Control method of water electrolysis system, and water electrolysis system

Abstract

To provide a control method of a water electrolysis system in which each operational state of multiple electrolysis stacks can be independently adjusted with high response and high efficiency.SOLUTION: Provided is a control method of a water electrolysis system comprising: an electrolysis stack for generating hydrogen and oxygen by electrolyzing water; a pure water supply device for supplying a pure water to the electrolysis stack; a first adjustment unit and a second adjustment unit, each of which is arranged between the electrolysis stack and the pure water supply device and is able to adjust the operational state of the electrolysis stack; and an operational state adjusting control unit that can adjust the operational state of the electrolysis stack by adjusting the first adjustment unit and the second adjustment unit. The operational state adjusting control unit operates the first adjustment unit based on the operational state after receiving the change order of the operational state of the electrolysis stack, and operates the second adjustment unit at the same time as the first adjustment unit based on the operational state when predetermined conditions are satisfied.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method for controlling a water electrolysis system and a water electrolysis system. [Background technology]

[0002] Unlike fossil fuels, hydrogen is a clean energy source that does not emit carbon dioxide when burned. For this reason, hydrogen has attracted attention as one of the clean energy sources needed to achieve carbon neutrality, and technological development is underway regarding the production, transportation, and use of hydrogen. In particular, because hydrogen can be produced anywhere by electrolyzing water, water electrolysis systems that can produce hydrogen by water electrolysis are attracting attention as a means of reducing energy imports and improving energy self-sufficiency. Plans are underway to introduce such water electrolysis systems on a large scale, primarily in Europe.

[0003] The basic structure of a water electrolysis system is an electrolytic cell (electrolysis stack) that performs water electrolysis, a power supply (e.g., a rectifier) ​​that supplies DC power to the electrolysis stack, and the power supply is connected to the power grid via a transformer. In addition, a device (defined as a pure water adjustment device in this book) is installed to supply pure water for electrolyzing water in the electrolysis stack, and to recover not only the hydrogen and oxygen generated in the electrolysis stack but also the pure water that was not used in electrolysis. The pure water adjustment device is equipped with a device for adjusting the pressure and flow rate of the pure water supplied to the electrolysis stack. The configuration and operation method of the water electrolysis system described above are disclosed in Patent Document 1, for example.

[0004] The water electrolysis system disclosed in Patent Document 1 includes multiple electrolysis stacks connected in series to a DC power supply, a water pump that supplies water to all of the series-connected electrolysis stacks, a large cooler that adjusts the temperature of the water supplied to all of the electrolysis stacks, a water flow control valve and a small cooler provided in a water supply pipe between the water pump or the large cooler and the electrolysis stacks, and a controller that controls the water pump, the large cooler, the small cooler, and the water flow control valve. The controller adjusts the amount of water supplied to each electrolysis stack with the water flow control valve and adjusts the temperature of the water supplied to each electrolysis stack with the small cooler. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2023 / 012944 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 discloses a water electrolysis system in which a water flow control valve and a small cooler are provided in each electrolysis stack to adjust the flow rate and temperature of pure water supplied to the electrolysis stacks, and a method for adjusting the water flow control valve and the small cooler to adjust the state of each electrolysis stack. However, Patent Document 1 only discloses a method for adjusting static characteristics, and does not disclose a method for transient adjustment of the water flow control valve and the small cooler to adjust dynamic characteristics. If this transient state is not adjusted appropriately, problems such as reduced efficiency and slow responsiveness may arise, such as flow loss due to adjustment of the water flow control valve, reduced efficiency due to increased load on the water pump to eliminate the decrease in flow rate caused by this increased flow loss, and time required to adjust the temperature using a small cooler.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a water electrolysis system control method and a water electrolysis system that are capable of independently adjusting the states of multiple electrolysis stacks with high response and high efficiency.

[0008] The above and other objects of the present invention and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0009] A method for controlling a water electrolysis system of the present invention is a method for controlling a water electrolysis system including an electrolysis stack that electrolyzes water to generate hydrogen and oxygen, a pure water supply device that supplies pure water to the electrolysis stack, a first adjustment unit installed between the electrolysis stack and the pure water supply device and capable of adjusting the operating state of the electrolysis stack, a second adjustment unit installed between the electrolysis stack and the pure water supply device and capable of adjusting the operating state of the electrolysis stack, and an operating state adjustment control unit that adjusts the first adjustment unit and the second adjustment unit to adjust the operating state of the electrolysis stack, wherein the operating state adjustment control unit operates the first adjustment unit based on the operating state after receiving a command to change the operating state of the electrolysis stack, and operates the second adjustment unit simultaneously with the first adjustment unit based on the operating state when a predetermined condition is satisfied.

[0010] The water electrolysis system of the present invention includes an electrolysis stack that electrolyzes water to generate hydrogen and oxygen, a pure water supply device that supplies pure water to the electrolysis stack, a first adjustment unit that is installed between the electrolysis stack and the pure water supply device and is capable of adjusting the operating state of the electrolysis stack, a second adjustment unit that is installed between the electrolysis stack and the pure water supply device and is capable of adjusting the operating state of the electrolysis stack, and an operating state adjustment control unit that adjusts the first adjustment unit and the second adjustment unit to adjust the operating state of the electrolysis stack, wherein the operating state adjustment control unit operates the first adjustment unit based on the operating state after receiving a command to change the operating state of the electrolysis stack, and operates the second adjustment unit simultaneously with the first adjustment unit based on the operating state when a predetermined condition is satisfied. [Effects of the Invention]

[0011] According to the present invention, the states of a plurality of electrolysis stacks can be independently adjusted with high response and high efficiency, and the states of the plurality of electrolysis stacks can be set to appropriate states.

[0012] Problems, configurations, and effects other than those described above will become clear from the following description of the embodiments. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing the device configuration of a water electrolysis system according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing a configuration of a pure water adjusting apparatus according to an embodiment of the present invention; [Figure 3] FIG. 1 is a diagram showing an apparatus configuration of an electrolysis stack group according to an embodiment of the present invention. [Figure 4] FIG. 2 is a control block diagram illustrating an electrolytic stack operation state adjustment control unit implemented in a controller according to an embodiment of the present invention. [Figure 5] FIG. 2 is a diagram illustrating a first adjustment unit that adjusts the operating state of the electrolysis stack according to the embodiment of the present invention. [Figure 6] FIG. 2 is a diagram illustrating a second adjustment unit that adjusts the operating state of the electrolysis stack according to an embodiment of the present invention. [Figure 7] FIG. 2 is a control block diagram of an electrolytic stack operating state adjustment control unit in the first embodiment. [Figure 8] 4 is a time chart showing how the electrolytic stack operational state adjustment control unit adjusts the temperature of the electrolytic stack in the first embodiment. [Figure 9] FIG. 2 is a control block diagram illustrating a case in which an electrolytic stack operational state adjustment control unit determines a target temperature value of the electrolytic stack for adjusting a deterioration state of the electrolytic stack in the first embodiment. [Figure 10] FIG. 10 is a control block diagram of an electrolytic stack operating state adjustment control unit in a second embodiment. [Figure 11]10 is a time chart showing how the electrolytic stack operational state adjustment control unit adjusts the voltage of the electrolytic stack in the second embodiment. [Figure 12] FIG. 11 is a control block diagram of an electrolytic stack operating state adjustment control unit in a third embodiment. [Figure 13] 10 is a time chart showing how the electrolytic stack operation state adjustment control unit adjusts the current of the electrolytic stack in the third embodiment. [Figure 14] 10 is a time chart illustrating how the electrolytic stack operation state adjustment control unit independently controls a plurality of heat exchangers and a plurality of flow rate adjustment valves to independently control the states of a plurality of electrolytic stacks in the fourth embodiment. [Figure 15] FIG. 2 is a control block diagram showing a configuration of an electrolytic stack operation state adjustment control unit according to an embodiment of the present invention. [Figure 16] 4 is a flowchart showing an operation process of an electrolytic stack operation state adjustment control unit according to the embodiment of the present invention. [Figure 17] 5 is a time chart showing how the electrolytic stack operation state adjustment control unit according to the embodiment of the present invention adjusts only the heat exchanger. [Figure 18] 4 is a time chart showing how the electrolytic stack operation state adjustment control unit adjusts only the flow rate adjustment valve according to the embodiment of the present invention. [Figure 19] 10 is a time chart showing how the electrolytic stack operation state adjustment control unit according to the embodiment of the present invention simultaneously operates a flow control valve and a device located upstream of a heat exchanger. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and the like. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications are possible by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, parts having the same function are designated by the same reference numerals, and repeated explanations thereof may be omitted.

[0015] <Water electrolysis system> 1 is a diagram showing the device configuration of a water electrolysis system 100 according to an embodiment of the present invention. In the water electrolysis system 100, an electrolysis stack group 11 is connected to a DC connection end 12b of a power converter 12, and pure water is electrolyzed into hydrogen and oxygen in accordance with the current applied from the power converter 12 to the electrolysis stack group 11. Furthermore, the pure water adjustment device 13 is connected to the electrolysis stack group 11 by three pipes 13a, 13b, and 13c. Pure water is supplied through the pipe 13a. Hydrogen generated in the electrolysis stack group 11 and pure water not used for water electrolysis are collected through the pipe 13b. Oxygen generated in the electrolysis stack group 11 and pure water not used for water electrolysis are collected through the pipe 13c. The water electrolysis system 100 further includes a controller 15 (control device). The controller 15 detects the operating states of the electrolysis stack group 11, the power converter 12, and the pure water preparation device 13 and adjusts the operating states.

[0016] The controller 15 is configured to include, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. The controller 15 is realized by a predetermined program (control program) stored in the ROM being loaded into the RAM and executed by the CPU. The program here is for causing a computer to execute a control method.

[0017] The water electrolysis system 100 has a configuration in which a transformer 6 is connected to an AC connection end 12a of a power converter 12, the transformer 6 is connected to a switch 3, and the switch 3 is connected to a grid 4. By adjusting the power converter 12, power is supplied from the grid 4 to the components of the water electrolysis system 100.

[0018] The controller 15 included in the water electrolysis system 100 has a function of receiving information output from an external device 5. The external device 5 may be, for example, a power supply facility or a power consumption facility installed in the vicinity of the water electrolysis system 100, a control device that comprehensively manages the power supply facility or the power consumption facility, an instruction from an organization that manages the state of a wide-area power grid, or electricity market trading information (electricity market information), for example, a spot electricity price.

[0019] Furthermore, the controller 15 also has a function of incorporating external information such as the voltages of the water electrolysis system 100 and the grid 4, and determines the operating state of the water electrolysis system 100 based on various pieces of information.

[0020] FIG. 2 is a diagram showing the configuration of the pure water preparation device 13 that constitutes the water electrolysis system 100. A valve 135 capable of adjusting the flow rate is connected to a pipe 13b through which hydrogen and pure water discharged from the electrolysis stack group 11 are transported. A gas-liquid separator 131 that separates hydrogen from pure water is connected downstream of the valve 135. A pure water tank 138 that stores pure water discharged from the gas-liquid separator 131 is connected downstream of the gas-liquid separator 131. A water pump 139 that transports the pure water under pressure is connected downstream of the pure water tank 138. A heat exchanger 1310 that adjusts the temperature of the pure water supplied to the electrolysis stack group 11 and a valve 137 that adjusts the flow rate of the pure water supplied to the electrolysis stack group 11 are connected downstream of the water pump 139, and the pure water is supplied to the electrolysis stack group 11 via a pipe 13a. A pressure adjustment valve 132 is connected to the gas-liquid separator 131, which adjusts the internal pressure of the gas-liquid separator 131 and supplies hydrogen to the outside of the water electrolysis system 100 via a pipe 132a. A valve 136 capable of adjusting the flow rate is connected to a pipe 13c through which oxygen and pure water discharged from the electrolysis stack group 11 are transported. A gas-liquid separator 133 that separates oxygen from pure water is connected downstream of the valve 136. The pure water discharged from the gas-liquid separator 133 is transported to a pure water tank 138. A pressure adjustment valve 134 is connected to the gas-liquid separator 133, which adjusts the internal pressure of the gas-liquid separator 133 and supplies oxygen to the outside of the water electrolysis system 100 via a pipe 134a.

[0021] FIG. 3 is a diagram showing the device configuration of the electrolysis stack group 11. In this embodiment, four electrolysis stacks #1, #2, #3, and #4 (111, 112, 113, and 114) are provided. The electrolytic stack #1 (111) and the electrolytic stack #2 (112) are electrically connected in series, and the electrolytic stack #3 (113) and the electrolytic stack #4 (114) are connected in series. Furthermore, a pair of the two electrolytic stacks connected in series is connected in parallel and connected to the DC side connection terminal 12b of the power converter 12. The four electrolysis stacks 111, 112, 113, and 114 are provided with first adjustment units 11a1, 11a2, 11a3, and 11a4 and second adjustment units 11b1, 11b2, 11b3, and 11b4, respectively, which are connected between the pipe 13a and the electrolysis stacks. Furthermore, two outlets for discharging gas generated from the four electrolysis stacks 111, 112, 113, and 114 and pure water not used in the water electrolysis reaction are connected to pipes 13b and 13c, respectively.

[0022] The electrolysis stacks 111, 112, 113, and 114 constituting the electrolysis stack group 11 can be broadly divided into alkaline and solid polymer electrolysis stacks. In this embodiment, it is assumed that solid polymer electrolysis stacks are used for the electrolysis stacks 111, 112, 113, and 114. The solid polymer electrolysis stacks have a faster response speed than the alkaline electrolysis stacks, and are therefore suitable for a water electrolysis system that follows fluctuations in renewable energy. Furthermore, the size of the solid polymer electrolysis stack can be made smaller than that of the alkaline electrolysis stacks, and therefore the solid polymer electrolysis stacks are suitable for a system that requires space-saving installation, such as offshore installation near an offshore wind power generation system.

[0023] FIG. 4 is a control block diagram showing the electrolytic stack operation state adjustment control unit 151 implemented in the controller 15. As shown in FIG. 4, the controller 15 includes an electrolytic stack operation state adjustment control unit 151. Then, the electrolytic stack operation state adjustment control unit 151 receives as input the target state values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) and the measured state values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114). Furthermore, the electrolytic stack operating state adjustment control unit 151 outputs command values ​​to the first adjustment units 11a1, 11a2, 11a3, and 11a4 (heat exchangers 21) and the second adjustment units 11b1, 11b2, 11b3, and 11b4 (flow rate adjustment valves 22). The target state values ​​and measured state values ​​of the electrolytic stacks #1, #2, #3, and #4 are target values ​​and measured values ​​of the states (for example, temperature, voltage, current, etc., which will be described later) of the electrolytic stacks #1, #2, #3, and #4.

[0024] FIG. 5 is a diagram showing first adjustment units 11a1, 11a2, 11a3, and 11a4 that adjust the operating state of the electrolysis stack. Hereinafter, the first adjustment units 11a1, 11a2, 11a3, and 11a4 are configured to include a heat exchanger 21 shown in FIG. 5 that is capable of adjusting temperature, and the heat exchanger 21 adjusts the temperature of the pure water supplied to the electrolysis stacks 111, 112, 113, and 114.

[0025] FIG. 6 is a diagram showing second adjustment units 11b1, 11b2, 11b3, and 11b4 that adjust the operating state of the electrolysis stack. Hereinafter, the second adjustment units 11b1, 11b2, 11b3, and 11b4 are configured to include a flow rate adjustment valve 22 shown in FIG. 6 that is capable of adjusting the flow rate, and the flow rate of the pure water supplied to the electrolysis stacks 111, 112, 113, and 114 is adjusted by this flow rate adjustment valve 22.

[0026] Below, specific configurations and methods for adjusting the operating states of multiple electrolysis stacks using heat exchangers and flow control valves are described as several embodiments. Note that it is assumed that the electrolysis stack has a characteristic in which the electrical resistance associated with the water electrolysis reaction changes with temperature, and the electrical resistance during the water electrolysis reaction in the electrolysis stack decreases when the temperature of the electrolysis stack is high.

[0027] <<Adjusting the temperature state of the electrolysis stack (first embodiment)>> Hereinafter, a case where the temperature state of the electrolysis stack is adjusted (first embodiment) will be described with reference to FIGS. FIG. 7 is a control block diagram of the electrolytic stack operation state adjustment control unit 151 implemented in the controller 15 in the first embodiment. This embodiment is an example of an operation in which the temperature of the electrolysis stack is controlled as the operating state of the electrolysis stack. In this embodiment, a sensor (temperature sensor) (not shown) is provided for each of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) of the electrolytic stack group 11 to measure the temperature of the electrolytic stacks #1, #2, #3, #4. As shown in FIG. 7, the electrolytic stack operation state adjustment control unit 151 receives as input the temperature target values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) and the temperature measurement values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) measured by the sensors (temperature sensors). Furthermore, the electrolytic stack operating state adjustment control unit 151 outputs command values ​​to the first adjustment units 11a1, 11a2, 11a3, and 11a4 (heat exchangers 21) and the second adjustment units 11b1, 11b2, 11b3, and 11b4 (flow rate adjustment valves 22).

[0028] 8 is a time chart showing how the electrolytic stack operation state adjustment control unit 151 adjusts the temperature of the electrolytic stack #1 (111) in the first embodiment. The horizontal axis represents time, and the vertical axis represents, from the top of the figure, the temperature of the electrolytic stack #1 (111), the state of the heat exchanger 11a1, and the state of the flow control valve 11b1, respectively, with the top of the figure representing high temperature, high heat exchanger output, and open flow control valve, respectively. In the state that has continued since time t0, after the temperature command value changes at time t1 to increase the temperature, the heat exchanger 11a1 increases its output to increase the temperature of the pure water, and the flow control valve 11b1 changes in the direction of closing the valve to reduce the flow rate of the pure water and increase the temperature. From time t1, as the difference between the measured temperature value and the target temperature value decreases, the output of heat exchanger 11a1 is gradually reduced, and flow rate adjustment valve 11b1 is opened. After that, after time t2 when the difference between the target temperature value and the measured temperature value becomes sufficiently small, the output of heat exchanger 11a1 is set to a medium level in accordance with the target temperature value, but the opening of flow control valve 11b1 is increased to the same open state as at time t0.

[0029] The output of the heat exchanger 11a1 is rapidly increased between times t1 and t2 in an attempt to rapidly increase the temperature of the electrolysis stack #1, but it takes time for the temperature of the pure water to increase. Therefore, by closing the flow rate control valve 11b1, the flow rate of the pure water is reduced, reducing the amount of heat that the pure water removes from the electrolysis stack #1, allowing the temperature of the electrolysis stack #1 to change with high responsiveness. Furthermore, by keeping the opening of the flow control valve 11b1 at the same level as at time t0 after time t2, the flow rate loss caused by the flow control valve 11b1 can be reduced, making it unnecessary to increase the output of the pump 139 upstream of the flow control valve 11b1 in accordance with the flow rate loss, thereby suppressing a decrease in efficiency. Furthermore, after time t2, the output of the heat exchanger 11a1 is set to medium, so that the target temperature value and the measured temperature value of the electrolysis stack #1 coincide with each other.

[0030] FIG. 9 is a control block diagram illustrating a case where the electrolytic stack operation state adjustment control unit 151 determines the target temperature value of the electrolytic stack for adjusting the deterioration state of the electrolytic stacks 111, 112, 113, and 114. In this case, the electrolytic stack deterioration state adjustment control unit 152 shown in FIG. 9 determines the temperature target values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) to be input to the electrolytic stack operation state adjustment control unit 151. 9 , the target deterioration levels of the electrolytic stacks #1, #2, #3, and #4 and the estimated deterioration levels of the electrolytic stacks #1, #2, #3, and #4 are input to the electrolytic stack deterioration state adjustment control unit 152. The electrolytic stack deterioration state adjustment control unit 152 determines the target temperature values ​​of the electrolytic stacks #1, #2, #3, and #4 (111, 112, 113, and 114) based on the target deterioration levels or the estimated deterioration levels. For example, if the deterioration state of electrolytic stacks #1, #2, #3, and #4 (111, 112, 113, and 114) is likely to deviate significantly from the average deterioration state of the multiple electrolytic stacks, or if it deviates significantly, the target temperature value is set lower than normal to suppress the progression of deterioration. Also, for example, if the deterioration of the electrolytic stacks #1, #2, #3, and #4 (111, 112, 113, and 114) is progressing slowly, the target temperature value is set to increase in order to accelerate the progression of the deterioration.

[0031] <<Adjusting the voltage state of the electrolysis stack (second embodiment)>> Hereinafter, a case where the voltage state of the electrolysis stack is adjusted (second embodiment) will be described with reference to FIGS. FIG. 10 is a control block diagram of the electrolytic stack operation state adjustment control unit 151 implemented in the controller 15 in the second embodiment. This embodiment is an example of an operation in which the voltage of the electrolysis stack is controlled as the operating state of the electrolysis stack. In this embodiment, a sensor (voltage sensor) (not shown) is provided for each of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) of the electrolytic stack group 11 to measure the voltage of the electrolytic stacks #1, #2, #3, #4. As shown in FIG. 10, the electrolytic stack operation state adjustment control unit 151 receives as input the target voltage values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) and the voltage measurement values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) measured by the sensors (voltage sensors). Furthermore, the electrolytic stack operating state adjustment control unit 151 outputs command values ​​to the first adjustment units 11a1, 11a2, 11a3, and 11a4 (heat exchangers 21) and the second adjustment units 11b1, 11b2, 11b3, and 11b4 (flow rate adjustment valves 22).

[0032] FIG. 11 is a time chart showing how the electrolysis stack operation state adjustment control unit 151 adjusts the voltage of the electrolysis stack #1 (111) in the second embodiment. The horizontal axis represents time, and the vertical axis represents, from the top of the figure, the voltage of the electrolysis stack #1 (111), the state of the heat exchanger 11a1, and the state of the flow control valve 11b1, with the top representing high voltage, high heat exchanger output, and open flow control valve, respectively. Note that FIG. 11 assumes that the temperature of the pure water supplied to the electrolysis stack 111 is increased to reduce the voltage of the electrolysis stack 111. In the state that has continued since time t0, after the voltage command value changes to lower the voltage at time t1, the heat exchanger 11a1 increases its output to raise the temperature of the pure water, and the flow control valve 11b1 changes in the direction of closing the valve to reduce the flow rate of the pure water and raise its temperature. From time t1, as the difference between the measured voltage value and the target voltage value decreases, the output of heat exchanger 11a1 is gradually reduced, and flow rate adjustment valve 11b1 is opened. After that, after time t2 when the difference between the target voltage value and the measured voltage value becomes sufficiently small, the output of heat exchanger 11a1 is set to a medium level in accordance with the target voltage value, but the opening of flow control valve 11b1 is increased to the same open state as at time t0.

[0033] The output of the heat exchanger 11a1 is rapidly increased between times t1 and t2 in an attempt to rapidly increase the temperature of the electrolysis stack #1, but it takes time for the temperature of the pure water to increase. Therefore, by closing the flow rate control valve 11b1, the flow rate of the pure water is reduced, reducing the amount of heat that the pure water removes from the electrolysis stack #1, allowing the temperature of the electrolysis stack #1 to change with high responsiveness. Furthermore, by keeping the opening of the flow control valve 11b1 at the same level as at time t0 after time t2, the flow rate loss caused by the flow control valve 11b1 can be reduced, making it unnecessary to increase the output of the pump 139 upstream of the flow control valve 11b1 in accordance with the flow rate loss, thereby suppressing a decrease in efficiency. Furthermore, after time t2, the output of the heat exchanger 11a1 is set to medium, so that the target voltage value and the measured voltage value of the electrolysis stack #1 coincide with each other.

[0034] This embodiment aims to adjust the efficiency of the water electrolysis system 100 by reducing a voltage difference that occurs between electrolysis stacks #1 (111) and #2 (112), which are electrically connected in series, by reducing the voltage difference, for example.

[0035] <<Adjusting the Current State of the Electrolysis Stack (Third Embodiment)>> Hereinafter, a case where the current state of the electrolysis stack is adjusted (third embodiment) will be described with reference to FIGS. 12 and 13. FIG. FIG. 12 is a control block diagram of the electrolytic stack operation state adjustment control unit 151 implemented in the controller 15 in the third embodiment. This embodiment is an example of an operation in which the current of the electrolysis stack is controlled as the operating state of the electrolysis stack. In this embodiment, a sensor (current sensor) (not shown) is provided for each of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) of the electrolytic stack group 11 to measure the current of the electrolytic stacks #1, #2, #3, #4. As shown in FIG. 12, the electrolytic stack operation state adjustment control unit 151 receives as input the target current values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) and the measured current values ​​of the electrolytic stacks #1, #2, #3, #4 (111, 112, 113, 114) measured by the sensors (current sensors). Furthermore, the electrolytic stack operating state adjustment control unit 151 outputs command values ​​to the first adjustment units 11a1, 11a2, 11a3, and 11a4 (heat exchangers 21) and the second adjustment units 11b1, 11b2, 11b3, and 11b4 (flow rate adjustment valves 22).

[0036] FIG. 13 is a time chart showing how the electrolysis stack operation state adjustment control unit 151 adjusts the current of the electrolysis stack #1 (111) in the third embodiment. The horizontal axis represents time, and the vertical axis represents the current of the electrolysis stack #1 (111), the state of the heat exchanger 11a1, and the state of the flow control valve 11b1, respectively, from the top of the diagram. The top of the diagram indicates a high current, a high heat exchanger output, and an open flow control valve, respectively. Note that FIG. 13 assumes that, in the electrical connection configuration of the electrolysis stack group 11 shown in FIG. 3, the temperature of the supplied pure water is increased to reduce the electrical resistance of the electrolysis stack #1 (111) so as to increase the current of the electrolysis stacks #1 (111) and #2 (112) and reduce the current of the electrolysis stacks #3 (113) and #4 (114). In the state that has continued since time t0, after the current command value changes to increase the current at time t1, the heat exchanger 11a1 increases its output to raise the temperature of the pure water, and the flow control valve 11b1 changes in the direction of closing the valve to reduce the flow rate of the pure water and raise its temperature. From time t1, as the difference between the measured current value and the target current value decreases, the output of heat exchanger 11a1 is gradually reduced, and flow rate adjustment valve 11b1 is opened. After that, after time t2 when the difference between the current target value and the current measurement value becomes sufficiently small, the output of heat exchanger 11a1 is set to a medium level in accordance with the current target value, but the opening of flow control valve 11b1 is increased to the same open state as at time t0.

[0037] The output of the heat exchanger 11a1 is rapidly increased between times t1 and t2 in an attempt to rapidly increase the temperature of the electrolysis stack #1, but it takes time for the temperature of the pure water to increase. Therefore, by closing the flow rate control valve 11b1, the flow rate of the pure water is reduced, reducing the amount of heat that the pure water removes from the electrolysis stack #1, allowing the temperature of the electrolysis stack #1 to change with high responsiveness. Furthermore, by keeping the opening of the flow control valve 11b1 at the same level as at time t0 after time t2, the flow rate loss caused by the flow control valve 11b1 can be reduced, making it unnecessary to increase the output of the pump 139 upstream of the flow control valve 11b1 in accordance with the flow rate loss, thereby suppressing a decrease in efficiency. Furthermore, after time t2, the output of the heat exchanger 11a1 is set to medium, so that the target current value and the measured current value of the electrolysis stack #1 coincide with each other.

[0038] This embodiment aims to adjust the efficiency of the water electrolysis system 100 by reducing the current difference that occurs when a current difference occurs between electrolysis stacks #1 (111) and #3 (113), which are electrically connected in parallel.

[0039] <<Independent Adjustment of Operational States of Multiple Electrolysis Stacks (Fourth Embodiment)>> In the above-described operation examples (first to third embodiments), the specific operations of the heat exchanger and the flow rate control valve that adjust the temperature and flow rate of the pure water supplied to the electrolysis stack during a transient state have been described, focusing on the electrolysis stack #1 (111). Hereinafter, a case where the operating states of a plurality of electrolysis stacks are adjusted independently by a plurality of heat exchangers and flow rate control valves (fourth embodiment) will be described with reference to FIG.

[0040] 14 is a time chart showing how the electrolytic stack operation state adjustment control unit 151 independently controls the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow rate control valves 11b1, 11b2, 11b3, and 11b4 to independently control the states of the electrolytic stacks 111, 112, 113, and 114. The horizontal axis represents time, and the vertical axis represents the states of the heat exchangers and the flow rate control valves, respectively, from the top of the figure, with the heat exchanger output being high and the flow rate control valve being open toward the top. Note that in this embodiment, as in the first to third embodiments described above, it is assumed that the temperatures of the electrolytic stacks 111, 112, 113, and 114 are increased. At time t1, a command to increase the temperature from the state maintained from time t0 is input to the electrolytic stack operation state adjustment control unit 151, thereby increasing the outputs of the heat exchangers 11a1, 11a2, 11a3, and 11a4, but the states of the heat exchangers 11a1, 11a2, 11a3, and 11a4 take different values. Similarly, at time t1, the flow rate control valves 11b1, 11b2, 11b3, and 11b4 are closed, but the states (opening degrees) of the flow rate control valves 11b1, 11b2, 11b3, and 11b4 are different. Furthermore, after time t2, it is determined that the difference between the target temperature value and the measured temperature value has become sufficiently small, and the heat exchangers 11a1, 11a2, 11a3, and 11a4 are maintained at a higher output than at time t0, and the flow rate control valves 11b1, 11b2, 11b3, and 11b4 are adjusted to maintain the same open state as at time t0. As a result, even when the target temperature states of the electrolysis stacks 111, 112, 113, and 114 are different, the electrolysis stacks 111, 112, 113, and 114 can be independently adjusted with high response and high efficiency by independently adjusting the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow rate control valves 11b1, 11b2, 11b3, and 11b4.

[0041] <<Example of electrolytic stack operation state adjustment control unit>> Hereinafter, a specific example of the electrolytic stack operation state adjustment control unit 151 implemented in the controller 15 will be described with reference to FIGS. 15 and 16. FIG.

[0042] FIG. 15 is a control block diagram showing the configuration of the electrolytic stack operation state adjustment control unit 151. Two proportional-integral control units 1511 and 1512 are provided to control the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow control valves 11b1, 11b2, 11b3, and 11b4, which adjust the temperature and flow rate of the pure water supplied to the voltage stacks #1, #2, #3, and #4 (111, 112, 113, and 114), respectively. The proportional-integral control units 1511 and 1512 calculate command values ​​(i.e., output target values ​​of the heat exchangers and target opening values ​​of the flow control valves) for the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow control valves 11b1, 11b2, 11b3, and 11b4 by proportional-integral control based on the difference between the target state values, which are target values ​​for the states (temperature, voltage, current, or deterioration) of the electrolytic stacks #1, #2, #3, and #4, and the estimated state values ​​measured or estimated using sensors.

[0043] FIG. 16 is a flowchart showing the operation process S100 of the electrolytic stack operation state adjustment control unit 151. First, in step S101, a command value for adjusting the state of the electrolytic stacks 111, 112, 113, and 114 is determined, and the process proceeds to the next step S102. In step S102, the proportional-plus-integral control section 1511 that determines the output command values ​​of the heat exchangers 11a1, 11a2, 11a3, and 11a4 is executed, and the process proceeds to the next step S103. In step S103, the proportional-plus-integral control section 1512 that determines the opening command values ​​for the flow rate adjustment valves 11b1, 11b2, 11b3, and 11b4 is executed, and the series of operations is completed.

[0044] <<Example of operation when adjusting using only one adjustment unit>> In each of the above-described embodiments, an example of operation has been shown in which the adjustment units of both the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow rate adjustment valves 11b1, 11b2, 11b3, and 11b4 operate. In contrast to this, by applying proportional-integral control as described above, if there are limitations on the command values ​​of the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow rate control valves 11b1, 11b2, 11b3, and 11b4, there may be cases where adjustment is made by only one of the adjustment units. An example of the operation in this case will be described below with reference to FIGS.

[0045] (Example of adjusting only the heat exchanger) 17 is a time chart showing how the electrolytic stack operation state adjustment control unit 151 adjusts only the heat exchanger 11a1. The horizontal axis represents time, and the vertical axis represents, from the top of the diagram, the temperature of the electrolytic stack #1 (111), the state of the heat exchanger 11a1, and the state of the flow control valve 11b1, with the top representing high temperature, high heat exchanger output, and open flow control valve. In the following, it is assumed that the temperature of the electrolytic stack #1 is reduced at time t1. If the opening degree of the flow rate control valve 11b1 has already reached its upper limit, even if there is a temperature decrease command at time t1, the flow rate control valve 11b1 remains open and decreases the output of the heat exchanger 11a1. After that, at time t2, when the difference between the target temperature and the measured temperature becomes sufficiently small, the output of the heat exchanger 11a1 is maintained lower than the state at time t0 to lower the temperature of the electrolysis stack #1 below the temperature state at time t0.

[0046] (Example of operation to adjust only the flow control valve) 18 is a time chart showing how the electrolytic stack operation state adjustment control unit 151 adjusts only the flow rate control valve 11b1. The horizontal axis represents time, and the vertical axis represents, from the top of the diagram, the temperature of the electrolytic stack #1 (111), the state of the heat exchanger 11a1, and the state of the flow rate control valve 11b1, respectively, with the top of the diagram representing high temperature, high heat exchanger output, and open flow rate control valve. In the following, it is assumed that the temperature of the electrolytic stack #1 is increased at time t1. If the output of the heat exchanger 11a1 has already reached its upper limit, even if a temperature increase command is issued at time t1, the heat exchanger 11a1 maintains high output and closes the flow rate control valve 11b1. After that, at time t2, when the difference between the target temperature and the measured temperature becomes sufficiently small, the flow rate control valve 11b1 is closed more than it was at time t0 to raise the temperature of the electrolysis stack #1 above the temperature state at time t0, thereby reducing the flow rate of the pure water and reducing the amount of heat transferred from the electrolysis stack #1 to the pure water, thereby raising the temperature of the electrolysis stack #1.

[0047] <<Example of cooperative operation between electrolysis stacks and pure water adjustment equipment>> 19, an example of cooperative operation of the heat exchangers 11a1, 11a2, 11a3, and 11a4 and the flow rate control valves 11b1, 11b2, 11b3, and 11b4 provided in the electrolysis stack group 11 and the pump 139, the heat exchanger 1310, and the valve 137 provided in the pure water adjustment device 13 will be described below. The pump 139, the heat exchanger 1310, and the valve 137 provided in the pure water adjustment device 13 correspond to the "upstream adjustment unit" according to the present invention.

[0048] In Figure 19, the horizontal axis represents time, and the vertical axis represents, from the top of the figure, the operation commands to the devices 137, 139, and 1310, the states of the heat exchangers 11a1, 11a2, 11a3, and 11a4, and the states of the flow control valves 11b1, 11b2, 11b3, and 11b4, with the top representing command 1 (operation performed), high heat exchanger output, and open flow control valve. Note that Figure 19 assumes that the temperatures of the electrolysis stacks 111, 112, 113, and 114 are increased. The state at time t0 is maintained until time t1, and after operation commands are issued to devices 137, 139, and 1310 at time t1, the outputs of heat exchangers 11a1, 11a2, 11a3, and 11a4 are changed to high and flow rate adjustment valves 11b1, 11b2, 11b3, and 11b4 are changed to closed states. After time t1, the high output state of the heat exchanger is reduced, and the opening of the flow rate adjustment valve is changed to an open state. After that, after time t2 when the temperatures of the electrolysis stacks 11, 112, 113, 114 have sufficiently increased, the outputs of the heat exchangers 11a1, 11a2, 11a3, 11a4 are maintained at a higher level than the level at time t0. As a result, even when changing the operating load (amount of hydrogen generated) of the water electrolysis system 100 to operate the pure water supply device 13, the heat exchangers 11a1, 11a2, 11a3, 11a4 and the flow rate control valves 11b1, 11b2, 11b3, 11b4 provided in the electrolysis stack group 11 operate in coordination, allowing the states of the electrolysis stacks 111, 112, 113, 114 to be changed more responsively and efficiently than when only the pure water supply device 13 is adjusted.

[0049] Although the above-described operational example of the embodiment of the present invention has been described with respect to a method for changing the heat exchanger and the flow control valve, the present invention is not limited to this. Although the example has been described in which the state of the heat exchanger and the state of the flow control valve are changed in a step-like manner to the target values ​​of temperature, voltage, and current, they may be changed in a ramp-like manner or in a fluctuating manner, or any command value that changes over time may be used.

[0050] In the above-described embodiment of the present invention, a heat exchanger is used as the first adjustment unit and a flow control valve is used as the second adjustment unit, but this is not limited to this. The second adjustment unit may be another device that has an adjustment function different from the operation state adjustment function of the first adjustment unit. By configuring in this manner, it is possible to suppress the disadvantages, particularly when there are disadvantages to operating the second adjustment unit despite the second adjustment unit's high response. The second adjustment unit may also be another device that is capable of adjusting the operating state by enhancing the adjusting function of the first adjustment unit for adjusting the operating state.

[0051] In the above-described embodiment and operation examples, heat exchangers 11a1, 11a2, 11a3, and 11a4 and flow control valves 11b1, 11b2, 11b3, and 11b4 are connected in series upstream of each electrolysis stack 111, 112, 113, and 114, and the heat exchangers are arranged upstream of the flow control valves. However, the control method according to the present invention can also be implemented by arranging the flow control valves upstream of the heat exchangers. However, because the volume of pure water changes and the flow rate also changes, the operating state of the electrolysis stack can be controlled more accurately by arranging the heat exchanger upstream and stabilizing the temperature before adjusting the flow rate.

[0052] As described in the above embodiment, the method for controlling a water electrolysis system according to the present invention has the following features. (1) A control method for a water electrolysis system including an electrolysis stack that electrolyzes water to generate hydrogen and oxygen, a pure water supply device that supplies pure water to the electrolysis stack, a first adjustment unit that is installed between the electrolysis stack and the pure water supply device and that is capable of adjusting the operating state of the electrolysis stack, a second adjustment unit that is installed between the electrolysis stack and the pure water supply device and that is capable of adjusting the operating state of the electrolysis stack, and an operating state adjustment control unit that adjusts the first adjustment unit and the second adjustment unit to adjust the operating state of the electrolysis stack, wherein the operating state adjustment control unit operates the first adjustment unit based on the operating state after receiving a command to change the operating state of the electrolysis stack, and operates the second adjustment unit simultaneously with the first adjustment unit based on the operating state when a predetermined condition is satisfied (see FIGS. 8, 11, and 13). This improves the responsiveness of temperature adjustment of the electrolysis stack and suppresses an increase in loss due to pure water flow rate control, thereby achieving high efficiency and maintaining an appropriate electrolysis state in the electrolysis stack.

[0053] (2) A method for controlling the water electrolysis system of (1), in which a plurality of first adjustment units and a plurality of second adjustment units are independently adjusted (see FIG. 14).

[0054] (3) In the method for controlling the water electrolysis system of (1), when the adjustment amount of either the first adjustment unit or the second adjustment unit reaches a limit value, only the first adjustment unit or the second adjustment unit is adjusted (see Figures 17 and 18).

[0055] (4) A control method for the water electrolysis system of (1), in which the first adjustment unit and the second adjustment unit are adjusted in conjunction with the operation of an upstream adjustment unit that adjusts one or more of the flow rate, pressure, and temperature of pure water upstream of the first adjustment unit and the second adjustment unit, and both the first adjustment unit and the second adjustment unit are adjusted during a period in which the difference between the state target value and the state measurement value is large, and when the difference between the state target value and the state measurement value has become sufficiently small, only the first adjustment unit is adjusted (see Figure 19).

[0056] In the method for controlling a water electrolysis system according to the present invention, the first adjustment unit can be a device capable of changing (increasing and / or decreasing) the temperature of pure water, such as a heat exchanger, a heater, or a cooler. By using a device capable of changing the temperature of the pure water, such as a heat exchanger, heater, or cooler, in the first adjustment unit, the temperature of the pure water supplied to the electrolysis stack can be changed, thereby changing the operating state of the electrolysis stack.

[0057] In the method for controlling a water electrolysis system according to the present invention, the second adjustment unit may be, for example, a flow rate adjustment valve that adjusts the flow rate of pure water. By using a flow rate control valve as the second control unit, the amount of pure water supplied to the electrolysis stack can be adjusted, thereby adjusting the operating state of the electrolysis stack.

[0058] In the method for adjusting a water electrolysis system according to the present invention, the predetermined condition is, for example, a period immediately after the operating state is changed, in which there is a large difference between the target value of the operating state and the measured value of the operating state.

[0059] In the method for adjusting a water electrolysis system according to the present invention, the command to change the operating state of the electrolysis stack is a command received by the electrolysis stack operating state adjustment control unit to change the operating state of the electrolysis stack. Specifically, this command corresponds to the temperature command value, voltage command value, current command value, etc. in the above-described embodiments.

[0060] It should be noted that the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations. [Explanation of symbols]

[0061] 3 switch, 4 system (AC power system), 5 external device, 6 transformer, 11 electrolysis stack group (electrolysis stack), 12 power converter, 12a AC side connection end, 12b DC side connection end, 13 pure water adjustment device, 13a, 13b, 13c pipe, 15 controller (control device), 100 water electrolysis system, 131, 133 gas-liquid separator, 132, 134 pressure adjustment valve, 135, 136, 137 valve, 138 pure water tank, 139 water pump, 1310 heat exchanger, 151 electrolysis stack operation state adjustment control unit, 152 electrolysis stack deterioration state adjustment control unit, 1511, 1512 proportional integral control unit, S100 operation processing

Claims

1. 1. A method for controlling a water electrolysis system comprising: an electrolysis stack that electrolyzes water to generate hydrogen and oxygen; a pure water supply device that supplies pure water to the electrolysis stack; a first adjustment unit that is installed between the electrolysis stack and the pure water supply device and is capable of adjusting an operating state of the electrolysis stack; a second adjustment unit that is installed between the electrolysis stack and the pure water supply device and is capable of adjusting the operating state of the electrolysis stack; and an operating state adjustment controller that adjusts the first adjustment unit and the second adjustment unit to adjust the operating state of the electrolysis stack, The operating state adjustment control unit operates the first adjustment unit based on the operating state after receiving a command to change the operating state of the electrolytic stack, and operates the second adjustment unit simultaneously with the first adjustment unit based on the operating state when a predetermined condition is satisfied. A method for controlling a water electrolysis system.

2. 2. The method for controlling a water electrolysis system according to claim 1, wherein the water electrolysis system includes a plurality of sets each including the electrolysis stack, the first adjustment unit, and the second adjustment unit, and the operating state adjustment control unit adjusts the first adjustment unit and the second adjustment unit of each of the plurality of sets independently for each of the plurality of sets.

3. 2. The method for controlling a water electrolysis system according to claim 1, wherein the second adjustment unit has an adjustment function for adjusting the operating state that is different from an adjustment function for adjusting the operating state that is performed by the first adjustment unit, and the adjustment function of the second adjustment unit adjusts the operating state by enhancing the adjustment function for adjusting the operating state that is performed by the first adjustment unit.

4. 2. The method for controlling a water electrolysis system according to claim 1, wherein the first adjustment unit is any one of a heat exchanger, a heater, and a cooler that adjusts the temperature of the pure water.

5. 2. The method for controlling a water electrolysis system according to claim 1, wherein the second adjusting unit is a flow rate adjusting valve that adjusts the flow rate of the pure water.

6. 2. The method for controlling a water electrolysis system according to claim 1, wherein the predetermined condition is a period immediately after the change in the operating state, in which a difference between a target value of the operating state and a measured value of the operating state is large.

7. 2. The method for controlling a water electrolysis system according to claim 1, wherein the operating condition is a temperature of the electrolysis stack.

8. 2. The method for controlling a water electrolysis system according to claim 1, wherein the operating state is a deterioration state of the electrolysis stack.

9. 2. The method for controlling a water electrolysis system according to claim 1, wherein the operating condition is a voltage of the electrolysis stack.

10. 2. The method for controlling a water electrolysis system according to claim 1, wherein the operating condition is a current flowing through the electrolysis stack.

11. 2. The method for controlling a water electrolysis system according to claim 1, wherein the water electrolysis system further comprises an upstream adjusting unit that supplies pure water to the first adjusting unit and the second adjusting unit and adjusts one or more of a flow rate, a pressure, and a temperature of the pure water, and wherein one or both of the first adjusting unit and the second adjusting unit are operated in conjunction with operation of the upstream adjusting unit.

12. a water electrolysis system comprising: an electrolysis stack that electrolyzes water to generate hydrogen and oxygen; a pure water supply device that supplies pure water to the electrolysis stack; a first adjustment unit that is installed between the electrolysis stack and the pure water supply device and is capable of adjusting an operating state of the electrolysis stack; a second adjustment unit that is installed between the electrolysis stack and the pure water supply device and is capable of adjusting the operating state of the electrolysis stack; and an operating state adjustment control unit that adjusts the first adjustment unit and the second adjustment unit to adjust the operating state of the electrolysis stack, The operating state adjustment control unit operates the first adjustment unit based on the operating state after receiving a command to change the operating state of the electrolysis stack, and operates the second adjustment unit simultaneously with the first adjustment unit based on the operating state when a predetermined condition is satisfied. A water electrolysis system characterized by:

13. 12. The water electrolysis system according to claim 11, wherein the water electrolysis system includes a plurality of sets, each of which includes the electrolysis stack, the first adjustment unit, and the second adjustment unit, and the operating state adjustment control unit adjusts the first adjustment unit and the second adjustment unit of each of the plurality of sets independently.

14. 12. The water electrolysis system according to claim 11, further comprising an upstream adjusting unit that supplies pure water to the first adjusting unit and the second adjusting unit and adjusts one or more of a flow rate, a pressure, and a temperature of the pure water, wherein one or both of the first adjusting unit and the second adjusting unit are operated in conjunction with operation of the upstream adjusting unit.

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