Control method of water electrolysis system and water electrolysis system

Abstract

To provide a control method of a water electrolysis system capable of reducing a response speed difference during transients of adjustment between current applied to an electrolysis stack and water.SOLUTION: The control device comprises the steps of determining a current command value to be applied to an electrolytic stack and determining a pure water adjustment amount command value for adjusting the pressure or / and flow rate of the water to be supplied to the electrolytic stack based on the current command value. The control device comprises a step A, in which when the current command value is changed toward a second current command value (current command value c2) that is different from a first current command value (current command value c1) and the pure water adjustment amount command value is changed toward a second pure water adjustment amount command value (pure water adjustment amount command value w2) that is different from a first pure water adjustment amount command value (pure water adjustment amount command value w1), a measured value of pressure or / and flow rate reaches the second pure water adjustment amount command value from the first pure water adjustment amount command value, before a measured value of the current applied from a power converter to the electrolytic stack reaches the second current command value from the first current command value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a control method for 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, it has attracted attention as one of the clean energies that can help achieve carbon neutrality, and technological development is underway regarding the production, transportation, and use of hydrogen. In particular, hydrogen can be produced anywhere by electrolyzing water, so water electrolysis systems that can produce hydrogen by water electrolysis have attracted attention as a means of reducing the amount of energy imported and improving energy self-sufficiency, and large-scale introduction is planned, mainly in Europe.

[0003] The basic configuration of a water electrolysis system includes an electrolytic cell (electrolysis stack) that performs water electrolysis, a power source (e.g., a rectifier) ​​for supplying DC power to the electrolysis stack, and a power source that is connected to a power grid via a transformer. In addition, a device (defined as a pure water adjustment device in this document) 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 not used in the 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. A method for operating a pure water adjustment device for such a water electrolysis system is disclosed in Patent Document 1.

[0004] Patent Document 1 discloses a method for operating a water electrolysis device in which power suppliers are provided on both sides of an electrolyte membrane, separators are laminated on the power suppliers, a first flow path for supplying water is formed between one power supplier and one separator, and a second flow path for flowing hydrogen obtained by electrolysis of water as high-pressure hydrogen at a pressure higher than that of the first flow path is formed between the other power supplier and the other separator. The method includes the steps of applying an electrolysis voltage to the water electrolysis device to perform water electrolysis treatment, detecting fluctuations in the electrolysis voltage during the water electrolysis treatment, and adjusting the pressure of the water supplied to the first flow path in response to the fluctuations in the electrolysis voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-180451 A Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the water pressure is adjusted based on the fluctuation of the electrolysis voltage of the electrolysis stack, so that the electrolysis state of the electrolysis stack can be appropriately adjusted. However, since there is a large difference between the response speed of the change in current that adjusts the voltage of the electrolysis stack and the response speed of the water pressure, the electrolysis state of the electrolysis stack may deviate from the appropriate state during the transition of the adjustment of the water pressure according to the current. By experiencing this transition many times, the electrolysis stack may deteriorate and the frequency of replacing the electrolysis stack may increase.

[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 can reduce a difference in response speed between a current applied to an electrolysis stack and a transitional state of water adjustment. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a water electrolysis system including a power converter capable of converting AC and DC and transmitting and receiving power between an AC side connection end and a DC side connection end, an electrolysis stack that electrolyzes water to generate hydrogen and oxygen, a pure water preparation device that supplies water to the electrolysis stack and recovers the hydrogen, the oxygen, and the water not used in the electrolysis, and a control device that controls the power converter and the pure water preparation device, the control device comprising: a step of determining a current command value to be applied to the electrolysis stack; and a pure water preparation device that adjusts the pressure and / or flow rate of the water supplied to the electrolysis stack based on the current command value. The method includes a step of determining a water adjustment amount command value, and a step of transmitting the current command value and the pure water adjustment amount command value to the power converter and the pure water conditioning device, and is characterized in that, when changing the current command value from a first current command value toward a second current command value which is a different value, and changing the pure water adjustment amount command value from the first pure water adjustment amount command value toward the second pure water adjustment amount command value which is a different value from the first pure water adjustment amount command value, a step A is provided in which an actual measurement value of the pressure and / or the flow rate is made to reach the second pure water adjustment amount command value from the first pure water adjustment amount command value before an actual measurement value of a current applied from the power converter to the electrolysis stack reaches the second current command value from the first current command value. Other aspects of the present invention will be described in the embodiments described later. Effect of the Invention

[0009] According to the present invention, the difference in response characteristics when adjusting the current and water pressure and / or flow rate of the electrolysis stack can be reduced, and the electrolysis state of the electrolysis stack can be made appropriate. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a device configuration of a water electrolysis system according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing a device configuration of a pure water adjusting apparatus according to an embodiment of the present invention. [Diagram 3]4 is a time chart showing the relationship between current and the amount of pure water adjusted in the first comparative example. [Figure 4] 11 is a time chart showing the relationship between current and the amount of pure water adjusted in the second comparative example. [Diagram 5] 4 is a time chart showing a first operation example of a current and an adjustment amount of pure water according to the first embodiment. [Figure 6] 5 is a flowchart showing an operation process of a first operation example of a current and an adjustment amount of pure water according to the first embodiment. [Figure 7] 10 is a time chart showing a second operation example of the current and the pure water adjustment amount according to the second embodiment. [Figure 8] 10 is a flowchart showing an operation process of a second operation example of a current and a pure water adjustment amount according to the second embodiment. [Figure 9] 13 is a time chart showing a third operation example of the current and the pure water adjustment amount according to the third embodiment. [Figure 10] 13 is a flowchart showing an operation process of a third operation example of a current and an adjustment amount of pure water according to the third embodiment. [Figure 11] 13 is a time chart showing a fourth operation example of the current and the pure water adjustment amount according to the fourth embodiment. [Figure 12] 13 is a flowchart showing an operation process of a fourth operation example of a current and a pure water adjustment amount according to the fourth embodiment. [Figure 13] FIG. 13 is a diagram showing the configuration of a water electrolysis system, peripheral devices, and systems according to a fifth embodiment. [Figure 14] 13 is a time chart showing a fifth operation example of the current and the pure water adjustment amount according to the fifth embodiment. [Figure 15] 13 is a flowchart showing an operation process of a fifth operation example of a current and an adjustment amount of pure water according to the fifth embodiment. [Figure 16] 13 is a time chart showing a sixth operation example of the current and the pure water adjustment amount according to the sixth embodiment. [Figure 17] 13 is a flowchart showing an operation process of a sixth operation example of a current and a pure water adjustment amount according to the sixth embodiment. [Figure 18]13 is a flowchart showing an operation process of an operation mode switching operation example according to the seventh embodiment. [Figure 19] 13 is a flowchart showing an operation process of a first operation example in an operation mode switching operation example according to the seventh embodiment. [Figure 20] 13 is a flowchart showing an operation process of a second operation example in the operation mode switching operation example according to the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. 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. In addition, in all the drawings for explaining the present invention, parts having the same functions are given the same reference numerals, and repeated explanations thereof may be omitted.

[0012] <Water electrolysis system> 1 is a diagram showing the 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 side connection end 12b of a power converter 12, and pure water is electrolyzed into hydrogen and oxygen in response to a current applied from the power converter 12 to the electrolysis stack group 11. A pure water adjustment device 13 is connected to the electrolysis stack group 11, and pure water is supplied from a pipe 13a, hydrogen generated in the electrolysis stack group 11 and pure water not used for water electrolysis are collected from a pipe 13b, and oxygen generated in the electrolysis stack group and pure water not used for water electrolysis are collected from a pipe 13c. The water electrolysis system 100 further includes a controller 15 (control device), and the controller 15 detects and adjusts the operating states of the electrolysis stack group 11, the power converter 12, and the pure water adjustment device 13.

[0013] The controller 15 is configured to include, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The controller 15 is realized by a predetermined program (control program) stored in the ROM being expanded in the RAM and executed by the CPU. The program here is for causing a computer to execute a control method.

[0014] The water electrolysis system 100 has a configuration in which a transformer 7 is connected to an AC connection end 12a of a power converter 12, the transformer 7 is connected to a switch 3, and the switch 3 is connected to a grid 4, and by adjusting the power converter 12, electric power is supplied from the grid 4 to the components of the water electrolysis system 100.

[0015] Furthermore, 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 and the power consumption facility, an instruction from an organization that manages the state of a wide-area power grid, or electricity market transaction information (electricity market information), for example, a spot electricity price.

[0016] Furthermore, the controller 15 also has a function of inputting external information such as information about the water electrolysis system 100 and the system voltage, and determines the operating state of the water electrolysis system 100 based on various pieces of information.

[0017] Here, the types of electrolysis stacks constituting the electrolysis stack group 11 are roughly divided into alkaline type and solid polymer type, and in this embodiment, a case where a solid polymer type water electrolysis stack is used as the electrolysis stack is assumed. The solid polymer type has a superior response speed to the alkaline type, and is suitable as a water electrolysis system for following fluctuations in renewable energy. In addition, the size of the electrolysis stack can be made smaller in the solid polymer type than in the alkaline type, and therefore it is suitable as a system that requires space saving, such as being installed offshore near an offshore wind power generation system.

[0018] 2 is a diagram showing the configuration of the pure water conditioning device 13 constituting 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 for separating hydrogen and pure water is connected downstream of the valve 135, a pure water tank 138 for storing the pure water discharged from the gas-liquid separator 131 is connected downstream of the gas-liquid separator 131, a water supply pump 139 for pressurizing and transporting the pure water is connected downstream of the pure water tank 138, a valve 137 capable of adjusting the flow rate of the pure water supplied to the electrolysis stack group 11 is connected downstream of the water supply pump 139, and the pure water is supplied to the electrolysis stack group 11 via the pipe 13a. A pressure adjustment valve 132 is connected to the gas-liquid separator 131, and the internal pressure of the gas-liquid separator 131 is adjusted, and hydrogen is supplied to the outside of the water electrolysis system 100 via the 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 and pure water is connected downstream of the valve 136, and the pure water discharged from the gas-liquid separator 133 is transported downstream of the gas-liquid separator 133 to a pure water tank 138. A pressure regulating valve 134 is connected to the gas-liquid separator 133, which regulates 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.

[0019] The means for adjusting the pressure of the pure water supplied to the electrolysis stack group 11 will be described below. As the first means for adjusting the pressure, it can be achieved by adjusting the internal pressure of the gas-liquid separation devices 131 and 133 with the pressure adjustment valves 132 and 134. As the second means for adjusting the pressure, it can be achieved by adjusting the output pressure of the water supply pump 139. As the third means for adjusting the pressure, it can be achieved by simultaneously implementing the first means for adjusting the pressure and the second means for adjusting the pressure. Hereinafter, in the embodiment, the pressure of pure water will be adjusted by any one of the means for adjusting the pressure.

[0020] Means for adjusting the flow rate of pure water supplied to the electrolytic stack group 11 are shown below. As the first means for adjusting the flow rate, it can be achieved by adjusting the opening degrees of the valves 135 and 136. As the second means for adjusting the flow rate, it can be achieved by adjusting the opening degree of the valve 137. As the third means for adjusting the flow rate, it can be achieved by simultaneously implementing the first means for adjusting the flow rate and the second means for adjusting the flow rate. Hereinafter, in the embodiment, the pressure of pure water will be adjusted by any one of the means for adjusting the pressure.

[0021] <<First Operating Example of Current and Pure Water Adjustment Amount>> Hereinafter, with reference to FIGS. 3 to 6, a first operating example of a control method for changing the current supplied to the electrolytic stack group 11 and the pure water adjustment amount will be described. Hereinafter, the pressure and / or flow rate of pure water is defined as the pure water adjustment amount. Also, the effective power command value p1 and the effective power command value p2, the current command value c1 and the current command value c2, and the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 will be described when each command value 1 is greater than each command value 2 (c1>c2, w1>w2), but this is not limiting, and the same operation method is also implemented when each command value 1 is less than each command value 2 (c1<c2, w1<w2).

[0022] FIG. 3 is a time chart showing the operation of the current and the pure water adjustment amount in the first comparative example. That is, FIG. 3 shows a time chart showing an example of the operation of the current and the pure water adjustment amount in a comparative example when the embodiment of the present invention is not applied, which is used for comparative explanation of the embodiment of the present invention. The horizontal axis of FIG. 3 indicates time, and the vertical axis indicates, from the top of the figure, the active power command value required for the water electrolysis system 100, the current applied to the electrolysis stack group 11, and the pure water adjustment amount. The top of the figure indicates a high active power command value, a large current, and a large pure water adjustment amount, respectively. Note that the current includes a command value shown by a solid line and an actual value shown by a dashed line, and the pure water adjustment amount also includes a command value shown by a solid line and an actual value shown by a dashed line.

[0023] The electrolytic stack group 11 is composed of multiple electrolytic stacks, and generally, the electrolytic stacks are connected in parallel to a power source to control the current of each electrolytic stack. On the other hand, when multiple electrolytic stacks are connected in series, the current is constant in all electrolytic stacks connected in series. When control is performed in response to a change in the active power command value, the sum of the power of each electrolytic stack is controlled to match the active power command value.

[0024] In the first comparative example, it is assumed that the active power command value requested of the water electrolysis system 100 is held at the active power command value p1 from time t0 to time t1, and then the active power command value p1 is decreased from time t1 to time t2 to the active power command value p2, and the active power command value p2 is held after time t2.

[0025] Note that time t1 may be the time when the change in the active power command value begins, or time t1 may be determined after detecting or receiving a change in the active power command value at a timing prior to time t1.

[0026] In the first comparative example, the current command value and the pure water adjustment amount command value are decreased from time t1 to time t2 in accordance with the change in the active power command value. As the current command value is changed from current command value c1 to current command value c2, the actual measured value of the current decreases from time t1 and coincides with the current command value c2 at time t3. Also, as the command value of the pure water adjustment amount is changed from pure water adjustment amount command value w1 to pure water adjustment amount command value w2, the actual measured value of the pure water adjustment amount starts to decrease from time t1 and coincides with the pure water adjustment amount command value w2 at time t4.

[0027] In this case, since the response speed of the current is faster than the response speed of the pure water adjustment amount, there is a time lag until each actual measurement value matches each command value 2 (the actual measurement value of the current matches the current command value c2 at time t3; the actual measurement value of the pure water adjustment amount matches the pure water adjustment amount command value w2 at time t4).

[0028] Due to such a difference in response speed, the state near the electrolytic membrane of the electrolytic stack group 11 may not be in an appropriate state. When the current is reduced as shown in FIG. 3, the change in the actual measured value of the pure water adjustment amount is slower than the decrease in the actual measured value of the current, so that the vicinity of the electrolytic membrane becomes more supercooled than in the steady state, which may increase the resistance value and reduce the efficiency of water electrolysis. Conversely to FIG. 3, when the actual measured value of the current is increased, the increase in the pure water adjustment amount relative to the increase in the current is slow, so that the generated hydrogen gas and oxygen gas are not sufficiently discharged, the relative area of ​​the electrolytic membrane becomes smaller, or the amount of pure water supplied decreases, so that the vicinity of the electrolytic membrane is overheated, which may lead to the deterioration of the electrolytic membrane. Experiencing such a state with a difference in response speed many times may lead to an increase in power loss and deterioration of the electrolytic stack.

[0029] The pure water adjustment amount (pure water adjustment amount command value) may be pressure, flow rate, or both pressure and flow rate, but it is the same in all cases (this also applies to Figures 4 and 5 described below).

[0030] FIG. 4 is a time chart showing the operation of the current and the pure water adjustment amount in the second comparative example. The horizontal and vertical axes in the figure are the same as those in FIG. 3, so the explanation will be omitted. FIG. 4 shows an operation example in which the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 are made equal. For example, by adjusting the pure water adjustment amount command values ​​w1 and w2 to a state in which the current is at the rated value and increasing the pure water adjustment amount regardless of the current, it is possible to avoid the retention of generated gas near the electrolytic membrane and overheating, which may occur in the example of FIG. 3. However, power is required to constantly maintain a high pure water adjustment amount, and the electrolytic resistance increases due to supercooling of the electrolytic membrane, which may decrease the electrolytic efficiency of the water electrolysis system 100 (increase in loss).

[0031] First Embodiment FIG. 5 is a time chart showing a first operation example of the current and the pure water adjustment amount according to the first embodiment. The horizontal and vertical axes of the figure are the same as those of FIG. 3, and therefore the explanation will be omitted. In FIG. 5, in order to eliminate the delay in the response speed of the actual value of the pure water adjustment amount relative to the response speed of the actual value of the current, the pure water adjustment amount command value is immediately changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2 at the time t1 when the active power command value starts to change from the active power command value p1 to the active power command value p2. This makes it possible to change the actual value of the pure water adjustment amount from the time t1 and make it match the pure water adjustment amount command value w2 by the time tA, which is earlier than the time t3 when the actual value of the current matches the current command value c2 (to make the actual value of the pure water adjustment amount reach the pure water adjustment amount command value w2 earlier than the time t3). That is, the controller 15, which is a control device, executes step A. This makes it possible to maintain the state near the electrolytic membrane in a more appropriate state than in the first comparative example described above.

[0032] That is, step A is a step in which, when changing the current command value from the first current command value (current command value c1) toward a second current command value (current command value c2) which is a different value, and changing the pure water adjustment amount command value from the first pure water adjustment amount command value (pure water adjustment amount command value w1) toward a second pure water adjustment amount command value (pure water adjustment amount command value w2) which is a different value, the actual measured value of the pressure and / or flow rate is made to reach the second pure water adjustment amount command value from the first pure water adjustment amount command value before the actual measured value of the current applied from the power converter 12 to the electrolytic stack group 11 reaches the second current command value from the first current command value.

[0033] On the other hand, in the case of Comparative Example 1 shown in Fig. 3, step B is used. Step B is a step of changing the current command value from the first current command value to the second current command value and changing the pure water adjustment amount command value from the first pure water adjustment amount command to the second pure water adjustment amount command value, in which, after the actual measurement value of the current reaches the second current command value from the first current command value, the actual measurement value of the pressure and / or the flow rate is made to reach the second pure water adjustment amount command value from the first pure water adjustment amount command value when changing the current command value from the first current command value to the second current command value and also changing the pure water adjustment amount command value from the first pure water adjustment amount command to the second pure water adjustment amount command value.

[0034] As compared to the present embodiment, in the second comparative example, as described above, electric power is required to constantly maintain a large amount of pure water adjustment, and the electrolytic resistance increases due to supercooling of the electrolytic membrane, which may result in a decrease in electrolysis efficiency (increased loss) of the water electrolysis system 100.

[0035] FIG. 6 is a flowchart showing the operation process S100 of the first operation example of the current and the pure water adjustment amount according to the first embodiment. The process of the flowchart shown in FIG. 6 is implemented in the controller 15 (see FIG. 1). In the description of the process, FIG. 4 will be referred to as appropriate. From a state in which the active power command value is held from time t0, the time is monitored in step S101, and if time t is less than time t1 (step S101, No), the process proceeds to step S102. In step S102, the current command value is held at the current command value c1 in accordance with the holding of the active power command value, and the process proceeds to step S103. In step S103, the pure water adjustment amount command value is held at the pure water adjustment amount command value w1 in accordance with the holding of the active power command value. In step S101, if time t is after time t1 (step S101, Yes), the process proceeds to step S104. In step S104, in order to quickly change the actual value of the pure water adjustment amount, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2, and the process proceeds to step S105. In step S105, the current command value is changed from the current command value c1 to the current command value c2 in accordance with the change in the active power command value, and the process proceeds to step S106. In step S106, the change in the current command value is monitored, and if the current command value has not reached the current command value c2 (step S106, No), the process continues with step S105. In step S106, after it is confirmed that the current command value matches the current command value c2 (step S106, Yes), the process proceeds to step S107. In step S107, the current command value is held at the current command value c2, and the series of operations ends.

[0036] <<Second operation example of current and pure water adjustment amount>> 7 and 8, a second operation example of the control method for changing the current supplied to the electrolysis stack group 11 and the pure water adjustment amount will be described. Note that the active power command value p1 and the active power command value p2, the current command value c1 and the current command value c2, and the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 will be described in a case where each command value 1 is greater than each command value 2, but this is not limited to the case, and a similar operation method is also performed when each command value 1 is smaller than each command value 2.

[0037] <Second embodiment> FIG. 7 is a time chart showing a second operation example of the current and the pure water adjustment amount according to the second embodiment. The horizontal and vertical axes of the figure are the same as those of FIG. 3, and therefore the explanation is omitted. In FIG. 7, in order to eliminate the delay in the response speed of the actual value of the pure water adjustment amount relative to the response speed of the actual value of the current, the pure water adjustment amount command value is immediately changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w3 at the time t1 when the active power command value starts to change from the active power command value p1 to the active power command value p2. At this time, in order to make the response speed of the actual value of the pure water adjustment amount faster than that of the first operation example, the pure water adjustment amount command value is changed to the pure water adjustment amount command value w3 which is smaller than the pure water adjustment amount command value w2. As a result, the actual value of the pure water adjustment amount is changed from the time t1, and can be made to coincide with the pure water adjustment amount command value w2 by the time tB which is earlier than the time t3 when the actual value of the current coincides with the current command value c2. After the actual measurement value of the pure water adjustment amount coincides with the pure water adjustment amount command value w2, the pure water adjustment amount command value w is changed from the pure water adjustment amount command value w3 to the pure water adjustment amount command value w2 at time tC so that the actual measurement value of the pure water adjustment amount coincides with the pure water adjustment amount command value w2. By the above adjustment, the state near the electrolytic membrane can be maintained in a more appropriate state than in the first comparative example.

[0038] As in the first operation example described above, time t1 may be the time when the change in the active power command value begins, or time t1 may be determined after detecting or receiving a change in the active power command value at a timing prior to time t1.

[0039] FIG. 8 is a flowchart showing the operation process S200 of the second operation example of the current and the pure water adjustment amount according to the second embodiment. The process of the flowchart shown in FIG. 8 is implemented in the controller 15 (see FIG. 1). In the description of the process, FIG. 7 will be referred to as appropriate. From a state in which the active power command value is held from time t0, the time is monitored in step S201, and if time t is less than time t1 (step S201, No), the process proceeds to step S202. In step S202, the current command value is held at the current command value c1 in accordance with the holding of the active power command value, and the process proceeds to step S203. In step S203, the pure water adjustment amount command value is held at the pure water adjustment amount command value w1 in accordance with the holding of the active power command value. In step S201, if time t is after time t1 (step S201, Yes), the process proceeds to step S204. In step S204, in order to quickly change the actual value of the pure water adjustment amount, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w3, and the process proceeds to step S205. In step S205, the current command value is changed from the current command value c1 to the current command value c2 in accordance with the change in the active power command value, and the process proceeds to step S206. In step S206, the change in the current command value is monitored, and if the current command value c has not reached the current command value c2 (step S206, No), the process proceeds to step S205. In step S206, after confirming that the current command value matches the current command value c2 (step S106, Yes), the process proceeds to step S207. In step S207, the current command value is held at the current command value c2, and the process proceeds to step S208. In step S208, the time is monitored, and if the time t is less than the time tC (step S208, No), the process returns to the process of step S207. In step S208, if time t is after time tC (Yes in step S208), the process proceeds to step S209. In step S209, in order to make the actual measurement value of the pure water adjustment amount coincide with the pure water adjustment amount command value w2, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w3 to the pure water adjustment amount command value w2, and then the series of operations is terminated.

[0040] As described above, the second operation example according to the second embodiment described in Figures 7 and 8 is different from the first operation example according to the first embodiment described in Figures 5 and 6 in that the actual measurement value of the pure water adjustment amount is undershoot (or overshoot) the second operation example, which allows the actual measurement value of the pure water adjustment amount to change more quickly than the first operation example.

[0041] <<Third operation example of current and pure water adjustment amount>> 9 and 10, a third operation example of the control method for changing the current supplied to the electrolysis stack group 11 and the pure water adjustment amount will be described. Note that the active power command value p1 and the active power command value p2, the current command value c1 and the current command value c2, and the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 will be described in a case where each command value 1 is greater than each command value 2, but this is not limited to the above, and a similar operation method is also performed when each command value 1 is smaller than each command value 2.

[0042] The third operation example according to the third embodiment described below differs from the first and second operation examples according to the first and second embodiments described in Figures 5 to 8 in that the time at which the actual value and command value of the pure water adjustment amount change changes from time tD after time t1.

[0043] <Third embodiment> FIG. 9 is a time chart showing a third operation example of the current and the pure water adjustment amount according to the third embodiment. The horizontal and vertical axes of the figure are the same as those of FIG. 3, so the explanation will be omitted. In FIG. 9, in order to eliminate the delay in the response speed of the actual value of the pure water adjustment amount relative to the response speed of the actual value of the current, the current command value is changed from the current command value c1 to the current command value c2 at time t1 when the active power command value starts to change from the active power command value p1 to the active power command value p2, but at time tD later than time t1, the pure water adjustment amount command value is immediately changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2. As a result, even when the actual value of the pure water adjustment amount is changed after time t1, it can be made to match the pure water adjustment amount command value w2 by time tE, which is earlier than time t3 when the actual value of the current matches the current command value c2. As a result, it is possible to maintain the state near the electrolytic membrane in a more appropriate state than in the first comparative example described above.

[0044] As in the above-described operation example, time t1 may be the time when the change in the active power command value starts, or time t1 may be determined after detecting or receiving a change in the active power command value at a timing prior to time t1.

[0045] FIG. 10 is a flowchart showing the operation process S300 of the third operation example of the current and the pure water adjustment amount according to the third embodiment. The process of the flowchart shown in FIG. 10 is implemented in the controller 15 (see FIG. 1). In the description of the process, FIG. 9 will be referred to as appropriate. From a state in which the active power command value is held from time t0, the time is monitored in step S301, and if time t is less than time t1 (step S301, No), the process proceeds to step S302. In step S302, the current command value is held at the current command value c1 in accordance with the holding of the active power command value, and the process proceeds to step S303. In step S303, the pure water adjustment amount command value is held at the pure water adjustment amount command value w1 in accordance with the holding of the active power command value. In step S301, if time t is after time t1 (step S301, Yes), the process proceeds to step S304. In step S304, the current command value is changed from the current command value c1 to the current command value c2 in accordance with the change in the active power command value, and the process proceeds to step S305. In step S305, the change in the current command value is monitored, and if the current command value has not reached the current command value c2 (step S305, No), the process proceeds to step S306. In step S306, the time t is monitored, and if the time t is less than the time tD (step S306, No), the process returns to step S304. In step S306, if the time t is after the time tD (step S306, Yes), the process proceeds to step S307. In step S307, in order to quickly change the actual value of the pure water adjustment amount, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2, and the process returns to step S304. After performing step S304, in step S305, it is confirmed that the current command value coincides with the current command value c2 (step S305, Yes), and then the process proceeds to step S308. In step S308, the current command value is held at the current command value c2, and then the series of operations is terminated.

[0046] <<Fourth operation example of current and pure water adjustment amount>> 11 and 12, a fourth operation example of the control method for changing the current supplied to the electrolysis stack group 11 and the pure water adjustment amount will be described. Note that the active power command value p1 and the active power command value p2, the current command value c1 and the current command value c2, and the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 will be described in a case where each command value 1 is greater than each command value 2, but this is not limited to the above, and a similar operation method is also performed when each command value 1 is smaller than each command value 2.

[0047] A fourth operation example according to the fourth embodiment described below differs from the first and second operation examples according to the first and second embodiments described in Figures 5 to 8 in that the times at which the actual value and command value of the pure water adjustment amount change change from time tF after time t1. Also, unlike the third operation example according to the third embodiment described in Figures 9 and 10, the actual value of the pure water adjustment amount is undershoot (or overshoot).

[0048] <Fourth embodiment> FIG. 11 is a time chart showing a fourth operation example of the current and the pure water adjustment amount according to the fourth embodiment. The horizontal and vertical axes of the figure are the same as those of FIG. 4, and therefore the explanation is omitted. In FIG. 11, in order to eliminate the delay in the response speed of the actual measurement value of the pure water adjustment amount relative to the response speed of the actual measurement value of the current, the current command value is changed from the current command value c1 to the current command value c2 at time t1 when the active power command value starts to change from the active power command value p1 to the active power command value p2, but at time tF later than time t1, the pure water adjustment amount command value is immediately changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w3. As a result, the actual measurement value of the pure water adjustment amount is changed from time tF, and can be made to match the pure water adjustment amount command value w2 by time tG, which is earlier than time t3 when the actual measurement value of the current matches the current command value c2. After the actual measurement value of the pure water adjustment amount coincides with the pure water adjustment amount command value w2, the pure water adjustment amount command value w is changed from the pure water adjustment amount command value w3 to the pure water adjustment amount command value w2 at time tH so that the actual measurement value of the pure water adjustment amount coincides with the pure water adjustment amount command value w2. By the above adjustment, the state near the electrolytic membrane can be maintained in a more appropriate state than in the first comparative example described above.

[0049] As in the above-described operation example, time t1 may be the time when the change in the active power command value starts, or time t1 may be determined after detecting or receiving a change in the active power command value at a timing prior to time t1.

[0050] FIG. 12 is a flowchart showing the operation process S400 of the fourth operation example of the current and the pure water adjustment amount according to the fourth embodiment. The process of the flowchart shown in FIG. 12 is implemented in the controller 15 (see FIG. 1). In the description of the process, FIG. 11 will be referred to as appropriate. From a state in which the active power command value is held from time t0, the time is monitored in step S401, and if time t is less than time t1 (step S401, No), the process proceeds to step S402. In step S402, the current command value is held at the current command value c1 in accordance with the holding of the active power command value, and the process proceeds to step S403. In step S403, the pure water adjustment amount command value is held at the pure water adjustment amount command value w1 in accordance with the holding of the active power command value. In step S401, if time t is after time t1 (step S401, Yes), the process proceeds to step S404. In step S404, the current command value is changed from the current command value c1 to the current command value c2 in accordance with the change in the active power command value, and the process proceeds to step S405. In step S405, the change in the current command value is monitored, and if the current command value has not reached the current command value c2 (step S405, No), the process proceeds to step S406. In step S406, the time t is monitored, and if the time t is less than the time tF (step S406, No), the process returns to step S404. In step S406, if the time t is after the time tF (step S406, Yes), the process proceeds to step S407. In step S407, in order to quickly change the actual measurement value of the pure water adjustment amount, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w3, and the process returns to step S404. After performing step S404, in step S405, it is confirmed that the current command value matches the current command value c2 (step S405, Yes), and then the process proceeds to step S408. In step S408, the current command value is held at the current command value c2, and then the process proceeds to step S409. In step S409, time t is monitored, and if time t is less than time tH (step S409, No), the process returns to the step immediately before step S409. In step S409, if time t is after time tH (step S409, Yes), the process proceeds to step S410. In step S410, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w3 to the pure water adjustment amount command value w2, and the series of operations is terminated.

[0051] <<Fifth operation example of current and pure water adjustment amount>> 13 to 15, a fifth operation example of the control method for changing the current supplied to the electrolysis stack group 11 and the pure water adjustment amount will be described. Note that the active power command value p1 and the active power command value p2, the current command value c1 and the current command value c2, and the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 will be described in a case where each command value 1 is greater than each command value 2, but this is not limited to the above, and a similar operation method is also performed when each command value 1 is smaller than each command value 2.

[0052] In the four operation examples of the first to fourth embodiments, the current command value and the pure water adjustment amount command value are determined based on the active power command value required for the water electrolysis system 100, and the current and the pure water adjustment amount change according to each command value. In the fifth operation example of the fifth embodiment described below, the external information input to the water electrolysis system 100 uses information that enables it to know in advance that the active power command value will change.

[0053] An example of the external information may be the active power or reactive power that determines the amount of hydrogen produced by the water electrolysis system 100 itself. The external information may be information that is installed in the peripheral equipment 6 and that directly or indirectly operates the water electrolysis system 100, and that sets in advance the time at which the active power or reactive power is to be changed using a touch panel or the like, and that changes the active power or reactive power at the time set by a timer.

[0054] Examples of the external information may include weather information, wind speed information and solar radiation information that can predict fluctuations in the output of a wind power generation system or a solar power generation system that supplies power to the water electrolysis system 100. This information may be weather forecast information, or output values ​​from a wind speed sensor or a solar radiation sensor located near the wind power generation system or the solar power generation system or in the area where the power generation system is installed.

[0055] An example of the external information may be electricity market price information that determines the price of electricity to be received by the water electrolysis system 100. The external information may be information that detects in advance the time when the electricity price will fluctuate and changes the active power in response to the fluctuation in the electricity price.

[0056] An example of the external information may be power information of facilities that supply power and are installed in the vicinity of the water electrolysis system 100. As described above, the external information may be power information output by a wind power generation system or a solar power generation system, or the power information may be determined based on the operating status or maintenance plan of a thermal power plant or a nuclear power plant.

[0057] An example of the external information may be load information of facilities that consume electricity and are installed in the vicinity of the water electrolysis system 100. The external information may be manufacturing equipment installed in a factory and consuming electricity, or large air conditioners, electric furnaces, or rotating machines, and may be based on information on their operating conditions (load conditions).

[0058] An example of the external information may be operation information of a device for storing electricity (power storage device) installed in the vicinity of the water electrolysis system 100. The operation status of the water electrolysis system 100 may be changed based on information on transmission and reception of electricity by charging and discharging the power storage device.

[0059] <Fifth embodiment> FIG. 13 is a diagram showing the configuration of a water electrolysis system, peripheral devices, and a system according to a fifth embodiment. A water electrolysis system 100 is connected to a system 4 via a transformer 7 and a switch 3, and a system including a peripheral facility 6 that transmits and receives power to and from the system 4 via a power line 6a. In addition to the power line 6a, the peripheral facility 6 receives information about the system 4 and transmits information about the peripheral facility 6 to the system 4 via a communication line 6b between the system 4 and the peripheral facility 6. The peripheral facility 6 transmits information about the peripheral facility 6 to the water electrolysis system 100 via the communication line 6c. In the fifth operation example, it is assumed that the power transmission and reception state of the peripheral facility 6 is transmitted in advance to the water electrolysis system 100 via the communication line 6c. In this way, the water electrolysis system 100 can know the power transmission and reception state of the peripheral facility 6 in advance, and can change the operating state of the water electrolysis system 100 in advance at a time before the active power command value is changed.

[0060] Fig. 14 is a time chart showing a fifth operation example of the current and the pure water adjustment amount according to the fifth embodiment. The horizontal and vertical axes of the figure are the same as those of Fig. 4, and therefore the explanation is omitted. In Fig. 14, in order to eliminate the delay in the response speed of the actual measurement value of the pure water adjustment amount relative to the response speed of the actual measurement value of the current, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2 at time t1 before the active power command value starts to change from the active power command value p1 to the active power command value p2 based on external information transmitted from the peripheral equipment 6. After that, at time tI, the current command value is changed from the current command value c1 to the current command value c2 as the active power command value changes from the active power command value p1 to the active power command value p2. In response to this, the actual measured value of the current starts to change from time tI and coincides with the current command value c2 by time tL, but by changing the pure water adjustment amount command value from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2 at time t1, the actual measured value of the pure water adjustment amount starts to change from time t1 and can reach the pure water adjustment amount command value w2 by time tJ. By the above adjustments, the condition near the electrolytic membrane can be maintained in a more appropriate state than in the above-mentioned first comparative example.

[0061] FIG. 15 is a flowchart showing an operation process S500 of a fifth operation example of the current and the pure water adjustment amount according to the fifth embodiment. The process of the flowchart shown in FIG. 15 is implemented in the controller 15 (see FIG. 1). In the description of the process, FIG. 12 will be referred to as appropriate. From a state in which the active power command value is held from time t0, the time is monitored in step S501, and if time t is less than time t1 (step S501, No), the process proceeds to step S502. In step S502, the current command value is held at the current command value c1 in accordance with the holding of the active power command value, and the process proceeds to step S503. In step S503, the pure water adjustment amount command value is held at the pure water adjustment amount command value w1 in accordance with the holding of the active power command value. In step S501, if time t is after time t1 (step S501, Yes), the process proceeds to step S504. In step S504, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w2, and the process proceeds to step S505. In step S505, the time is monitored, and if the time t is less than the time tI (step S505, No), the process returns to step S504. In step S505, if it is determined that the time t is after the time tI (step S505, Yes), the process proceeds to step S506. In step 506, the current command value is changed from the current command value c1 toward the current command value c2, and the process proceeds to step 507. In step S507, it is monitored whether the current command value matches the current command value c2, and if the current command value does not match the current command value c2 (step S507, No), the process returns to the process of step S506. In step 507, after it is determined that the current command value matches the current command value c2 (step S507, Yes), the process proceeds to step S508. In step S508, the current command value is held at the current command value c2, and then the series of operations is terminated.

[0062] <<Sixth operation example of current and pure water adjustment amount>> 16 and 17, a sixth operation example of the control method for changing the current supplied to the electrolysis stack group 11 and the pure water adjustment amount will be described. Note that the active power command value p1 and the active power command value p2, the current command value c1 and the current command value c2, and the pure water adjustment amount command value w1 and the pure water adjustment amount command value w2 will be described in a case where each command value 1 is greater than each command value 2, but this is not limited to the above, and a similar operation method is also performed when each command value 1 is smaller than each command value 2.

[0063] In the sixth operation example described below, similarly to the above-described fifth operation example, it is assumed that the water electrolysis system 100 receives external information from the peripheral equipment 6 and knows in advance that the active power command value will be changed.

[0064] Moreover, the sixth operation example differs from the fifth operation example according to the fifth embodiment described with reference to FIGS. 13 to 15 in that the actual measurement value of the pure water adjustment amount is undershoot (or overshoot).

[0065] Sixth Embodiment FIG. 16 is a time chart showing a sixth operation example of the current and the pure water adjustment amount according to the sixth embodiment. The horizontal and vertical axes of the figure are the same as those of FIG. 4, and therefore the explanation is omitted. In FIG. 16, in order to eliminate the delay in the response speed of the actual measurement value of the pure water adjustment amount relative to the response speed of the actual measurement value of the current, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w3 at time t1 before the active power command value starts to change from the active power command value p1 to the active power command value p2 based on external information transmitted from the peripheral equipment 6. Thereafter, at time tN, the active power command value is changed from the active power command value p1 to the active power command value p2, and as the change is completed by time tP, the current command value is changed from the current command value c1 to the current command value c2, and the change is completed by time tQ. In response to this, the actual value of the current starts to change from time tN and coincides with the current command value c2 by time tQ, but by changing the pure water adjustment amount command value from w1 to w3 at time t1, the actual value of the pure water adjustment amount starts to change from time t1 and can reach the pure water adjustment amount command value w2 by time tM. Also, by changing the pure water adjustment amount command value from w3 to w2 at time tO, the actual value of the pure water adjustment amount is made to coincide with the pure water adjustment amount command value w2 after time t3. By the above adjustments, the state near the electrolytic membrane can be maintained in a more appropriate state than in the first comparative example described above.

[0066] FIG. 17 is a flowchart showing the operation process S600 of the sixth operation example of the current and the pure water adjustment amount according to the sixth embodiment. The process of the flowchart shown in FIG. 17 is implemented in the controller 15 (see FIG. 1). In the description of the process, FIG. 16 will be referred to as appropriate. From a state in which the active power command value is held from time t0, the time is monitored in step S601, and if time t is less than time t1 (step S601, No), the process proceeds to step S602. In step S602, the current command value is held at the current command value c1 in accordance with the holding of the active power command value, and the process proceeds to step S603. In step S603, the pure water adjustment amount command value is held at the pure water adjustment amount command value w1 in accordance with the holding of the active power command value. In step S601, if time t is after time t1 (step S601, Yes), the process proceeds to step S604. In step S604, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w1 to the pure water adjustment amount command value w3, and the process proceeds to step S605. In step S605, the time is monitored, and if the time t is less than the time tN (step S605, No), the process returns to step S604. In step S605, if it is determined that the time t is after the time tN (step S605, Yes), the process proceeds to step S606. In step S606, the current command value is changed from the current command value c1 toward the current command value c2, and the process proceeds to step S607. In step S607, it is monitored whether the current command value matches the current command value c2, and if the current command value does not match the current command value c2 (step S607, No), the process proceeds to step S608. In step S608, the time is monitored, and if the time t is less than the time tO (step S608, No), the process returns to step S606. In step S608, if the time t is after the time tO (step S608, Yes), the process proceeds to step S609. In step S609, the pure water adjustment amount command value is changed from the pure water adjustment amount command value w3 to the pure water adjustment amount command value w2, and the process proceeds to step S606. In step S607, after it is confirmed that the current command value coincides with the current command value c2 (step S607, Yes), the process proceeds to step S610. In step S610, the current command value is maintained at the current command value c2, and then the series of operations ends.

[0067] <<Example of operation mode switching>> The first operation example of the first embodiment to the sixth operation example of the sixth embodiment have been described above. In these examples, it was assumed that the operation mode is changed from Comparative Example 1 and Comparative Example 2 to any of the operation modes of the first to sixth operation examples, and the selected operation mode of any of the first to sixth operation examples is continued. Below, an operation example is described in which an operation mode including Comparative Example 1 and Comparative Example 2 is selected based on the state of the water electrolysis system 100 and external information, rather than continuing any of the operation modes of the first to sixth operation examples.

[0068] Seventh embodiment FIG. 18 is a flowchart showing an operation process S700 of an operation mode switching operation example according to the seventh embodiment. In step S701, information collection for mode switching is performed. For example, the information may be the presence or absence of an abnormal state in the components of the water electrolysis system 100, the presence or absence of maintenance, the presence or absence of a mode switching command based on external information, or the change direction of the active power command value. After performing step S701, in step S702, it is determined whether or not the mode switching can be performed. If the mode switching is OK, the process proceeds to step S703, and if the mode switching is not possible, the process proceeds to step S704. In step S703, the mode switching is determined to be OK, and one of the first to sixth operation examples of the embodiment is performed, and then the series of operations is terminated. In step S704, the operation of Comparative Example 1 or Comparative Example 2 is performed, and then the series of operations is terminated.

[0069] A specific example of step S703 in the flow chart shown in FIG. 18 will be described below with reference to FIGS.

[0070] <<First operation example in operation mode switching operation example>> 19 is a flowchart showing operation processing S703a of a first operation example in an operation mode switching operation example according to the seventh embodiment. In step S703a1, it is monitored whether the active power command value changes (whether the active power command value p1 and the active power command value p2 match), and if it is determined that the active power command value changes (the active power command value p1 and the active power command value p2 do not match) (step S703a1, No), the process proceeds to step S703a2, and if it is determined that the active power command value does not change (the active power command value p1 and the active power command value p2 match) (step S703a1, Yes), the series of operations is terminated. Note that the "first operation example" here relates to switching of operation modes, and is different from the first operation example (first embodiment) of the current and the pure water adjustment amount shown in FIG. 5 described above.

[0071] In step S703a2, the direction of change of the active power command value is monitored, and if the active power command value p1 is greater than the active power command value p2 (step S703a2, Yes), the process proceeds to step S703a3, and if the active power command value p1 is less than the active power command value p2 (step S703a2, No), the process proceeds to step S703a4. In step S703a3, under the conditions that the current command value c1 is set to be greater than the current command value c2 and the pure water adjustment amount command value w1 is set to be greater than the pure water adjustment amount command value w2, any one of the above-mentioned first to sixth operation examples is executed, and the series of operations is terminated.

[0072] In step S703a4, under the conditions that the current command value c1 is set to be smaller than the current command value c2 and the pure water adjustment amount command value w1 is set to be smaller than the pure water adjustment amount command value w2, any one of the first to sixth operation examples described above is executed, and the series of operations is terminated. By executing the mode switching shown in Fig. 19, the first to sixth operation examples are selected based on the direction of change in the active power command value, and the condition near the electrolytic membrane of the electrolysis stack group 11 can be adjusted to an appropriate state based on the operating state of the water electrolysis system 100.

[0073] <<Second operation example in the operation mode switching operation example>> 20 is a flowchart showing operation processing S703b of a second operation example in the operation mode switching operation example according to the seventh embodiment. In step S703b1, it is monitored whether the active power command value changes (whether the active power command value p1 and the active power command value p2 match), and if it is determined that the active power command value changes (the active power command value p1 and the active power command value p2 do not match) (step S703b1, No), the process proceeds to step S703b2, and if it is determined that the active power command value does not change (the active power command value p1 and the active power command value p2 match) (step S703b1, Yes), the series of operations is terminated. It should be noted that the "second operation example" here relates to switching of the operation mode, and is different from the second operation example (second embodiment) of the current and the pure water adjustment amount shown in FIG. 7 described above.

[0074] In step S703b2, the direction of change of the active power command value is monitored, and if the active power command value p1 is greater than the active power command value p2 (step S703b2, Yes), the process proceeds to step S703b3, and if the active power command value p1 is less than the active power command value p2 (step S703b2, No), the process proceeds to step S703b4. In step S703b3, under the conditions that the current command value c1 is set to be greater than the current command value c2 and the pure water adjustment amount command value w1 is set to be greater than the pure water adjustment amount command value w2, any one of the above-mentioned first to sixth operation examples is executed, and the series of operations is terminated.

[0075] In step S703b4, the above-mentioned Comparative Example 1 or Comparative Example 2 is executed under the conditions that the current command value c1 is set to be smaller than the current command value c2 and the pure water adjustment amount command value w1 is set to be smaller than the pure water adjustment amount command value w2, and the series of operations is terminated. In particular, the second operation example shown in FIG. 20 is characterized in that the embodiment according to the present invention is executed when the active power command value is decreased, and Comparative Example 1 or Comparative Example 2 is executed when the active power command value is increased. By executing the mode switching shown in FIG. 20, the first to sixth operation examples and Comparative Example 1 or Comparative Example 2 are selected based on the direction of change of the active power command value, and the state near the electrolytic membrane of the electrolysis stack group 11 can be adjusted to an appropriate state based on the operating state of the water electrolysis system 100.

[0076] The above-mentioned first to sixth operation examples of the embodiment of the present invention have been described with respect to the methods of changing the active power command value, the current command value, and the pure water adjustment amount command value, but the present invention is not limited to this. Although the above-mentioned examples have been described in which the active power command value, the current command value, and the pure water adjustment amount command value are changed in a ramp-like manner, they do not have to be linear, and a change in which the slope changes over time may be made. Furthermore, instead of changing the pure water adjustment amount command value in a step-like manner, the pure water adjustment amount command value may be changed in a ramp-like manner or with a changing slope. Any change method may be used as long as it does not specify the change form of each command value and shortens the response speed difference between the actual measurement value of the pure water adjustment amount and the actual measurement value of the current.

[0077] As described above, the method for controlling the water electrolysis system according to this embodiment has the following features. (1) A method for controlling a water electrolysis system including a power converter 12 capable of converting AC and DC and transmitting and receiving electric power between an AC side connection end 12a and a DC side connection end 12b, an electrolysis stack (electrolysis stack group 11) that electrolyzes water to generate hydrogen and oxygen, a pure water adjustment device 13 that supplies water to the electrolysis stack and recovers hydrogen and oxygen discharged from the electrolysis stack and water not used in the electrolysis, and a control device (controller 15) that controls the power converter 12 and the pure water adjustment device 13, in which the control device performs the steps of: determining a current command value to be applied to the electrolysis stack; and determining a pure water adjustment amount command value that adjusts the pressure and / or flow rate of water supplied to the electrolysis stack based on the current command value. and a step of transmitting a current command value and a pure water adjustment amount command value to the power converter 12 and the pure water adjusting device 13, and includes a step A of changing the current command value from the first current command value (current command value c1) toward a second current command value (current command value c2) which is a different value, and changing the pure water adjustment amount command value from the first pure water adjustment amount command value (pure water adjustment amount command value w1) toward a second pure water adjustment amount command value (pure water adjustment amount command value w2) which is a different value, before the actual measurement value of the current applied from the power converter 12 to the electrolysis stack reaches the second current command value from the first current command value (see Figs. 5 and 6). This reduces the difference in response characteristics when adjusting the current of the electrolysis stack and the pressure and / or flow rate of water, and makes it possible to make the electrolysis state of the electrolysis stack appropriate.

[0078] (2) A method for controlling the water electrolysis system according to (1) above, wherein the actual measured value of the pressure and / or flow rate changes so as to overshoot or undershoot during a period in which the actual measured value of the current reaches the second current command value from the first current command value (see Figs. 7, 8, 11, and 12).

[0079] (3) A method for controlling the water electrolysis system of (1), wherein when the current command value is changed from a first current command value to a second current command value and the pure water adjustment amount command value is changed from the first pure water adjustment amount command value to the second pure water adjustment amount command value, the actual measured value of the current changes from the first current command value to the second current command value, and then the actual measured value of the pressure and / or flow rate changes from the first pure water adjustment amount command value to the second pure water adjustment amount command value (see Figures 9, 10, 11, and 12).

[0080] (4) A method for controlling the water electrolysis system of (1) above, wherein when the current command value is changed from a first current command value to a second current command value and the pure water adjustment amount command value is changed from the first pure water adjustment amount command value to the second pure water adjustment amount command value, the actual measured value of the pressure and / or flow rate changes from the first pure water adjustment amount command value to the second pure water adjustment amount command value before the actual measured value of the current changes from the first current command value to the second current command value (see Figures 14 and 15).

[0081] (5) A method for controlling a water electrolysis system according to (4) above, wherein it is determined based on external information input from outside the water electrolysis system to a control device that the actual value of the pressure and / or flow rate will change from the first pure water adjustment amount command value to the second pure water adjustment amount command value before the actual value of the current changes from the first current command value to the second current command value (see Figures 16 and 17).

[0082] (6) A method for controlling the water electrolysis system of (1), comprising step B of changing the current command value from a first current command value to a second current command value and changing the pure water adjustment amount command value from the first pure water adjustment amount command to the second pure water adjustment amount command value after the actual measured value of the current reaches the second current command value from the first current command value, and further comprising a step of selecting step A and step B according to external information and / or a state of the water electrolysis system, and a step of switching between step A and step B (see Figures 18, 19 and 20).

[0083] (7) The method for controlling a water electrolysis system according to (6) above, characterized in that step A is not executed when an abnormality occurs in the water electrolysis system or when maintenance is being performed. [Explanation of symbols]

[0084] 3 Switchgear 4 systems (AC power system) 5 External device 6 Peripheral Facilities 6a power line 6b, 6c communication line 7. Transformers 11 Electrolytic stack group (electrolytic stack) 12 Power Converter 12a AC side connection end 12b DC side connection end 13 Pure water adjustment device 13a, 13b, 13c pipes 15 Controller 100 Water electrolysis system 131, 133 Gas-liquid separation equipment 132, 134 Pressure regulating valve 135, 136, 137 Valves 138 Pure Water Tank 139 Water Pump S100, S200, S300, S400, S500, S600, S700, S700a, S700b Operation process p1 Active power command value p2 Active power command value c1 Current command value (first current command value) c2 Current command value (second current command value) w1 Pure water adjustment amount command value (first pure water adjustment amount command value) w2 Pure water adjustment amount command value (second pure water adjustment amount command value) w3 Pure water adjustment amount command value (third pure water adjustment amount command value)

Claims

1. A method for controlling a water electrolysis system comprising: a power converter capable of converting AC and DC and transmitting and receiving electric power between an AC side connection end and a DC side connection end; an electrolysis stack that electrolyzes water to generate hydrogen and oxygen; a pure water adjustment device that supplies water to the electrolysis stack and recovers the hydrogen, the oxygen, and the water not used in the electrolysis discharged from the electrolysis stack; and a control device that controls the power converter and the pure water adjustment device, The control device determines a current command value to be applied to the electrolytic stack; determining a pure water adjustment amount command value for adjusting the pressure and / or flow rate of the water supplied to the electrolysis stack based on the current command value; and transmitting the current command value and the pure water adjustment amount command value to the power converter and the pure water adjustment device, When changing the current command value from the first current command value to a second current command value which is a different value, and when changing the pure water adjustment amount command value from the first pure water adjustment amount command value to the second pure water adjustment amount command value which is a different value, A step A of causing an actual measurement value of the pressure or / and the flow rate to reach the second pure water adjustment amount command value from the first pure water adjustment amount command value before an actual measurement value of a current applied from the power converter to the electrolysis stack reaches the second current command value from the first current command value.

2. A method for controlling a water electrolysis system comprising:

2. A method for controlling a water electrolysis system according to claim 1, comprising: During a period during which the actual measured value of the current is caused to reach the second current command value from the first current command value, the actual measured value of the pressure and / or the flow rate changes so as to overshoot or undershoot.

2. A method for controlling a water electrolysis system comprising:

3. A method for controlling a water electrolysis system according to claim 1, comprising: When changing the current command value from the first current command value to the second current command value and changing the pure water adjustment amount command value from the first pure water adjustment amount command value to the second pure water adjustment amount command value, After the actual measurement value of the current changes from the first current command value toward the second current command value, the actual measurement value of the pressure and / or the flow rate changes from the first pure water adjustment amount command value toward the second pure water adjustment amount command value.

2. A method for controlling a water electrolysis system comprising:

4. A method for controlling a water electrolysis system according to claim 1, comprising: When changing the current command value from the first current command value to the second current command value and changing the pure water adjustment amount command value from the first pure water adjustment amount command value to the second pure water adjustment amount command value, The actual measurement value of the pressure and / or the flow rate changes from the first pure water adjustment amount command value to the second pure water adjustment amount command value before the actual measurement value of the current changes from the first current command value to the second current command value.

2. A method for controlling a water electrolysis system comprising:

5. A method for controlling a water electrolysis system according to claim 4, comprising: It is determined based on external information inputted to the control device from outside the water electrolysis system that the actual measurement value of the pressure and / or the flow rate will change from the first pure water adjustment amount command value to the second pure water adjustment amount command value before the actual measurement value of the current changes from the first current command value to the second current command value.

2. A method for controlling a water electrolysis system comprising:

6. A method for controlling a water electrolysis system according to claim 5, comprising: The external information is active power and / or reactive power required for the water electrolysis system.

2. A method for controlling a water electrolysis system comprising:

7. A method for controlling a water electrolysis system according to claim 5, comprising: The external information is weather information.

2. A method for controlling a water electrolysis system comprising:

8. A method for controlling a water electrolysis system according to claim 5, comprising: The external information is electricity market information.

2. A method for controlling a water electrolysis system comprising:

9. A method for controlling a water electrolysis system according to claim 5, comprising: The external information is power information of a facility that supplies power and is installed in the vicinity of the water electrolysis system.

2. A method for controlling a water electrolysis system comprising:

10. A method for controlling a water electrolysis system according to claim 5, comprising: The external information is load information of equipment that consumes electricity and is installed in the vicinity of the water electrolysis system.

2. A method for controlling a water electrolysis system comprising:

11. A method for controlling a water electrolysis system according to claim 5, comprising: The external information is power information transmitted and received by a facility for storing power installed in the vicinity of the water electrolysis system.

2. A method for controlling a water electrolysis system comprising:

12. A method for controlling a water electrolysis system according to claim 1, comprising: When changing the current command value from the first current command value to the second current command value and changing the pure water adjustment amount command value from the first pure water adjustment amount command value to the second pure water adjustment amount command value, A step B includes making the actual measurement value of the pressure or / and the flow rate reach the second pure water adjustment amount command value from the first pure water adjustment amount command value after the actual measurement value of the current reaches the second current command value from the first current command value, selecting step A or step B in response to external information and / or a state of the water electrolysis system; A step of switching between the step A and the step B.

2. A method for controlling a water electrolysis system comprising:

13. A method for controlling a water electrolysis system according to claim 12, comprising: Step A is not executed when an abnormality occurs or maintenance is performed on the water electrolysis system.

2. A method for controlling a water electrolysis system comprising:

14. A water electrolysis system comprising: a power converter capable of converting AC and DC and transmitting and receiving electric power between an AC side connection end and a DC side connection end; an electrolysis stack that electrolyzes water to generate hydrogen and oxygen; a pure water adjustment device that supplies water to the electrolysis stack and recovers the hydrogen, the oxygen, and the water not used in the electrolysis discharged from the electrolysis stack; and a control device that controls the power converter and the pure water adjustment device, the control device determines a current command value to be applied to the electrolytic stack, determines a pure water adjustment amount command value for adjusting the pressure and / or flow rate of the water supplied to the electrolytic stack based on the current command value, and transmits the current command value and the pure water adjustment amount command value to the power converter and the pure water adjustment device, When the current command value is changed from a first current command value to a second current command value which is a different value, and the pure water adjustment amount command value is changed from a first pure water adjustment amount command value to a second pure water adjustment amount command value which is a different value, a step A of causing an actual measurement value of the pressure or / and the flow rate to reach the second pure water adjustment amount command value from the first pure water adjustment amount command value before an actual measurement value of a current applied from the power converter to the electrolysis stack reaches the second current command value from the first current command value.

Images