter 410c can be configured to convert a voltage level V2 to a voltage level V4 that is applied to the first electrolyzer module 108-1 in the pair of electrolyzer modules, while the fourth converter 410d can be configured to convert a voltage V2 to a voltage level V5 that is applied the second electrolyzer module 108-2. In contrast to the implementation described in reference to FIG. 4 above, the system 600 depicts the PMU 608 connected to the PV system 614. In this implementation, the MCD 212 and the LCD 214 can provide control information to the PMU 608 to adjust voltage levels from PV system 614. The PV system 614 can be is a single photovoltaic panel, but in some implementations, the PV system 614 is an array of photovoltaic panels. The PV system 614 can be configured to supply electrical power to the electrolyzer modules 108-1 and 108-2, providing backup power to the pair of electrolyzer modules. The implementation depicted in FIG. 6 provides an additional layer of reliability to operate the electrolyzer modules, e.g., compared to implementations in which the PMU only connects to a power supply, e.g., PMU 408. The PMU 608 also differs from the implementation described in reference to FIG. 4 above in that the circuit 606 for the PMU 608 includes the second converter 610b to control voltage levels from the PV system 614. For example, the second converter 610b can be configured to adjust voltage level V3 of the PV system 614 and draw power from the PV system 614. The power from the PV system 614 can be provided to the electrolyzer module 108-1 at voltage level V4 and / or electrolyzer module 108-2 at voltage level V5, by the third converter 610c and the fourth converter 610d respectively. In some implementations, the power may be stored in the energy subsystem 202 of the PMU 608 and / or provided to an power supply through terminals 609.

[0172] The PMU 608 depicted in FIG. 6 can provide an advantage of integrating a variable DC source, such as the PV system 614, to provide power to the pair of electrolyzer modules 108. For example, interruptions to power provided to the pair of electrolyzer modules 108 can be remedied by the power from the PV system 614, thereby preventing interruptions to electrolyzer module as the module performs electrolysis. These interruptions of electrical power to the electrolyzer modules 108 may result from faults or halted operations of an power supply connected to the electrolyzer modules 108, e.g., at terminals 609 of the PMU 208. The PV system 614 can be configured to provide DC voltage to the electrolyzer modules 108 and prevent interruptions while operating in electrolysis mode.

[0173] Although variable DC voltage sources, such as PV arrays, panels, etc., can be limited in when and how long the source can receive power, the PMU 608 can compensate for the operational variability of the PV system 614. For example, a PV system 614 such as a PV array of panels converts light into electrical power when exposed to sunlight. Since the amount and timing of the electrical power generated by the PV array varies based on environmental factors (e.g., length of daytime, presence of precipitation), solely relying on the PV system 614 as an electrical power source for the electrolyzer module 108 may not be sufficient. Thus, the electrical power from the PV system 614 can be used to supplement electrical operation of the electrolyzer module 108. In some cases, the PV system 614 can operate as a primary power supply while another power supply source operates a backup source. Alternatively, the PV system 614 can operate a back-up power supply while another power supply operates as a primary power source.

[0174] Another advantage of connecting the PV system 614 to the PMU 608 to supply power for operation of the electrolyzer modules 108 is that a PV system 614 provides DC voltage. In contrast to the AC voltage provided by an electrical grid (e.g., an example power supply), the DC voltage from the PV system can be adjusted to an appropriate voltage level for one or both of the electrolyzer modules 108 without having to perform AC -DC conversion, e.g., through the first converter 610a. Thus, the PV system 614 can provide DC voltage without some of the disadvantages of performing AC -DC conversion, such as overheating, voltage loss, harmonic currents, noise, etc.

[0175] As discussed in reference to previous implementations, the MCD 212 can independently control each of the converters, the management system 204, and the LCD 214 to adjust voltage levels for independent and precise control of each electrolyzer module 108-1 and 108-2, and the PV system 614. In particular, the LCD 214 can receive status information that includes voltage level sensor measurements from the electrolyzer modules 108 (e.g., sensors 120) and / or the PV system 614 (e.g., by sensors in the LCD 214). The LCD 214 can provide the status information to the MCD 212, in which the MCD 212 is configured to determine whether to draw power from the DC voltage of the PV system 614 or to convert voltage from a connected AC power supply at the terminals 609. The MCD 212 can generate control information with switching signals indicating that the voltage levels for the electrolyzer modules 108 can be provided (e.g., converting, regulating) from the PV system 614 instead of the connected power supply. In some implementations, the MCD 212 determines that the voltage levels for the electrolyzer modules 108-1 can be converted or regulated from a combination of the PV system 614 and the connected power supply.

[0176] FIG. 7 is a schematic diagram depicting an example electrolyzer system 700 that includes the power supply 352 (e.g., a multi-phase system) of FIG. 3 coupled to a cascaded, power management system 751. The power management system 751 includes multiple arrays of PMUs 608, e.g., described in reference to FIG. 6 above. In the present example, the multiple PMUs 608 are arranged in three arrays (700-PA, 700-PB, and 700-PC) and similar to the arrays 300 of FIG. 3B, each array 700 is coupled to a different phase of the power supply 352. The electrolyzer system 700 also optionally includes the transformer 354, e.g., described in reference to FIG. 3B above, to step down voltages at each phase of the power supply 352.

[0177] Each PMU 608 of the multiple PMUs 608 depicted in FIG. 7 has the same structure as shown in the example PMU 606 depicted in FIG. 6 above, e.g., each PMU being connected to a pair of electrolyzer modules and a PV system 614. Similar to FIG. 5, each of the arrays 700 includes N connected PMUs in connected in series and N pairs of electrolyzer modules that are connected the N-connected PMUs. In contrast to FIG. 5, each PMU of each of the arrays 700 is coupled to a PV system 614. As an example, the first PMU 608a-l in the array 700-PA (e.g., corresponding to phase A of the power supply 352) connects to electrolyzer modules 108a-l and 108-2, as well as a PV system 614a-l. The last PMU 608a-N in the array 700-PA is connected to a pair of electrolyzer modules 108a- (2N-1) and 108-2N, as well as a PV system 614a-N. Although FIG. 7 depicts each PV system 614 connected to each respective PMU 608, multiple PV systems 614 in an array 700 can be connected in series. Connecting the PV systems 614 in series in the same array can allow for electrical power to be shared across different PMUs an array of the power management system 751.

[0178] As described in reference to FIG. 6 above, the connection of PV systems 614a-l through 614 to the PMUs 608 can allow the MCD 212 to generate control information based on the DC voltage input that the PV systems 614 are capable of outputting. In particular, the MCD 212 allows for the responsive utilization of electrical power from the PV systems 614 to provide electrical redundancy for the connected electrolyzer modules 108 of the PMUs 608. In some cases, the LCD 214 for a PMU 608 with a connected PV system 614 can provide control information based on the voltage levels provided by the connected PV system 614.

[0179] Referring to FIG. 7, each PV system 614 connects to each PMU 608 of the power management system 751. The connection of a PV system 614 to a respective PMU 608 allows electrical power to be drawn from the PV system 614 to the connected electrolyzer modules 108. The PMU 608 to which the PV system 614 is connected to can adjust the voltage levels for the connected electrolyzer modules of the PMU 608. For example, the MCD 212, the LCD 214, or the MCD 212 and the LCD 214, can generate a control signal that causes the PMU 608 to adjust output voltage / current from the PV system 614 to provide additional voltage / current to the connected electrolyzer modules 108 of the PMU 608. As discussed in reference to FIG. 6 above, the PV systems 614 provide advantages as a back-up power supply or alternative power supply in maintaining operability of the connected electrolyzer modules 108.

[0180] FIG. 8 is a schematic diagram of an example system 800 having an electrolyzer stack 130 (e.g., described in reference to FIG. 1 A above) coupled to a PMU 808. The PMU 808 can be configured to utilize the electrolyzer stack 130 as an energy source during fuelcell mode. Alternatively, the electrolyzer stack 130 can be configured as a load of the PMU 808 during electrolysis mode. Similar to the PMU 208 described in reference to FIG. 2A above, the PMU 808 includes an energy subsystem 202 that connects to a power management circuit 806 (“circuit 806”). The circuit 806 controls switching circuitry to convert or invert voltages. FIG. 8 also similarly depicts the control system 205 (e.g., the MCD 212 and the LCD 212), which can provide control information to the circuit 806. For example, the circuit 806 can be configured to control voltage levels between the electrolyzer stack 130 and terminals 809-1 and 809-2 of the PMU 808. The circuit 806 also includes a capacitor 812 to filter noise resulting from the conversion of voltage level VI to voltage level V2, or vice versa.

[0181] In contrast to FIG. 2A, the circuit 806 includes a transformer 814 that connects the second converter 810b of the circuit 806 to a third converter 810c of the circuit 806. The third converter 806 applies a voltage V3 to the electrolyzer stack 130, by terminals 809-3 and 809-4, The PMU 808 connects to the electrolyzer stack 130 at terminals 809-3 and 809- 4, applying a voltage level V3 from the third converter 806 to the electrolyzer stack 130. The PMU 808 depicted in FIG. 8 is configured to apply a portion of the voltage needed to configure the electrolyzer stack 130. Multiple PMUs 808 can be connected to a power supply, each PMU 808 providing a respective portion of the voltage threshold to configure the electrolyzer stack 130 in fuel cell mode or electrolysis mode.

[0182] The implementation depicted in FIG. 8 is particularly suited for independent and precise control of electrolyzer systems with high voltage demands, e.g., compared to voltage levels applied to individual electrolyzer modules 108. Because the electrolyzer stack 130 is a stack of electrolyzer modules connected in series, the voltage thresholds for configuring the electrolyzer stack 130 as a whole may be substantially higher (e.g., 150 to 250 Volts), compared to voltage thresholds for a single electrolyzer module (e.g., 50 Volts divided among the electrolyzer cells of the electrolyzer module). Thus, the circuit 806 includes the transformer 814 between the second converter 810b and the third converter 810c to account for the high voltage and current demands of the electrolyzer stack 130 as a whole. In particular, the transformer 814 includes a primary winding 814a that connects to the second converter 810b and a secondary winding 814b that connects to the third converter 810c. The transformer 814 adjusts voltage between the primary winding 814a and the secondary winding 814b, e.g., to step up or step down voltage levels. The transformer 814 has a greater capacity to step down high voltage levels to lower voltage levels, e.g., compared to converters described in previous implementations above. In some implementations, the transformer 814 can be configured to step voltage levels to a higher voltage level.

[0183] The transformer 814 also provides galvanic isolation between the electrolyzer stack 130 and the PMU 808 that is connected to the electrolyzer stack 130. In particular, galvanic isolation prevents the flow of corrosion-causing galvanic current in cases of electrical faults in the circuitry of components between the electrolyzer stack 130, the PMU 808, and any connected devices (e.g., power supplies, loads) of the PMU 808. The transformer 812 isolations a portion of the circuit 806 (e.g., converter 810c) connected to the electrolyzer stack 130 at terminals 809-3 and 809-4 from the remaining portion of the circuit 806, e.g., converters 810a and 810b. Other systems connected the PMU 808, such as a load or supply at terminals 809-1 and 809-2, can also be protected by isolating the electrolyzer stack 130 at the transformer 814. As an example, an electrolyzer stack 130 operating in fuel cell mode provides electrical current to a load of the PMU 808 connected at terminals 809-1 and 809- 2. The control system 205 can be configured to determine fault conditions resulting from operation of the electrolyzer stack 130 (e.g., a surge of current), and / or resulting from the components of the PMU 808, e.g., the switches of the converters 810. In response to detecting a fault condition in one isolated portion of the circuit 806, the control system 205 can adjust operation (e.g., switching circuits) of the circuit 806 to prevent the fault condition from affecting other portions of the circuit 806.

[0184] As illustrated, FIG. 8 depicts the second converter 810b and the third converter 810c having a pulse symbol, indicating that the two converters are configured to perform pulsewidth modulation. In more detail, the two converters can provide an target pulse frequency to deliver pulses of DC signals to the electrolyzer stack 130. The MCD 212 determines a target pulse frequency for the electrolyzer stack 130 to achieve temperature balancing across the electrolyzer modules of the electrolyzer stack 130. The target pulse frequency for the electrolyzer stack 130 is a frequency selected to reduce cell impedance (the ability of the cells in the electrolyzer modules of the stack 130 to resist the flow of current through the cells). Reducing the cell impedance of electrolyzer cells improves electrochemical process efficiency performed by the electrolyzer cells of an electrolyzer module in a stack. Furthermore, reducing cell impedance allows a wider range of current densities for the electrolyzer modules of the electrolyzer stack. A wider range of current densities allows for the electrolyzer stack 130 to operate with lower temperatures due to the efficient flow of current to the load.

[0185] In some implementations, determining a target pulse frequency includes obtaining impedance measurements of an electrolyzer module 108 or the electrolyzer stack 130 through an impedance measurement unit, e.g., a sensor from sensors 120. For example, an impedance measurement unit can be configured to apply a perturbation signal to the cells of an electrolyzer (e.g., an electrolyzer module and / or stack), and obtain a frequency response from the cells to determine an impedance of the cells. The control system 205 can generate control information for the PMUs to perform PWM based on the determined cell impedance of the electrolyzer at a particular frequency, e.g., a frequency associated with a low or minimal cell impedance for the electrolyzer.

[0186] In some implementations, the control system 205 can generate and provide a perturbation signal (e.g., a perturbation voltage and / or perturbation current) to a PMU, e.g., PMU 808 that is connected to an electrolyzer. The perturbation signal can be provided to the connected electrolyzer module and / or stack to determine a frequency response of the cells of the electrolyzer module and / or stack. The perturbation signal can be a wideband signal, e.g., a signal that includes a broad range of frequencies. For example, in some implementations, the frequency range of the perturbation signal extends from the millihertz (mHz) to the kilohertz (kHz) range, e.g., from 10 mHz to 10 kHz. Other frequency ranges are also possible.

[0187] The PMU 808 can control converters 810 to introduce the perturbation signal by providing a perturbation reference signal, which can include a reference voltage or current waveform with components for multiple frequencies. Referring to FIG. 2A, the control system 205 (e.g., by the MCD 212) generates a normalized reference voltage waveform (Vrn) and modulation indexes (Mi) as outputs for the converters of the PMU. The modulation indexes and the Vm are used to generate switching signals for the converter The perturbation reference signal can have a lower amplitude than the normalized reference signal Vm of the control information generated by the control system 205, e.g., to distinguish the perturbation from the Vrn for the converters of the PMU.

[0188] The impedance measurement unit measures the impedance of the electrolyzer when a perturbation signal (e.g., perturbation voltage and / or current) is introduced to the connected electrolyzer of the PMU. The impedance measurement unit can record current measurements and voltage measurements of the connected electrolyzer and determine an impedance of electrolyzer based on the current and voltage measurements.

[0189] In some implementations, the impedance measurement unit and / or the LCD 214 includes, or is electrically coupled to, a shunt resistor (not shown) electronically placed across the output terminals of the electrolyzer module or stack for measurement. Voltage across and current through the shunt resistor can be measured to determine a gain measurement and a phase measurement across a range of frequencies. In some implementations, the LCD 214 can measure the voltage and current or receive the voltage and current measurements from additional voltage and current sensors (e.g., from sensors 120) electrically coupled to measure the voltage and current of the shunt resistor. The LCD 214 can provide the voltage and current measurements to the MCD 212 over communication paths or links, e.g., as described in reference to FIGS. 15A through D below. In some implementations, the impedance measurement unit performs a Fourier Transform or a Fast Fourier Transform (FFT) in order to provide a phase angle and magnitude for impedance across a broad frequency spectrum.

[0190] In some implementations, the bandwidth of the perturbation signal can be half of the switching frequency of converter 810, which can be referred to as the converter’s natural bandwidth. By injecting current at a broad range of frequencies to the connected electrolyzer module 108 and / or stack 130, an impedance measurement unit from the sensors 120 can determine the response of the cells of the electrolyzer for many different frequencies, providing wideband impedance measurements. These measurements can be used to detect different types of energy degradations, e.g., cell degradations.

[0191] The control system 205 can determine a pulse frequency for the electrolyzer stack 130 through the MCD 212, the LCD 214, or both the MCD 212 and the LCD 214. The control system 205 determines a pulse frequency for the electrolyzer stack 130 based on the electrolytic conditions of the electrolyzer stack 130 as a whole, or electrolytic conditions of each electrolyzer module in the electrolyzer stack 130. The target pulse frequency can be generated based on the measured impedance of electrolyzer cells, to determine pulse frequency that results in a minimized impedance across a spectrum of pulse frequencies. The electrolytic conditions can include temperature, reaction efficiency, current, voltage, current density, among other parameters of an electrolyzer module in the electrolyzer stack 130 and / or electrolyzer stack 130 as a whole. The control system 205 determines a pulse frequency and varies the switching frequency of the converters 810, while maintaining operability conditions for the electrolyzer stack 130. The operability conditions can include cell voltage limits, target current density of the electrolyzer modules in the electrolyzer stack, and / or temperature limits. As an example, the PMU 808 can provide a voltage with a varied pulse-width, thereby increasing or decreasing the output duty cycle of the voltage applied by the PMU 808 to the electrolyzer stack 130. The resulting pulse-width modulated signal can result in a change in the current density of the cells in the electrolyzer stack 130, which results in a correlating change in the yield of the electrolyzer stack. For example, increasing current density in electrolysis mode can increase a yield of gases but also increases temperature, while decreasing current density reduces a yield of gases and decreases temperature of electrolyzer cells (e.g., to prevent overheating of the cells). The pulse-width modulate signals allows for increased efficiency in generating outputs of the electrolyzer stack by increasing current density while simultaneously maintaining temperature limits.

[0192] FIG. 9 is a schematic diagram of an example electrolyzer system 900. Similar to FIG. 3B, the electrolyzer system 900 includes the multi-phase power supply 352 coupled to a cascaded, power management system 951. The power management system 951 includes multiple arrays of PMUs 808, e.g., described in reference to FIG. 8 above. In the present example, the multiple PMUs 808 are arranged in three arrays (900-PA, 900-PB, and 900-PC), with each array coupled to a different phase of the power supply 352. In contrast to FIG. 3B, each array 900 is coupled to the electrolyzer stack 130. Additionally, each of the last PMUs in a respective array includes a pair of terminals (e.g., terminals 809- 1 and 809-2, referring to FIG. 8) and can be connected to each other by a respective second terminal from each of the last PMUs in the array, e.g., terminal 809-2. The last PMU of each array can be connected to each other at a DC bus 908 (e.g., a common connection) to allow for the flow of power to and from the electrolyzer stack 130.

[0193] Each PMU 808 in an array includes a respective circuit 806 configured to convert power from the power supply 352 by the connected grid 358. The circuit 806 can also be configured to invert DC power generated from the electrolyzer stack 130 connected to the PMU, e.g., to provide power to the electric grid 358. For example, the PMUs 808a-l to 808a-N of array 900-PA supplies a portion of electrical power to the electrolyzer stack 130. PMUs 808b-l to 808b-N for array 900-PB and 808c-l to 808c-N for array 900-PC each supply a respective portion of power the electrolyzer stack 130. In each array, the PMUs 808 for a phase of grid 358 can be configured by the control system 205 to provide a portion of electrical power for the phase corresponding to the array, to the connected electrolyzer stack 130. Each array is independently controlled by signals provided by the control system 205, e.g., the MCD 212 and / or the LCD 214 for the respective PMUs of the array.

[0194] Each PMU 808 of the multiple PMUs 808 depicted in FIG. 9 has the same structure as shown in the example PMU 808 depicted in FIG. 8 above. Each PMU 808 is configured to convert AC power supplied by a respective phase of the grid 358 into regulated DC power, which can then be further provided to the load of the PMU, e.g., the electrolyzer stack 130. Each PMU 808 for the electrolyzer stack can also invert DC power from the electrolyzer stack 130 operating in fuel-cell mode into supplying AC power for the grid 358. In some implementations, each PMU 808 also inverts DC power stored in an energy storage device coupled to the PMU 808 to supply power for the grid 358 or the connected electrolyzer stack 130. Each PMU can be configured by the MCD 212 to have a voltage rating and / or current rating as an input in a respective array for the PMU. The voltage and / or current rating from each array is provided for input to the electrolyzer stack 130. Similar to FIG. 3B, the MCD 212 provides coordinated control activity through switching signals for the PMUs 808 to achieve a target current, current density, and / or voltage level for the electrolyzer stack.

[0195] In contrast to FIG. 3B, the MCD 212 determines control activity that provides a voltage level to each PMU 808 in the power management system 951 to operate electrolyzer stack 130. The voltage applied to the electrolyzer stack 130 by array of PMUs 808 can be independently controlled, e.g., by the MCD 212 and / or the LCDs 214 of the control system 205. For example, the control system 205 can configure each PMU 808 in an array to convert voltages from the supply 352 and provide a respective contribution to the total voltage for the array, which is then applied at the DC bus 908. The total voltage of the array can be applied to the electrolyzer stack 130 through the DC bus 908, so that the electrolyzer stack 130 operates in an electrolysis mode. Alternatively, the control system 205 can configure each PMU in an array to convert voltages from the supply 352 to provide a respective voltage contribution to the total voltage of the array at the DC bus 908. The total voltage of the array is applied to the electrolyzer stack 130 to operate to the electrolyzer stack 130 in fuel cell mode.

[0196] Similar to the electrolyzer modules 108 in FIG. 3B, the control system 205 can adjust voltage levels to adjust gas flow rates, temperatures, etc. of the electrolyzer stack 130, by adjusting voltage contributions from different PMUs 808 in the power management system 951. In some implementations, the control system 205 can balance voltage levels across different PMUs 808 while maintaining an operational mode of the electrolyzer stack 130 within temperature limits and / or gas flow rate limits.

[0197] FIG. 10 is a schematic diagram of an example electrolyzer system 1000. Similar to FIG. 9, the electrolyzer system 1000 includes the multi -phase power supply 352 coupled to a cascaded, power management system 1051. The power management system 1051 includes multiple arrays of PMUs 808 arranged in arrays 900, e.g., described in reference to FIG. 9 above. In contrast to the electrolyzer system 900, the electrolyzer system 1000 depicts each PMU 808 connected to a respective electrolyzer module 108, e.g., similar to the electrolyzer system 350 depicted in FIG. 3B. In contrast to the PMUs 208 of the electrolyzer system 350, the PMUs 808 of the electrolyzer system 1000 each include the transformer 814, described in reference to FIG. 8 above. The circuit 806 for each PMU 808 includes the transformer 814, thereby providing an isolated circuit topology for the converters 810 of the circuit 806. For example, the electrolyzer system 1000 may be desirable for high-voltage applications, low-voltage applications with additional safety considerations, etc., in contrast to electrolyzer system 350. As another example, the PMU 808 may be desirable for electrolyzer systems that are coupled to each other, such as multiple electrolyzer modules coupled to each other, a electrolyzer module coupled to an electrolyzer stack, or multiple electrolyzer stacks coupled to each other. In some implementations, electrolyzer systems with non-isolated circuit topologies may be desirable for applications that demand smaller physical constraints for the PMUs of the power management system.

[0198] FIG. 11 is a schematic diagram of an example system 1100 having an electrolyzer stack 130 (e.g., described in reference to FIG. 1 A above) and an electrolyzer module 108 coupled to a PMU 1108. The system 1100 depicted in FIG. 11 is an implementation that allows for precise, simultaneous voltage control of different types of electrolyzers, such as the electrolyzer module 108 and the electrolyzer stack 130. The PMU 1108 can be configured to utilize the electrolyzer stack 130 and / or the electrolyzer module 108 as an energy source during fuel-cell mode. Alternatively, the electrolyzer stack 130 and / or the electrolyzer module can be configured as a load of the PMU 1108 during electrolysis mode. In some implementations, the PMU 1108 is configured to operate the electrolyzer module 108 and the electrolyzer stack 130 in different modes relative to each other. For example, this can include operating the electrolyzer module in fuel cell mode while operating the electrolyzer stack 130 in electrolysis mode, or vice-versa.

[0199] The implementation depicted in FIG. 11 is particularly suited for independent and precise control for electrolyzer systems that combine different types of electrolyzer modules and stacks. Some types of electrolyzers (e.g., alkaline) may be unidirectional while other types of electrolyzers (e.g., PEM, AEM, SOEC) may be either unidirectional or bidirectional. The system 1100 allows for mixed types of electrolyzers to be controlled by the same power management unit, e.g., PMU 1108, and control system 205. operate in a single-mode (e.g., fuel cell or electrolysis mode), depending on a type of electrochemical process performed by the electrolyzer, that may be limited to a single electrochemical process. For example, either or both of the electrolyzer module 108 or the electrolyzer stack 130 may be a unidirectional electrolyzer.

[0200] The system 1100 may also particularly suited for a mix of high-voltage and low- voltage applications. Similar to the PMUs 808 described in reference to FIG. 9, the PMU 1108 may be configured to support high-voltage electrolyzers, such as the electrolyzer stack 130, which can receive a high voltage (e.g., ~ 100 Volts) to configure the operational mode of electrolyzer cells (e.g., ~ 1.6 Volts) of the electrolyzer stack. In some cases, the PMU 1108 can be configured low-voltage electrolyzers, such as an electrolyzer module, which can receive a low voltage (e.g., 20 Volts) to configure the operational mode of electrolyzer cells (e.g., with a voltage threshold of - 1.6 Volts) of the electrolyzer module.

[0201] Similar to the PMU 808 of FIG. 8, the PMU 1108 connects to the electrolyzer stack 130 by terminals 1108-3 and 1108-4. The PMU 1108 applies a voltage level V4 from the third converter 806 to the electrolyzer stack 130. The PMU 808 depicted in FIG. 8 is configured to apply a portion of the voltage needed to configure the electrolyzer stack 130. Multiple PMUs 808 can be connected to a power supply, each PMU 808 providing a respective portion of the voltage threshold to configure the electrolyzer stack 130 in fuel cell mode or electrolysis mode.

[0202] Similar to the PMU 208 described in reference to FIG. 2A above, the PMU 808 includes an energy subsystem 202 that connects to a power management circuit 1106 (“circuit 1106”). The circuit 1106 controls switching circuitry to convert or invert voltages for the PMU 808. FIG. 11 also similarly depicts the control system 205 (e.g., the MCD 212 and the LCD 212), which can provide control information to the circuit 1106. For example, the circuit 1106 can be configured by the control system 205 to control voltage levels between the electrolyzer stack 130 and / or the electrolyzer module 108. The control system 205 can also configure the circuit 1108 to convert the applied voltage at terminals 1109-1 and 1109-2 of the PMU 1108. The circuit 1106 includes a first converter 1110a that connects to a second converter 1110b, which further connects to a capacitor 1112. Similar to FIG. 8, the capacitor 1112 can filter noise resulting from the conversion of voltage level VI to voltage level V2, or vice versa.

[0203] The circuit 1106 includes a transformer 1114 to allow for an isolated converter topology between multiple converters of the circuit 1106. For example, FIG. 11 depicts a second converter 1110b connected to the transformer 1114, but also depicts a third converter 1110c and fourth converter 11 lOd connected the transformer 1114. Similar to the transformer 814 of FIG. 8, the transformer 1114 includes a primary winding 1114a that connects to the second converter 1110b.

[0204] In contrast to a single secondary winding 814b depicted in FIG. 8, the transformer 1114 includes two secondary windings 1114b and 1114c. The secondary winding 1114b connects to the third converter 1110c, which connects the PMU 1108 to the electrolyzer module 108 and applies voltage level V3 to the connected the electrolyzer module 108. The secondary winding 1114c connects to the fourth converter 11 lOd, which connects the PMU 1108 to electrolyzer stack 130 and applies voltage level V4 to the connected the electrolyzer stack 130. Although FIG. 11 depicts the transformer 1114 with two secondary windings, the transformer 1114 can include any number of secondary windings. Each of the secondary windings can be coupled to a respective converter (e.g., converters 1110c, l l lOd) that applies a voltage level to a connected device of the respective converter, e.g., an electrolyzer module, an electrolyzer stack, and / or a photovoltaic system.

[0205] The PMU 1108 connects to the electrolyzer module 1108, and configures the third converter 1110c to apply a voltage level V3 to the connected electrolyzer module 108. The third converter 1110c can be configured to operate similarly to the second converter 210b of FIG. 2A, e.g., receiving switching signals from control information generated by the control system 205. In contrast to the converter 210b, the third converter 1110c is connected to the secondary side (e.g., by the secondary winding 1114b) and thus isolated from converters on the primary side (e.g., converters 1110b and 1110a) of the transformer 1114.

[0206] As the PMU 1108 electrically couples to both the electrolyzer module 108 and the electrolyzer stack 130, the system 1100 includes the transformer 1114 to provide galvanic isolation between the electrolyzer module 108 and the electrolyzer stack 130. The transformer 1114 provides galvanic isolation between the electrolyzer module 108 and portions of the circuit 1106 on the primary side of the transformer 1114, e.g., the second converter 1110b and the first converter 1110a. Similarly, the transformer 1114 provides galvanic isolation between to the electrolyzer stack 130 and the primary side of the transformer 1114.

[0207] Similar to the system 800 described in reference to FIG. 8 above, the control system 205 can determine a pulse frequency for the electrolyzer stack 130 and / or the electrolyzer module 108 through the MCD 212, the LCD 214, or both the MCD 212 and the LCD 214. The control system 205 determines a pulse frequency for the connected electrolyzer stack 130 and / or the connected electrolyzer module 108, based on the electrolytic conditions of either connected electrolyzer. For example, the control system 205 can obtain sensor measurements by the LCD 214 of the PMU 1108 or MCD 212 to detect electrolytic conditions of the electrolyzer module 108. The control system 205 determines a pulse frequency and varies the switching frequency of the converters 1110, while maintaining operability conditions for the electrolyzer stack 130 and / or the electrolyzer module 108. The control system 205 can similarly increase or decrease the output duty cycle of the voltage applied by the PMU 808 to the electrolyzer stack 130 and / or the electrolyzer module 108 to cause an adjustment in the current density of the cells of the respective electrolyzer.

[0208] FIG. 12 is a schematic diagram of an example electrolyzer system 1200. Similar to FIG. 10, the electrolyzer system 1200 includes the multi -phase power supply 352 coupled to a cascaded, power management system 1251. The power management system 1251 includes PMUs arranged in arrays, in which each PMU is an example PMU 1108 described in reference to FIG. 11 above. The arrays of the PMUs 1108 are arranged in arrays 1200 (e.g., “1200-PA”, “1200-PB”, and “1200-PC”). Similar to the arrays 900 described in reference to FIG. 9 above, each array 1200 corresponds to a phase of the power supply 352. The electrolyzer system 1200 is an example implementation that combines the implementations depicted in FIGS. 9 and 10. For example, the PMUs 1108 in an array 1200 are connected in series, and each array connects to a DC bus 1208 to be electrically coupled to the electrolyzer stack 130. In addition to being coupled to the electrolyzer stack 130, each PMU 1108 in an array 1200 is also coupled to a respective electrolyzer module 108. In particular, each PMU 1108 in the power management system 1251 includes the transformer 1114 to provide galvanic isolation, e.g., between the electrolyzer module 108 and the electrolyzer stack 130. As discussed in reference to FIG. 11, the transformer 1114 also provides galvanic isolation between converters directly connected to the secondary side of the transformer 1114 (e.g., converters 1110c and l l lOd), and converters that are directly connected to the primary side of the transformer 1114 (e.g., converters 1110b and converters 1110a).

[0209] In contrast to the electrolyzer systems 900 and 1000 the electrolyzer system 1100 depicts each PMU 1108 connected to a respective electrolyzer module 108 and the electrolyzer stack 130. As described in reference to FIG. 11 above, some types of electrolyzers are unidirectional while other types of electrolyzers are bidirectional. The electrolyzer system 1100 allows for the electrolyzer modules 108 and the electrolyzer stack 130 to share the same control circuitry, and can be configured to operate in different modes relative to each other.

[0210] The electrolyzer system 1100 may be desirable for a combination of high-voltage applications and low-voltage applications, e.g., in contrast low-voltage operations by electrolyzer system 350. The electrolyzer system 1100 is particularly suited for high-power applications from the electrolyzer stack 130 (e.g., a high voltage electrolyzer), while simultaneously supporting low-power applications from the electrolyzer modules 108 (e.g., a low voltage electrolyzer.) Thus, the implementation depicted in FIG. 12 allows for an electrolyzer system 1100 that is configured by the control system 205 to provide precise control for the electrolyzer stack 130 and the electrolyzer modules 108, thereby supporting both high and low power applications. In some implementations, the electrolyzer stack 130 can be replaced with a photovoltaic (PV) system such as a PV array for medium to high voltage applications.

[0211] In some implementations, the electrolyzer stack 130 can include a number of substacks of electrolyzer modules. For example, the electrolyzer stack 130 can include three sub-stacks, each sub-stack having 100 electrolyzer modules, e.g., electrolyzer cells 108-1 through 108-100, connected in series. Each electrolyzer module can have a nominal voltage, e.g., 2 Volts each for a total voltage of 200 volts across all modules in a sub-stack. Each electrolyzer module include electrolyzer cells that have the same cross-sectional area, e.g., 100 cm2, as the cells in the other electrolyzer modules of the sub-stack. The electrolyzer modules of a sub-stack can be grouped into a number of electrolyzer subsystems. For example, a sub-stack can have four electrolyzer subsystems, each subsystem having twenty-five electrolyzer modules connected in series. The nominal voltage for the electrolyzer modules in a subsystem is the total voltage of electrolyzer modules, e.g., 2 Volts per electrolyzer module with twenty-five electrolyzer modules connected in series results in a total voltage of 50 Volts.

[0212] Each sub-stack of the electrolyzer stack 130 can be configured to draw DC current (e.g., at 20 to 60 Amps) to operate the cells of the electrolyzer modules at a target current density, e.g., 200 to 600 mA / cm2. The electrolyzer stack 130 receives power from the PMUs 808, in which each phase of three-phase power supply 352 can connect to a substack (e.g., a subset) of the substacks. A single phase of a three-phase power supply, e.g., 480 Volts, provides a portion of AC power, e.g., at 277 Volts, to each sub-stack by a coupling module with a multi-phase connect. Each electrolyzer sub-stack receives an equal portion of the power supply 352, e.g., ~69 Volts of AC power from dividing 277 Volts across the four substacks, which can be converted by the respective PMUs 808 to achieve a target voltage and current, e.g., 98 Volts of DC power. The electric power converted by PMUs 808 can be converted to a target voltage and current within thresholds for the electrolyzer stack 130, e.g., an upper limit of 100 Volts of AC power and within a range of current 20 to 60 Amps.

[0213] FIG. 13 is a schematic diagram of an example electrolyzer system 1300 that is similar to electrolyzer system 1200, but replaces the electrolyzer stack 130 with a PV system 614, e.g., described in reference to FIG. 6 above. In contrast to FIG. 11, the fourth converter 11 lOd of the PMU 1108, which is connected to the secondary winding 1114 of the transformer 114, couples to the PV system instead of the electrolyzer stack 130. Referring to the arrays 1200 of FIG. 13, each array of PMUs 1108 from the arrays 1200 connect to the PV system 130 at the DC bus 1208. The PV system 614 can have a medium to high voltage level, e.g., relative to the electrolyzer modules 108 connected to the PMUs 1108. The electrolyzer modules 108 can be powered by the PV system 614 to generate hydrogen, with additional power from the power supply 352 through the grid 358. Hydrogen generated by the electrolyzer modules 108 from power provided by the PV system 614 may have reduced carbon emissions, compared to power supplies from the power supply 352. In some implementations, the energy subsystems 202 of the PMUs 208 can also provide additional power if the PV system 614 and / or the power supply 352 is insufficient, e.g., to achieve a target voltage level for the electrolyzer modules 108.

[0214] Integrating photovoltaic systems with electrolyzer systems (e.g., electrolyzer modules and stacks described in reference to FIGS. 1A through IE above) can provide renewable-energy source based operation of electrolyzer systems. For example, arrays of photovoltaic panels can be connected in series to provide high DC voltage, e.g., 1.5 kV, but can also be connected in some combination of series and parallel provide medium DC voltage, e.g., 600V through 1 kV, and can be combined in parallel provide low DC voltage, e.g., 48 V. In all of these examples, the PV system supplies power to the electrolyzer system, with additional power back-up from the energy storage systems and the electric grid. The PMUs 1108 provide balanced operations between these different types of sources to minimize electricity consumption from the electric grid, thereby reducing carbon emissions by utilizing renewable energy from the PV system 614.

[0215] FIG. 14 is a flowchart diagram depicting an example process 1400 for supplying power to electrolyzer systems using a power management system, as described in reference to FIGS. 3B, 5, 7, 9, 10, 12, and 13 above. Briefly, the process 1400 includes receiving an input voltage by a first power management unit of a plurality of power management units (1410), determining, by a control system for the plurality of power management units, a target voltage level for a first electrolyzer module that is coupled to the first power management unit (1420), and generating, by the control system and based on the target voltage level, control information for the first power management unit (1430).

[0216] The process 1400 includes receiving, by a first power management unit of a plurality of power management units, an input voltage (1410). The input voltage can be provided by a power supply, such as power supply 352 described above in reference to FIG. 3B above. The input voltage may be an AC or DC voltage. The input voltage can be received from a single-phase power supply. In some implementations, the input voltage is a voltage received from a single phase of a multi-phase power supply.

[0217] The first power management unit can include an AC -DC converter, a DC-DC converter, or a DC-AC converter, to convert the input voltage from a power supply to be applied to an electrolyzer module, stack, or some combination thereof, connected to the first power management unit. In some implementations, a pair of converters can be connected by an energy buffer, a capacitor, a transformer, or any appropriate circuit components used by the power management unit to convert the input voltage level to a target voltage level. A converter of the PMU can be coupled to terminals of the PMU to receive an input voltage, and the remaining converters can be connected (e.g., in series, in parallel) such that each converter couples to other terminals of the PMU.

[0218] In some implementations, the PMU includes an energy storage system to store electrical power from the power supply. In some implementations, the PMU is coupled to a photovoltaic device (e.g., a solar panel, an array of solar panels), to receive some (e.g., in addition to an input voltage from a power supply) or all of the input voltage, (e.g., instead of an input voltage from the power supply).

[0219] The process 1400 includes determining, by a control system for the plurality of PMUs, a target voltage level for a first electrolyzer module that is coupled to the first power management unit (1420). The control system (e.g., control system 205) includes a master control device (e.g., MCD 212) and a plurality of local control devices (e.g., LCDs 214) communicatively coupled to the MCD. Each LCD (e.g., LCD 214) from the plurality of LCDs (e.g., LCDs 214) is coupled to a respective PMU (e.g., PMU 208) from the plurality of PMUs (e.g., PMUs 208). The target voltage level can be a voltage level that configures the connected electrolyzer module of the PMU (e.g., the first electrolyzer module connected to the first power management unit) in electrolysis mode or fuel cell mode, based on a threshold voltage. For example, a target voltage level above the voltage threshold configures the electrolyzer module (e.g., by applying the target voltage) in electrolysis mode, while a target voltage level below the voltage threshold configures the electrolyzer module in fuel cell mode.

[0220] In some implementations, the process 1400 includes obtaining sensor data from a sensor (e.g., temperature, fluid flow, voltage, current, or some combination thereof) of the electrolyzer module. The process 1400 can include determining the target voltage level for the first electrolyzer module based on the first sensor data. The sensor data can include a temperature of the electrolyzer module, a rate of fluid flow to or from the electrolyzer module, a voltage level of the first electrolyzer module, and / or a level of current of the first electrolyzer module. In some implementations, the control system can obtain a second set of sensor data from a second electrolyzer module different from the first electrolyzer and determine a target voltage level for either or both of the first electrolyzer module or the second electrolyzer module, based on the first sensor data and the second sensor data.

[0221] The process 1400 includes generating, by the control system and based on the target voltage level, control information for the first power management unit. The control information is configured to cause the first power management unit to output the target voltage level to the first electrolyzer module coupled to the power management unit (1430). In some implementations, generating the control information includes generating switching signals to control operation of the converters of the power management unit. For example, the control system 205 (e.g., by an LCD 214 of the PMU and / or the MCD 212) can provide the control signals to the PMU 208, e.g., to the controllers of the PMUs.

[0222] In some implementations, providing the control signals to the PMU can include providing subsets of control signals to different converters of the PMUs. For example, the control system 205 can provide a first subset of control signals to a first converter coupled to a first terminal of the PMU that is arranged to receive an input voltage, e.g., an AC or DC voltage from a power supply. The control system can provide a second subset of control signals to a second converter coupled to a second terminal of the PMU and a third subset of control signals to a third converter coupled to a third terminal of the PMU. Each of the second converter and the third converter can be coupled to a respective electrolyzer module, similar to the implementation described in reference to FIGS. 4 and 5 above. In some implementations, the PMU includes a fourth converter coupled to an electrolyzer stack or a photovoltaic source, similar to the implementations described in reference to FIGS. 7, 11, and 12 above.

[0223] In some implementations, the control signals have a pulse-width modulated duty cycle corresponding to a target output voltage of the power management unit to apply to one or more electrolyzer modules connected to the power management unit. For example, the control signals can allow the delivery of pulses of DC signals at target pulse frequency to an electrolyzer stack, electrolyzer module, etc. The target pulse frequency can be an optimal frequency that reduces cell impedance of the electrolyzer module and / or stack, thereby improving electrochemical reaction efficiency through a wider range of current densities. As discussed above in reference to FIG. 8 above, the wider range of current densities allows for operation of connected loads (e.g., electrolyzer modules, an electrolyzer stack) at lower temperatures due to the efficient flow of current to the load.

[0224] Examples of Applications of Electrolyzer Systems

[0225] Stationary applications are those in which the modular electrolyzer system is located in a fixed location during use, although it may be capable of being transported to alternative locations when not in use. When operating in fuel cell mode, modules of the electrolyzer system can be configured as an energy source, thereby providing electrical power to one or more loads. The module-based electrolyzer system resides in a static location while providing electrical energy for consumption by one or more other entities (e.g., in fuel cell mode), or drawing electrical energy from power supplies to generate hydrogen through electrolysis. The electrolyzer system can generate hydrogen for storage, and / or as a fuel for fuel cell-based applications, e.g., transportation. A hydrogen-based fuel source have lower carbon emissions (e.g., a reduced carbon footprint)

[0226] Examples of stationary applications in which the embodiments disclosed herein can be used include, but are not limited to: energy systems for use by or within one or more residential structures or locales, energy systems for use by or within one or more industrial structures or locales, energy systems for use by or within one or more commercial structures or locales, energy systems for use by or within one or more governmental structures or locales (including both military and non-military uses), energy systems for charging the mobile applications described below (e.g., a charge source or a charging station), and systems that convert solar power, wind, geothermal energy, fossil fuels, or nuclear reactions into electricity for storage. Stationary applications often supply loads such as grids and microgrids, motors, and data centers. A stationary energy system can be used in either a storage or non- storage role.

[0227] In describing embodiments herein, reference may be made to a particular stationary application (e.g., grid, micro-grid, data centers, cloud computing environments) or mobile application (e.g., an electric car). Such references are made for ease of explanation and do not mean that a particular embodiment is limited for use to only that particular mobile or stationary application. Embodiments of systems providing power to a motor can be used in both mobile and stationary applications. While certain configurations may be more suitable to some applications over others, all example embodiments disclosed herein are capable of use in both mobile and stationary applications unless otherwise noted.

[0228] Examples of Power Management Units

[0229] A power management unit can include one or more energy storage devices and a power electronics converter and, if desired, an energy buffer. FIGS. 15A-16B are block diagrams depicting additional example embodiments of system 200 with PMU 208. Similar to FIG. 2A above, the system 1500 depicts a power management unit 1508 having a power converter 1502, an energy buffer 1504, and an energy storage system 1506. The converter 1502 can be a voltage converter or a current converter. The embodiments are described herein with reference to voltage converters, although the embodiments are not limited to such. The converter 1502 can be configured to convert a direct current (DC) signal from energy storage 1506 into an alternating current (AC) signal and output it over power connection 1510 (e.g., an inverter). The converter 1502 can be configured to convert a DC or AC signal from a power supply, e.g., a single-phase AC source, a multi -phase AC source, a DC source. The converter 1502 can also receive an AC or DC signal over connection 1510 and apply it to energy storage 1506 with either polarity in a continuous or pulsed form. As discussed in reference to FIGS. 2A through 2F, the converter 1502 can be or include an arrangement of switches (e.g., power transistors) such as a half bridge of full bridge (H-bridge). In some embodiments, the converter 1502 includes only switches and the converter (and the module as a whole) does not include a transformer.

[0230] The converter 1502 can be also (or alternatively) be configured to perform AC to DC conversion (e.g., a rectifier) such as to charge a DC energy source from an AC source, DC to DC conversion, and / or AC to AC conversion (e.g., in combination with an AC -DC converter). In some embodiments, such as to perform AC-AC conversion, the converter 1502 can include a transformer, either alone or in combination with one or more power semiconductors (e.g., switches, diodes, thyristors, and the like). In other embodiments, such as those where weight and cost is a significant factor, the converter 1502 can be configured to perform the conversions with only power switches, power diodes, or other semiconductor devices and without a transformer.

[0231] An energy buffer 1504 can dampen or filter fluctuations in current across the DC line or link (e.g., +VDCL and -VDCL as described in reference to FIG. 2B above), to assist in maintaining stability in the DC link voltage. These fluctuations can be relatively low (e.g., kilohertz) or high (e.g., megahertz) frequency fluctuations or harmonics caused by the switching of the converter 1502, or other transients. These fluctuations can be absorbed by buffer 1504 instead of being passed to storage 1506 or to ports of the converter 1502.

[0232] Power connection 1510 is a connection for transferring energy or power to, from and through PMU 1508. The PMU 1508 can output energy from energy storage 1506 to power connection 1510, where it can be transferred to other PMUs of the system or to a load, e.g., an electrolyzer module connected to a PMU. The PMU 1508 can also receive energy from other PMUs 1508 or a power supply. The routing of energy or power into and out of the PMU 1508 is performed by converter 1502 under the control of the LCD 1514 (or another entity of system 1500).

[0233] In the embodiment of FIG. 2B, an LCD 214 is implemented as a component of the PMU 208 (e.g., within a shared module housing) and is connected to and capable of communication with converter 250A via internal communication path 218-1 through 218- 3, e.g., shared bus or discrete connections. In the embodiment of FIG. 15A, the LCD 1514 is included as a component separate from the PMU 1508 and is connected to and capable of communication with the converter 1502 via communication path 1516. The LCD 1514 can also be capable of receiving signals from, and transmitting signals to, the energy buffer 1504 and / or energy storage 1506 over paths 1516, or 1515.

[0234] The PMU 1508 can also include monitor circuitry 1509 configured to monitor (e.g., collect, sense, measure, and / or determine) one or more aspects of PMU 1508 and / or the components thereof, such as voltage, current, temperature or other operating parameters that constitute status information (or can be used to determine status information by, e.g., LCD 1514). The status information can describe the state of power received by power connection 1510, and / or the state of the energy storage 1506 of the PMU 1508 to allows for determinations as to how much to utilize the energy source in comparison to other sources in system 1500. The status information can also describe the state of other components (e.g., voltage, temperature, and / or presence of a fault in buffer 1504, temperature and / or presence of a fault in converter 1502, presence of a fault elsewhere in PMU 1508, etc.) can be used in the utilization determination as well.

[0235] The monitor circuitry 1509 can include one or more sensors, shunts, dividers, fault detectors, Coulomb counters, controllers or other hardware and / or software configured to monitor such aspects. The monitor circuitry 1509 can be separate from the various components 1502, 1504, and 1506, or can be integrated with each component 1502, 1504, and 1506 (as shown in FIGS. 15A-15B), or any combination thereof. In some embodiments, monitor circuitry 1509 can be part of or shared with a battery management system (BMS) for an battery energy storage 1504. Discrete circuitry is not needed to monitor each type of status information, as more than one type of status information can be monitored with a single circuit or device, or otherwise algorithmically determined without the need for additional circuits.

[0236] The physical configuration or layout of PMU 1508 can take various forms. In some embodiments, PMU 1508 can include a common housing in which all module components, e.g., converter 1502, buffer 1504, and storage 1506, are housed, along with other optional components such as an integrated LCD 1514. In other embodiments, the various components can be separated in discrete housings that are secured together. The PMU 1508 can electrically couple to electrochemical systems that include electrolyzer modules, stacks, and other types of electrolyzer devices. The physical configuration or layout of electrolyzer devices can include a common housing for the electrolyzer components such as sensors, circuitry, voltage cells, electrode materials, diaphragms, etc. Further description of the physical configuration or layout of electrolyzer devices is described in reference to FIG. 1 A through IE above.

[0237] FIG. 15C is a block diagram depicting an example implementation of a PMU 1508 having a first housing 1520 that holds an energy storage 1506 of the PMU and accompanying electronics such as monitor circuitry, a second housing 1522 that holds PMU electronics such as converter 1502, energy buffer 1504, and other accompany electronics such as monitor circuitry, and a third housing 1524 that holds the LCD 1514 (not shown) for the PMU 1508. In some implementations, the PMU electronics (e.g., including the converters and related circuitry) and LCD 1514 can be housed within the same single housing. In some cases, the PMU electronics, LCD 1514, and energy storage can be housed within the same single housing for the PMU 1508. Electrical connections between the various PMU components can proceed through the housings 1520, 1522, 1524 and can be exposed on any of the housing exteriors for connection with other devices such as other PMUs 1508 or MCD 1512.

[0238] Referring to FIG. 3, the PMUs 208 of system 300 can be physically arranged with respect to each other in various configurations that depend on the needs of the electrolyzer modules and number of electrolyzer modules in an electrolyzer system 308.. For example, in a stationary application where system 300 provides power for a microgrid, the PMUs 208 can be placed in one or more racks or other frameworks. Alternatively, the PMUs 208 can be secured together and located within a common housing, referred to as a pack. A rack or a pack may have its own dedicated cooling system shared across all modules. The cooling system may also be configured to provide cooling for systems and devices connected to the PMU 308, such as electrolyzer modules, to reduce heat generated by performing electrochemical processes, e.g., electrolysis, reverse-electrolysis. The system 300 can be implemented with one or more racks (e.g., for parallel supply to a microgrid) or one or more packs (e.g., serving different motors of a vehicle), or combination thereof.

[0239] Examples of these and further configurations are described in IntT. Appl. No. PCT / US2020 / 025366, filed March 27, 2020 and titled Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto, which is incorporated by reference herein in its entirety for all purposes.

[0240] FIG. 15D is a block diagram depicting an example electrical configuration of power management unit 208 of FIG. 2A. The embodiment is described as having one LCD 214 per PMU 208, with the LCD 214 housed within the associated PMU, but can be configured, e.g., external to the PMU, as described in FIG. 15 A above.. FIG. 15D depicts a first example configuration of a PMU 208 within system 1500. The PMU 208 includes energy storage 206, energy buffer 217, and converter 252 A. Each component has power connection ports (e.g., terminals, connectors) into which power can be input and / or from which power can be output, referred to herein as IO ports. Such ports can also be referred to as input ports or output ports depending on the context. The system 1500 depicts terminals 1 and 2 configured to receive power through a power connection 1510.

[0241] Energy storage 203 can be configured as any of the energy storage types described herein (e.g., a battery, a HED capacitor,). In some implementations, a electrolyzer module of the PMU 208 is configured provide power in fuel cell mode to be stored in energy storage 203, e.g., generating electrical power from reverse-electrolysis of hydrogen and oxygen. Ports IO1 and IO2 of energy storage 203 can be connected to ports IO1 and IO2, respectively, of energy buffer 217. Energy buffer 217 can be configured to buffer or filter high and low frequency energy pulsations arriving at buffer 217 through converter 252A, which can otherwise degrade the performance of PMU 208 to apply a voltage to the connected electrolyzer module of the PMU 208. The topology and components for buffer 217 are selected to accommodate the maximum permissible amplitude of these high frequency voltage pulsations. Several (non-exhaustive) example embodiments of energy buffer 217 are depicted in the schematic diagrams of FIGS. 16A-16C. In FIG. 16A, buffer 217 is an electrolytic and / or film capacitor CEB, in FIG. 16B buffer 217 is a Z-source network 710, formed by two inductors LEB1 and LEB2 and two electrolytic and / or film capacitors CEB1 and CEB2, and in FIG. 16C buffer 217 is a quasi Z-source network 720, formed by two inductors LEB1 and LEB2, two electrolytic and / or film capacitors CEB1 and CEB 2 and a diode DEB.

[0242] Ports 103 and 104 of energy buffer 217 can be connected to ports 101 and 102, respectively, of converter 252A, which can be configured as any of the power converter types described herein.

[0243] Referring to the control system 205 of FIG. 2A, the control system 205 can perform various functions with respect to the components of power management units 208A and 208B. These functions can include management of the protection of energy buffer 217 from over-current, over-voltage and high temperature conditions, and control and protection of converter 252A.

[0244] For example, to manage (e.g., adjust by increasing, decreasing, or maintaining) utilization of energy storage 203, the LCD 214 can receive one or more monitored voltages, temperatures, and currents from the energy storage 203 (or monitor circuitry). The monitored voltages can be at least one of, preferably all, voltages of each elementary component independent of the other components (e.g., each individual battery cell, HED capacitor,) of the storage 203, or the voltages of groups of elementary components as a whole (e.g., voltage of the battery array, and / or HED capacitor array,). Similarly the monitored temperatures and currents can be at least one of, preferably all, temperatures and currents of each elementary component independent of the other components of the storage 203, or the temperatures and currents of groups of elementary components as a whole, or any combination thereof. The monitored signals can be status information, with which the LCD 214 can perform one or more of the following: calculation or determination of a real capacity, actual State of Charge (SOC) and / or State of Health (SOH) of the elementary components or groups of elementary components; set or output a warning or alarm indication based on monitored and / or calculated status information; and / or transmission of the status information to the MCD 212. The LCD 214 can receive control information (e.g., a modulation index, synchronization signal) from MCD 212 and use this control information to generate switch signals for converter 252 that manage the utilization of the storage 203.

[0245] To protect the energy buffer 217, the LCD 114 can receive one or more monitored voltages, temperatures, and currents from the energy buffer 217 (or monitor circuitry). The monitored voltages can be at least one of, preferably all, voltages of each elementary component of buffer 217 (e.g., of CEB, CEB1, CEB2, LEB1, LEB2, DEB) independent of the other components, or the voltages of groups of elementary components or buffer 217 as a whole (e.g., between 101 and 102 or between 103 and 104). Similarly the monitored temperatures and currents can be at least one of, preferably all, temperatures and currents of each elementary component of buffer 217 independent of the other components, or the temperatures and currents of groups of elementary components or of buffer 217 as a whole, or any combination thereof. The monitored signals can be status information, with which the LCD 214 can perform one or more of the following: set or output a warning or alarm indication; communicate the status information to the MCD 212; or control the converter 252A to adjust (increase or decrease) the utilization of storage 203, an electrolyzer connected to the PMU 208, and PMU 208 as a whole for buffer protection.

[0246] To control and protect the converter 252, the LCD 214 can receive the control information from the MCD 212 (e.g., a modulated reference signal, or a reference signal and a modulation index), which can be used with a PWM technique in the LCD 214 to generate the control signals for each switch (e.g., SI through S6). LCD 114 can receive a current feedback signal from a current sensor of converter 252A, which can be used for overcurrent protection together with one or more fault status signals from driver circuits (not shown) of the converter switches, which can carry information about fault statuses (e.g., short circuit or open circuit failure modes) of all switches of converter 252A. Based on this data, the LCD 214 can make a decision on which combination of switching signals to be applied to manage utilization of PMU 208 to control operation of any connected electrolyzers, e.g., electrolyzer modules and / or stacks, and potentially bypass or disconnect converter 252A (and the PMU module 208) from system 1500.

[0247] Control Methodology Examples

[0248] The concepts described with respect to the three-phase embodiment of FIG. 3B can be extended to power management systems 351 generating other phases of power. For example, a non-exhaustive list of additional examples includes: a power management system 351 having two arrays 300, each of which is configured to generate a single phase AC signal having a different phase angle (e.g., 180 degrees apart): a power management system 351 having four arrays 300, each of which is configured to generate a single phase AC signal having a different phase angle (e.g., 90 degrees apart): power management system 351having five arrays 300, each of which is configured to generate a single phase AC signal having a different phase angle (e.g., 72 degrees apart); and power management system 351having six arrays 300, each array configured to generate a single phase AC signal having a different phase angle (e.g., 60 degrees apart).

[0249] FIG. 17A is a graph of voltage versus time depicting an example of an output voltage waveform 1702 of converter, e.g., converter 210. FIG. 17B is a plot of voltage versus time depicting an example single phase AC output signal 1704 generated by array 300 of PMUs coupled in series. For ease of description, the embodiments herein will be described in the context of a PWM control technique, although the embodiments are not limited to such. Other classes of techniques can be used. One alternative class is based on hysteresis, examples of which are described in Int’l Publ. Nos. WO 2018 / 231810A1, WO 2018 / 232403A1, and WO 2019 / 183553A1, which are incorporated by reference herein for all purposes.

[0250] As mentioned, control of an electrolyzer system (e.g., system 300, 1000, 1200, 1300) can be performed according to various methodologies, such as hysteresis or PWM. Several examples of PWM include space vector modulation and sine pulse width modulation, where the switching signals for converters (e.g., converter 210) are generated with a phase shifted carrier technique that continuously rotates utilization of each PMU (e.g., PMU 208) to equally distribute power among them.

[0251] FIGS. 17C-17F are plots depicting an example embodiment of a phase-shifted PWM control methodology that can generate a multilevel output PWM waveform using incrementally shifted two-level waveforms. An X-level PWM waveform can be created by the summation of (X-l) / 2 two-level PWM waveforms. These two-level waveforms can be generated by comparing a reference waveform Vref to carriers incrementally shifted by 360° / (X-l). The carriers are triangular, but the embodiments are not limited to such. A nine- level example is shown in FIG. 17C (using four PMUs 208). The carriers are incrementally shifted by 3607(9-1) = 45° and compared to Vref. The resulting two-level PWM waveforms are shown in FIG. 17E. These two-level waveforms may be used as the switching signals for semiconductor switches (e.g., SI though S6) of converters 210. As an example with reference to FIG. 17E, for a one-dimensional array 304 of power management units 208 include four power management units 208 each with a converter 210, the 0° signal is for control of S3 and the 180° signal for S6 of the first power management unit 208-1, the 45° signal is for S3 and the 225° signal for S6 of the power management unit 208-2, the 900signal is for S3 and the 2700signal is for S6 of the third power management unit 208-3, and the 1350signal is for S3 and the 3150signal is for S6 of the fourth power management unit 208-4. The signal for S3 is complementary to S4 and the signal for S5 is complementary to S6 with sufficient dead-time to avoid shoot through of each half-bridge. FIG. 17F depicts an example single phase AC waveform produced by superposition (summation) of output voltages from the four PMUs 208.

[0252] An alternative is to utilize both a positive and a negative reference signal with the first (N-l) / 2 carriers. A nine-level example is shown in FIG. 17D. In this example, the 0° to 135° switching signals (FIG. 17E) are generated by comparing +Vref to the 0° to 135° carriers of FIG. 17D and the 180° to 315° switching signals are generated by comparing - Vref to the 0° to 135° carriers of FIG. 17D. However, the logic of the comparison in the latter case is reversed. Other techniques such as a state machine decoder may also be used to generate gate signals for the switches of converter 210.

[0253] In multi-phase system embodiments, the same carriers can be used for each phase, or the set of carriers can be shifted as a whole for each phase. For example, in a three phase system with a single reference voltage (Vref), each array 300 can use the same number of carriers with the same relative offsets as shown in FIGS. 17C and 17D, but the carriers of the second phase are shift by 120 degrees as compared to the carriers of the first phase, and the carriers of the third phase are shifted by 240 degrees as compared to the carriers of the first phase. If a different reference voltage is available for each phase, then the phase information can be carried in the reference voltage and the same carriers can be used for each phase. In many cases the carrier frequencies will be fixed, but in some example embodiments, the carrier frequencies can be adjusted, which can help to reduce losses in electrolyzer modules and / or electrolyzer modules in an electrolyzer stack under high current conditions.

[0254] The appropriate switching signals can be provided to each PMU 208 by control system 205. For example, MCD 212 can provide Vref and the appropriate carrier signals to each LCD 214 depending upon the power management unit 208 that LCD 214 controls, and the LCD 214 can then generate the switching signals. Or all LCDs 214 in an array can be provided with all carrier signals and the LCD can select the appropriate carrier signals.

[0255] The relative utilizations of each power management unit 208 can adjusted based on status information to perform balancing or of one or more parameters as described herein. Balancing of parameters can involve adjusting utilization to minimize parameter divergence over time as compared to a system where individual electrolyzer module utilization adjustment is not performed. FIG. 18A is a block diagram depicting an example embodiment of an array controller 1800 of control system 205 for a single-phase AC or DC array of power management units. The array controller 1800 can include a peak detector 1802, a divider 1804, and an intraphase (or intra array) balance controller 1806. The array controller 1800 can receive a reference voltage waveform (Vr) and status information about the electrolyzer modules 108 for each of the N PMUs 208 in an array 300 (e.g., state of charge (SOCi), temperature (Ti), capacity (Qi), and voltage (Vi)) as inputs, and generate a normalized reference voltage waveform (Vm) and modulation indexes (Mi) as outputs. For example, the normalized reference voltage and modulation index is provided to the local control device of a respective PMU to adjust output voltage, current, current density, etc. for the electrolyzer device of the PMU. The peak detector 1802 detects the peak (Vpk) of Vr, which can be specific to the phase that controller 1800 is operating with and / or balancing. The divider 1804 generates Vrn by dividing Vr by its detected Vpk. The intraphase balance controller 1806 uses Vpk along with the status information (e.g., SOCi, Ti, Qi, Vi, etc.) to generate modulation indexes Mi for each PMU , e.g., PMU 208, within an array, e.g., array 300 being controlled.

[0256] The controller 1806 can generate an Mi for each power management unit 208 using any type or combination of types of status information (e.g., gas flow rate (GFR), temperature (T), Q, voltage, current) of an electrolyzer module 108 described herein. For example, when using GFR and T of a connected electrolyzer module 108, a power management unit 208 can have a relatively high Mi if GFR is relatively high and temperature is relatively low as compared to other power management units 208 in an array, e.g., array 300. In some implementations, parameters including current, GFR, gas pressure, as well as temperature of electrolyzer modules, stacks, or some combination thereof, are controlled by the control system 205, e.g., LCD 214 and / or MCD 212. For example, the control system 205 can balance output of the electrolyzer modules based on temperature and hydrogen gas flow rate.

[0257] If either GFR is relatively low or T is relatively high, then the PMU 208 of the connected electrolyzer module 108 can have a relatively low Mi, resulting in less utilization than other electrolyzer modules 108 connected to an array of connected PMUs. Controller 1806 can determine Mi such that the sum of output voltages from the connected PMUs does not exceed Vpk. For example, Vpk can be the sum of the products of the applied voltage of each PMU and Mi for that PMU (e.g., Vpk = M1V1+M2V2+M3V3 . . . +MNVN, etc). A different combination of modulation indexes, and thus respective voltage contributions by the PMUs, may be used but the total generated voltage should remain the same.

[0258] Controller 1800 can control operation, to the extent it does not prevent achieving the gas output requirements of the system at any one time (e.g., such as during maximum rate of hydrogen production), such that GFR of the electrolyzer modules connected to each PMU remains balanced or converges to a balanced condition if they are unbalanced, and / or such that temperature of the electrolyzer module(s) connected to each module remains balanced or converges to a balanced condition if they are unbalanced. In some cases, when the PMU 208 includes a connected energy subsystem 202 with energy storage 206, the power flow in and out of the connected electrolyzer module 108 for the PMU can be regulated such that the power from energy storage does not cause an GFR deviation. Balancing of GFR and temperature can indirectly cause some balancing of SOH of the energy storage 203, e.g., when connecting energy storage devices such as batteries to the power management unit for a connected electrolyzer module. Voltage and current can be directly balanced if desired, but in many embodiments the main goal of the system is to balance GFR and temperature, and balancing of GFR can lead to balance of voltage and current in a highly symmetric systems where electrolyzer modules are of similar capacity and impedance.

[0259] Since balancing all parameters may not be possible at the same time (e.g., balancing of one parameter may further unbalance another parameter), a combination of balancing any two or more parameters (T, Q, SOH, V, I, GFR) may be applied with priority given to either one depending on the requirements of the application. Priority in balancing can be given to GFR over other parameters (T, Q, SOH, V, I), with exceptions made if one of the other parameters (T, Q, SOH, V, I) reaches a severe unbalanced condition outside a threshold.

[0260] Balancing between arrays 300 of different phases (or arrays of the same phase, e.g., if parallel arrays are used) can be performed concurrently with intraphase balancing. FIG. 18B depicts an example embodiment of an Q-phase (or Q-array) controller 1850 configured for operation in an Q-phase system 100, having at least Q arrays 300, where Q is any integer greater than one. Controller 1850 can include one interphase (or interarray) controller 1810 and Q intraphase balance controllers 1806-PA . . . 1806-PQ for phases PA through PQ, as well as peak detector 1802 and divider 1804 (FIG. 18 A) for generating normalized references VmPA through VrnPQ from each phase-specific reference VrPA through VrPQ. Intraphase controllers 1806 can generate Mi for each PMU 208 of each array 300 as described with respect to FIG. 18 A. Interphase balance controller 1810 is configured or programmed to balance aspects of PMUs 208 across the entire multi-dimensional system, for example, between arrays of different phases.

[0261] Controllers 1800 and 1850 (as well as balance controllers 1806 and 1810) can be implemented in hardware, software or a combination thereof within control system 205. Controllers 1800 and 1850 can be implemented within MCD 212, distributed partially or fully among LCDs 214, or may be implemented as discrete controllers independent of MCD 212 and LCDs 214.

[0262] Embodiments of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, in tangibly-embodied computer software or firmware, in computer hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a tangible non-transitory storage medium for execution by, or to control the operation of, data processing apparatus. The computer storage medium can be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of them. Alternatively or in addition, the program instructions can be encoded on an artificially-generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus.

[0263] The term “data processing apparatus” refers to data processing hardware and encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can also be, or further include, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). The apparatus can optionally include, in addition to hardware, code that creates an execution environment for computer programs, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0264] A computer program which may also be referred to or described as a program, software, a software application, an app, a module, a software module, a script, or code) can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A program may, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data, e.g., one or more scripts stored in a markup language document, in a single file dedicated to the program in question, or in multiple coordinated files, e.g., files that store one or more modules, sub-programs, or portions of code. A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a data communication network.

[0265] For a system of one or more computers to be configured to perform particular operations or actions means that the system has installed on it software, firmware, hardware, or a combination of them that in operation cause the system to perform the operations or actions. For one or more computer programs to be configured to perform particular operations or actions means that the one or more programs include instructions that, when executed by data processing apparatus, cause the apparatus to perform the operations or actions.

[0266] As used in this specification, an “engine,” or “software engine,” refers to a hardware-implemented or software implemented input / output system that provides an output that is different from the input. An engine can be implemented in dedicated digital circuitry or as computer-readable instructions to be executed by a computing device. Each engine can be implemented on any appropriate type of computing device, e.g., servers, mobile phones, tablet computers, notebook computers, music players, e-book readers, laptop or desktop computers, PDAs, smart phones, or other stationary or portable devices, that includes one or more processors and computer readable media. Additionally, two or more of the engines may be implemented on the same computing device, or on different computing devices.

[0267] The processes and logic flows described in this specification can be performed by one or more programmable computers executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, e.g., an FPGA or an ASIC, or by a combination of special purpose logic circuitry and one or more programmed computers. Computers suitable for the execution of a computer program can be based on general or special purpose microprocessors or both, or any other kind of central processing unit. Generally, a central processing unit will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a central processing unit for performing or executing instructions and one or more memory devices for storing instructions and data. The central processing unit and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magnetooptical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a Global Positioning System (GPS) receiver, or a portable storage device, e.g., a universal serial bus (USB) flash drive, to name just a few.

[0268] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magnetooptical disks; and CD-ROM and DVD-ROM disks.

[0269] To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on a host device having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and pointing device, e.g, a mouse, trackball, or a presence sensitive display or other surface by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user’s device in response to requests received from the web browser. Also, a computer can interact with a user by sending text messages or other forms of message to a personal device, e.g., a smartphone, running a messaging application, and receiving responsive messages from the user in return. While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially be claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0270] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0271] Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain some cases, multitasking and parallel processing may be advantageous.

[0272] Various aspects of the present subject matter are set forth below, in review of, and / or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following embodiments. In other words, an emphasis is on the fact that each feature of the embodiments can be combined with each and every other feature unless explicitly stated or taught otherwise.

[0273] In many embodiments, an electrolyzer system includes a plurality of power management units, each power management unit in the plurality of power management units includes a first converter coupled to a first terminal of the power management unit, a second converter coupled to a second terminal of the power management unit, and an energy buffer coupled between the first converter and the second converter. The electrolyzer system includes a plurality of electrolyzer modules, wherein the second terminal of each power management unit is coupled to at least one respective electrolyzer module of the plurality of electrolyzer modules. The electrolyzer system includes a control system configured to control operation of the power management units, the control system including a master control device and a plurality of local control devices communicatively coupled to the master control device, each local control device being configured to provide control information to a respective power management unit.

[0274] In some embodiments, each power management unit is coupled to at least one electrolyzer module of the plurality of electrolyzer modules. The at least one electrolyzer module from the plurality of electrolyzer modules can be a bidirectional electrolyzer module. The plurality of electrolyzers can be coupled together in series and are arranged in a stack. The plurality of power management units can be coupled in series through the first terminal of each power management unit. A first power management unit of the plurality of power management units is coupled to a power source.

[0275] In some embodiments, the plurality of power management units can be arranged in multiple arrays, each array including multiple power management units coupled in series. Each array of the multiple arrays of power management units can be coupled to a different phase of a multi-phase power source. The electrolyzer system can also include a coupling module coupled between the plurality of power management units and a power source. The coupling module can include at least one of a filter, a voltage or current sensor circuit, a switch, and a fuse breaker. In some embodiments, a first electrolyzer module of the plurality of electrolyzer modules is coupled to a first power management unit, and a second electrolyzer module of the plurality of electrolyzer modules is coupled to the first power management unit.

[0276] In some embodiments, the first electrolyzer module is coupled to the second converter of the first power management unit, and the second electrolyzer module of the plurality of electrolyzer modules is coupled to a third converter of the first power management unit. The third converter can be coupled to the energy buffer of the power management unit.

[0277] In some embodiments, the electrolyzer system includes a photovoltaic system coupled to a first power management unit of the plurality of power management units. The photovoltaic system can be coupled to a fourth converter of the first power management unit, and the fourth converter is coupled to the energy buffer of the first power management unit.

[0278] In some embodiments, at least one power management unit of the plurality of power management units includes a third converter between the energy buffer and the second converter and a transformer coupled between the second converter and the third converter. The transformer can include an additional winding coupled to a fourth converter.

[0279] In some embodiments, the first converter is an AC -DC converter and the second converter is a DC-DC converter.

[0280] In some embodiments, each power management unit includes an energy subsystem coupled in parallel with the first converter and the energy buffer. The energy subsystem can include an energy storage device and an energy management control system. The energy management control system includes a controller configured to adjust operation of the energy storage device to (i) store power from the power management unit in the energy storage device, or (ii) discharge power from the energy storage device to the power management unit.

[0281] In some embodiments, an electrolyzer module from the plurality of electrolyzer modules is configured to perform (i) electrolysis, or (ii) reverse-electrolysis, based on a voltage level applied by the respective power management unit to which the electrolyzer module is coupled. The electrolyzer module from the plurality of electrolyzer modules can include a sensor configured to capture sensor measurements of the electrolyzer module.

[0282] In some embodiments, the master control device is configured to generate control information for the respective power management unit of the electrolyzer module, based on the sensor measurements of the electrolyzer module. The control information can include switching signals for at least one of (i) the first converter, (ii) the second converter, or (iii) additional converters, of the power management unit.

[0283] In some embodiments, at least one of (i) the first converter, or (ii) the second converter of the power management unit includes a half h-bridge circuit. The half h-bridge circuit can be further coupled to an additional half h-bridge circuit by a transformer winding. The transformer winding can be configured to transfer power the half h-bridge circuit and the additional half h-bridge circuit.

[0284] In many embodiments, a method includes receiving, by a first power management unit of a plurality of power management units, an input voltage, determining, by a control system for the plurality of power management units, a target voltage level for a first electrolyzer module that is coupled to the first power management unit, wherein the control system includes a master control device and a plurality of local control devices communicatively coupled to the master control device, each local control device from the plurality of local control devices being coupled to a respective power management unit, and generating, by the control system and based on the target voltage level, control information for the first power management unit, wherein the control information is configured to cause the first power management unit to output the target voltage level to the first electrolyzer module coupled to the power management unit.

[0285] In some embodiments, the method includes obtaining first sensor data from at least one sensor of the first electrolyzer module, and determining the target voltage level for the first electrolyzer module based on the first sensor data. The at least one sensor can include at least one of a temperature sensor configured to measure a temperature of the first electrolyzer module, a fluid flow sensor configured to measure a rate of fluid flow to or from the first electrolyzer module, a voltage sensor configured to measure a voltage level of the first electrolyzer module, or a current sensor configured to measure a level of current of the first electrolyzer module.

[0286] In some embodiments, the method includes obtaining second sensor data from at least one sensor of an additional electrolyzer module, and wherein determining the target voltage level for the first electrolyzer module based on the second sensor data and the first sensor data.

[0287] In some embodiments, the input voltage is received from a single-phase or multiphase power source.

[0288] In some embodiments, generating the control information includes generating, by the local control device of the first power management unit, switch control signals. The method can include providing the control signals to the power management unit.

[0289] In some embodiments, the method includes providing the control signals to the power management unit includes providing a first subset of control signals to a first converter of the power management unit and providing a second subset of control signals to a second converter of the power management unit. The first converter can be coupled to a first terminal of the power management unit that is arranged to receive the input voltage, and the second converter can be coupled to a second terminal of the power management unit that is coupled to the first electrolyzer module. In some embodiments, the first converter is coupled to the second converter through an energy buffer.

[0290] In some embodiments, the method includes providing the control signals to the power management unit includes providing a first subset of control signals to a first converter of the power management unit, providing a second subset of control signals to a second converter of the power management unit, and providing a third subset of control signals to a third converter of the power management unit. The first converter can be coupled to a first terminal of the power management unit that is arranged to receive the input voltage, the second converter can be coupled to a second terminal of the power management unit that is coupled to the first electrolyzer module, and the third converter can be coupled to a third terminal of the power management unit that is coupled to a second electrolyzer module. Providing the control signals to the power management unit can include providing a fourth subset of control signals to a fourth converter of the power management unit, the fourth converter being coupled to a fourth terminal of the power management unit that is coupled to a photovoltaic source.

[0291] In some embodiments, the first converter is an AC -DC converter, and the second converter is a DC-DC converter.

[0292] In some embodiments, the target voltage can be a voltage level required to operate the first electrolyzer module in an electrolysis mode. The target voltage can be a voltage level required to operate the first electrolyzer module in a fuel cell mode.

[0293] In some embodiments, the control signals can include a pulse-width modulated duty cycle corresponding to a target output voltage of the power management unit to apply to one or more electrolyzer modules connected to the power management unit.

[0294] A person of ordinary skill in the art would understand that the a “module” as that term is used herein, refers to a device or a sub-system within a larger system, and that system does not have to be configured to permit each individual module to be physically removable and replaceable with respect to the other modules. For example, a system may be packaged in a common housing that does not permit removal and replacement any one module, without disassembly of the system as a whole. However, any and all embodiments herein can be configured such that each module is removable and replaceable with respect to the other modules in a convenient fashion, such as without disassembly of the system.

[0295] The term “master control device” is used herein in a broad sense and does not require implementation of any specific protocol such as a master and slave relationship with any other device, such as the local control device. 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.

[0296] 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.

[0297] 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.

[0298] 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).

[0299] Any and all signals described herein can be communicated wirelessly except where noted or logically implausible. Communication circuitry can be included for wireless communication. The communication circuitry can be implemented as one or more chips and / or components (e.g., transmitter, receiver, transceiver, and / or other communication circuitry) that perform wireless communications over links under the appropriate protocol (e.g., Wi-Fi, Bluetooth, Bluetooth Low Energy, Near Field Communication (NFC), Radio Frequency Identification (RFID), proprietary protocols, and others). One or more other antennas can be included with communication circuitry as needed to operate with the various protocols and circuits. In some embodiments, communication circuitry can share antenna for transmission over links. Processing circuitry can also interface with communication circuitry to perform the reverse functions necessary to receive a wireless transmission and convert it into digital data, voice, and / or video. RF communication circuitry can include a transmitter and a receiver (e.g., integrated as a transceiver) and associated encoder logic.

[0300] 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.

[0301] 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 an object oriented programming language such as Java, JavaScript, Smalltalk, C++, C#, Transact-SQL, XML, PHP or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages.

[0302] 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.

[0303] To the extent the embodiments disclosed herein include or operate in association with memory, storage, and / or computer readable media, then that memory, storage, and / or computer readable media are non -transitory. Accordingly, to the extent that memory, storage, and / or computer readable media are covered by one or more claims, then that memory, storage, and / or computer readable media is only non-transitory. The terms “non- transitory” and “tangible” as used herein, are intended to describe memory, storage, and / or computer readable media excluding propagating electromagnetic signals, but are not intended to limit the type of memory, storage, and / or computer readable media in terms of the persistency of storage or otherwise. For example, “non-transitory” and / or “tangible” memory, storage, and / or computer readable media encompasses volatile and non-volatile media such as random access media (e.g., RAM, SRAM, DRAM, FRAM, etc.), read-only media (e.g., ROM, PROM, EPROM, EEPROM, flash, etc.) and combinations thereof (e.g., hybrid RAM and ROM, NVRAM, etc.) and variants thereof.

[0304] What is claimed is:

Claims

CLAIMS1. An electrolyzer system comprising: a plurality of power management units, each power management unit in the plurality of power management units comprising a first converter coupled to a first terminal of the power management unit, a second converter coupled to a second terminal of the power management unit, and an energy buffer coupled between the first converter and the second converter; a plurality of electrolyzer modules, wherein the second terminal of each power management unit is coupled to at least one respective electrolyzer module of the plurality of electrolyzer modules; and a control system configured to control operation of the power management units, the control system comprising a master control device and a plurality of local control devices communicatively coupled to the master control device, each local control device being configured to provide control information to a respective power management unit.

2. The electrolyzer system of claim 1, wherein each power management unit is coupled to at least one electrolyzer module of the plurality of electrolyzer modules.

3. The electrolyzer system of claims 1 or 2, wherein at least one electrolyzer module from the plurality of electrolyzer modules is a bidirectional electrolyzer module.

4. The electrolyzer system of any preceding claim, wherein the plurality of electrolyzers are coupled together in series and are arranged in a stack.

5. The electrolyzer system of any preceding claim, wherein the plurality of power management units are coupled in series through the first terminal of each power management unit.

6. The electrolyzer system of claim 5, wherein a first power management unit of the plurality of power management units is coupled to a power source.

7. The electrolyzer system of any of claims 1-4, wherein the plurality of power management units are arranged in multiple arrays, each array comprising multiple power management units coupled in series.

8. The electrolyzer system of claim 7, wherein each array of the multiple arrays of power management units is coupled to a different phase of a multi-phase power source.

9. The electrolyzer system of any preceding claim further comprising a coupling module coupled between the plurality of power management units and a power source.

10. The electrolyzer system of claim 9, wherein the coupling module comprises at least one of a filter, a voltage or current sensor circuit, a switch, and a fuse breaker.

11. The electrolyzer system of any preceding claim, wherein a first electrolyzer module of the plurality of electrolyzer modules is coupled to a first power management unit, and a second electrolyzer module of the plurality of electrolyzer modules is coupled to the first power management unit.

12. The electrolyzer system of claim 11, wherein the first electrolyzer module is coupled to the second converter of the first power management unit, and the second electrolyzer module of the plurality of electrolyzer modules is coupled to a third converter of the first power management unit.

13. The electrolyzer system of claim 12, wherein the third converter is coupled to the energy buffer of the power management unit.

14. The electrolyzer system of any preceding claim comprising a photovoltaic system coupled to a first power management unit of the plurality of power management units.

15. The electrolyzer system of claim 14, wherein the photovoltaic system is coupled to a fourth converter of the first power management unit, and the fourth converter is coupled to the energy buffer of the first power management unit.

16. The electrolyzer system of any preceding claim, wherein at least one power management unit of the plurality of power management units comprises: a third converter between the energy buffer and the second converter; and a transformer coupled between the second converter and the third converter.

17. The electrolyzer system of claim 16, wherein the transformer comprises an additional winding coupled to a fourth converter.

18. The electrolyzer system of any preceding claim, wherein the first converter comprises an AC -DC converter and the second converter comprises a DC-DC converter.

19. The electrolyzer system of any preceding claim, wherein each power management unit comprises an energy subsystem coupled in parallel with the first converter and the energy buffer.

20. The electrolyzer system of claim 19, wherein the energy subsystem comprises an energy storage device and an energy management control system.

21. The electrolyzer system of claim 20, wherein the energy management control system comprises a controller configured to adjust operation of the energy storage device to (i) store power from the power management unit in the energy storage device, or (ii) discharge power from the energy storage device to the power management unit.

22. The electrolyzer system of claim any preceding claim, wherein an electrolyzer module from the plurality of electrolyzer modules is configured to perform (i) electrolysis, or (ii) reverse-electrolysis, based on a voltage level applied by the respective power management unit to which the electrolyzer module is coupled.

23. The electrolyzer system of any preceding claim, wherein an electrolyzer module from the plurality of electrolyzer modules comprises a sensor configured to capture sensor measurements of the electrolyzer module.

24. The electrolyzer system of claim 23, wherein the master control device is configured to generate control information for the respective power management unit of the electrolyzer module, based on the sensor measurements of the electrolyzer module.

25. The electrolyzer system of claim 24, wherein the control information comprises switching signals for at least one of (i) the first converter, (ii) the second converter, or (iii) additional converters, of the power management unit.

26. The electrolyzer system of claim 1, wherein at least one of (i) the first converter, or (ii) the second converter of the power management unit comprises a half h-bridge circuit.

27. The electrolyzer system of claim 26, wherein the half h-bridge circuit is further coupled to an additional half h-bridge circuit by a transformer winding, wherein the transformer winding is configured to transfer power the half h-bridge circuit and the additional half h-bridge circuit.

28. A method comprising: receiving, by a first power management unit of a plurality of power management units, an input voltage; determining, by a control system for the plurality of power management units, a target voltage level for a first electrolyzer module that is coupled to the first power management unit, wherein the control system comprises a master control device and a plurality of local control devices communicatively coupled to the master control device, each local control device from the plurality of local control devices being coupled to a respective power management unit; and generating, by the control system and based on the target voltage level, control information for the first power management unit, wherein the control information is configured to cause the first power management unit to output the target voltage level to the first electrolyzer module coupled to the power management unit.

29. The method of claim 28, comprising:obtaining first sensor data from at least one sensor of the first electrolyzer module, wherein determining the target voltage level for the first electrolyzer module is based on the first sensor data.

30. The method of claim 29, wherein the at least one sensor comprises at least one of a temperature sensor configured to measure a temperature of the first electrolyzer module, a fluid flow sensor configured to measure a rate of fluid flow to or from the first electrolyzer module, a voltage sensor configured to measure a voltage level of the first electrolyzer module, or a current sensor configured to measure a level of current of the first electrolyzer module.

31. The method of any of claims 29-30, further comprising: obtaining second sensor data from at least one sensor of an additional electrolyzer module, wherein determining the target voltage level for the first electrolyzer module is based on the second sensor data and the first sensor data.

32. The method of any claims 28-31, wherein the input voltage is received from a single-phase or multi-phase power source.

33. The method of any of claims 28-32, wherein generating the control information comprises generating, by the local control device of the first power management unit, switch control signals, the method further comprising providing the control signals to the power management unit.

34. The method of claim 33, wherein providing the control signals to the power management unit comprises providing a first subset of control signals to a first converter of the power management unit and providing a second subset of control signals to a second converter of the power management unit, wherein the first converter is coupled to a first terminal of the power management unit that is arranged to receive the input voltage, and the second converter is coupled to a second terminal of the power management unit that is coupled to the first electrolyzer module.

35. The method of claim 34, wherein the first converter is coupled to the second converter through an energy buffer.

36. The method of claim 33, wherein providing the control signals to the power management unit comprises: providing a first subset of control signals to a first converter of the power management unit; providing a second subset of control signals to a second converter of the power management unit; and providing a third subset of control signals to a third converter of the power management unit, wherein the first converter is coupled to a first terminal of the power management unit that is arranged to receive the input voltage, the second converter is coupled to a second terminal of the power management unit that is coupled to the first electrolyzer module, and the third converter is coupled to a third terminal of the power management unit that is coupled to a second electrolyzer module.

37. The method of claim 36, wherein providing the control signals to the power management unit comprises providing a fourth subset of control signals to a fourth converter of the power management unit, the fourth converter being coupled to a fourth terminal of the power management unit that is coupled to a photovoltaic source.

38. The method of any of claims 34-37, wherein the first converter is an AC -DC converter, and the second converter is a DC-DC converter.

39. The method of any of claims 28-38, wherein the target voltage comprises a voltage level required to operate the first electrolyzer module in an electrolysis mode.

40. The method of any of claims 28-38, wherein the target voltage comprises a voltage level required to operate the first electrolyzer module in a fuel cell mode.

41. The method of claim 28-39, wherein the control signals comprise a pulse-width modulated duty cycle corresponding to a target output voltage of the power management unit to apply to one or more electrolyzer modules connected to the power management unit.

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