Renewable energy-linked water electrolysis system, and control device and control method of renewable energy-linked water electrolysis system

Abstract

A control device (19) of a renewable energy-linked water electrolysis system (11) comprises: an acquisition unit (21) that acquires both an output power restriction command value (R_Grid) and an electrolysis power upper limit value (P_UP); a calculation unit (23) that calculates a generation power threshold value (R_SUM) which is the sum of the output power restriction command value (R_Grid) and the electrolysis power upper limit value (P_UP); a setting unit (25) that sets a generation power upper limit value (R_UP) pertaining to a renewable energy generation system (13) to be less than or equal to the generation power threshold value (R_SUM) calculated by the calculation unit (23); and a coordination control unit (27) that coordinates and implements output control of generation power pertaining to the renewable energy generation system (13) and electrolysis power control pertaining to a water electrolysis system (17), such that the generation power pertaining to the renewable energy generation system (13) does not exceed the generation power upper limit value (R_UP).

Description

Renewable Energy-linked Water Electrolysis System, as well as Control Device and Control Method for Renewable Energy-linked Water Electrolysis System

[0001] The present invention relates to a renewable energy-linked water electrolysis system, as well as a control device and a control method for the renewable energy-linked water electrolysis system.

[0002] Hydrogen is a clean energy that does not emit carbon dioxide during combustion, unlike fossil fuels that emit carbon dioxide during combustion. Hydrogen has attracted attention as one of the clean energies for achieving carbon neutrality, and technological developments related to the production, transportation, and utilization of hydrogen are underway.

[0003] Hydrogen can be produced anywhere by electrolyzing water. Therefore, a water electrolysis system that produces hydrogen by water electrolysis has attracted attention as a means to reduce the energy import volume and improve the energy self-sufficiency rate. The water electrolysis system is planned for future mass introduction mainly in Europe.

[0004] Regarding the electric power used for hydrogen production by the water electrolysis system, efforts are also being made to produce green hydrogen by utilizing the output of a power generation device using renewable energy (referred to as a "renewable energy power generation system"). For example, a water electrolysis system is connected to a connection point where renewable energy (sometimes abbreviated as "renewable energy") is connected to the grid or in the vicinity thereof, and the water electrolysis system connected to the renewable energy power generation system consumes the generated electric power from the renewable energy to produce hydrogen. For the sake of convenience in explanation, a system with such a configuration is referred to as a renewable energy-linked water electrolysis system.

[0005] Patent Document 1 discloses an invention relating to the operation method of a renewable energy interconnected water electrolysis system. The renewable energy interconnected water electrolysis system described in Patent Document 1 is a renewable energy output system having a renewable energy power generation facility and a variable power utilization device, and capable of supplying surplus output to an external power grid. The system includes a control unit that acquires power generation information from the renewable energy power generation facility and controls the amount of power supplied that is consumed by the variable power utilization device from the power generation. The control unit uses an output Pf obtained by smoothing the time-series output P of the renewable energy power generation facility with a predetermined time constant, and a predetermined function F with Pf as a variable, to calculate the electrolysis power Pe of the variable power utilization device from the equation Pe = P - [Pf - F(Pf)] (where the maximum value of F(Pf) = the upper limit electrolysis power of the variable power utilization device), and controls the system to supply the calculated electrolysis power to the variable power utilization device and supply the surplus output to an external power grid.

[0006] Japanese Patent Publication No. 2016-226238

[0007] Patent Document 1 discloses a method for operating a water electrolysis system when no output restrictions are imposed on the renewable energy power generation system. However, as water electrolysis systems become more widespread, it is anticipated that situations in which output restrictions are imposed on renewable energy power generation systems will become more frequent. In such cases, when operating a water electrolysis system using electricity generated by a renewable energy power generation system, if output restrictions are imposed on the renewable energy power generation system, there is a risk that the water electrolysis system may not be able to be operated properly.

[0008] The present invention was made to solve the above-mentioned problems, and aims to provide a renewable energy-connected water electrolysis system that can be properly operated even when the renewable energy generation system is subject to output limitations when operating the water electrolysis system using electricity generated by the renewable energy generation system, as well as a control device and control method for the renewable energy-connected water electrolysis system. Other problems, configurations, and effects will be described in detail in the following embodiments.

[0009] To solve the above problems, the renewable energy interconnected water electrolysis system according to the present invention comprises a renewable energy power generation system that outputs power generated using renewable energy to at least the grid, and a water electrolysis system connected to the grid via a common interconnection point for the renewable energy power generation system, which produces hydrogen by electrolyzing water in response to the output of the power generated, and the control device that controls the output of the power generated by the renewable energy power generation system and the electrolysis power of the water electrolysis system, the control device comprising: an acquisition unit that acquires an output power limit command value for the renewable energy power generation system and an electrolysis power upper limit value which is the upper limit of the electrolysis power for the water electrolysis system, respectively; a calculation unit that calculates a power generation threshold value which is the sum of the output power limit command value and the electrolysis power upper limit value acquired by the acquisition unit; and a setting unit that sets the power generation upper limit value which is the upper limit of the power generated by the renewable energy power generation system to be less than or equal to the power generation threshold value calculated by the calculation unit. The most important feature of this system is that it is configured to include a coordinated control unit that coordinates the output control of the renewable energy generation system and the electrolysis power control of the water electrolysis system so that the generated power of the renewable energy generation system does not exceed the upper limit of generated power set by the setting unit.

[0010] According to the present invention, when operating a water electrolysis system using the power output of a renewable energy generation system, even when the output of the renewable energy generation system is limited, the operating rate of both the renewable energy generation system and the water electrolysis system can be appropriately ensured. Other issues, configurations, and effects will be described in detail in the following embodiments.

[0011] This is a block diagram illustrating the schematic configuration of a renewable energy-connected water electrolysis system according to an embodiment of the present invention. This is a block diagram illustrating a first example of setting the upper limit of the output value by a setting unit belonging to the water electrolysis system provided in the renewable energy-connected water electrolysis system. This is a block diagram illustrating a second example of setting the upper limit of the output value by a setting unit belonging to the water electrolysis system provided in the renewable energy-connected water electrolysis system. This is a schematic configuration diagram of the water electrolysis system provided in the renewable energy-connected water electrolysis system. This is a schematic configuration diagram of the water electrolysis device provided in the water electrolysis system. This is a schematic configuration diagram of the pure water adjustment device provided in the water electrolysis system. This is a flowchart diagram for explaining the operation of the control device of the renewable energy-connected water electrolysis system. This is a time chart diagram for explaining the operation of the control device of the renewable energy-connected water electrolysis system. This is a time chart diagram for explaining the operation of the first operating mode related to the control device of the renewable energy-connected water electrolysis system. This is a time chart diagram for explaining the operation of the second operating mode related to the control device of the renewable energy-connected water electrolysis system. This is a time chart diagram for explaining the operation of the third operating mode related to the control device of the renewable energy-connected water electrolysis system. This is a time chart diagram illustrating the operation of a water electrolysis system in a renewable energy-connected water electrolysis system when the electrolysis power is offset. This is a time chart diagram illustrating the operation of the control device of the renewable energy-connected water electrolysis system in its normal operating mode.

[0012] A renewable energy-connected water electrolysis system, as well as a control device and control method for the renewable energy-connected water electrolysis system according to embodiments of the present invention, will be described in detail with reference to the drawings as appropriate. In the following figures, common reference numerals are generally used between components having common functions or between components having mutually corresponding functions, and redundant explanations are omitted. The size and shape of components may be represented schematically by being modified or exaggerated for the sake of explanation.

[0013] [Outline Configuration of Renewable Energy Interconnected Water Electrolysis System 11] The outline configuration of the renewable energy interconnected water electrolysis system 11 according to an embodiment of the present invention will be described with reference to Figures 1A to 1C as appropriate. Figure 1A is a block diagram showing the outline configuration of the renewable energy interconnected water electrolysis system 11 according to an embodiment of the present invention. Figure 1B is a block diagram showing an example of setting the upper limit of the output value by the setting unit 25 belonging to the water electrolysis system 17 provided in the renewable energy interconnected water electrolysis system 11. Figure 1C is a block diagram showing an example of setting the upper limit of the output value by the setting unit 25 belonging to the water electrolysis system 17 provided in the renewable energy interconnected water electrolysis system 11.

[0014] As shown in Figure 1A, the renewable energy grid-connected water electrolysis system 11 comprises a renewable energy power generation system 13 that outputs generated electricity generated using renewable energy such as solar, wind, and hydropower to at least the grid 15; a water electrolysis system 17 connected to the grid 15 via a common connection point 16 to the renewable energy power generation system 13, which produces hydrogen by electrolyzing water in response to the output of the generated electricity; and a control device 19 that coordinates the output control of the generated electricity related to the renewable energy power generation system 13 and the electrolysis power control related to the water electrolysis system 17. The grid 15 is, for example, a power grid such as the commercial power grid.

[0015] The renewable energy generation system 13 and the water electrolysis system 17 are interconnected via a communication medium 18 (whether wired or wireless). Each of the renewable energy generation system 13 and the water electrolysis system 17 is configured to exchange various information, including the power generation command value for the renewable energy generation system 13 and the electrolysis power command value and electrolysis power rating value for the water electrolysis system 17, via the communication medium 18 and the control device 19, respectively.

[0016] In the renewable energy interconnected water electrolysis system 11 according to the present invention, part or all of the power generated by the renewable energy power generation system 13 is consumed by the electrolysis power generated by the water electrolysis system 17. When such power generation is consumed and a surplus differential power (power generation - electrolysis power) is generated, the system is configured to transmit that differential power to the grid 15.

[0017] The renewable energy generation system 13 comprises a renewable energy generator (not shown) that generates electricity using renewable energy, and a renewable energy control device (not shown) that controls the output of the generated electricity from the renewable energy generator. The renewable energy generation system 13 is configured to output the generated electricity generated using renewable energy to the grid 15 and the water electrolysis system 17 via the interconnection point 16.

[0018] As a premise, in the renewable energy interconnected water electrolysis system 11 according to the embodiment of the present invention, it is assumed that, for example, the output of power generated by the renewable energy power generation system 13 is restricted based on the request of the grid operator who operates the grid 15, the operating status of the water electrolysis system 17, etc. Specifically, it is assumed that an output power restriction command value R_Grid has been issued to the renewable energy power generation system 13, indicating that the upper limit of the output should be restricted. In cases where an output restriction is imposed on the power generated by the renewable energy power generation system 13, in order to ensure the stable operation of the grid 15, the amount of power supplied to the grid 15 from the power generated by the renewable energy power generation system 13 is limited to less than the output power restriction command value R_Grid.

[0019] Furthermore, the renewable energy power generation system 13 is capable of outputting power exceeding the output power limit command value R_Grid when the water electrolysis system 17 is in an operational state. In this case, as described above, part or all of the power generated by the renewable energy power generation system 13 is consumed by the electrolysis power of the water electrolysis system 17, and the electrolysis power consumed by the water electrolysis system 17 is set based on a predetermined electrolysis power upper limit value P_UP (details will be described later). As a result, the transmission power value R_SY, which is the differential power output from the renewable energy interconnected water electrolysis system 11 to the grid 15, can be accurately limited to less than the output power limit command value R_Grid.

[0020] [Outline Configuration of Water Electrolysis System 17] The outline configuration of the water electrolysis system 17, which constitutes a part of the renewable energy interconnected water electrolysis system 11 according to an embodiment of the present invention, will be described with reference to Figures 2A to 2C as appropriate. Figure 2A is an outline configuration diagram of the water electrolysis system 17 provided in the renewable energy interconnected water electrolysis system 11. Figure 2B is an outline configuration diagram of the water electrolysis device 31 provided in the water electrolysis system 17. Figure 2C is an outline configuration diagram of the pure water adjustment device 33 provided in the water electrolysis system 17.

[0021] As shown in Figure 2A, the water electrolysis system 17 is comprised of a water electrolyzer 31, a pure water adjustment device 33, a power converter 35, an electrolysis control device 37, a switch 39, and a transformer 38. The water electrolyzer 31 in the water electrolysis system 17 plays the role of producing hydrogen by electrolyzing pure water supplied by the pure water adjustment device 33 with power supplied via the DC connection terminal 35b of the power converter 35.

[0022] As shown in Figure 2B, the water electrolysis apparatus 31 is configured to include, for example, first to fourth electrolytic stacks 32A to 32D. When no particular distinction is required between the first to fourth electrolytic stacks 32A to 32D, they are collectively referred to as the electrolytic stack 32.

[0023] In the water electrolysis device 31, the first and second electrolytic stacks 31A and 31B are electrically connected in series, and the third and fourth electrolytic stacks 31C and 31D are electrically connected in series. The pairs of the first and second electrolytic stacks 31A and 31B, and the pairs of the third and fourth electrolytic stacks 31C and 31D, are electrically connected in parallel to the DC side connection terminal 35b of the power converter 35.

[0024] Each of the first to fourth electrolytic stacks 32A to 32D is connected to a pure water pipe 33a, a hydrogen water pipe 33b, and an oxygen water pipe 33c, respectively, for the inflow and outflow of pure water supplied by the pure water adjustment device 33. The hydrogen water pipe 33b installed in the electrolytic stack 32 discharges pure water (hydrogen water) containing hydrogen produced by the electrolysis of pure water in the electrolytic stack 32. The oxygen water pipe 33c installed in the electrolytic stack 32 discharges pure water (oxygen water) containing oxygen produced by the electrolysis of pure water in the electrolytic stack 32.

[0025] Flow rate adjustment units 32A1 to 32D1 are interposed between the pure water piping 33a and each of the first to fourth electrolytic stacks 32A to 32D to adjust the amount of pure water flowing in.

[0026] There are two main types of electrolytic stacks 32 provided in the water electrolysis device 31: alkaline type and solid polymer type. In this embodiment, although not particularly limited, the case in which a solid polymer type is used as the electrolytic stack 32 is illustrated. The solid polymer type electrolytic stack 32 has an advantage over the alkaline type electrolytic stack in terms of response speed. Therefore, the solid polymer type electrolytic stack 32 is preferable for use in a water electrolysis system 17 where it is required to keep up with fluctuations in renewable energy. Furthermore, the solid polymer type electrolytic stack 32 has an advantage over the alkaline type electrolytic stack in terms of space saving. Therefore, the solid polymer type electrolytic stack 32 is preferable for use in a water electrolysis system 17 where space saving is required, such as in an offshore wind power generation system.

[0027] As shown in Figure 2C, the pure water adjustment device 33 supplies pure water to the water electrolysis device 31 and also plays a role in recovering the hydrogen and oxygen produced by the electrolysis of pure water in the water electrolysis device 31 by separating them from the pure water (hydrogen water and oxygen water) discharged from the water electrolysis device 31.

[0028] The pure water adjustment device 33 is comprised of a pure water tank 41, a first gas-liquid separator 43, and a second gas-liquid separator 45.

[0029] The pure water tank 41 has the function of storing pure water supplied to the water electrolysis device 31, as well as pure water separated into gas and liquid by the first gas-liquid separator 43 and the second gas-liquid separator 45.

[0030] A pure water piping 33a, used to supply pure water to the water electrolysis device 31, is connected to the pure water tank 41. The pure water piping 33a is equipped with a water supply pump 41a, a heat exchanger 41b, and a flow control valve 41c, in order from closest to the pure water tank 41.

[0031] The pure water stored in the pure water tank 41 is transported under pressure by the water pump 41a, its temperature is adjusted by the heat exchanger 41b, and its flow rate is adjusted by the flow control valve 41c before being supplied to the water electrolysis device 31 via the pure water piping 33a.

[0032] The first gas-liquid separation device 43 receives pure water (hydrogen water) containing hydrogen produced by the electrolysis of pure water by the water electrolysis device 31 via the hydrogen water piping 33b, and has the function of recovering hydrogen by performing a gas-liquid separation treatment on the received hydrogen water. The hydrogen water piping 33b connected to the first gas-liquid separation device 43 is equipped with a flow control valve 43a for adjusting the amount of hydrogen water flowing in.

[0033] A pure water tank 41 is connected to the first gas-liquid separator 43 via a pure water pipe 43b. The pure water after the gas-liquid separation treatment by the first gas-liquid separator 43 is sent to the pure water tank 41 via the pure water pipe 43b.

[0034] The first gas-liquid separator 43 is connected to a hydrogen storage tank 34 via a hydrogen pipe 43c. The hydrogen pipe 43c is equipped with a pressure regulating valve 43d for adjusting the internal pressure of the first gas-liquid separator 43. The hydrogen after the gas-liquid separation process in the first gas-liquid separator 43 is sent to the hydrogen storage tank 34 via the pressure regulating valve 43d and the hydrogen pipe 43c, respectively.

[0035] The second gas-liquid separation device 45 receives oxygen-containing pure water (oxygenated water) produced by the electrolysis of pure water by the water electrolysis device 31 via the oxygenated water piping 33c, and has the function of recovering oxygen by performing gas-liquid separation treatment on the received oxygenated water. The oxygenated water piping 33c, which is connected in communication with the first gas-liquid separation device 43, is provided with a flow rate control valve 45a for adjusting the amount of oxygenated water flowing in.

[0036] A pure water tank 41 is connected to the second gas-liquid separator 45 via a pure water pipe 45b. The pure water after the gas-liquid separation treatment by the second gas-liquid separator 45 is sent to the pure water tank 41 via the pure water pipe 45b.

[0037] The second gas-liquid separator 45 is connected to the atmosphere via an oxygen pipe 45c. The oxygen pipe 45c is equipped with a pressure regulating valve 45d for adjusting the internal pressure of the second gas-liquid separator 45. The oxygen after the gas-liquid separation process in the second gas-liquid separator 45 is discharged to the atmosphere via the pressure regulating valve 45d and the oxygen pipe 45c, respectively. However, an oxygen storage tank (not shown) may be connected to the second gas-liquid separator 45, and the oxygen after the gas-liquid separation process in the second gas-liquid separator 45 may be stored in the oxygen storage tank (not shown).

[0038] In the water electrolysis system 17, water electrolysis is performed using power supplied to the water electrolyzer 31 via a power converter 35, etc. Specifically, as shown in Figure 2A, a transformer 38 is connected to the AC side connection terminal 35a of the power converter 35. The transformer 38 is connected to the grid 15 via a switch 39. The water electrolysis system 17 performs water electrolysis by supplying power from the grid 15 (power generated by the renewable energy generation system 13) to the water electrolyzer 31 by adjusting the output of the power converter 35.

[0039] To accurately perform such water electrolysis, the water electrolysis system 17 is equipped with an electrolysis control device 37. The electrolysis control device 37 acquires information on the operating status, including the operating status of the water electrolysis device 31, the pure water adjustment device 33, the power converter 35, and the switch 39, and plays a role in performing accurate electrolysis control based on the acquired operating status.

[0040] [Control device 19 of renewable energy-connected water electrolysis system 11] Next, the control device 19 of the renewable energy-connected water electrolysis system 11 will be described with reference to Figure 1A. The control device 19 of the renewable energy-connected water electrolysis system 11 has the function of coordinating the output control of the generated power related to the renewable energy power generation system 13 and the electrolysis power control related to the water electrolysis system 17.

[0041] To realize the above functions, the control device 19 of the renewable energy interconnected water electrolysis system 11 is configured to include an acquisition unit 21, a calculation unit 23, a setting unit 25, and a coordination control unit 27, as shown in Figure 1A.

[0042] The acquisition unit 21 has a function of acquiring an output power limit command value R_Grid related to the renewable energy power generation system 13 and an electrolysis power upper limit value P_UP which is the upper limit value of the electrolysis power related to the water electrolysis system 17, respectively.

[0043] Here, as described above, the output power limit command value R_Grid related to the renewable energy power generation system 13 is the upper limit value of the power generation power related to the renewable energy power generation system 13, which is imposed based on the request of the power system operator operating the power system 15, the operating state of the water electrolysis system 17, etc. for the purpose of stable operation of the power system 15.

[0044] In the case where an output limit of the power generation power related to the renewable energy power generation system 13 is imposed, the control device 19 of the renewable energy linked water electrolysis system 11 operates to cooperate in performing output control of the power generation power related to the renewable energy power generation system 13 and electrolysis power control related to the water electrolysis system 17, based on the fact that the power transmission power value R_SY output from the renewable energy linked water electrolysis system 11 to the power system 15 should be limited to less than the output power limit command value R_Grid.

[0045] In addition, the acquisition unit 21 acquires information on power supply facilities and power consumption facilities related to the renewable energy power generation system 13, information on control devices that comprehensively manage power supply facilities and power consumption facilities, instruction information from an organization that manages the operating state of a wide-area power system, and power market trading information (power market information). Examples of the power market trading information include spot price information of electricity rates.

[0046] Furthermore, the acquisition unit 21 acquires each information of the power generation power prediction value R_PR, the power generation power rated value R_RV, the power generation power measurement value R_MV, and the power generation power command value R_CV related to the renewable energy power generation system 13, voltage information related to the power system 15, hydrogen remaining amount information related to the hydrogen storage tank 34, and each information of the electrolysis power rated value P_RV, the electrolysis power upper limit value P_UP, the electrolysis power measurement value P_MV, and the electrolysis power command value P_CV related to the water electrolysis system 17.

[0047] The calculation unit 23 calculates a power generation power threshold value R_SUM (=R_Grid + P_UP: refer to FIG. 4) which is the sum of the output power limit command value R_Grid and the electrolysis power upper limit value P_UP acquired by the acquisition unit 21.

[0048] The setting unit 25 basically sets the upper limit value of the generated power R_UP, which is the upper limit value of the generated power related to the renewable energy power generation system 13, to be not more than the generated power threshold value R_SUM calculated by the calculation unit 23.

[0049] Also, as shown in the first setting example of FIG. 1B, the setting unit 25 may set the upper limit value of the electrolysis power P_UP related to the water electrolysis system 17 based on the rated value of the electrolysis power P_RV related to the water electrolysis system 17. Specifically, for example, the setting unit 25 may set the rated value of the electrolysis power P_RV related to the water electrolysis system 17 as the upper limit value of the electrolysis power P_UP related to the water electrolysis system 17 (P_UP = P_RV). Here, the rated value of the electrolysis power P_RV related to the water electrolysis system 17 is the value of the electrolysis power that can stably execute the water electrolysis process related to the water electrolysis system 17.

[0050] Also, as shown in the second setting example of FIG. 1C, the setting unit 25 may set the upper limit value of the electrolysis power P_UP related to the water electrolysis system 17 based on the storage state related to the hydrogen storage tank 34 (storage device: see FIG. 2C) that stores the hydrogen produced by the water electrolysis system 17. The hydrogen storage tank 34 is equipped with a hydrogen remaining amount sensor (not shown) that detects the remaining amount of the stored hydrogen. The remaining amount of hydrogen detected by the hydrogen remaining amount sensor is sent to the setting unit 25 via the acquisition unit 21.

[0051] For example, the setting unit 25 may adopt a configuration in which the upper limit value of the electrolysis power P_UP related to the water electrolysis system 17 is set large in the case where the remaining amount of hydrogen is small and set small in the case where the remaining amount of hydrogen is large based on the remaining amount of hydrogen detected by the hydrogen remaining amount sensor.

[0052] Specifically, for example, if the hydrogen remaining amount in the hydrogen storage tank 34 is below a predetermined remaining amount threshold, the setting unit 25 considers that there is room to store the produced hydrogen and sets the upper limit of electrolysis power P_UP for the water electrolysis system 17 to a value based on the remaining amount of hydrogen (with room) in the hydrogen storage tank 34. In this case, the setting unit 25 may also set the upper limit of electrolysis power P_UP for the water electrolysis system 17 to a predetermined value (for example, the electrolysis power rating P_RV) that takes into account that the water electrolysis system 17 is in an operating state in which it can perform water electrolysis processing without any particular restrictions, instead of a value based on the remaining amount of hydrogen (with room) in the hydrogen storage tank 34.

[0053] On the other hand, if the remaining amount of hydrogen in the hydrogen storage tank 34 exceeds a predetermined remaining amount threshold, the setting unit 25 considers that there is no room to store the produced hydrogen and sets the upper limit value P_UP of the electrolysis power for the water electrolysis system 17 to a value based on the remaining amount of hydrogen in the hydrogen storage tank 34 (no room to spare). In this case, the setting unit 25 should set the upper limit value P_UP of the electrolysis power for the water electrolysis system 17 to a predetermined value (for example, zero) that takes into account that the water electrolysis process for the water electrolysis system 17 is in an operating state where it is not possible to perform water electrolysis.

[0054] The coordinated control unit 27 basically coordinates the output control of the power generated by the renewable energy power generation system 13 and the electrolysis power control of the water electrolysis system 17 so that the measured power generation value R_MV for the renewable energy power generation system 13 does not exceed the upper limit value R_UP for power generation set by the setting unit 25. Alternatively, the power generation command value R_CV for the renewable energy power generation system may be used instead of the measured power generation value R_MV for the renewable energy power generation system 13.

[0055] The control device 19 of the renewable energy-linked water electrolysis system 11, configured as described above, is composed of a computer equipped with, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. In the control device 19, a predetermined program (control program) stored in the ROM is loaded into the RAM and executed by the CPU to be implemented. The program referred to here is a program that causes the computer to execute a control method.

[0056] [Operation of the Control Device 19 of the Renewable Energy Interconnected Water Electrolysis System 11] Next, the operation of the control device 19 of the renewable energy interconnected water electrolysis system 11 will be explained with reference to Figure 3. Figure 3 is a flowchart illustrating the operation of the control device 19 of the renewable energy interconnected water electrolysis system 11. As a prerequisite, in the renewable energy interconnected water electrolysis system 11 according to the embodiment of the present invention, an output limit on the power generated by the renewable energy power generation system 13 is imposed. Specifically, an output power limit command value R_Grid is issued to the renewable energy power generation system 13, indicating that the output upper limit should be limited. Furthermore, when the water electrolysis system 17 is in an operational state, the renewable energy power generation system 13 is capable of outputting power exceeding the output power limit command value R_Grid.

[0057] In step S11 shown in Figure 3, the acquisition unit 21 provided in the control device 19 of the renewable energy interconnected water electrolysis system 11 performs basic information acquisition processing. Specifically, the acquisition unit 21 acquires the output power limit command value R_Grid related to the renewable energy power generation system 13, and the electrolysis power upper limit value P_UP, which is the upper limit value of the electrolysis power related to the water electrolysis system 17. The acquisition unit 21 also acquires information on the predicted power generation value R_PR, the power generation power rating value R_RV, the power generation power measurement value R_MV, and the power generation power command value R_CV related to the renewable energy power generation system 13, voltage information related to the grid 15, hydrogen remaining amount information related to the hydrogen storage tank 34, and information on the electrolysis power rating value P_RV, the electrolysis power upper limit value P_UP, the electrolysis power measurement value P_MV, and the electrolysis power command value P_CV related to the water electrolysis system 17.

[0058] In step S12, the control device 19 of the renewable energy interconnected water electrolysis system 11 determines whether or not it has acquired the output power limit command value R_Grid related to the renewable energy power generation system 13.

[0059] If the determination in step S12 does not result in the acquisition of the output power limit command value R_Grid related to the renewable energy power generation system 13, the control device 19 of the renewable energy-connected water electrolysis system 11 proceeds to step S13. On the other hand, if the determination in step S12 results in the acquisition of the output power limit command value R_Grid related to the renewable energy power generation system 13, the control device 19 of the renewable energy-connected water electrolysis system 11 jumps the process to step S14. According to the preconditions, the control device 19 of the renewable energy-connected water electrolysis system 11 will jump the process to step S14 based on the determination in step S12.

[0060] In step S13, the control device 19 of the renewable energy-connected water electrolysis system 11 performs coordinated control related to the normal operating mode. After that, the control device 19 terminates the series of operations. The coordinated control related to the normal operating mode will be described in detail later.

[0061] In step S14, the calculation unit 23 of the control device 19 of the renewable energy interconnected water electrolysis system 11 calculates the generation power threshold R_SUM (= R_Grid + P_UP: see Figure 4), which is the sum of the output power limit command value R_Grid and the electrolysis power upper limit value P_UP acquired by the acquisition unit 21.

[0062] In step S15, the control device 19 of the renewable energy interconnected water electrolysis system 11 determines whether the predicted power generation value R_PR for the renewable energy power generation system 13 is equal to or greater than the power generation threshold R_SUM (R_PR => R_SUM?). In step S15, it is determined whether the operating state of the renewable energy power generation system 13 is in a state where it can output power exceeding the power generation threshold R_SUM, which is the sum of the output power limit command value R_Grid and the electrolysis power upper limit value P_UP.

[0063] If the determination in step S15 indicates that the predicted power generation value R_PR for the renewable energy power generation system 13 is greater than or equal to the power generation threshold R_SUM (Yes in step S15), the control device 19 of the renewable energy interconnected water electrolysis system 11 proceeds to step S16. On the other hand, if the determination in step S15 indicates that the predicted power generation value R_PR for the renewable energy power generation system 13 is less than the power generation threshold R_SUM (No in step S15), the control device 19 of the renewable energy interconnected water electrolysis system 11 jumps to step S17.

[0064] In step S16, the coordination control unit 27 in the control device 19 of the renewable energy-connected water electrolysis system 11 performs coordination control related to the first operating mode. After that, the control device 19 terminates the series of operations. Details of the coordination control related to the first operating mode will be described later.

[0065] In step S17, the control device 19 of the renewable energy interconnected water electrolysis system 11 determines whether the predicted power generation value R_PR for the renewable energy power generation system 13 is equal to or greater than the upper limit value P_UP for electrolysis power related to the water electrolysis system 17 (R_PR => P_UP?). In step S17, it is determined whether the operating state of the renewable energy power generation system 13 is in a state in which the water electrolysis treatment related to the water electrolysis system 17 can be sufficiently performed.

[0066] If the determination in step S17 indicates that the predicted power generation value R_PR for the renewable energy power generation system 13 is greater than or equal to the upper limit value P_UP for electrolysis power related to the water electrolysis system 17 (Yes in step S17), the control device 19 of the renewable energy interconnected water electrolysis system 11 proceeds to step S18. On the other hand, if the determination in step S17 indicates that the predicted power generation value R_PR for the renewable energy power generation system 13 is less than the upper limit value P_UP for electrolysis power related to the water electrolysis system 17 (No in step S17), the control device 19 of the renewable energy interconnected water electrolysis system 11 jumps to step S19.

[0067] In step S18, the coordination control unit 27 in the control device 19 of the renewable energy-connected water electrolysis system 11 performs coordination control related to the second operating mode. After that, the control device 19 terminates the series of operations. Details of the coordination control related to the second operating mode will be described later.

[0068] In step S19, the coordination control unit 27 in the control device 19 of the renewable energy-connected water electrolysis system 11 performs coordination control related to the third operating mode. After that, the control device 19 terminates the series of operations. Details of the coordination control related to the third operating mode will be described later.

[0069] [Time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11] Next, the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 will be explained with reference to Figure 4. Figure 4 is a time chart diagram used to explain the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11. In Figure 4, the horizontal axis represents time, and the vertical axis represents power. Figure 4 shows the time-series changes of the electrolysis power upper limit value P_UP related to the water electrolysis system 17, the output power limit command value R_Grid related to the renewable energy power generation system 13, and the power generation power threshold R_SUM (= R_Grid + P_UP), which is the sum of these two values.

[0070] As shown in Figure 4, during the period from time t0 to t1, the predicted power generation value R_PR for the renewable energy generation system 13 is less than the upper limit value P_UP for electrolytic power related to the water electrolysis system 17 (No. in step S17). This corresponds to (step S19: third operating mode) in the operation flowchart shown in Figure 3. During the same period from time t0 to t1, the measured power generation value R_MV (substantially equivalent to the power generation command value R_CV) for the renewable energy generation system 13 follows a common trajectory with the predicted power generation value R_PR and the measured electrolytic power value P_MV (substantially equivalent to the electrolytic power command value P_CV) for the water electrolysis system 17. In short, during the same period from time t0 to t1, all of the power generated by the renewable energy generation system 13 is consumed by the electrolytic power related to the water electrolysis system 17. In this case, the transmission power value R_SY output to the system 15 becomes zero (transmission power value R_SY = power generation measurement value R_MV - electrolysis power measurement value P_MV = 0). During the same period t0-t1, the electrolysis power range P_EL_RG related to the water electrolysis system 17 can be expressed as a range from zero to the upper limit of electrolysis power P_UP, as shown in Figure 4.

[0071] During the period from time t1 to t2, the predicted power generation value R_PR for the renewable energy power generation system 13 is less than the power generation threshold R_SUM (No in step S15) and greater than or equal to the electrolytic power upper limit P_UP for the water electrolysis system 17 (Yes in step S17). This corresponds to (step S18: second operating mode) in the operation flowchart shown in Figure 3. During the same period from time t1 to t2, the measured power generation value R_MV for the renewable energy power generation system 13 (substantially equivalent to the power generation command value R_CV) follows a common trajectory with the predicted power generation value R_PR. However, the measured electrolytic power value P_MV for the water electrolysis system 17 (substantially equivalent to the electrolytic power command value P_CV) follows a common trajectory with the electrolytic power upper limit P_UP for the water electrolysis system 17. In short, during the period t1-t2, a portion of the power generated by the renewable energy generation system 13 [electrolysis power upper limit P_UP] is consumed by the electrolysis power of the water electrolysis system 17, and the surplus power [= power generation measurement value R_MV - electrolysis power upper limit P_UP] is transmitted to the grid 15. In this case, the transmitted power value R_SY output to the grid 15 takes the value of the power range P_SY_RG [electrolysis power upper limit P_UP to power generation threshold R_SUM] that is transmitted to the grid 15 (transmitted power value R_SY = power generation measurement value R_MV - electrolysis power upper limit P_UP).

[0072] During the period from time t2 to t3, the predicted power generation value R_PR for the renewable energy power generation system 13 is greater than or equal to the power generation threshold R_SUM (Yes in step S15). This corresponds to (step S16: first operating mode) in the operation flowchart shown in Figure 3. During the same period from time t2 to t3, the measured power generation value R_MV (substantially equivalent to the power generation command value R_CV) for the renewable energy power generation system 13 is smaller than the predicted power generation value R_PR, following a trajectory common to the power generation threshold R_SUM. Similarly, the measured electrolysis power value P_MV (substantially equivalent to the electrolysis power command value P_CV) for the water electrolysis system 17 also follows a trajectory common to the electrolysis power upper limit value P_UP for the water electrolysis system 17. In short, during the period from time t2 to t3, the portion of the predicted power generation value R_PR related to the renewable energy power generation system 13 that exceeds the power generation threshold R_SUM is restricted (measured power generation value R_MV = power generation threshold R_SUM: see "Power generation range P_LM_RG to which output restrictions are imposed on the renewable energy power generation system" shown in Figure 4). Also, during the period from time t2 to t3, a portion of the power generated by the renewable energy power generation system 13 [= power generation threshold R_SUM] [electrolysis power upper limit P_UP] is consumed by the electrolysis power related to the water electrolysis system 17, and the surplus power [= power generation threshold R_SUM - electrolysis power upper limit P_UP] is transmitted to the grid 15. In this case, the transmitted power value R_SY output to the grid 15 can be expressed as [transmitted power value R_SY = power generation threshold R_SUM - electrolysis power upper limit P_UP].

[0073] The operation during the period from time t3 to t4 is substantially the same as the operation during the period from time t1 to t2, so the redundant explanation is omitted. Similarly, the operation during the period from time t4 onward is substantially the same as the operation during the period from time t0 to t1, so the redundant explanation is omitted.

[0074] [Time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the first operating mode] Next, the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the first operating mode will be explained with reference to Figure 5. Figure 5 is a time chart diagram used to explain the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the first operating mode.

[0075] In the first operating mode, the setting unit 25 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sets the measured power generation value R_MV (substantially equivalent to the power generation command value R_CV) related to the renewable energy power generation system 13 to a value common to the power generation threshold R_SUM. In addition, the setting unit 25 in the control device 19 sets the measured electrolysis power value P_MV (substantially equivalent to the electrolysis power command value P_CV) related to the water electrolysis system 17 to a value common to the electrolysis power upper limit value P_UP.

[0076] Next, the coordination control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the power generation threshold R_SUM, which is the power generation command value R_CV for the renewable energy power generation system 13, to the renewable energy power generation system 13. In response, the renewable energy power generation system 13 controls the output of the generated power while maintaining the power generation threshold R_SUM as the power generation command value R_CV.

[0077] Furthermore, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the electrolysis power upper limit value P_UP, which is the electrolysis power command value P_CV for the water electrolysis system 17, to the water electrolysis system 17. In response, the renewable energy power generation system 13 performs electrolysis power control while maintaining the electrolysis power upper limit value P_UP as the electrolysis power command value P_CV.

[0078] In the first operating mode, a portion of the power generated by the renewable energy generation system 13 [= power generation threshold R_SUM] [electrolysis power upper limit P_UP] is consumed as electrolysis power by the water electrolysis system 17, and the surplus power [= power generation threshold R_SUM - electrolysis power upper limit P_UP] is transmitted to the grid 15.

[0079] [Time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the second operating mode] Next, the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the second operating mode will be explained with reference to Figure 6. Figure 6 is a time chart diagram used to explain the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the second operating mode.

[0080] In the second operating mode, the setting unit 25 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sets the measured power generation value R_MV (substantially equivalent to the power generation command value R_CV) related to the renewable energy power generation system 13 to a value common to the predicted power generation value R_PR. In addition, the setting unit 25 in the control device 19 sets the measured electrolysis power value P_MV (substantially equivalent to the electrolysis power command value P_CV) related to the water electrolysis system 17 to a value common to the electrolysis power upper limit value P_UP.

[0081] Next, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the predicted power generation value R_PR, which is the power generation command value R_CV for the renewable energy power generation system 13, to the renewable energy power generation system 13. In response, the renewable energy power generation system 13 controls the output of the generated power without output restrictions, while keeping the power generation command value R_CV in line with the predicted power generation value R_PR.

[0082] Furthermore, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the electrolysis power upper limit value P_UP, which is the electrolysis power command value P_CV for the water electrolysis system 17, to the water electrolysis system 17. In response, the renewable energy power generation system 13 performs electrolysis power control while maintaining the electrolysis power upper limit value P_UP as the electrolysis power command value P_CV.

[0083] In the second operating mode, a portion of the power generated by the renewable energy power generation system 13 [= predicted power generation value R_PR] [upper limit of electrolysis power P_UP] is consumed as electrolysis power by the water electrolysis system 17, and the surplus power [= predicted power generation value R_PR - upper limit of electrolysis power P_UP] is transmitted to the grid 15.

[0084] [Time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the third operating mode] Next, the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the third operating mode will be explained with reference to Figure 7. Figure 7 is a time chart diagram used to explain the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in the third operating mode.

[0085] In the third operating mode, the setting unit 25 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sets the measured power generation value R_MV (substantially equivalent to the power generation command value R_CV) related to the renewable energy power generation system 13 to a value common to the predicted power generation value R_PR. In addition, the setting unit 25 in the control device 19 sets the measured electrolysis power value P_MV (substantially equivalent to the electrolysis power command value P_CV) related to the water electrolysis system 17 to a value common to the predicted power generation value R_PR.

[0086] Next, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the predicted power generation value R_PR, which is the power generation command value R_CV for the renewable energy power generation system 13, to the renewable energy power generation system 13. In response, the renewable energy power generation system 13 controls the output of the generated power without output restrictions, while keeping the power generation command value R_CV in line with the predicted power generation value R_PR.

[0087] Furthermore, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the power generation command value R_CV, which is the electrolysis power command value P_CV related to the water electrolysis system 17, to the water electrolysis system 17. In response, the renewable energy power generation system 13 performs electrolysis power control while making the electrolysis power command value P_CV follow the power generation command value R_CV.

[0088] In the third operating mode, the water electrolysis system 17 is operated in accordance with the power output command value of the renewable energy power generation system 13, so as to follow the output of the renewable energy power generation system 13. All of the power generated by the renewable energy power generation system 13 [= predicted power output value R_PR] [= power output command value R_CV] is consumed by the electrolysis power of the water electrolysis system 17. As a result, there is no surplus power, and therefore it is not transmitted to the grid 15.

[0089] Figure 8 is a time chart illustrating the operation when the electrolysis power of the water electrolysis system 17, which is provided in the renewable energy-linked water electrolysis system 11, is offset.

[0090] In the first to third operating modes, the water electrolysis system 17 is operated based on an electrolysis power command value P_CV obtained by subtracting an offset from the power that the water electrolysis system 17 can consume.

[0091] This offset is provided, for example, to prevent the water electrolysis system 17 from receiving power from the grid 15 when the water electrolysis system 17 consumes the power generated by the renewable energy generation system 13, and the electrolysis power consumed by the water electrolysis system 17 exceeds the power generated by the renewable energy generation system 13.

[0092] With this configuration, it is possible to realize a renewable energy-connected water electrolysis system 11 suitable for applications that produce hydrogen using only renewable energy, as well as a control device 19 and control method for the renewable energy-connected water electrolysis system 11.

[0093] [Time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in normal operation mode] Next, the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in normal operation mode (comparative example) will be explained with reference to Figure 9. Figure 9 is a time chart diagram used to explain the time-series operation of the control device 19 of the renewable energy-connected water electrolysis system 11 in normal operation mode (comparative example).

[0094] In the normal operation mode (comparative example: see step S13 shown in Figure 3), the setting unit 25 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sets the measured power generation value R_MV (substantially equivalent to the power generation command value R_CV) related to the renewable energy power generation system 13 to a value common to the predicted power generation value R_PR. In addition, the setting unit 25 in the control device 19 sets the measured electrolysis power value P_MV (substantially equivalent to the electrolysis power command value P_CV) related to the water electrolysis system 17 to a value that follows the power generation command value R_CV during the period from time t0 to t11 and from time t14 onwards, while setting it to a value common to the electrolysis power upper limit value P_UP during the period from time t11 to t14.

[0095] Next, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the predicted power generation value R_PR, which is the power generation command value R_CV for the renewable energy power generation system 13, to the renewable energy power generation system 13. In response, the renewable energy power generation system 13 controls the output of the generated power without output restrictions, while keeping the power generation command value R_CV in line with the predicted power generation value R_PR.

[0096] Furthermore, the coordinate control unit 27 in the control device 19 of the renewable energy interconnected water electrolysis system 11 sends the power generation command value R_CV and the electrolysis power upper limit value P_UP, which are the electrolysis power command value P_CV related to the water electrolysis system 17, to the water electrolysis system 17. In response, the renewable energy power generation system 13 controls the electrolysis power while keeping the electrolysis power command value P_CV in line with the power generation command value R_CV during the period from time t0 to t11 and from time t14 onward, while controlling the electrolysis power while fixing the electrolysis power command value P_CV to the electrolysis power upper limit value P_UP during the period from time t11 to t14.

[0097] During the period from time t0 to t11 and from time t14 onward in normal operation mode, the water electrolysis system 17 is operated to follow the power generation command value R_CV of the renewable energy power generation system 13. In this case, all of the power generated by the renewable energy power generation system 13 [= power generation command value R_CV] is consumed by the electrolysis power of the water electrolysis system 17. As a result, there is no surplus power, and therefore it is not transmitted to the grid 15.

[0098] On the other hand, during the period from time t11 to t14 in normal operation mode, the renewable energy generation system 13 is operated to follow the predicted power generation value R_PR. The water electrolysis system 17 is operated with the electrolysis power upper limit value P_UP fixed. In this case, a portion of the power generated by the renewable energy generation system 13 [= electrolysis power upper limit value P_UP] is consumed by the electrolysis power of the water electrolysis system 17, and the surplus power [= power generation measurement value R_MV - electrolysis power upper limit value P_UP] is transmitted to the grid 15.

[0099] As described in the embodiments above, the renewable energy interconnected water electrolysis system 11, and the control device 19 and control method for the renewable energy interconnected water electrolysis system 11 according to the present invention have the following features. For the renewable energy interconnected water electrolysis system 11, the water electrolysis system 17 is operated based on, for example, an output power limit command value R_Grid sent from an external source and the operating status of the renewable energy power generation system 13. At the same time, based on the output power limit command value R_Grid, etc., the coordinate control unit 27 provided in the control device 19 of the renewable energy interconnected water electrolysis system 11 (which may also be a control device provided in the renewable energy power generation system 13 and the water electrolysis system 17) sets the upper limit value R_UP for power generation related to the renewable energy power generation system 13 and the upper limit value P_UP for electrolysis power related to the water electrolysis system 17, respectively. Based on the set power generation command value R_CV (upper limit value R_UP) and electrolysis power command value P_CV (upper limit value P_UP), the output control of power generation related to the renewable energy power generation system 13 and the electrolysis power control of the water electrolysis system 17 are coordinated. With this configuration, the renewable energy generation system 13 can output power exceeding the output power limit command value R_Grid, and the water electrolysis system 17 can also generate electrolysis power up to the electrolysis power upper limit value P_UP. As a result, the utilization rate of both equipment can be increased.

[0100] [Other Embodiments] The embodiments and examples described above illustrate examples of the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these descriptions. This is because the present invention can be implemented in various forms without departing from its gist or its main features.

[0101] Furthermore, it is possible to replace some of the configurations of the embodiments described here with those of other embodiments, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace some of the configurations of each embodiment with those of other embodiments.

[0102] Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it can be assumed that almost all components are interconnected.

[0103] Finally, each component, function, processing unit, etc., provided in the control device 19 of the renewable energy-linked water electrolysis system 11 according to the embodiment of the present invention may be implemented in hardware, either partially or entirely, by designing them as an integrated circuit, for example. Alternatively, each of the above-mentioned components, functions, processing units, etc., may be implemented in software by having a processor interpret and execute a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in a recording device such as memory, a hard disk, or an SSD (Solid State Drive), or in a recording medium such as an IC card, an SD card, or a DVD (Digital Versatile Disk).

[0104] 11 Renewable energy grid-connected water electrolysis system 13 Renewable energy power generation system 15 Grid 17 Water electrolysis system 19 Control device 21 Acquisition unit 23 Calculation unit 25 Setting unit 27 Coordination control unit P_UP Electrolysis power upper limit value R_Grid Output power limit command value R_SUM Power generation threshold value

Claims

1. A renewable energy interconnected water electrolysis system comprising: a renewable energy generation system that outputs power generated using renewable energy to at least the grid; and a water electrolysis system connected to the grid via a common interconnection point for the renewable energy generation system, which receives the output of the generated power and produces hydrogen by electrolyzing water, wherein the system includes a control device that controls the output of the generated power related to the renewable energy generation system and the electrolysis power related to the water electrolysis system, the control device comprising: an acquisition unit that acquires an output power limit command value related to the renewable energy generation system and an electrolysis power limit value which is the upper limit of the electrolysis power related to the water electrolysis system, respectively; a calculation unit that calculates a power generation threshold value which is the sum of the output power limit command value and the electrolysis power limit value acquired by the acquisition unit; and a setting unit that sets the power generation limit value which is the upper limit of the generated power related to the renewable energy generation system to be less than or equal to the power generation threshold value calculated by the calculation unit. A renewable energy-connected water electrolysis system is characterized by comprising: a coordinated control unit that coordinates the output control of the power generated by the renewable energy power generation system and the electrolysis power control of the water electrolysis system so that the power generated by the renewable energy power generation system does not exceed the upper limit of power generation set by the setting unit; and 2. A control device for a renewable energy-connected water electrolysis system comprising: a renewable energy power generation system that outputs power generated using renewable energy to at least the grid; and a water electrolysis system connected to the grid via a common interconnection point for the renewable energy power generation system, which produces hydrogen by electrolyzing water in response to the output of the power generated, the control device comprising: an acquisition unit that acquires an output power limit command value for the renewable energy power generation system and an electrolysis power limit value which is the upper limit of the electrolysis power for the water electrolysis system; a calculation unit that calculates a power generation threshold value which is the sum of the output power limit command value and the electrolysis power limit value acquired by the acquisition unit; a setting unit that sets the power generation limit value which is the upper limit of the power generated for the renewable energy power generation system to be less than or equal to the power generation threshold value calculated by the calculation unit; and a coordinated control unit that coordinates the output control of the power generated for the renewable energy power generation system and the electrolysis power control for the water electrolysis system so that the power generated for the renewable energy power generation system does not exceed the power generation limit value set by the setting unit.

3. A control device for a renewable energy-connected water electrolysis system according to claim 2, wherein the setting unit sets an upper limit value of the electrolysis power for the water electrolysis system based on the rated value of the electrolysis power for the water electrolysis system, and the coordinated control unit coordinates the output control of the power generated by the renewable energy power generation system and the electrolysis power control for the water electrolysis system so that the electrolysis power for the water electrolysis system does not exceed the set upper limit value of the electrolysis power.

4. A control device for a renewable energy-connected water electrolysis system according to claim 2, wherein the setting unit sets an upper limit of electrolysis power for the water electrolysis system based on the storage state of a hydrogen storage device for hydrogen produced by the water electrolysis system, and the coordinated control unit coordinates the output control of the power generated by the renewable energy power generation system and the electrolysis power control for the water electrolysis system so that the electrolysis power for the water electrolysis system does not exceed the set upper limit of electrolysis power.

5. A control device for a renewable energy-connected water electrolysis system according to claim 3, wherein the setting unit satisfies the conditions under which the output of the power generated by the renewable energy generation system can be controlled to exceed the power generation threshold, and the predicted value of the power generated by the renewable energy generation system belongs to a first region exceeding the power generation threshold, the setting unit sets the power generated by the renewable energy generation system to the power generation threshold, while setting the electrolytic power of the water electrolysis system to the electrolytic power rated value of the water electrolysis system, and the coordinating control unit coordinately controls the output of the power generated by the renewable energy generation system and the electrolytic power of the water electrolysis system based on the power generated by the renewable energy generation system and the electrolytic power of the water electrolysis system set by the setting unit.

6. A control device for a renewable energy-connected water electrolysis system according to claim 3, wherein the setting unit satisfies the condition that the output of the power generated by the renewable energy generation system can be controlled to be less than the power generation threshold and more than the electrolytic power rating value for the water electrolysis system, and when the predicted power generated by the renewable energy generation system belongs to a second region in which the predicted value of power generated exceeds the electrolytic power rating value and is less than the power generation threshold, the setting unit sets the power generated by the renewable energy generation system to a value belonging to the second region, while setting the electrolytic power for the water electrolysis system to the electrolytic power rating value for the water electrolysis system, and the coordinated control unit coordinately controls the output of the power generated by the renewable energy generation system and the electrolytic power for the water electrolysis system based on the power generated by the renewable energy generation system and the electrolytic power for the water electrolysis system set by the setting unit.

7. A control device for a renewable energy-connected water electrolysis system according to claim 3, wherein the setting unit sets the power generated by the renewable energy generation system to a value common to the electrolysis power of the water electrolysis system when the predicted power generated by the renewable energy generation system falls within a third region where the power generated by the renewable energy generation system is less than or equal to the rated electrolysis power of the water electrolysis system, and the coordinated control unit coordinately controls the output of the power generated by the renewable energy generation system and the electrolysis power of the water electrolysis system based on the power generated by the renewable energy generation system and the electrolysis power of the water electrolysis system set by the setting unit.

8. A control device for a renewable energy-connected water electrolysis system according to claim 3, wherein the setting unit sets the electrolytic power related to the water electrolysis system to a value that is smaller by a predetermined offset from the generated power when the power generated by the renewable energy generation system satisfies the condition that the power generated by the water electrolysis system is controlled to be smaller than the rated electrolytic power value of the water electrolysis system, and the coordinated control unit causes the output control of the power generated by the renewable energy generation system and the electrolytic power control of the water electrolysis system to be performed in coordination based on the electrolytic power related to the water electrolysis system set by the setting unit.

9. A control method for a control device of a renewable energy interconnected water electrolysis system comprising: a renewable energy power generation system that outputs power generated using renewable energy to at least the grid; and a water electrolysis system connected to the grid via a common interconnection point for the renewable energy power generation system, which produces hydrogen by electrolyzing water in response to the output of the power generated, the control method comprising: an acquisition step of acquiring an output power limit command value for the renewable energy power generation system and an electrolysis power limit value which is the upper limit of the electrolysis power for the water electrolysis system; a calculation step of calculating a power generation threshold value which is the sum of the acquired output power limit command value and the electrolysis power limit value; a setting step of setting the power generation limit value which is the upper limit of the power generated for the renewable energy power generation system to be less than or equal to the calculated power generation threshold value; and a coordinated control step of coordinating the output control of the power generated for the renewable energy power generation system and the electrolysis power control for the water electrolysis system so that the power generated for the renewable energy power generation system does not exceed the set power generation limit value.

10. A method for controlling a renewable energy-connected water electrolysis system according to claim 9, characterized in that, in the setting step, an upper limit value of the electrolysis power for the water electrolysis system is set based on the rated value of the electrolysis power for the water electrolysis system, and in the coordinated control step, the output control of the power generated by the renewable energy power generation system and the electrolysis power control for the water electrolysis system are coordinated so that the electrolysis power for the water electrolysis system does not exceed the set upper limit value of the electrolysis power.

11. A method for controlling a renewable energy-connected water electrolysis system according to claim 9, characterized in that, in the setting step, an upper limit of electrolysis power for the water electrolysis system is set based on the storage state of a hydrogen storage device for hydrogen produced by the water electrolysis system, and in the coordinated control step, the output control of the power generated by the renewable energy power generation system and the electrolysis power control for the water electrolysis system are coordinated so that the electrolysis power for the water electrolysis system does not exceed the set upper limit of electrolysis power.

12. A method for controlling a renewable energy-connected water electrolysis system according to claim 10, wherein in the setting step, the power output of the renewable energy generation system is set to the power output threshold when the conditions for controllable above the power output threshold are met and the predicted power output value of the renewable energy generation system falls within a first region exceeding the power output threshold, while the electrolysis power of the water electrolysis system is set to the electrolysis power rated value of the water electrolysis system, and in the coordinated control step, the output control of the power output of the renewable energy generation system and the electrolysis power control of the water electrolysis system are coordinated based on the set power output of the renewable energy generation system and the electrolysis power of the water electrolysis system.

13. A method for controlling a renewable energy-connected water electrolysis system according to claim 10, wherein in the setting step, the output of the power generated by the renewable energy generation system is set to a value belonging to the second region, where the predicted value of the power generated by the renewable energy generation system is greater than the rated value of the electrolysis power and greater than the rated value of the electrolysis power of the water electrolysis system, and in the coordinated control step, the output control of the power generated by the renewable energy generation system and the electrolysis power control of the water electrolysis system are performed in coordination based on the set power generated by the renewable energy generation system and the electrolysis power of the water electrolysis system.

14. A method for controlling a renewable energy-connected water electrolysis system according to claim 10, wherein the setting step is to set the power generated by the renewable energy generation system to a value common to the electrolysis power of the water electrolysis system when the predicted power generated by the renewable energy generation system is less than or equal to the rated electrolysis power of the water electrolysis system, and the coordinated control step is to coordinate the output control of the power generated by the renewable energy generation system and the electrolysis power control of the water electrolysis system based on the set power generated by the renewable energy generation system and the electrolysis power of the water electrolysis system.

15. A method for controlling a renewable energy-connected water electrolysis system according to claim 10, wherein in the setting step, when the conditions are met for controlling the power generated by the renewable energy power generation system to be smaller than the rated electrolysis power of the water electrolysis system, the electrolysis power of the water electrolysis system is set to a value that is smaller than the power generated by a predetermined offset; and in the coordinated control step, the output control of the power generated by the renewable energy power generation system and the electrolysis power control of the water electrolysis system are coordinated based on the set electrolysis power of the water electrolysis system.

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