Control device for water electrolysis system, renewable energy-coordinated water electrolysis system, and control method for water electrolysis system
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HITACHI LTD
- Filing Date
- 2025-11-18
- Publication Date
- 2026-08-06
Smart Images
Figure JP2025040268_06082026_PF_FP_ABST
Abstract
Description
Control Device for Water Electrolysis System, Renewable Energy-Integrated Water Electrolysis System, and Control Method for Water Electrolysis System
[0001] The present invention relates to a control device for a water electrolysis system, a renewable energy-integrated water electrolysis system, and a control method for a 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 is attracting attention as one of the clean energies for achieving carbon neutrality, and technological development related to the production, transportation, and utilization of hydrogen is 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 amount of imported energy and improve the energy self-sufficiency rate. The water electrolysis system is planned for future large-scale introduction mainly in Europe.
[0004] Regarding the electric power used for hydrogen production by a 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 produces hydrogen by consuming the generated electric power from renewable energy (renewable energy generated electric power).
[0005] Conventionally, an example of this type of invention is described in Japanese Patent Publication No. 2016-226238 (Patent Document 1). Specifically, Patent Document 1 describes a renewable energy output system having a renewable energy power generation facility and a variable power utilization device, which is capable of supplying surplus output to an external power grid, and which 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 power, and 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 electrolytic power Pe of the variable power utilization device from the formula Pe = P - [Pf - F(Pf)] (where the maximum value of F(Pf) = the upper limit electrolytic power of the variable power utilization device), and controls the system to supply the calculated electrolytic 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] In the invention described in Patent Document 1, the water electrolysis system consumes a portion of the fluctuations in renewable energy generation power, thereby absorbing the fluctuations in renewable energy generation power and reducing the component of renewable energy generation power that causes grid voltage fluctuations. However, unlike a battery storage system, the water electrolysis system can only consume power, so if the renewable energy generation power falls below the smoothed output Pf of the renewable energy generation power, it may not be possible to absorb the fluctuating component by adjusting the operation of the water electrolysis system.
[0008] On the other hand, in order to ensure the utilization rate of the water electrolysis system, the system may be operated continuously at a constant load without frequent starting and stopping. For example, even when consuming renewable energy, the water electrolysis load of the system may be set to be less than or equal to the fluctuation range of the renewable energy generation, and the system may operate continuously. In this case, since the water electrolysis system is operated at a constant load without following the fluctuations of the renewable energy generation, it may not be able to absorb the fluctuations of the renewable energy generation, and the impact of the renewable energy generation on the grid voltage may not be reduced.
[0009] To solve the above-mentioned problems, the present invention aims to provide a control device for a water electrolysis system that can appropriately reduce the impact of renewable energy power generation on grid voltage fluctuations when operating a water electrolysis system using power generated from a renewable energy power generation system, by adjusting the water electrolysis load of the water electrolysis system.
[0010] To solve the above-mentioned problems, the present invention provides a control device for a water electrolysis system that is connected to a grid via a common interconnection point with a renewable energy power generation system that outputs power generated using renewable energy to the grid, and which produces hydrogen by electrolyzing water in response to the output of the power generated, wherein the control device comprises a renewable energy power acquisition unit that acquires renewable energy power which is power generated output by the renewable energy power generation system, and a water electrolysis system load command value setting unit that sets a value obtained by multiplying the acquired renewable energy power by a predetermined proportional gain as a command value for the water electrolysis load of the water electrolysis system.
[0011] According to the present invention, when operating a water electrolysis system using the power output of a renewable energy power generation system, even under conditions where the connected grid voltage fluctuates significantly, the water electrolysis system can produce hydrogen while simultaneously reducing the grid voltage fluctuations, thereby supporting grid operators in appropriately managing the grid voltage.
[0012] Issues, configurations, and effects other than those mentioned above will be described in detail in the following embodiments.
[0013] This is a schematic diagram showing a general renewable energy power generation system and a water electrolysis system. This is a schematic diagram showing a renewable energy power generation system and a water electrolysis system according to an embodiment of the present invention. This is a schematic diagram showing a renewable energy power generation system and a water electrolysis system according to an embodiment of the present invention. This is a schematic diagram of a water electrolysis system provided in a renewable energy grid-connected water electrolysis system. This is a schematic diagram of a water electrolysis device provided in a water electrolysis system. This is a schematic diagram of a pure water adjustment device provided in a water electrolysis system. This is a configuration diagram of the electrolysis control device for a water electrolysis system. This is a block diagram of the load command value setting unit of a water electrolysis system. This is a diagram showing the characteristics of the proportional gain in the load command value setting unit of a water electrolysis system. This is a time chart diagram showing a comparative example method implemented in the control device of a water electrolysis system. This is a time chart diagram for explaining the operation of the electrolysis control device of a water electrolysis system. This is a flowchart diagram for explaining the operation of the electrolysis control device of a water electrolysis system. This is a block diagram of the load command value setting unit of a water electrolysis system. This is a diagram showing the characteristics of the variable proportional gain in the load command value setting unit of a water electrolysis system. This is a time chart diagram for explaining the operation of the electrolysis control device of a water electrolysis system. This is a flowchart diagram for explaining the operation of the electrolysis control device of a water electrolysis system. This is a block diagram of the load command value setting unit of a water electrolysis system. This is a block diagram of the load command value setting section of the water electrolysis system.
[0014] A control device for a water electrolysis system according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
[0015] In the diagrams below, common reference numerals are generally used to indicate components with common functions or components with mutually corresponding functions, and redundant explanations are omitted. For the sake of clarity, the size and shape of components may be simplified or exaggerated for illustrative purposes.
[0016] [Schematic diagram showing a renewable energy-linked water electrolysis system] A schematic diagram showing a renewable energy-linked water electrolysis system consisting of a renewable energy power generation system and a water electrolysis system according to an embodiment of the present invention will be explained with reference to Figures 1A to 1C as appropriate.
[0017] Figure 1A is a schematic diagram showing a typical renewable energy-linked water electrolysis system consisting of a renewable energy power generation system 11 and a water electrolysis system 17. As shown in Figure 1A, the system consists of a renewable energy power generation system 11 that outputs generated electricity using renewable energy such as solar, wind, and hydropower to at least the grid 13, and a water electrolysis system 17 that is connected to the grid 13 via a common interconnection point 15 to the renewable energy power generation system 11, and produces hydrogen by electrolyzing water in response to the output of the generated electricity. The grid 13 is, for example, a power grid such as the commercial power grid.
[0018] In this configuration, part or all of the electricity generated by the renewable energy power generation system 11 is consumed by the electrolysis power generated by the water electrolysis system 17. When such electricity is consumed and a surplus differential power (generated power - electrolysis power) is generated, this differential power is transmitted to the grid 13.
[0019] In contrast, in the renewable energy linked water electrolysis system of the present invention, the water electrolysis system 17 acquires the power generated by the renewable energy power generation system 11. Figure 1B is a schematic diagram showing a first example thereof. For example, the renewable energy power generation system 11 and the water electrolysis system 17 are interconnected via a communication medium 18 (whether wired or wireless), and each of the renewable energy power generation system 11 and the water electrolysis system 17 is configured so that the electrolysis control device 37 of the water electrolysis system 17, which will be described later, can receive the measured value of the power generated by the renewable energy power generation system 11 via the communication medium.
[0020] Figure 1C is a schematic diagram showing a second example in which the water electrolysis system 17 acquires the power generated by the renewable energy generation system 11. Although not explicitly shown in the figure, for example, a sensor for measuring the transmitted power is installed on the power line between the renewable energy generation system 11 and the interconnection point 15, and the electrolysis control device 37 of the water electrolysis system 17 is configured to receive the signal. [Schematic configuration of the water electrolysis system 17] The schematic configuration of the water electrolysis system 17 according to an embodiment of the present invention will be described with reference to Figures 2A to 2C as appropriate.
[0021] Figure 2A is a schematic diagram of the water electrolysis system 17. Figure 2B is a schematic diagram of the water electrolysis device 31 included in the water electrolysis system 17. Figure 2C is a schematic diagram of the pure water adjustment device 33 included in the water electrolysis system 17.
[0022] 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 produces hydrogen by electrolyzing pure water supplied by the pure water adjustment device 33, receiving power through the DC connection terminal 35b of the power converter 35.
[0023] 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.
[0024] In the water electrolysis device 31, the first and second electrolytic stacks 32A and 32B are electrically connected in series, and the third and fourth electrolytic stacks 32C and 32D are electrically connected in series. The pairs of the first and second electrolytic stacks 32A and 32B, and the pairs of the third and fourth electrolytic stacks 32C and 32D, are electrically connected in parallel to the DC side connection terminal 35b of the power converter 35.
[0025] 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.
[0026] 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.
[0027] The electrolytic stack 32 in the water electrolysis device 31 can be broadly classified into alkaline type and solid polymer type. In this embodiment, although not particularly limited, the case in which the solid polymer type is used as the electrolytic stack 32 is given as an example.
[0028] The solid polymer electrolytic stack 32 has an advantage over the alkaline electrolytic stack in terms of response speed. Therefore, the solid polymer electrolytic stack 32 is preferable for application to the water electrolysis system 17, which is required to keep up with fluctuations in renewable energy.
[0029] Furthermore, the solid polymer type electrolytic stack 32 has an advantage in terms of space saving compared to the alkaline type electrolytic stack. For this reason, the solid polymer type electrolytic stack 32 is preferable for application to water electrolysis systems 17 where space saving is required, such as offshore wind power generation systems.
[0030] As shown in Figure 2C, the pure water adjustment device 33 supplies pure water to the water electrolysis device 31 and recovers the hydrogen and oxygen produced by the electrolysis of pure water in the water electrolysis device 31 by separating the gas and liquid from the pure water (hydrogen water and oxygen water) discharged from the water electrolysis device 31.
[0031] The pure water adjustment device 33 comprises a pure water tank 41, a first gas-liquid separator 43, and a second gas-liquid separator 45. 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. The pure water tank 41 is connected to a pure water pipe 33a used for supplying pure water to the water electrolysis device 31. The pure water pipe 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] Furthermore, 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.
[0036] 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.
[0037] 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.
[0038] Furthermore, 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.
[0039] Furthermore, an oxygen storage tank (not shown) may be connected to the second gas-liquid separation device 45, and the oxygen after the gas-liquid separation process performed by the second gas-liquid separation device 45 may be stored in the oxygen storage tank (not shown).
[0040] 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 13 via a switch 39. The water electrolysis system 17 performs water electrolysis by supplying power from the grid 13 (i.e., power generated in the renewable energy power generation system 11) to the water electrolyzer 31 by adjusting the output of the power converter 35.
[0041] To accurately perform the water electrolysis treatment, 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, for example, through a communication medium 51 (each dashed arrow in Figure 2A), and performs accurate electrolysis control based on the acquired operating status. [First Embodiment of the Electrolysis Control Device 37 of the Water Electrolysis System 17] Next, a first embodiment of the operation of the electrolysis control device 37 of the water electrolysis system 17 will be described with reference to Figures 3A to 6.
[0042] As shown in Figure 3A, the electrolysis control device 37 of the water electrolysis system 17 has a renewable energy generation power acquisition unit 21A and a water electrolysis system load command value setting unit 21B, and is composed of a computer equipped with, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. (not shown). In the electrolysis control device 37, a predetermined program (control program) stored in the ROM is loaded into the RAM and executed by the CPU to be realized. The program referred to here is one that causes the computer to execute a control method.
[0043] As described above, the renewable energy power acquisition unit 21A acquires the measured value of the generated power related to the renewable energy power generation system 11, or acquires the measured value of a sensor or the like that measures the transmitted power installed on the power line between the renewable energy power generation system 11 and the connection point 15.
[0044] Based on the acquired measured value (renewable energy generated power P_RE), the electrolysis system load command value setting unit 21B sets the load command value (electrolysis system load command value) P_EL for the electrolyzer 31 (that is, the power consumption value in the electrolyzer).
[0045] FIG. 3B is a block diagram of the electrolysis system load command value setting unit 21B using the proportional gain in the present embodiment, and FIG. 3C is a diagram showing the characteristics of the proportional gain. As shown in FIG. 3B, the electrolysis system load command value setting unit 21B determines the electrolysis system load command value P_EL by multiplying the renewable energy generated power P_RE by the proportional gain 22. Further, as shown in FIG. 3C, this proportional gain 22 maintains a constant value without depending on the change in the renewable energy generated power P_RE.
[0046] Next, in order to explain the operation of the electrolysis control device 37 of the electrolysis system 17 according to the first embodiment of the present invention, first, as a comparative example, the operation control means of the electrolysis system by a method in which the load command setting by the above-described proportional gain 22 is not performed will be described.
[0047] FIG. 4 is a time chart showing a method of a comparative example implemented in the control device of the electrolysis system. The horizontal axis of the figure indicates time, and the vertical axis indicates, from above in the figure, (a) renewable energy generated power, (b) electrolysis system load command value, and (c) transmitted power transmitted from the connection point to the system. The upper part of the figure indicates that the renewable energy generated power is high, the load command value of the electrolysis system is high, and the transmitted power from the connection point to the system is high, respectively. Also, on the three vertical axes, the rated power value P_RE_Rated of the renewable energy power generation system is described so that the magnitudes can be compared. The scales of the same vertical axis are the same, and the time axes of the horizontal axis are aligned and displayed.
[0048] Note that the renewable energy generated power indicates the measured value. Further, since the electrolysis system load command value allows the electrolysis system 17 to operate following the command value, it is assumed that the load command value and the load measured value match. Also, generally, it is assumed that the power transmitted from the connection point to the grid is proportional to the grid voltage. In the following, although the grid voltage adjustment function by the grid operator is also provided in the grid, a short-term phenomenon before the grid voltage is adjusted by the adjustment is assumed.
[0049] Here, the method according to the comparative example is assumed to keep the electrolysis system at a constant load command value P_EL_Rated without depending on the renewable energy generated power, as shown in the middle of FIG. 4. Note that this P_EL_Rated indicates the rated load of the electrolysis system 17, and a value smaller than the minimum value of the renewable energy generated power (a) shown in the uppermost part of FIG. 4 is assumed.
[0050] As shown in the uppermost part of FIG. 4, while the generated power of the renewable energy generation system 11, i.e., the renewable energy generated power (a), changes, in the method according to the comparative example, since the electrolysis system 17 operates at a constant load as shown in the middle of FIG. 4, as shown in the lowermost part of FIG. 4, the power transmitted from the connection point to the grid (c) is consumed by the electrolysis system 17 such that (b) P_EL_Rated is subtracted from (a) the renewable energy generated power. Therefore, the fluctuation component of the renewable energy generated power remains as it is. As a result, the grid voltage changes, and there is a possibility that the amplitude of the grid voltage similar to that in the lowermost part of FIG. 4 changes. Thereby, there is a possibility that the devices connected to the same grid 13 malfunction. Particularly, when the renewable energy generation system 11 is connected to a grid 13 with a high impedance, i.e., a weak grid, this tendency becomes prominent. Therefore, consideration is necessary when a large amount of the renewable energy generation system 11 is introduced in the future.
[0051] FIG. 5 is a time chart showing the operation of the electrolysis system load command value setting unit 21B according to the first embodiment of the present invention. Since the horizontal and vertical axes of the figure are the same as those in FIG. 4, detailed description thereof is omitted. In FIG. 5, the method according to the comparative example is shown by a dashed line, and the embodiment of the present invention is shown by a solid line. Note that the renewable energy generated power in the uppermost part of FIG. 5 is the same for the method according to the comparative example and the embodiment of the present invention, and is shown by a solid line.
[0052] As shown in Figure 3, the operating means according to the first embodiment of the present invention calculates the water electrolysis system load command value by multiplying the renewable energy generation power by a proportional gain 22. Therefore, as shown in the middle of Figure 5, it changes according to the renewable energy generation power, with P_EL_Rated as the upper limit. As a result, the power transmitted from the interconnection point to the grid (c) shown in the bottom of Figure 5 matches the value obtained by subtracting the water electrolysis system load command value (= measured value) in the middle (b) from the renewable energy generation power (a) in the top (a). Therefore, the range of change is smaller than the range of change of "Δ_CV" confirmed by the method of the comparative example, and changes with a range of change of "Δ_PR1". In this way, because the range of change of power transmitted from the interconnection point to the grid is small, the range of change of grid voltage is also small. Therefore, by applying the first embodiment of the present invention, fluctuations in grid voltage caused by renewable energy generation power can be reduced.
[0053] The operating means according to the first embodiment of the present invention is performed based on the state of the components of the water electrolysis system 17 shown in Figure 2. For example, if the electrolysis stack 32 is deteriorating due to aging, the deterioration may progress further due to an increase in the load on the electrolysis stack 32. Therefore, in order to protect the water electrolysis system 17, the operating means according to the first embodiment may not be implemented.
[0054] In other words, a control unit is provided that monitors the condition of the components and surrounding equipment constituting the water electrolysis system 17 and determines whether or not it is possible to operate according to this embodiment. If the control unit determines that it is "operable," that is, only under conditions where the components and surrounding equipment are in good condition, the operating means according to the first embodiment may be implemented. If it determines that it is "not possible to operate," the operating means according to the first embodiment may not be implemented.
[0055] Alternatively, if the system voltage of system 13 fluctuates significantly and to avoid widespread power outages, the operating means according to the first embodiment of the present invention may be implemented regardless of the state of the water electrolysis system 17 (even in situations where deterioration due to aging or other factors is observed).
[0056] Figure 6 is a flowchart showing the processing of the electrolysis control device 37 according to the first embodiment of the present invention. In step S11 shown in Figure 6, it is determined whether it is necessary to reduce the system voltage fluctuation by the water electrolysis system 17. If the answer is Yes, the process proceeds to step S12. If the answer is No, the series of operations is terminated without taking any action, in order to maintain the state before the execution of this flowchart.
[0057] In step S12, it is determined whether the components of the water electrolysis system 17 and related equipment are in a normal state. If there are no problems (Yes), the process proceeds to step S13. If there are problems (No), the series of operations is terminated without taking any action, maintaining the state before this flowchart was implemented.
[0058] In the following step S13, the renewable energy generated power P_RE is acquired, and the process proceeds to step S14. In step S14, as shown in Figure 3B, the water electrolysis system load command value setting unit 21B sets the proportional gain 22, and the process proceeds to step S15. The value of the proportional gain 22 (gain) is predetermined by empirical rules, etc., but it may also be increased or decreased by monitoring the change range "Δ_PR1" of the grid voltage (c) shown in Figure 5.
[0059] In step S15, the result of multiplying the renewable energy generation power by a proportional gain is set as the load command value for the water electrolysis system 17, and the series of operations ends. By operating the water electrolysis system 17 according to the water electrolysis system load setting value determined through these steps, the fluctuations that the renewable energy generation system 11 has on the grid voltage of the grid 13 can be reduced by the operation of the water electrolysis system 17, as described above.
[0060] Next, a second embodiment of the electrolysis control device 37 of the water electrolysis system 17 will be described with reference to Figures 7A to 10B. In this embodiment, as in the first embodiment shown in Figure 3A, the water electrolysis system load command value setting unit 21B determines the water electrolysis system load command value P_EL based on the renewable energy power generation power P_RE acquired by the renewable energy power generation power acquisition unit 21A.
[0061] Figure 7A is a block diagram of the water electrolysis system load command value setting unit 21B using a variable proportional gain in this embodiment, and Figure 7B is a diagram showing the characteristics of the variable proportional gain.
[0062] As shown in Figure 7A, the water electrolysis system load command value setting unit 21B sets the water electrolysis system load command value P_EL as the result of multiplying the renewable energy generation power P_RE by the variable proportional gain 23 determined by the variable gain determination unit 25. As shown in Figure 7B, the above-mentioned variable proportional gain 23 has the characteristic of increasing as the renewable energy generation power increases, for example. In other words, it increases the variable proportional gain as the renewable energy generation power increases and decreases the variable proportional gain as the renewable energy generation power decreases.
[0063] Using Figure 8, the operation of the electrolysis control device 37 according to this embodiment will be explained in comparison with the comparative example method shown in Figure 4 and the first embodiment of the present invention shown in Figure 5. Figure 8 is a time chart diagram showing the operation of the water electrolysis system load command value setting unit 21B according to this embodiment. The horizontal and vertical axes of the figure are the same as in Figures 4 and 5, so a detailed explanation is omitted. In Figure 8, the operation of the comparative example method is shown with a dashed line, the operation of the first embodiment is shown with a dashed line, and the operation of this embodiment is shown with a solid line. Note that the renewable energy generation power in the uppermost section of Figure 8 is the same in all three embodiments, so it is shown with a solid line.
[0064] As shown in Figure 7A, the operating means according to this embodiment calculates the water electrolysis system load command value by multiplying the renewable energy generation power by a variable proportional gain 23. Therefore, as shown in the middle of Figure 8, P_EL_Rated is changed according to the renewable energy generation power, with P_EL_Rated as the upper limit. In particular, unlike the first embodiment shown in Figure 5, as shown in Figure 7B, the variable proportional gain 23 is changed according to the magnitude of the renewable energy generation power. Therefore, unlike the first embodiment, the larger the renewable energy generation output, the larger the water electrolysis system load command value P_EL is set to.
[0065] As a result, the power transmitted from the interconnection point to the grid (c) shown in the bottom row of Figure 8 matches the value obtained by subtracting the water electrolysis system load command value (measured value) in the middle row (b) from the renewable energy generation power in the top row (a). Therefore, the range of change is smaller than "Δ_CV" confirmed by the comparative example method and is also smaller than the range of change of "Δ_PR1" in the second embodiment, resulting in a change of "ΔP_PR2". This makes the range of change in the power transmitted from the interconnection point to the grid the smallest of the three methods, and thus the range of change in grid voltage the smallest. Therefore, by applying this embodiment, fluctuations in grid voltage caused by renewable energy generation power can be reduced.
[0066] Similar to the first embodiment, the operating means according to this embodiment is executed based on the state of the components of the water electrolysis system 17 shown in Figure 2. That is, if the electrolysis stack is deteriorating, the operating means according to this embodiment may not be implemented in order to protect the state of the water electrolysis system 17, or if the system voltage of the system 13 is fluctuating greatly and a wide-area power outage may be avoided, the operating means according to this embodiment may be forced to be implemented regardless of the state of the water electrolysis system 17.
[0067] Figure 9 is a flowchart showing the processing of the electrolytic control device 37 according to this embodiment. Steps S21 to S23 shown in Figure 9 are the same as steps S11 to S13 in the processing flowchart of the first embodiment shown in Figure 6, so their explanation is omitted.
[0068] In step S24, as shown in Figure 7B, the variable proportional gain 23 is determined by the water electrolysis system load command value setting unit 21B, and the process proceeds to step S25. The slope of the variable proportional gain 23 is predetermined by empirical rules or the like, but it may also be increased or decreased by monitoring the change range "Δ_PR2" of the system voltage (c) shown in Figure 8.
[0069] In step S25, the result of multiplying the renewable energy generated power by a variable proportional gain is set as the load command value for the water electrolysis system 17, and the series of operations ends. By operating the water electrolysis system 17 according to the water electrolysis system load setting value determined through these steps, the fluctuations that the renewable energy generation system 11 has on the grid voltage of the grid 13 can be reduced by the operation of the water electrolysis system 17, as described above.
[0070] Figure 10A is a block diagram showing the means for determining the variable proportional gain of the water electrolysis system load command value setting unit 21B in this embodiment. In the second embodiment, the variable proportional gain was determined according to the renewable energy generation power P_RE based on the characteristics shown in Figure 7B, and the determined variable proportional gain was multiplied by the renewable energy generation power P_RE to determine the water electrolysis system load command value P_EL. However, for example, if the value of the renewable energy generation power P_RE fluctuates greatly up and down in a very short period of time, or if noise is included when measuring the value of the renewable energy generation power P_RE, the value of the variable proportional gain will also change accordingly. As a result, the water electrolysis system load command value will also fluctuate greatly, which may cause the control of the water electrolysis system to become unstable because it cannot keep up, or it may not be possible to appropriately reduce the fluctuation range of grid power.
[0071] Therefore, in this embodiment, as shown in Figure 10A, the variable gain determination unit 25 determines the value of the variable proportional gain 23 based on the output obtained by filtering the value of the renewable energy power generation P_RE with the digital filter 24, and the water electrolysis system load command value P_EL is determined by multiplying the value of the renewable energy power generation P_RE by the variable proportional gain 23.
[0072] The digital filter 24 may be, for example, a first-order lag filter that blocks short-period fluctuation components of renewable energy power generation P_RE. By applying digital filtering, it becomes possible to stably control the water electrolysis system even when the value of renewable energy power generation P_RE fluctuates greatly or contains noise during measurement.
[0073] Alternatively, as shown in Figure 10B, processing using a moving average 24A may be applied instead of the digital filter 24. That is, similar to Figure 10A, the variable gain determination unit 25 determines the value of the variable proportional gain 23 based on the output obtained by applying a moving average to the renewable energy power generation power P_RE, and the water electrolysis system load command value P_EL is determined by multiplying the value of the renewable energy power generation power P_RE by the variable proportional gain 23.
[0074] As described above, the electrolysis control device 37 of the water electrolysis system 17 according to each embodiment of the present invention has the following features. When operating the water electrolysis system 17 using the power output of the renewable energy power generation system 11, even under conditions where the voltage of the connected grid 13 fluctuates significantly, the water electrolysis system 17 produces hydrogen while adjusting the load based on changes in the renewable energy power output. By consuming a portion of the fluctuating component of the renewable energy power generation, the grid voltage fluctuations of the grid 13 can be reduced, thereby supporting grid operators in appropriately managing the grid voltage.
[0075] 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. The present invention can be implemented in various forms without departing from its gist or its main features.
[0076] Furthermore, it is possible to replace some of the configurations of the embodiments described here with those of other embodiments, and even 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.
[0077] 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.
[0078] Finally, some or all of the components, functions, and processing units in the water electrolysis system 17 according to the embodiment of the present invention may be implemented in hardware, for example, by designing them as integrated circuits. Alternatively, the above-mentioned components, functions, and processing units may be implemented in software by having a processor interpret and execute programs that realize their respective functions. 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).
[0079] 11: Renewable energy generation system 13: Grid 17: Water electrolysis system 21A: Renewable energy generation power acquisition unit 21B: Water electrolysis system load command value setting unit 22: Proportional gain 23: Variable proportional gain 24: Digital filter 24A: Moving average 25: Variable gain determination unit 37: Electrolysis control device
Claims
1. A control device for a water electrolysis system that is connected to a grid via a common interconnection point with a renewable energy power generation system that outputs power generated using renewable energy to the grid, and which produces hydrogen by electrolyzing water in response to the output of the power generated, the control device comprising: a renewable energy power acquisition unit that acquires renewable energy power which is power generated output by the renewable energy power generation system; and a water electrolysis system load command value setting unit that sets a value obtained by multiplying the acquired renewable energy power by a predetermined proportional gain as a command value for the water electrolysis load of the water electrolysis system.
2. A control device according to claim 1, characterized in that the proportional gain is a variable gain that changes based on the value of the renewable energy generated power.
3. A control device according to claim 2, characterized in that it increases the variable gain in accordance with an increase in renewable energy generation power and decreases the variable gain in accordance with a decrease in renewable energy generation power.
4. A control device according to claim 3, characterized in that the variable gain increases in accordance with an increase in the filtered value, which is the value obtained by applying a digital filter to the renewable energy generated power, and decreases the variable gain in accordance with a decrease in the value obtained by applying the digital filter.
5. A control device according to claim 3, characterized in that it increases the variable gain in accordance with an increase in the moving average value of the renewable energy generated power and decreases the variable gain in accordance with a decrease in the moving average value.
6. A control device according to claim 2, comprising an operation feasibility determination unit that determines whether or not to operate by setting the proportional gain to the variable gain based on the status of the components constituting the water electrolysis system or peripheral equipment, wherein if the operation feasibility determination unit determines that operation is not possible, the control device stops the operation of multiplying the proportional gain by the renewable energy generated power.
7. A renewable energy linked 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 with the renewable energy power generation system, which receives the output of the power generated and produces hydrogen by electrolyzing water, wherein the water electrolysis system has a control device, and the control device comprises: a renewable energy power acquisition unit that acquires renewable energy power which is power generated output by the renewable energy power generation system; and a water electrolysis system load command value setting unit that sets a value obtained by multiplying the acquired renewable energy power by a predetermined proportional gain as a command value for the water electrolysis load of the water electrolysis system.
8. A control method for a water electrolysis system that is connected to a grid via a common interconnection point with a renewable energy power generation system that outputs power generated using renewable energy to the grid, and which produces hydrogen by electrolyzing water in response to the output of the power generated, wherein the water electrolysis system has a control device including a renewable energy power acquisition unit and a water electrolysis system load command value setting unit, the renewable energy power acquisition unit acquires renewable energy power which is power generated output by the renewable energy power generation system, and the water electrolysis system load command value setting unit sets a value obtained by multiplying the acquired renewable energy power by a predetermined proportional gain as the command value for the water electrolysis load of the water electrolysis system.