Hydrogen production system, and control system and method thereof

Abstract

A control system for a hydrogen production system is proposed. The hydrogen production system includes a plurality of electrolyzers and a plurality of converter modules each of which is coupled to one or more of the plurality of electrolyzers. The control system includes: a plurality of local controllers each of which is coupled with one or more of the plurality of converter modules and one more of the plurality of the electrolyzers; and a system controller in communication with the plurality of local controllers. The system controller is configured to receive an external dispatch value and electrolyzer state information regarding states of the plurality of electrolyzers, and to determine internal dispatch values for one or more electrolyzer from the plurality of electrolyzers based on the external dispatch value and the electrolyzer state information. A least one local controller from the plurality of local controllers associated with the one or more electrolyzers is configured to receive the internal dispatch values from the system controller, and to control operations of the one or more electrolyzers according to the internal dispatch values.

Description

HYDROGEN PRODUCTION SYSTEM, AND CONTROL SYSTEM AND METHOD THEREOFTECHNICAL FILED

[0001] The present disclosure relates to a hydrogen production system and a control method and a control system for the hydrogen production system.BACKGROUND

[0002] Hydrogen is an energy carrier which may be used to de-carbonize in many use cases such as transportation over a long distance by heavy payload trucks, flight or ferries, steelmaking, and ammonia production. Hydrogen has also been proposed as an enabler for future power systems for achieving high penetration of intermittent renewable sources. To make the production of hydrogen climate-friendly, the hydrogen can be produced by means of electrolysis (splitting water into oxygen and hydrogen) using electricity from renewable sources.

[0003] Typically, an electrolyzer can be coupled with at least one power electronic converter for converting an AC grid voltage into a DC voltage to power the electrolyzer. International Energy Agency has reported over hundreds of large-scale electrolyzer projects related to powering from hundreds to thousands of megawatts. For example, a 500 MW electrolyzer plant is implemented by including a number of 5 MW electrolyzer stacks each of which is integrated with a dedicated power supply. In such a large- scale electrolyzer plant, there might be multiple electrolyzers with unbalanced states, for example, due to the electrolyzers coming from large electrolyzer projects in different phases and thus difference in electrolyzer degradations. In this case, the hydrogen production efficiency will beaffected, so there is a need to provide a solution that facilitates better hydrogen production efficiency.SUMMARY

[0004] According to an embodiment of the disclosure, a control system for a hydrogen production system is provided. The hydrogen production system includes a plurality of electrolyzers and a plurality of converter modules each of which is coupled to one or more of the plurality of electrolyzers. The control system includes: a plurality of local controllers each of which is coupled with one or more of the plurality of converter modules and one more of the plurality of the electrolyzers; and a system controller in communication with the plurality of local controllers, wherein the system controller is configured to receive an external dispatch value and electrolyzer state information regarding states of the plurality of electrolyzers, and to determine internal dispatch values for one or more electrolyzer from the plurality of electrolyzers based on the external dispatch value and the electrolyzer state information, and wherein at least one local controller from the plurality of local controllers associated with the one or more electrolyzers is configured to receive the internal dispatch values from the system controller, and to control operations of the one or more electrolyzers according to the internal dispatch values.

[0005] In an example, the state of each electrolyzer comprises a dynamic state and a predetermined state of the electrolyzer.

[0006] In an example, the dynamic state of the electrolyzer comprises one or more of: - an aging state determined based on at least one of a current, a voltage, and an internal resistance of the electrolyzer; - an efficiency state determined based on at least one of a temperature and a load rate of the electrolyzer; - an electrical connectivity state determined based on the connection of the electrolyzer to an electrical grid and / or an alternativesource including renewable sources; and - an availability state comprising an available state in which the electrolyzer can be operated to produce hydrogen and an unavailable state in which the electrolyzer cannot be operated to produce hydrogen.

[0007] In an example, the predetermined state of the electrolyzer comprises one or more of a pre-determined current range, a pre-determined voltage range, a pre-determined load rate range and a pre-determined temperature range of the electrolyzer.

[0008] In an example, the system controller is configured to determine the internal dispatch values further based on a system state of the hydrogen production system, and the system state comprises one or more of: -a storage capacity state of a hydrogen storage unit connected to at least one electrolyzer; and - a gas connectivity state relating to a gas pipeline network connected to at least one electrolyzer.

[0009] In an example, the external dispatch value comprises at least one of: a value indicating total electrical power to be consumed from an electrical grid to power the one or more electrolyzers comprised in the hydrogen production system, and a value indicating a total amount of hydrogen production to be produced by the one or more electrolzers comprised in the hydrogen production system.

[0010] In an example, the internal dispatch values comprise at least one of: values indicating electrical power to be provided to each of the one or more electrolyzers ; and values indicating hydrogen production to be produced by each of the one or more electrolyzers.

[0011] In an example, the internal dispatch values comprise: - a value indicating an amount of green hydrogen production to be produced by using renewable power; and / or - a value indicating an amount of hydrogen production to be produced by using grid power.

[0012] In an example, the system controller is further configured to, before determining the internal dispatch values, select the one or more electrolyzers from the plurality of electrolyzers based on the electrolyzer state information.

[0013] In an example, said at least one local controller associated with the one or more electrolyzers is configured to determine set points for controlling the operations of the one or more electrolyzers according to the internal dispatch values.

[0014] In an example, the set points comprises at least one of: - a power set point for controlling the powering of each of the one or more electrolyzers; and - a hydrogen set point for controlling the hydrogen production to be produced by each of the one or more electrolyzers.

[0015] In an example, the set points further comprise one or more of the following set points for the operation of each of the one or more electrolyzers when each of the one or more electrolyzers is operated based on the power set point and / or the hydrogen set point: - a flow rate set point for controlling a flow rate of cooling water flowing through the electrolyzer; and - a temperature set point for controlling the temperature of the electrolyzer.

[0016] According to another embodiment of the present disclosure, a hydrogen production system is provided. The hydrogen production system includes a plurality of electrolyzers; a plurality of converter modules each of which is coupled to one or more of the plurality of electrolyzers; a plurality of local controllers each of which is coupled with one or more of the plurality of converter modules and one more of the plurality of the electrolyzers; and a system controller in communication with the plurality of local controllers, wherein the system controller is configured to receive an external dispatch value and electrolyzer state information regarding states of the plurality of electrolyzers, and to determine internal dispatchvalues for one or more electrolyzer from the plurality of electrolyzers based on the external dispatch value and the electrolyzer state information, and wherein at least one local controller from the plurality of local controllers associated with the one or more electrolyzers is configured to receive the internal dispatch values from the system controller, and to control operations of the one or more electrolyzers according to the internal dispatch values.

[0017] In an example, the plurality of electrolyzers comprises: a first set of electrolyzers powered by a first electrical network coupled to a power grid; and a second set of electrolyzers powered by a second electrical network coupled to a renewable energy source.

[0018] In an example, the first electrical network is coupled to a fuel cell system which produces electrical power for the first electrical network by using hydrogen output from at least one of the plurality of electrolyzers.

[0019] In an example, at least one of the first set of electrolyzers is coupled to a first hydrogen storage unit; and / or at least one of the second set of electrolyzers is coupled to a second hydrogen storage unit.

[0020] In an example, the hydrogen production system further comprises a switch coupled between the first electrical network and the second electrical network to allow electrical power to be transferred between the first electrical network and the second electrical network.

[0021] According to yet another embodiment of the present disclosure, a method for controlling the hydrogen production system described above is provided. The method includes the steps of: receiving an external dispatch value and electrolyzer state information regarding states of the plurality of electrolyzers; selecting one or more electrolyzers from the plurality of electrolyzers based on the electrolyzer state information; determining internal dispatch values for the one or more electrolyzers based on the external dispatch value and the electrolyzer state information;and controlling operations of the one or more electrolyzers according to the internal dispatch values.

[0022] In an example, the method further includes the step of: determining the internal dispatch values such that usage of renewable power is prioritized over usage of grid power to meet a hydrogen production demand and / or for hydrogen storage.

[0023] In an example, the method further includes the step of: determining the internal dispatch values such that the one or more electrolyzers are operated to meet predetermined hydrogen production or storage demand and to minimize energy to operate the hydrogen production system.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The disclosed aspects will hereinafter be described in connection with the appended drawings that are provided to illustrate but not to limit the scope of the disclosure.

[0025] Figure 1 is a block diagram of an exemplary hydrogen production system according to an embodiment of the present disclosure.

[0026] Figure 2 is a block diagram of an exemplary hydrogen production system according to another embodiment of the present disclosure.

[0027] Figure 3 is a block diagram of an exemplary hydrogen production system according to yet another embodiment of the present disclosure.

[0028] Figure 4 is a flowchart of a method for controlling a hydrogen production system according to an embodiment of the present disclosure.DETAILED DESCRIPTIONExample systems

[0029] Examples of the disclosure provide a power to gas system, especially a hydrogen production system including one or more hydrogen based units (subsystems ) which can produce hydrogen and also contribute to grid services.

[0030] A hydrogen production system utilizes electrical energy from a grid and / or renewable sources and converts the electrical energy into hydrogen gas using a power-to-gas system (e.g. hydrogen electrolyzers), which may be used for industrial purposes or stored for later use. At the time of need, the stored hydrogen can be used for generation of power with a gas-to-power system (e.g. a fuel cell system) or other industrial purposes (e.g. used in a steel plant, for powering an automobile, etc.). A hydrogen production system can be a large hydrogen plant with a plurality of hydrogen electrolyzers located in one geographical area or can be a collection of several small hydrogen plants distributed in different geographical areas. A smallest hydrogen plant can be a basic unit / subsystem for production of hydrogen. A basic unit / subsystem will be further described in subsequent paragraphs.

[0031] Each of the plurality of electrolyzers is powered with a variable DC power source, and power to the electrolyzers is provided according to the hydrogen production requirements. The variable DC power source is provided with power converters. The power converters can be implemented as AC-DC converters, or AC-DC converters along with DC- DC converters when powering from an electrical grid or AC source. The power converters can be implemented as DC-DC converters when powering from a DC source. A basic unit / subsystem in a hydrogen production system therefore includes an electrolyzer (can include one or more stacks of electrolyzer cells) connected with a converter module (e.g.a AC-DC converter, or a DC-DC converter, or a combination of a AC -DC converter and a DC-DC converter) and a local controller for managing the operation of the basic unit / subsystem.

[0032] Figure 1 shows a hydrogen production system 100 according to an embodiment of the present disclosure. The hydrogen production system 100 includes a plurality of subsystems (1A, IB... IN), wherein each subsystem includes an electrolyzer, a power converter module (hereafter referred to as converter module) and a local controller to manage the operation of the subsystem (e.g., the operation of the electrolyzer and the converter module in the subsystem) for the best or optimum efficiency of power consumption of the subsystem and for the insurance of the normal operation of the electrolyzer in the subsystem. Operations of the plurality of subsystems are managed by the system controller 140 for the best or optimum efficiency of power consumption or hydrogen production of the hydrogen production system 100.

[0033] The hydrogen production system 100 can also be said to include a plurality of electrolyzers 111-1 In, a plurality of converter modules 121~12n, a plurality of local controllers 131~13n, and a system controller 140. As shown in Figure 1, the plurality of electrolyzers 111-1 In, the plurality of converter modules 121~12n, and the plurality of local controllers 131~13n can be arranged into modules of basic units to form a plurality of hydrogen production subsystems 1A-1N. For example, the subsystem 1A (a basic unit) includes the converter module 121, the electrolyzer 111 and the local controller 131, the subsystem IB (another basic unit) includes the converter module 122, the electrolyzer 112 and the local controller 132...the subsystem IN includes the converter module 12n, the electrolyzer 1 In and the local controller 13n. These subsystems can be arranged as a part of one hydrogen plant, or arranged in different hydrogen plants located in one site (geographical location) or arranged in severalnearby geographical locations connected via one or more electrical power networks. These subsystems can serve different utilities / industrial entities respectively and each subsystem can be independently operated, yet in coordination with other subsystems with the techniques of the invention, especially coordinated with internal dispatch control according to examples of the invention.

[0034] In addition, the hydrogen production system 100 can include or be coupled to a hydrogen storage unit 150. At least one electrolyzer (e.g., the electrolyzer 111) is coupled to the hydrogen storage unit 150 so that at least part of hydrogen produced by the least one electrolyzer can be stored in the hydrogen storage unit 150. In an example, when there is cheap and excess electrical energy available, excess hydrogen produced by the electrolyzers in the hydrogen production system 100 can be transferred to the hydrogen storage unit 150 through a gas pipeline and stored in the hydrogen storage unit 150.

[0035] According to examples of the present disclosure, the hydrogen production system is capable of operating in different modes. In an example, the hydrogen production system can be operated in a power to gas mode to produce hydrogen. In another example, the hydrogen production system includes or is coupled with a fuel cell system and thus can be operated in a gas to power mode to meet a demand for electricity. In yet another example, the hydrogen production system includes or is coupled with a hydrogen storage unit, and thus can be operated in a mixture mode where some electrolyzers are operated to produce hydrogen to meet a hydrogen demand from a hydrogen user and other electrolyzers are operated to produce hydrogen for hydrogen storage.

[0036] According to an example of the disclosure, when it is in peak seasons of renewable energy or there is cheap and excess electrical energy available, one or more electrolyzers in the hydrogen production system canbe operated at a higher capacity over hydrogen demand, where excessive hydrogen can be store in the hydrogen storage unit. The stored hydrogen can be provided to the fuel cell system to produce electrical energy when it is in seasons with low renewable energy availability or there is no cheap or excess electrical energy available.

[0037] According to an example of the disclosure, one or more electrolyzers in the hydrogen production system can be operated to produce an agreed amount of hydrogen for an industrial purpose or deliver of hydrogen through pipelines.

[0038] The subsystem 1A will be introduced in detail below. Each subsystem can be implemented in a similar manner, so descriptions of the subsystem 1A can also be applied to other subsystems.

[0039] With continuing reference to Figure 1, the converter module 121 is coupled to a DC bus or an AC bus (see the thick black solid line to which each converter module is coupled). The DC bus or the AC bus can be coupled to a grid connection (PCC) via a converter (CON) and a transformer (T). The DC bus or the AC bus can also be coupled to a battery energy storage system (BESS) via a converter (CON). The AC bus can also be coupled to a diesel generator (DG) via a transformer (T) and a converter (CON). In this way, the converter module 121 can obtain electrical energy from the grid, and also can obtain electrical energy from the BESS or the DG in the case of short-term power outage or insufficient power from the grid. The converter module 121 can include one or more converters and at least one of the one or more converters includes a controlled device (e.g., IGBT or MOSFET) or a semi-controlled device (e.g., thyristor), so that powering of the electrolyzer 111 can be controlled by operating the converter module 121. The converter module 121 can include a converter controller (not shown) to control the controlled device or the semi-controlled device of the converter module 121 according to apower set point received from the local controller 131.

[0040] The electrolyzer 111 can include one electrolysis stack or include multiple electrolysis stacks connected in series or in parallel. The electrolyzer 111 can include or is coupled to various sensors (not shown) for measuring a current, a voltage and a temperature of the electrolyzer 111, and purity of hydrogen produced by the electrolyzer 111. The electrolyzer 111 can include auxiliary devices (not shown). For example, the auxiliary devices can include a cooling device to adjust a temperature of the water to be input into the electrolyzer 111 and a pump to adjust a flow rate of cooling water flowing through the electrolyzer 111. It is noted that, in examples of the disclosure, the electrolyzer refers to a hydrogen electrolyzer. For example, the electrolyzer uses electricity to break water into hydrogen and oxygen in an electrolysis process. Through such an electrolysis process, the electrolyzer creates hydrogen gas.

[0041] The local controller 131 sends the electrolyzer state information on the state of the electrolyzer 111 to the system controller 140 and receives an internal dispatch value for the electrolyzer 111 from the system controller 140 via a wired or wireless communication bus (see the thin black solid line to which each local controller is coupled). Then, the local controller 131 generates set points according to the internal dispatch value to control the converter module 121 and the auxiliary devices (e.g., the pump and the cooling device) in the subsystem 1A. In this way, the local controller 131 manages the operation of individual devices in the subsystem 1A by determining set points to ensure best / optimal operation of the subsystem 1A.

[0042] The system controller 140 is in communication with an external node N and receives an external dispatch value from the external node N. The external node N can include one or more entities such as a DSO (Distribution System Operator), a TSO (Transmission System Operator)and an asset management system, and can also include one or more hydrogen users such as refinery or hydrogen refueling stations. The system controller 140 determines an internal dispatch value for each electrolyzer and sends the determined internal dispatch value to a local controller corresponding to the electrolyzer. For example, the system controller 140 sends the internal dispatch value determined for the electrolyzer 111 to the local controller 131, the internal dispatch value determined for the electrolyzer 112 to the local controller 132... the internal dispatch value determined for the electrolyzer 1 In to the local controller 13n.

[0043] It is noted that, although it is shown in Figure 1 that each subsystem includes one electrolyzer, one converter module and one local controller, according to examples of the disclosure, it can also be implemented as a subsystem including one converter module, multiple electrolyzers connected in series or parallel and one local controller for managing operations of the one converter module and multiple electrolyzers in the subsystem. According to examples of the disclosure, it can also be implemented as a subsystem including multiple converter modules, multiple electrolyzers and one local controller for managing operations of the multiple converter modules and the multiple electrolyzers.

[0044] Figure 2 shows a hydrogen production system 200 according to another embodiment of the disclosure. The hydrogen production system 200 includes a plurality of electrolyzers 211~21n, a plurality of converter modules 221~22n, a plurality of local controllers 231~23n and a system controller 240. In addition, the hydrogen production system 200 can include or be coupled to a hydrogen storage unit 250. At least one electrolyzer (e.g., the electrolyzer 211) is coupled to the hydrogen storage unit 250 so that at least part of hydrogen produced by the least one electrolyzer can be stored in the hydrogen storage unit 250. In an example, in peak seasons of renewable energy, excess hydrogen produced by theelectrolyzers in the hydrogen production system 200 can be transferred to the hydrogen storage unit 250 through a gas pipeline and stored in the hydrogen storage unit 250. As shown in Figure 2, the hydrogen production system 200 can include a plurality of subsystems2A~2N for hydrogen production. Each subsystem includes one of the electrolyzers 211~21n, one of the converter modules 221~22n, and one of the local controllers 231~23n.

[0045] In the hydrogen production system 200, the electrolyzers, the converter modules, the local and system controllers as well as the subsystems can be respectively implemented in a similar manner to that of the hydrogen production system 100, so the relevant description above can also be applied here. The hydrogen production system 200 differs from the hydrogen production system 100 in that each converter module is coupled to a renewable energy source (e.g., wind, solar, or geothermal) via a DC or AC bus (see the thick black solid line to which each converter module is coupled). Therefore, the hydrogen generated by the electrolyzers in the hydrogen production system 200 is green hydrogen. The green hydrogen can be provided to a fuel cell (FC) to generate electrical power, can be stored in the hydrogen storage unit 250 and can also be transmitted through a gas pipeline to hydrogen users, such as refinery or hydrogen refueling stations.

[0046] Figure 3 shows a hydrogen production system 300 according to yet another embodiment of the disclosure. The hydrogen production system 300 can be regarded as a combined system of the above-mentioned systems 100 and 200. The hydrogen production system 300 includes a first set of electrolyzers 111~1 In that are powered by a first electrical network (i.e., an electrical grid) and a second set of electrolyzers 211~21n that are powered by a second electrical network (i.e., renewable energy). The hydrogen production system 300 also includes a system controller 340 thatcommunicates with each of the local controllers 13 l~13n and 23 l~23n and determines an internal dispatch value for each of the electrolyzers 111-1 In and 211~21n. In the hydrogen production system 300, the electrolyzers, the converter modules, the local and system controllers as well as the subsystems can be respectively implemented in a similar manner to that of the hydrogen production system 100, so the relevant description above can also be applied here.

[0047] In an example, the hydrogen production system 300 also includes a switch SW arranged between the first electrical network and the second electrical network. When the switch SW is an ON state, electrical power can be transferred between the first electrical network and the second electrical network. For example, in the case of the switch being an ON state, when in peak seasons of renewable energy, renewable energy can be transferred to the first electrical network from the second electrical network, and when there is cheap and excess electrical energy available, electrical power can be transferred to the second electrical network from the first electrical network. When the switch SW is in an OFF state, electrical power cannot be transferred between the first electrical network and the second electrical network.

[0048] According to examples of another aspect of the disclosure, a control system for a hydrogen production system is provided. The control system includes a plurality of local controllers and a system controller (which can also be referred to as a plant controller). The hydrogen production system can be one of the above mentioned hydrogen production systems 100-300. In an example, the plurality of local controllers can be implemented by means of the plurality of local controllers 131~13n, and the system controller can be implemented by means of the system controller 140. In another example, the plurality of local controllers can be implemented by means of the plurality of local controllers 23 l~23n, andthe system controller can be implemented by means of the system controller 240. In yet another example, the plurality of local controllers can be implemented by means of the plurality of local controllers 131~13n and 231~23n, and the system controller can be implemented by means of the system controller 340.

[0049] It is noted that, according to examples of the disclosure, the local controllers and the system controller can be implemented by means of hardware or software or a combination of hardware and software, including code stored in a non-transitory computer-readable medium such as a memory and implemented as instructions executed by a processor. Regarding the part implemented by means of hardware, it may be implemented in an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a data signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microcontroller, a microprocessor, an electronic unit, or a combination thereof. The part implemented by software may include a microcode, a program code or code segments. The software may be stored in a machine-readable storage medium, such as a memory, or on the cloud.Example methods

[0050] Further to example systems described above, example methods are now described. It should be understood that the operations involved in the following methods need not be performed in the precise order described. Rather, various operations may be performed in a different order or simultaneously, and operations may be added or omitted.

[0051] A method 400 for controlling any of the above-mentioned hydrogen production systems 100-300 according to an embodiment of the present disclosure will be introduced with reference to Figure 4. The abovedescriptions for the hydrogen production systems 100-300 are also applicable here. In the below, the method 400 will be introduced using controlling the hydrogen production systems 100 as an example.

[0052] At block 402, the system controller 140 obtains electrolyzer state information of the electrolyzers 111-1 In, obtains system state information on a state of the hydrogen production system 100, and an external dispatch value.

[0053] At block 4021, the system controller 140 obtains the electrolyzer state information of the electrolyzers 111-1 In based on measured parameters and predetermined parameters of the electrolyzers 111-1 In. The electrolyzer state information includes first information on dynamic states of the electrolyzers 111-1 In that can be obtained based on the measured parameters and second information on predetermined states of the electrolyzers 111-1 In that can be obtained based on the predetermined parameters.

[0054] In an example, each of the local controllers 111-1 In receives measured parameters of an electrolyzer that measured by various sensors (not shown) included in or coupled to the electrolyzer. The measured parameters include an electrical parameter such as a current and a voltage of the electrolyzer, a thermal parameter such as a temperature of the electrolyzer and a gas parameter such a flow rate and purity of hydrogen output from the electrolyzer. The system controller 140 can obtain the first information by receiving the measured parameters from the local controllers 131~13n and determining the dynamic states of the electrolyzers 111-1 In based on the measured parameters. The system controller 140 can obtain the second information by receiving operating constraints on the electrolyzers 111-1 In from a server S.

[0055] Electrolyzer state-dynamic state

[0056] Examples of the dynamic state of an electrolyzer will beintroduced. The dynamic state of each electrolyzer includes one or more of the following states.1) An aging stateThe aging state of an electrolyzer can be determined based on an internal resistance of the electrolyzer and the internal resistance of the electrolyzer can be calculated based on the current and voltage of the electrolyzer and using an electrolyzer model included in the control system.2) An efficiency stateThe efficiency state of an electrolyzer can be determined based on the aging, temperature and load rate of the electrolyzer.3) An electrical connectivity stateThe electrical connectivity state of an electrolyzer includes a state in which the electrolyzer is connected to an electrical grid or a state in which the electrolyzer is connected to a renewable energy source. The electrical connectivity state of an electrolyzer also includes a state in which the electrolyzer can obtain electrical power from alternative sources such as a DG or a BESS.4) An availability stateThe availability state of an electrolyzer includes an available state in which the electrolyzer is not in maintenance and a power supply system and auxiliary devices of the electrolyzer are in a normal operation state such that the electrolyzer can be operated to produce hydrogen and an unavailable state in which the electrolyzer is in maintenance or the power supply system or auxiliary devices of the electrolyzer are in an abnormal state such that the electrolyzer cannot be operated to produce hydrogen. It is noted that, when the purity of the hydrogen output by an electrolyzer is lower than a predetermined purity threshold, the electrolyzer will be set to an unavailable state. The availability state of an electrolyzer also includesa reduced availability state in which the electrolyzer has a pre-scheduled or a pre-committed constrain of hydrogen usage.

[0057] It is noted that, in the case of the hydrogen production system 300, the electrical connectivity state can be changed by the switch SW in the hydrogen production system 300.

[0058] Electrolyzer state-predetermined state

[0059] The predetermined state of an electrolyzer includes one or more of: a pre-determined current range, a pre-determined voltage range, a predetermined load rate range and a pre-determined temperature range of the electrolyzer. These parameter ranges can be predetermined as operating constraints of the electrolyzer and stored in the server S.

[0060] At block 4022, the system controller 140 obtains the system state information on the state of the hydrogen production system 100.

[0061] System state

[0062] The system state of the hydrogen production system 100 can include one or more of: 1) a storage capacity state of the hydrogen storage unit 150 connected to at least one electrolyzer, and 2) a gas connectivity state relating to a gas pipeline network (not shown) connected to the hydrogen production system 100.

[0063] At block 4023, the system controller 140 receives an external dispatch value from the external node N. Examples of the external node N can be referred to the above relevant description. Examples of the external dispatch value are introduced in the below.

[0064] External dispatch value

[0065] In an example, the external dispatch value includes a value indicating total electrical power to be consumed from an electrical grid to power the selected one or more electrolyzers. The total electrical powercan be the electrical power available for the hydrogen production system 100 from the electrical grid. In another example, the external dispatch value includes a value indicating a hydrogen demand, that is, the hydrogen production to be produced by the selected one or more electrolzers. In yet another example, the external dispatch value includes both the value indicating the total electrical power to be consumed from an electrical grid and the value indicating a hydrogen demand. In yet another example, the external dispatch value includes a value indicating available renewable energy. In yet another example, the external dispatch value includes a value indicating electricity price. In this example, the electricity price will influence the external dispatch value. For example, the hydrogen production should increase when the electricity price is low and reduce when the electricity price is high.

[0066] It is noted that the external dispatch value can change over time. For example, the value indicating the electrical power available from the electrical grid can be a curve representing the available electrical power versus time.

[0067] At block 404, the system controller 140 selects one or more electrolyzers from the plurality of electrolyzers 111—1 In based on the electrolyzer state information. Then, the system controller 140 only dispatch power or hydrogen production among the selected electrolyzers. In an example, the system controller 140 selects the one or more electrolyzers that are in the available state based on the electrolyzer state information. In another example, the system controller 140 selects the least aged and most efficient one or more electrolyzers among the electrolyzers l l l l ln based on the electrolyzer state information. In yet another example, the system controller 140 selects the one or more electrolyzers that produce the highest hydrogen purity among the electrolyzers 111~1 In.

[0068] At block 406, the system controller 140 determines internaldispatch values for the selected one or more electrolyzers based on the external dispatch value and the electrolyzer state information. For example, the system controller 140 determines an internal dispatch value for each of the selected one or more electrolyzers based on the external dispatch value and the electrolyzer state information. In some examples, the system controller 140 determines the internal dispatch values further based on the system state information.

[0069] Internal dispatch value

[0070] In general, the system controller 140 determines the internal dispatch values such that each of the one or more electrolyzers is operated at a hydrogen production rate that minimizes the total energy to operate the hydrogen production system. Moreover, in the case that renewable power is available, the system controller 140 determines the internal dispatch values such that usage of renewable power is prioritized over usage of grid power to meet hydrogen production requirement and / or for hydrogen storage. Examples of the internal dispatch values are introduced in the below.

[0071] In an example, the internal dispatch values include values indicating power to be provided to each of the one or more electrolyzers. That is to say, the internal dispatch values are the values based on power distribution among the one or more electrolyzers. In another example, the internal dispatch values include values indicating hydrogen production to be produced by each of the one or more electrolyzers. That is to say, the internal dispatch values are the values based on hydrogen production distribution among the one or more electrolyzers. In yet another example, the internal dispatch values include values based on power distribution among one part of two or more electrolyzers and values based on hydrogen production distribution among another part of the two or more electrolyzers. In yet another example, the internal dispatch values include valuesindicating hydrogen production of green hydrogen to be produced by the one or more electrolyzers using renewable power and values indicating hydrogen production of hydrogen to be produced by the one or more electrolyzers using grid power. In yet another example, the internal dispatch values include values each indicating a hydrogen production rate of each of the one or more electrolyzers which corresponds to the efficiency of the electrolyzer.

[0072] At block 408, the system controller 140 sends the determined internal dispatch values to corresponding local controllers. For example, the system controller 140 sends each of the determined internal dispatch values to a corresponding local controller. For example, the system controller 140 determines the internal dispatch values for selected eletrolyzers 111 and 112, and then the system controller 140 sends the internal dispatch value determined for the electrolyzer 111 to the local controller 131 and sends the internal dispatch value determined for the electrolyzer 112 to the local controller 132.

[0073] At block 410, each of the corresponding local controllers determines set points for controlling the operation of an electrolyzer according to the internal dispatch value received from the system controller 140.

[0074] Set point

[0075] The set points can include a power set point for controlling the powering of the electrolyzer. The set points can also include a flow rate set point for controlling a flow rate of cooling water flowing through the electrolyzer. The set points can also include a temperature set point for controlling a temperature of the electrolyzer.

[0076] According to examples of the disclosure, the hydrogen production efficiency of an electrolyzer is related to the temperature of the electrolyzer, and thus the electrolyzer has the predetermined temperaturerange for operating at optimal efficiency. Moreover, the temperature of the electrolyzer is influenced by the flow rate of cooling water flowing through the electrolyzer. The local controller controls the temperature of the electrolyzer to be within the predetermined temperature range by means of the temperature set point, and controls the flow rate of the cooling water flowing through the electrolyzer by means of the flow rate set point such that the temperature of the electrolyzer reaches the temperature according to the temperature set point.

[0077] At block 412, each of the corresponding local controllers the operation of an electrolyzer controls according to the set points. For example, the local controller can send the power set point to a converter controller such that the converter controller controls the powering of the electrolyzer according to the power set point. The local controller can send the flow rate set point and the temperature set point to an electrolyzer controller that controls operations of auxiliary devices (e.g., a pump and a cooling device) of the electrolyzer such that the electrolyzer controller controls operations of the auxiliary devices according to the received set points.

[0078] Some examples of the method 400 are introduced below.

[0079] In general, the hydrogen production system could be either grid- connected in the industrial area or remotely located close to renewables such as PV and wind. In either case, the hydrogen production system needs to adjust operations of the electrolyzers comprised in the hydrogen production system coordinatively taking consideration of the energy price, available renewable power (wind, solar and hydro), and even the provision of grid ancillary services (A / S). In this manner, the hydrogen production system is operated at a large variable load and the hydrogen is produced at a lower price. Moreover, the TSO could have more dispatchable resource to stabilize the grid.

[0080] The hydrogen production system could be connected to transmission grid or remotely connected and coordinated with renewables (solar PV plant or wind farms). Hydrogen production of the system is based on the power demand which could be an optimized schedule considering energy price, renewables contribution, grid operators dispatching control for provision of A / S. As the hydrogen is the end product, the production is more flexible.

[0081] According to some examples, the hydrogen production system is connected to transmission grid, and the hydrogen production system is part of an industrial system including refineries (green steel) or chemical plants. In this case, hydrogen production is a demand target as it is required in other industrial processes, and hydrogen production has the flexibility depending on the available hydrogen storage.

[0082] According to some examples, the dispatching based on electrolyzer states is proposed to facilitate a better hydrogen production efficiency and to prolong and balance lifetime of the electrolyzers comprised in the hydrogen production system, rather than equally distribute the power demand or hydrogen demand to all electrolyzers, because electrolyzer states can be quite different in a large-scale electrolyzer plant. This could be due to reasons of (a) multi-phase large electrolyzer project, for example, a 2 -phase project where the electrolyzers in phase- 1 have already been operating for a year or two until phase -2 is completed; (b) replacement of faulty electrolyzers during operation; and (c) difference in electrolyzer degradations along with long-term usage at different operation conditions.

[0083] First example

[0084] In a first example, the external node N is a power supplier such as a power company. The external dispatch value is a value indicating a total electrical power Ptotai that the power company can provide to thehydrogen production system 100. The external dispatch value can be a curve representing variation of the total electrical power over time. For example, the curve represents variation of the total electrical power at different times of the day or in different months of a year.

[0085] In this example, the internal dispatch values are determined based on power distribution of the total electrical power among the plurality of electrolyzers 111-1 In. In this case, each internal dispatch value represents electrical power to be supplied to an electrolyzer and can be expressed as a percentage of the total electrical power. Such power distribution enables the total hydrogen production produced by the plurality of electrolyzers 111-1 In is maximized in the case that the total electrical power to be supplied to the plurality of electrolyzers 111-1 In is pre-fixed to the total electrical power. In this way, the efficiency of the hydrogen production system 100 can be improved.

[0086] In an example, a power distribution optimization model is used to implement the power distribution. The power distribution optimization model can include the following sub-models.1) Sub-model IThe sub- model I is expressed as the following function: the sum of electrical power consumed by the plurality of electrolyzers 111-1 In is equal to the total electrical power Ptotai.2) Sub-model IIThe sub- model II is expressed as the following function: the sum of currents of the plurality of electrolyzers 111-1 In is the maximized. Because the hydrogen production of an electrolyzer is positively related to its current, the sum of the currents being maximized is equivalent to the total hydrogen production of the plurality of electrolyzers 111-1 In being maximized.3) Sub-model IIIThe sub- model III is expressed as the following constraints: the current, voltage, power and load rate of each electrolyzer meet corresponding predetermined ranges according to the predetermined state of each electrolyzer.

[0087] Second example

[0088] In a second example, the external node N can be a hydrogen user such as a refinery or a hydrogenation station. The external dispatch value can be a hydrogen demand that the hydrogen user requires. For example, that external dispatch value is the total hydrogen production FQ total to be produced by the plurality of electrolyzer 111-1 In.

[0089] In this example, the internal dispatch value is determined based on hydrogen distribution of the total hydrogen production among the plurality of electrolyzers 111-1 In. In this case, the internal dispatch value for each electrolyzer represents the hydrogen production to be produced by the electrolyzer and can be expressed as a percentage of the total hydrogen production. Such hydrogen production distribution enables the total electrical power consumed by the plurality of electrolyzers 111-1 In is minimized in the case that the total hydrogen production to be produced by the plurality of electrolyzers 111-1 In is pre-fixed to the total hydrogen production H2 total.

[0090] In an example, a hydrogen production distribution optimization model is used to implement the hydrogen distribution. The hydrogen production distribution optimization model can include the following submodels.

[0091] 1) Sub-model I

[0092] The sub- model I is expressed as the following function: the sum of hydrogen production to be produced by the plurality of electrolyzersl l l-l ln is equal to the total hydrogen production H2_total. Because the hydrogen production of an electrolyzer is positively related to its current, this sub-model can also be expressed as the sum of currents of the electrolyzers 111-1 In is equivalent to a predetermined value corresponding to the total hydrogen production H2_total.

[0093] 2) Sub-model II

[0094] The sub- model II is expressed as the following function: the total electrical power consumed by the plurality of electrolyzers 111-1 In is minimized.

[0095] 3) Sub-model III

[0096] The sub- model III is expressed as the following constraints: the current, voltage, power and load rate of each electrolyzer meet corresponding predetermined ranges according to the predetermined state of each electrolyzer.

[0097] Third example

[0098] In a third example, the external dispatch value includes both a value indicating a total electrical power Ptotai to the hydrogen production system 100 and a value indicating a hydrogen demand. This situation may occur when the system controller 140 receives the external dispatch value from both electrical power utilities and hydrogen users. In this situation, the hydrogen storage unit / process can be used to balance the electrical power supply with the hydrogen demand. For example, when the hydrogen produced by the total electrical power Ptotai cannot meet the hydrogen demand, the hydrogen stored in the hydrogen storage unit is used to ensure the hydrogen demand can be met. In another example, when electricity price is cheap and the hydrogen production that produced by using the total electrical power Ptotai is greater than the hydrogen demand, the excess hydrogen can stored in the hydrogen storage unit.

[0099] It is noted that the power distribution solution according to the first example and the hydrogen production distribution solution according to the second example are applicable to this example. That is, the first or second example can be implemented in combination with the third example.

[0100] Fourth example

[0101] In a fourth example, the use of renewable energy is maximized to produce hydrogen. This example is described below with reference to Figure 3.

[0102] In a case where the available renewable energy is enough for producing the demand hydrogen, the electrolyzers 211-2 In powered by renewable energy are operated to produce green hydrogen, and the electrolyzers 111-1 In powered by grid power are not operated to produce hydrogen.

[0103] In a case where the available renewable energy is not enough for producing the demand hydrogen, the electrolyzers 211-2 In are operated to produce green hydrogen by making the most use of the available renewable energy, and the electrolyzers 111-1 In powered by grid power are operated to produce hydrogen, such that the total hydrogen produced by the electrolyzers 111-1 In and the electrolyzers 211-2 In can meet the demand hydrogen.

[0104] It is noted that the power distribution solution according to the first example and the hydrogen distribution solution according to the second example are applicable to this example. That is, the first or second example can be implemented in combination with the fourth example.

[0105] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to otheraspects. Thus, the claims are not intended to be limited to the aspects shown herein. All structural and functional equivalent transformations to the elements of the various aspects of the present disclosure, which are known or to be apparent to those skilled in the art, are intended to be covered by the claims.

Claims

WHAT IS CLAIMED IS:

1. A control system for a hydrogen production system, the hydrogen production system comprising a plurality of electrolyzers and a plurality of converter modules each of which is coupled to one or more of the plurality of electrolyzers, the control system comprising: a plurality of local controllers each of which is coupled with one or more of the plurality of converter modules and one more of the plurality of the electrolyzers; and a system controller in communication with the plurality of local controllers, wherein the system controller is configured to receive an external dispatch value and electrolyzer state information regarding states of the plurality of electrolyzers, and to determine internal dispatch values for one or more electrolyzer from the plurality of electrolyzers based on the external dispatch value and the electrolyzer state information, and wherein at least one local controller from the plurality of local controllers associated with the one or more electrolyzers is configured to receive the internal dispatch values from the system controller, and to control operations of the one or more electrolyzers according to the internal dispatch values.

2. The control system of claim 1, wherein the state of each electrolyzer comprises a dynamic state and a predetermined state of the electrolyzer.

3. The control system of claim 2, wherein the dynamic state of the electrolyzer comprises one or more of:- an aging state determined based on at least one of a current, a voltage, and an internal resistance of the electrolyzer;- an efficiency state determined based on at least one of a temperature and a load rate of the electrolyzer;- an electrical connectivity state determined based on the connection of the electrolyzer to an electrical grid and / or an alternative source including renewable sources; and- an availability state comprising an available state in which the electrolyzer can be operated to produce hydrogen and an unavailable state in which the electrolyzer can not be operated to produce hydrogen.

4. The control system of any of claims 2-3, wherein the predetermined state of the electrolyzer comprises one or more of a pre-determined current range, a pre-determined voltage range, a pre-determined load rate range and a predetermined temperature range of the electrolyzer.

5. The control system any of any of claims 1-4, wherein the system controller is configured to determine the internal dispatch values further based on a system state of the hydrogen production system, and the system state comprises one or more of:-a storage capacity state of a hydrogen storage unit connected to at least one electrolyzer; and- a gas connectivity state relating to a gas pipeline network connected to at least one electrolyzer.

6. The control system of any of claims 1-5, wherein the external dispatch value comprises at least one of: a value indicating total electrical power to be consumed from an electrical grid to power the one or more electrolyzers comprised in the hydrogen production system, anda value indicating a total amount of hydrogen production to be produced by the one or more electrolzers comprised in the hydrogen production system.

7. The control system of any of claims 1-6, wherein the internal dispatch values comprise at least one of: values indicating electrical power to be provided to each of the one or more electrolyzers ; and values indicating hydrogen production to be produced by each of the one or more electrolyzers.

8. The control system of any of claims 1-7, wherein the internal dispatch values comprise:- a value indicating an amount of green hydrogen production to be produced by using renewable power; and / or- a value indicating an amount of hydrogen production to be produced by using grid power.

9. The control system of any of claims 1-8, wherein the system controller is further configured to, before determining the internal dispatch values, select the one or more electrolyzers from the plurality of electrolyzers based on the electrolyzer state information.

10. The control system of any of claims 1-9, wherein said at least one local controller associated with the one or more electrolyzers is configured to determine set points for controlling the operations of the one or more electrolyzers according to the internal dispatch values.

11. The control system of claim 10, wherein the set points comprises at least one of:- a power set point for controlling the powering of each of the one or more electrolyzers; and- a hydrogen set point for controlling the hydrogen production to be produced by each of the one or more electrolyzers.

12. The control system of claim 11, wherein the set points further comprise one or more of the following set points for the operation of each of the one or more electrolyzers when each of the one or more electrolyzers is operated based on the power set point and / or the hydrogen set point:- a flow rate set point for controlling a flow rate of cooling water flowing through the electrolyzer; and- a temperature set point for controlling the temperature of the electrolyzer.

13. A hydrogen production system comprising a plurality of electrolyzers; a plurality of converter modules each of which is coupled to one or more of the plurality of electrolyzers; a plurality of local controllers each of which is coupled with one or more of the plurality of converter modules and one more of the plurality of the electrolyzers; and a system controller in communication with the plurality of local controllers, wherein the system controller is configured to receive an external dispatch value and electrolyzer state information regarding states of theplurality of electrolyzers, and to determine internal dispatch values for one or more electrolyzer from the plurality of electrolyzers based on the external dispatch value and the electrolyzer state information, and wherein at least one local controller from the plurality of local controllers associated with the one or more electrolyzers is configured to receive the internal dispatch values from the system controller, and to control operations of the one or more electrolyzers according to the internal dispatch values.

14. The hydrogen production system of claim 13, wherein the plurality of electrolyzers comprises: a first set of electrolyzers powered by a first electrical network coupled to a power grid; and a second set of electrolyzers powered by a second electrical network coupled to a renewable energy source.

15. The hydrogen production system of claim 14, wherein the first electrical network is coupled to a fuel cell system which produces electrical power for the first electrical network by using hydrogen output from at least one of the plurality of electrolyzers.

16. The hydrogen production system of claim 14, wherein at least one of the first set of electrolyzers is coupled to a first hydrogen storage unit; and / or at least one of the second set of electrolyzers is coupled to a second hydrogen storage unit.

17. The hydrogen production system of claim 14, wherein the hydrogenproduction system further comprises a switch coupled between the first electrical network and the second electrical network to allow electrical power to be transferred between the first electrical network and the second electrical network.

18. A method for controlling the hydrogen production system of any of claims 13-17, comprising: receiving an external dispatch value and electrolyzer state information regarding states of the plurality of electrolyzers; selecting one or more electrolyzers from the plurality of electrolyzers based on the electrolyzer state information; determining internal dispatch values for the one or more electrolyzers based on the external dispatch value and the electrolyzer state information; and controlling operations of the one or more electrolyzers according to the internal dispatch values.

19. The method of claim 18, further comprising: determining the internal dispatch values such that usage of renewable power is prioritized over usage of grid power to meet a hydrogen production demand and / or for hydrogen storage.

20. The method of claim 18, further comprising: determining the internal dispatch values such that the one or more electrolyzers are operated to meet predetermined hydrogen production or storage demand and to minimize energy to operate the hydrogen production system.

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