Hydrogen production system, power supply apparatus, and control method for hydrogen production system

Abstract

To provide a hydrogen production system capable of suppressing adverse effects on an external power source that may occur in accordance with the response from the hydrogen production system at the occurrence of an abnormality in the external power source, thereby stabilizing the external power source and preventing degradation of a hydrogen production apparatus due to current fluctuation after the abnormality is eliminated.SOLUTION: A hydrogen production system of the present invention comprises: a hydrogen production apparatus; a power supply section that outputs direct current to the hydrogen production apparatus; and a control section that monitors a voltage of an external power source and controls the direct current output from the power supply section based on a monitoring result of the voltage, wherein when a voltage drop in the external power source is detected, the control section decreases a value of the direct current output from the power supply section to a predetermined direct current value greater than zero to continue operation of the hydrogen production apparatus, and thereafter, when the voltage recovery of the external power source is detected, increases the value of the direct current to a specific direct current value according to a predetermined increasing mode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hydrogen production system, a power supply device, and a method for controlling a hydrogen production system. [Background technology]

[0002] Various water electrolysis devices (hydrogen production devices) equipped with a water splitting stack having a solid polymer electrolyte membrane that electrolyzes circulating water to generate hydrogen gas and oxygen gas separately, and methods for controlling such devices have been proposed (see, for example, Patent Document 1). Patent Document 1 proposes the following start-up method for a water electrolysis device to efficiently obtain high-purity hydrogen gas and oxygen gas. When the current flowing through the water electrolysis stack is lower than the rated current, the voltage of the water electrolysis stack is set to be less than a preset upper voltage limit, and the current flowing through the water electrolysis stack is increased to the rated current. When the voltage of the water electrolysis stack is equal to or higher than the upper voltage limit, the current flowing through the water electrolysis stack is maintained. [Prior art documents] [Non-patent literature]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-59503 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, a hydrogen generation system including a hydrogen production device is connected to an external power source, such as a commercial power source or a renewable energy power generation system, and power is supplied from the external power source to the hydrogen production device. Furthermore, since the amount of hydrogen produced per unit time in a hydrogen production system is proportional to the power consumption, in order to meet the demand for large-scale production of hydrogen gas, it is necessary to operate multiple hydrogen production systems in parallel to increase the electrical capacity (installation capacity).

[0005] However, because large-scale hydrogen production systems have a large installed capacity, there is a possibility that the external power source may be adversely affected depending on how the hydrogen production system responds to a voltage drop (abnormal occurrence) in the external power source. For example, when the hydrogen production system is interconnected with a commercial power source (power grid), if the hydrogen production system is disconnected (decoupled) from the external power source at the same time as the voltage of the commercial power source (grid voltage) drops, there is a possibility that the grid voltage will increase significantly. In particular, in a large-scale system consisting of multiple hydrogen production systems, if multiple hydrogen production systems are simultaneously decoupled at the same time as the grid voltage drops, the adverse effects on the power grid as described above will be even greater. Therefore, when using a commercial power source as the external power source for a hydrogen production system, it is important to stabilize the external power source (power grid).

[0006] Furthermore, if the power supplied to the hydrogen production system is immediately restored to the rated operating value after the abnormality in the external power supply is resolved, the current flowing through the water electrolysis stack may fluctuate suddenly, which may cause deterioration of the water electrolysis stack. Note that the start-up method of a water electrolysis apparatus disclosed in Patent Document 1 does not take into consideration the above-mentioned issues that occur after the abnormality in the external power supply is resolved.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a technology that can stabilize the external power supply by suppressing adverse effects on the external power supply that may occur depending on the response of the hydrogen production system when an abnormality occurs in the external power supply, and that can prevent deterioration of the hydrogen production device due to current fluctuations after the abnormality is resolved. [Means for solving the problem]

[0008] In order to solve the above problems, the hydrogen production system of the present invention comprises a hydrogen production device and a power supply unit that converts AC power input from an external power source into DC power and outputs DC current to the hydrogen production device. The hydrogen production system of the present invention also comprises a control unit that monitors the voltage of the external power source and controls the DC current output from the power supply unit based on the voltage monitoring results. When the control unit detects a voltage drop in the external power source, it reduces the value of the DC current output from the power supply unit to a predetermined DC current value greater than 0, thereby continuing operation of the hydrogen production device. Thereafter, when the control unit detects a recovery in the voltage of the external power source, it increases the value of the DC current to a specific DC current value at a predetermined increasing rate.

[0009] To solve the above problem, the power supply device of the present invention includes a power supply unit that converts AC power input from an external power source into DC power and outputs the DC current to an external device. The power supply device of the present invention also includes a control unit that monitors the voltage of the external power source and controls the DC current output from the power supply unit based on the voltage monitoring result. When the control unit detects a voltage drop in the external power source, it reduces the value of the DC current output from the power supply unit to a predetermined DC current value greater than 0, thereby continuing operation of the external device. Thereafter, when the control unit detects a recovery in the voltage of the external power source, it increases the value of the DC current to a specific DC current value at a predetermined increasing rate.

[0010] Furthermore, to solve the above-mentioned problems, the control method for a hydrogen production system of the present invention includes a control unit monitoring the voltage of an external power supply. The control method for a hydrogen production system also includes, when the control unit detects a voltage drop in the external power supply, reducing the value of the DC current output from the power supply unit to a predetermined DC current value greater than 0, thereby continuing operation of the hydrogen production device. The control method for a hydrogen production system also includes, when the control unit detects a voltage recovery in the external power supply, increasing the value of the DC current to a specific DC current value at a predetermined increasing rate. [Effects of the Invention]

[0011] According to the present invention having the above configuration, it is possible to stabilize the external power supply by suppressing adverse effects on the external power supply that may occur depending on the response of the hydrogen production system when an abnormality occurs in the external power supply, and it is also possible to prevent deterioration of the hydrogen production device due to current fluctuations after the abnormality is resolved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a hydrogen production system according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a diagram showing an example of the control operation of the electrolysis current when an abnormality occurs in the external power supply, which is performed in the hydrogen production system according to the first embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing a modified example of the control operation of the electrolysis current when an abnormality occurs in the external power supply, which is performed in the hydrogen production system according to the first embodiment of the present invention. [Figure 4] 3 is a flowchart showing the procedure of a control process for an electrolytic current performed in the hydrogen production system according to the first embodiment of the present invention. [Figure 5] FIG. 10 is a diagram showing an example of the control operation of the electrolysis current when an abnormality occurs in the external power supply, which is performed in the hydrogen production system according to the second embodiment of the present invention. [Figure 6] FIG. 10 is a diagram showing another example of the control operation of the electrolysis current when an abnormality occurs in the external power supply, which is performed in the hydrogen production system according to the second embodiment of the present invention. [Figure 7] 10 is a flowchart showing the procedure of a control process for an electrolysis current performed in a hydrogen production system according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a schematic configuration diagram of a hydrogen production system according to a third embodiment of the present invention. [Figure 9] FIG. 10 is a diagram showing an example of the control operation of the electrolysis current when an abnormality occurs in the external power supply, which is performed in the hydrogen production system according to the third embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing another example of the control operation of the electrolysis current when an abnormality occurs in the external power supply, which is performed in the hydrogen production system according to the third embodiment of the present invention. [Figure 11]10 is a flowchart showing the procedure of a control process for an electrolysis current performed in a hydrogen production system according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a hydrogen production device system according to various embodiments of the present invention and a method for controlling a direct current (hereinafter referred to as "electrolysis current") output to the hydrogen production device will be specifically described with reference to the drawings.

[0014] 1. First embodiment [Configuration of hydrogen production system] 1 is a schematic diagram of a hydrogen production system according to a first embodiment of the present invention. For the sake of simplicity, only components related to control of electrolysis current in the hydrogen production system are shown.

[0015] 1, the hydrogen production system 1 includes a hydrogen production device 10, a first storage tank 11, a first gas-liquid separator 12, a second gas-liquid separator 13, a liquid junction 14, a second storage tank 15, and a third storage tank 16. The hydrogen production system 1 also includes a power conditioner 20 (power supply device), and the power conditioner 20 has a power conversion unit 21 (power supply unit) and a current control unit 22 (control unit).

[0016] 1, the hydrogen production device 10 is connected to a first storage tank 11, a first gas-liquid separator 12, and a second gas-liquid separator 13 via piping (thick solid lines in FIG. 1). The first gas-liquid separator 12 is connected to a liquid junction 14 and a second storage tank 15 via piping, and the second gas-liquid separator 13 is connected to the liquid junction 14 and a third storage tank 16 via piping. In addition, the liquid junction 14 is connected to the first storage tank 11 via piping.

[0017] The power conversion unit 21 in the power conditioner 20 is electrically connected to the hydrogen production device 10 and a commercial power supply 5 provided outside the hydrogen production system 1. In the power conditioner 20, the power conversion unit 21 is electrically connected to a current control unit 22. Three-phase AC power is supplied from the commercial power supply 5 to the power conditioner 20.

[0018] [Configuration and operation of each part] The hydrogen production device 10 includes multiple electrolysis stacks each made of a solid polymer electrolyte membrane. Each electrolysis stack in the hydrogen production device 10 electrolyzes pure water for hydrogen production supplied from a first storage tank 11 to generate hydrogen and oxygen. The hydrogen production device 10 then discharges the generated hydrogen to a first gas-liquid separator 12 and discharges the generated oxygen to a second gas-liquid separator 13. At this time, the hydrogen and oxygen are discharged in a state where they are mixed with water vapor.

[0019] The first storage tank 11 stores the pure water that flows in from the liquid junction 14 as pure water for hydrogen production. The first storage tank 11 then discharges the stored pure water for hydrogen production to the hydrogen production device 10.

[0020] The first gas-liquid separator 12 separates hydrogen and water vapor (moisture) from the mixture of hydrogen and water vapor that has flowed in. The first gas-liquid separator 12 then discharges the separated hydrogen into the second storage tank 15 and the separated moisture into the liquid junction 14.

[0021] The second gas-liquid separator 13 separates oxygen and water vapor (moisture) from the mixture of oxygen and water vapor that has flowed in. The second gas-liquid separator 13 then discharges the separated oxygen into the third storage tank 16 and the separated moisture into the liquid junction 14.

[0022] The liquid confluence 14 combines the water separated in the first gas-liquid separator 12 and the water separated in the second gas-liquid separator 13, and discharges the combined water (pure water) into the first storage tank 11.

[0023] The second storage tank 15 stores the hydrogen separated in the first gas-liquid separator 12, and the third storage tank 16 stores the oxygen separated in the second gas-liquid separator 13.

[0024] The power conversion unit 21 includes a power conversion element, converts AC power supplied (input) from the commercial power supply 5 into DC power, and supplies (outputs) the converted DC power to the hydrogen production device 10 (external device). Although not shown, the power conversion unit 21 is provided with a voltmeter for monitoring the voltage of the commercial power supply 5.

[0025] The current control unit 22 acquires a voltage value (hereinafter referred to as "commercial power supply voltage value") measured by a voltmeter (not shown) provided in the power conversion unit 21 for monitoring the voltage of the commercial power supply 5. Then, the current control unit 22 controls (adjusts) the value of the electrolysis current output from the power conversion unit 21 to the hydrogen production device 10 based on the acquired commercial power supply voltage value. Specifically, the current control unit 22 sets a target electrolysis current value according to the acquired commercial power supply voltage value, and outputs an output command (control signal) including information on the target electrolysis current value to the power conversion unit 21. Then, when the output command for the target electrolysis current value is input, the power conversion unit 21 is controlled so that the electrolysis current of the target electrolysis current value is output to the hydrogen production device 10. Although not shown, the current control unit 22 can be configured by, for example, a microprocessor including a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), and has various functions such as a calculation function and a communication function.

[0026] [Power conditioner control overview] In this embodiment, when a voltage drop (abnormality) of the commercial power supply 5 is detected, the value of the electrolysis current output from the power conditioner 20 to the hydrogen production device 10 is set to the minimum current value (hereinafter referred to as the "minimum electrolysis current value") required for operation (operation) of the hydrogen production device 10. In other words, when a voltage drop (abnormality) of the commercial power supply 5 is detected, the hydrogen production system 1 is not disconnected from the commercial power supply 5, and the hydrogen production device 10 continues to operate (hereinafter referred to as the "minimum current operation") at a minimum electrolysis current value (predetermined DC current value, minimum current value) greater than 0 (A).

[0027] If such minimum current operation is performed after an abnormality is detected in the commercial power supply 5 (external power supply), the hydrogen production system 1 will not be disconnected, thereby suppressing the adverse effects on the commercial power supply 5 (power system) that may occur as a result of the disconnection.

[0028] The minimum electrolysis current value is set appropriately depending on the configuration of the hydrogen production device 10 (for example, the installed capacity, etc.). The minimum electrolysis current value may be changed depending on the degree of voltage drop of the external power supply (mild, medium, severe, etc.). In this case, the recovery mode of the electrolysis current after the abnormality of the external power supply is resolved (the increase mode of the electrolysis current during the recovery operation period, which will be described later) differs depending on the degree of the voltage drop of the external power supply, and fluctuations in the electrolysis current after the abnormality is resolved can be minimized.

[0029] Furthermore, in this embodiment, when elimination (voltage recovery) of a voltage drop (abnormality) in the commercial power supply 5 is detected, the value of the electrolysis current output to the hydrogen production device 10 is increased in a stepwise manner from the minimum electrolysis current value to the rated value of the electrolysis current (hereinafter referred to as the "rated electrolysis current value") to recover. Hereinafter, this manner of increase in the electrolysis current value will be referred to as a "step increase" (predetermined increase manner), and operation during the step increase period will be referred to as a "recovery operation."

[0030] That is, in this embodiment, when it is detected that the voltage drop (abnormality) of the commercial power supply 5 has been resolved, a period is provided in which the hydrogen production device 10 is operated at one or more electrolysis current values ​​between the minimum electrolysis current value and the rated electrolysis current value during the process of increasing the electrolysis current value to the rated electrolysis current value (specific DC current value). Note that, hereinafter, one or more electrolysis current values ​​between the minimum electrolysis current value and the rated electrolysis current value are referred to as "intermediate electrolysis current values."

[0031] When such recovery operation is performed after the abnormality in the commercial power supply 5 (external power supply) is resolved, the value of the electrolysis current output to the hydrogen production device 10 is not immediately restored to the rated electrolysis current value (rated operating value), thereby preventing abrupt fluctuations in the electrolysis current input to the hydrogen production device 10. As a result, it is possible to suppress deterioration of the water electrolysis stack that would otherwise be caused by abrupt fluctuations in the electrolysis current after the abnormality in the commercial power supply 5 (external power supply) is resolved.

[0032] During the recovery operation period after the abnormality in the external power supply is resolved, it is preferable to adjust the electrolysis current command value (electrolysis current value) so that the rate of change of the electrolysis current is a rate of change that can suppress deterioration of the water electrolysis stack. In this case, during the recovery operation period after the abnormality in the external power supply is resolved, it is possible to suppress deterioration of the water electrolysis stack and recover the voltage of the external power supply in the shortest time possible.

[0033] [Example of power conditioner control operation] Here, in this embodiment, a specific example of control of the electrolytic current by the power conditioner 20 when a voltage drop (abnormality) occurs in the commercial power supply 5 will be described. Fig. 2 is a diagram showing the relationship between the change characteristics of the commercial power supply voltage value and the change characteristics of the target electrolytic current value (hereinafter referred to as the "electrolytic current command value") included in the output command output from the current control unit 22 to the power conversion unit 21 when the voltage of the commercial power supply 5 drops. The horizontal axis of each change characteristic in Fig. 2 represents time, the vertical axis of the change characteristic of the commercial power supply voltage represents the voltage value, and the vertical axis of the change characteristic of the electrolytic current command value represents the current value. In addition, in the example shown in Fig. 2, an example will be described in which only one intermediate electrolytic current value is provided for step increase during the recovery operation period.

[0034] 2 shows the change characteristics of the electrolysis current command value, but the change characteristics (electrolysis current value and its change mode) of the value of the electrolysis current actually output from the power conversion unit 21 to the hydrogen production device 10 are also similar to the change characteristics of the electrolysis current command value. Therefore, the change characteristics of the electrolysis current command value shown in FIG. 2 are essentially the change characteristics of the value of the electrolysis current output from the power conversion unit 21 to the hydrogen production device 10.

[0035] In the example shown in FIG. 2, consider the following case where a voltage drop (abnormality) occurs in the commercial power supply 5. First, during normal operation at the rated commercial power supply voltage Vc, a drop (abnormality) in the commercial power supply voltage is detected at time t1. The commercial power supply voltage then drops to an abnormal voltage Vcm (for example, 20% of the rated voltage Vc), and this abnormal voltage Vcm state continues until time t3. Then, at time t3, an increase in the commercial power supply voltage (abnormality resolution) is detected, and the commercial power supply voltage then increases from the abnormal voltage Vcm to the rated voltage Vc. That is, in the example shown in FIG. 2, the period before time t1 is the pre-abnormality period, the period from time t1 to time t3 is the voltage drop (abnormality) period, and the period from time t3 onwards is the post-abnormality resolution period.

[0036] In the above-described example of an abnormality occurring in the commercial power supply 5, when the current control unit 22 detects a drop (abnormality) in the commercial power supply voltage value at time t1, the current control unit 22 starts processing to reduce the electrolysis current value to the minimum electrolysis current value. Specifically, at time t2, the current control unit 22 starts processing to reduce the electrolysis current command value to be output to the power conversion unit 21 from a value Ic corresponding to the rated electrolysis current value (hereinafter referred to as the "rated electrolysis current command value") to a command value Icm corresponding to the minimum electrolysis current value (hereinafter referred to as the "minimum electrolysis current command value"). As a result, at time t2, control of normal operation ends and control of minimum current operation starts.

[0037] 2 corresponds to a minute time difference in processing from the detection of a drop in the commercial power supply voltage value by the current control unit 22 to the output of an electrolysis current command value (output command) at the start of minimum current operation. Therefore, from a macroscopic perspective, the time t2 when minimum current operation starts is approximately the same time as the time t1 when a drop in the commercial power supply voltage value is detected.

[0038] After time t2, the current control unit 22 reduces the electrolysis current command value to the minimum electrolysis current command value Icm, and thereafter maintains the electrolysis current command value at the minimum electrolysis current command value Icm until an increase in the commercial power supply voltage value (elimination of the abnormality) is detected.

[0039] Thereafter, at time t3, when the current control unit 22 detects an increase in the commercial power supply voltage value (abnormality elimination), the current control unit 22 starts processing to step-up the electrolysis current value to its rated value. Specifically, at time t4, the current control unit 22 starts processing to step-up the electrolysis current command value to be output to the power conversion unit 21 from the minimum electrolysis current command value Icm to the rated electrolysis current command value Ic. As a result, at time t4, control of the minimum current operation ends and control of the recovery operation starts.

[0040] 2 corresponds to a minute time difference in processing from the detection of a voltage rise in the commercial power supply 5 by the current control unit 22 to the output of an electrolysis current command value (output command) at the start of recovery operation. Therefore, from a macroscopic perspective, the time t4 when recovery operation starts is approximately the same time as the time t3 when a rise in the voltage value of the commercial power supply is detected.

[0041] After time t4, the current control unit 22 increases the electrolysis current command value up to the rated electrolysis current command value Ic while changing the electrolysis current command value in accordance with the elapsed time in a preset step increase manner.

[0042] 2, after the start of recovery operation, the current control unit 22 first increases the electrolysis current command value to a command value Ics corresponding to an intermediate electrolysis current value (hereinafter referred to as the "intermediate electrolysis current command value"), and then maintains the electrolysis current command value at the intermediate electrolysis current command value Ics (target value of DC current) for a certain period of time. Next, after the certain period has elapsed, the current control unit 22 increases the electrolysis current command value to the rated electrolysis current command value Ic, and then maintains the electrolysis current command value at the rated electrolysis current command value Ic for the period until time t5. Then, at time t5, the current control unit 22 ends control of recovery operation, and resumes control of normal operation after time t5.

[0043] The electrolysis current step increase mode and recovery operation period are set, for example, according to the configuration (e.g., facility capacity) of the hydrogen production apparatus 10, so as to prevent deterioration of the hydrogen production apparatus 10 (water electrolysis stack) due to fluctuations in electrolysis current after the abnormality in the external power supply is resolved. In the above-mentioned electrolysis current step increase mode, the period for which the intermediate electrolysis current command value Ics is maintained may be the same as or different from the period for which the rated electrolysis current command value Ic is maintained.

[0044] [Modification of control mode during recovery operation period] The manner in which the electrolysis current command value (electrolysis current value) changes during the recovery operation period when the voltage of the commercial power supply 5 drops (when an abnormality occurs) is not limited to the step increase manner shown in Fig. 2. Any manner can be adopted as long as the fluctuation in the electrolysis current after the abnormality in the commercial power supply 5 (external power supply) is not degraded by the hydrogen production device 10 (water electrolysis stack). An example of such a manner is shown in Fig. 3.

[0045] Fig. 3 shows a control example in which the change in the electrolysis current command value during the recovery operation period is not stepwise but curved, i.e., the electrolysis current command value is increased in a sweeping manner. The horizontal axis of each change characteristic in Fig. 3 represents time, the vertical axis of the change characteristic of the commercial power supply voltage represents the voltage value, and the vertical axis of the change characteristic of the electrolysis current command value represents the current value. Note that the example shown in Fig. 3 is simply a variation of the control mode of the electrolysis current command value during the recovery operation period in the example described in Fig. 2, and the control mode during operation periods other than the recovery operation period is the same as that described in Fig. 2.

[0046] 3, the current control unit 22 increases the electrolysis current command value to the rated electrolysis current command value Ic while changing (decreasing) the rate of change of the electrolysis current command value (the slope of the change characteristic in the drawing) over time from time t4 onwards. At this time, the rate of change of the electrolysis current command value is set to a rate of change that enables deterioration of the water electrolysis stack to be suppressed.

[0047] However, from the viewpoint of ease of control of the electrolytic current during the recovery operation period, the step increase mode shown in FIG. 2 is superior to the sweep increase mode shown in FIG.

[0048] [Power conditioner control process flow] Next, the specific contents of the control process of the electrolytic current output to the hydrogen production device 10, which is performed by the power conditioner 20 in this embodiment, will be described with reference to the drawings. Fig. 4 is a flowchart showing the procedure of the control process of the electrolytic current in this embodiment, which is performed by the power conditioner 20. The control process of the electrolytic current described below is executed on software by a CPU (not shown) included in the current control unit 22 of the power conditioner 20.

[0049] First, current control unit 22 performs a process of monitoring the commercial power supply voltage (S1). In this process, current control unit 22 acquires a commercial power supply voltage value measured by a voltmeter (not shown) provided in power conversion unit 21 for monitoring the voltage of commercial power supply 5, and monitors (recognizes) the operating state of commercial power supply 5 based on the acquired commercial power supply voltage value.

[0050] Next, current control unit 22 determines whether or not a voltage drop (abnormality) has occurred in commercial power supply 5, based on the commercial power supply voltage value acquired in the process of S1 (S2). In this process, current control unit 22 determines whether or not the state of commercial power supply 5 is a voltage drop (abnormality) period (see the change characteristics of the commercial power supply voltage value in FIG. 2). Therefore, in the period from the detection of a voltage drop (abnormality) in commercial power supply 5 to the detection of a voltage rise (abnormality resolution), the determination result in S2 is a Yes determination, and in other periods (the period before the abnormality and the period after the abnormality is resolved), the determination result in S2 is a No determination.

[0051] In detecting a voltage drop (occurrence of an abnormality) and a voltage rise (resolution of the abnormality) of the commercial power supply 5 performed in the process of S2, the voltage value to be compared with the current commercial power supply voltage value may be, for example, the commercial power supply voltage value from a predetermined time ago (for example, several seconds). Also, in the process of S2, for example, the presence or absence of a drop or rise in the commercial power supply voltage may be determined by comparing the average value of the commercial power supply voltage value from the current time until a predetermined time ago with the average value of the commercial power supply voltage value from a time before a predetermined time ago until a predetermined time ago.

[0052] In the determination process of S2, the current control unit 22 may determine whether the currently performed operation is the minimum current operation (see the change characteristics of the electrolysis current command value in FIG. 2). In this case, during the minimum current operation period, the determination result of S2 is Yes, and during other operation periods (normal operation period and recovery operation period), the determination result of S2 is No.

[0053] In the process of S2, if the current control unit 22 determines that a voltage drop (abnormality) has occurred in the commercial power supply 5 (if S2 is determined to be Yes), the current control unit 22 performs a process of setting the minimum current operation (S3).

[0054] In the process of S3, the current control unit 22 sets the electrolysis current command value appropriately according to the elapsed time, for example, so that the value of the electrolysis current drops to the minimum electrolysis current value after the start of the minimum current operation. Also, for example, after the value of the electrolysis current drops to the minimum electrolysis current value, in the process of S3, the current control unit 22 sets the electrolysis current command value to the minimum electrolysis current command value so that the value of the electrolysis current is maintained at the minimum electrolysis current value.

[0055] In the process of S3, the current control unit 22 stores the value of the dropped commercial power supply voltage as an abnormal voltage value. Furthermore, in the process of S3, the current control unit 22 stores, for example, the current time as the time when the abnormality occurred. Therefore, during the minimum current operation period, the time (time when the abnormality occurred) for each process of S3 from the time when the voltage drop (abnormality) of the commercial power supply 5 occurred to the time when the abnormality was resolved and the abnormal voltage value at each time are stored. Note that data such as the abnormal voltage value and the time when the abnormality occurred is stored in a RAM (not shown) included in the current control unit 22. Then, after the process of S3, the current control unit 22 performs the process of S7 described below.

[0056] Returning to the explanation of the processing of S2, if the current control unit 22 determines in the processing of S2 that a voltage drop (abnormality) has not occurred in the commercial power supply 5 (if the determination in S2 is No), the current control unit 22 determines whether or not the current operation period is a recovery operation period (S4). In this processing, the current control unit 22 determines whether or not an abnormal voltage value was stored at a time a specific time before the present (for example, about several seconds). If an abnormal voltage value was stored at a time a specific time before the present, the current control unit 22 determines that the current operation period is a recovery operation period, and the determination result in S4 is Yes. If an abnormal voltage value was not stored at a time a specific time before the present, the current control unit 22 determines that the current operation period is a normal operation period, and the determination result in S4 is No.

[0057] In the process of S4, if the current control unit 22 determines that the current operation period is a recovery operation period (if the determination in S4 is Yes), the current control unit 22 performs a setting process for recovery operation (S5).

[0058] In the process of S5, the current control unit 22 appropriately sets the electrolytic current command value in a stepwise increase manner according to the time elapsed since the start of the recovery operation. For example, after the start of the recovery operation, the current control unit 22 first appropriately sets the electrolytic current command value according to the time elapsed since the start of the recovery operation so that the value of the electrolytic current increases to a predetermined intermediate electrolytic current value. Then, after the value of the electrolytic current reaches the predetermined intermediate electrolytic current value, the current control unit 22 sets the electrolytic current command value to a predetermined intermediate electrolytic current command value so that the value of the electrolytic current is maintained at the predetermined intermediate electrolytic current value for a certain period of time. Furthermore, after the timing at which the value of the electrolytic current is increased from the predetermined intermediate electrolytic current value to another intermediate electrolytic current value or the rated electrolytic current value, the current control unit 22 appropriately sets the electrolytic current command value according to the time elapsed since that timing so that the value of the electrolytic current increases to the other intermediate electrolytic current value or the rated electrolytic current value. After the value of the electrolytic current reaches the other intermediate electrolytic current or the rated electrolytic current value, the current control unit 22 sets the electrolytic current command value to the other intermediate electrolytic current command value or the rated electrolytic current command value so that the other intermediate electrolytic current or the rated electrolytic current value is maintained for a certain period. After the process of S5, the current control unit 22 performs the process of S7 described below.

[0059] On the other hand, if the current control unit 22 determines in the process of S4 that the current operation period is not the recovery operation period (if the determination in S4 is No), the current control unit 22 performs a setting process for normal operation (S6).

[0060] In the process of S6, the current control unit 22 sets an electrolysis current command value for normal operation. Specifically, the current control unit 22 sets the electrolysis current command value to a rated electrolysis current command value. After the process of S6, the current control unit 22 performs the process of S7 described below.

[0061] After the process of S3, S5, or S6, the current control unit 22 performs an electrolysis current control process (S7). In this process, the current control unit 22 outputs an output command (control signal) including information on the electrolysis current command value set in the process of S3, S5, or S6 to the power conversion unit 21. Based on this output command, the electrolysis current value output from the power conversion unit 21 to the hydrogen production device 10 is adjusted to the electrolysis current command value.

[0062] After the process of S7, the current control unit 22 ends the control process of the electrolysis current. However, in this embodiment, while the hydrogen production system 1 is in operation, the above-described control process of the electrolysis current (the processes of S1 to S7) is constantly and repeatedly executed by the power conditioner 20.

[0063] [Various effects] As described above, in this embodiment, even when an abnormality occurs in the commercial power supply 5 (external power supply), the hydrogen production system 1 is not disconnected, but the electrolysis current is reduced to the minimum electrolysis current value and operation is continued. Therefore, it is possible to suppress the above-mentioned adverse effects on the commercial power supply 5 that may occur when the hydrogen production system 1 is disconnected when an abnormality occurs in the commercial power supply 5.

[0064] Furthermore, in this embodiment, after the abnormality in the commercial power supply 5 (external power supply) is resolved, the electrolysis current value is not immediately restored to the rated operating value, but is instead restored by increasing the electrolysis current value in steps. This makes it possible to suppress deterioration of the water electrolysis stack due to a sudden change in the electrolysis current after the abnormality in the commercial power supply 5 is resolved.

[0065] In other words, in this embodiment, the adverse effects on the external power supply that may occur depending on the response of the hydrogen production system 1 when an abnormality occurs in the external power supply are suppressed, thereby stabilizing the external power supply and preventing deterioration of the hydrogen production device 10 due to current fluctuations after the abnormality is resolved.

[0066] 2. Second embodiment Next, a hydrogen production system according to a second embodiment of the present invention and a method for controlling an electrolytic current output to a hydrogen production device will be described. In the following, in this embodiment, devices and components having the same functions as those in the first embodiment will be described using the same reference numerals.

[0067] In the hydrogen production system 1 of the first embodiment described above, even if a voltage drop (abnormality) occurs in the commercial power supply 5, the hydrogen production system 1 is not disconnected from the commercial power supply 5, but instead outputs the minimum electrolysis current value to the hydrogen production device 10 and continues operation. However, if operation continues for too long in a state where the commercial power supply 5 is abnormal (voltage drop), there is a possibility that the water electrolysis stack in the hydrogen production device 10 will deteriorate.

[0068] Therefore, in this embodiment, when the duration of operation at an abnormal voltage value of the commercial power source 5 reaches a specific period, the hydrogen production system 1 is temporarily disconnected to prevent deterioration of the water electrolysis stack. Thereafter, when the abnormality (voltage drop) of the commercial power source 5 is resolved, the hydrogen production system 1 is reconnected to the commercial power source 5 and recovery operation is started. Furthermore, in this embodiment, if the duration of operation at an abnormal voltage value of the commercial power source 5 is less than the specific period, the electrolysis current control process is performed in the same manner as in the first embodiment. Note that the specific period, which serves as a threshold for the duration of operation at an abnormal voltage value of the commercial power source 5, is set appropriately depending on the configuration of the hydrogen production device 10 (for example, the facility capacity, etc.).

[0069] The configuration of the hydrogen production system 1 of this embodiment and the connection between the hydrogen production system 1 and the commercial power source 5 are the same as those of the first embodiment described above with reference to Fig. 1. Therefore, illustration and description of the configuration of the hydrogen production system 1 and the connection between the hydrogen production system 1 and the commercial power source 5 will be omitted here.

[0070] [Example of power conditioner control operation] First, with reference to Figures 5 and 6, an example of control of the electrolysis current by the power conditioner 20 in the present embodiment when a voltage drop (abnormality) occurs in the commercial power supply 5 will be specifically described. Note that, although the examples shown in Figures 5 and 6 show the change characteristics of the electrolysis current command value, these change characteristics of the electrolysis current command value are essentially the change characteristics of the value of the electrolysis current output from the power conversion unit 21 to the hydrogen production device 10.

[0071] (1) Example of control when operation duration at abnormal voltage value is less than a specific period Fig. 5 is a diagram showing the relationship between the change characteristics of the commercial power supply voltage value and the change characteristics of the electrolysis current command value when the duration of operation at an abnormal voltage value of the commercial power supply 5 is less than a specific period (dth in the diagram). The horizontal axis of each change characteristic in Fig. 5 represents time, the vertical axis of the change characteristics of the commercial power supply voltage represents voltage value, and the vertical axis of the change characteristics of the electrolysis current command value represents current value. Note that the change characteristics of the commercial power supply voltage value and the electrolysis current command value shown in Fig. 5 are the same as those explained in Fig. 2 (the first embodiment), so explanation of the change characteristics of the commercial power supply voltage value and the electrolysis current command value shown in Fig. 5 will be omitted.

[0072] In the example shown in Fig. 5, the duration of operation at the abnormal voltage value Vcm (time t3-time ts) is less than the specific period dth (time te-time ts), so the electrolytic current control process is performed in the same manner as in the example shown in Fig. 2 described in the first embodiment. Therefore, the change characteristics of the electrolytic current command value shown in Fig. 5 are the same as those described in Fig. 2.

[0073] In this embodiment, an example will be described in which the start time of the operation duration at the abnormal voltage value Vcm, which serves as a parameter for determining whether or not to temporarily disconnect the hydrogen production system 1, is set to the time ts when the voltage value of the commercial power source 5 drops to the abnormal voltage value Vcm. However, the present invention is not limited to this. For example, the start time of the operation duration at the abnormal voltage value Vcm may be set to the time when the voltage drop of the commercial power source 5 is detected (time t1 in FIG. 5) or the start time of minimum current operation (time t2 in FIG. 5).

[0074] (2) Example of control when operation continues at abnormal voltage for a specific period or longer Fig. 6 shows the relationship between the change characteristics of the commercial power supply voltage value and the change characteristics of the electrolysis current command value when operation at an abnormal voltage value of the commercial power supply 5 continues for a specific period (dth in the figure) or longer. The horizontal axis of each change characteristic in Fig. 6 represents time, the vertical axis of the change characteristics of the commercial power supply voltage represents voltage value, and the vertical axis of the change characteristics of the electrolysis current command value represents current value. In addition, the example shown in Fig. 6 explains an example in which two intermediate electrolysis current values ​​are set for step increase during the recovery operation period.

[0075] In the example shown in FIG. 6, consider the following case where a voltage drop (abnormality) occurs in the commercial power supply 5. First, during normal operation at the rated commercial power supply voltage Vc, a drop (abnormality) in the commercial power supply voltage is detected at time t1. Thereafter, the commercial power supply voltage drops to an abnormal voltage Vcm (e.g., 20% of the rated voltage Vc), and this abnormal voltage Vcm state continues until time t13. Then, at time t13, an increase in the commercial power supply voltage (abnormality resolution) is detected, and thereafter the commercial power supply voltage increases from the abnormal voltage Vcm to the rated voltage Vc. That is, in the example shown in FIG. 6, the period before time t1 is the pre-abnormality period, the period from time t1 to time t13 is the voltage drop (abnormality) period, and the period after time t13 is the post-abnormality resolution period. Then, in the example shown in FIG. 6, the period of operation continuing at the abnormal voltage Vcm (time t13-time ts) is equal to or longer than the specific period dth (time te-time ts).

[0076] In the above-described example of an abnormality occurring in the commercial power supply 5, when the current control unit 22 detects a drop (abnormality) in the commercial power supply voltage value at time t1, the current control unit 22 starts processing to reduce the electrolysis current value to the minimum electrolysis current value. Specifically, at time t2, the current control unit 22 starts processing to reduce the electrolysis current command value output to the power conversion unit 21 from the rated electrolysis current command value Ic to the minimum electrolysis current command value Icm. As a result, at time t2, control of normal operation ends and control of minimum current operation starts.

[0077] 6 corresponds to a minute time difference in processing from the detection of a voltage drop in the commercial power supply by the current control unit 22 to the output of an electrolysis current command value (output command) at the start of minimum current operation. Therefore, from a macroscopic perspective, the time t2 when minimum current operation starts is approximately the same as the time t1 when a drop in the commercial power supply voltage value is detected.

[0078] After time t2, the current control unit 22 reduces the electrolysis current command value to the minimum electrolysis current command value Icm, and then maintains the electrolysis current command value at the minimum electrolysis current value Icm until time tf when it outputs a parallel-off command for the hydrogen production system 1.

[0079] At time te, when the current control unit 22 detects that the duration of operation at the abnormal voltage value Vcm has reached the specific period dth, the current control unit 22 outputs a command (parallel-off command) to the power conversion unit 21 to parallel-off the hydrogen production system 1 at time tf. Specifically, the current control unit 22 sets the electrolysis current command value to 0 (A), and outputs an output command including the electrolysis current command value (0 (A)) as the parallel-off command to the power conversion unit 21. As a result, from time tf, the electrolysis current command value starts to decrease to 0 (A), and after that, when the electrolysis current command value decreases to 0 (A), the electrolysis current command value is maintained until an increase in the commercial power supply voltage value (elimination of the abnormality) is detected.

[0080] 6, the time lag between time te when the duration of operation at the abnormal voltage value Vcm reaches the specific period dth and time tf when the parallel-off command is output corresponds to a minute time difference in the processing from the determination of parallel-off by current control unit 22 to the output of the parallel-off command. Therefore, from a macroscopic perspective, time tf when the parallel-off command is output is approximately the same time as time te when the duration of operation at the abnormal voltage value Vcm reaches the specific period dth.

[0081] Thereafter, at time t13, when the current control unit 22 detects an increase in the commercial power supply voltage value (abnormality elimination), the current control unit 22 starts a process of stepping up the electrolysis current value to its rated value. Specifically, at time t14, the current control unit 22 starts a process of stepping up the electrolysis current command value included in the output command output to the power conversion unit 21 from 0 (A) to the rated electrolysis current command value Ic. As a result, at time t14, the parallel-out control ends and the recovery operation control starts.

[0082] 6, the time lag between time t13 when an increase in the commercial power supply voltage value is detected and time t14 when the recovery operation starts corresponds to a minute time difference in the processing from when the current control unit 22 detects an increase in the voltage of the commercial power supply 5 to when the electrolysis current command value (output command) is output at the start of the recovery operation. Therefore, from a macroscopic perspective, time t14 when the recovery operation starts is approximately the same time as time t13 when an increase in the commercial power supply voltage value is detected.

[0083] After time t14, the current control unit 22 increases the electrolysis current command value up to the rated electrolysis current command value Ic while changing the electrolysis current command value in accordance with the elapsed time in a preset step increase manner.

[0084] In the example shown in Fig. 6, after the start of recovery operation, the current control unit 22 first increases the electrolysis current command value to a first intermediate electrolysis current command value Ics1, and then maintains the electrolysis current command value at the first intermediate electrolysis current command value Ics1 for a certain period of time. Next, after the certain period of time has elapsed, the current control unit 22 increases the electrolysis current command value to a second intermediate electrolysis current command value Ics2, and then maintains the electrolysis current command value at the second intermediate electrolysis current command value Ics2 for a certain period of time. Next, after the certain period of time has elapsed, the current control unit 22 increases the electrolysis current command value to the rated electrolysis current command value Ic, and then maintains the electrolysis current command value at the rated electrolysis current command value Ic for a period of time until time t15. Then, at time t15, the current control unit 22 ends control of the recovery operation, and resumes control of the normal operation after time t15.

[0085] In the example shown in FIG. 6, the sweep increase mode described in FIG. 3 may also be adopted as the mode of change of the electrolysis current command value during the recovery operation period.

[0086] [Power conditioner control process flow] Next, the specific contents of the control process of the electrolytic current output to the hydrogen production device 10, which is performed by the power conditioner 20 in this embodiment, will be described with reference to the drawings. Fig. 7 is a flowchart showing the procedure of the control process of the electrolytic current in this embodiment, which is performed by the power conditioner 20. The control process of the electrolytic current described below is executed on software by a CPU (not shown) included in the current control unit 22 of the power conditioner 20.

[0087] The steps S11, S12, and S15 to S19 in the electrolytic current control process of this embodiment shown in Fig. 7 are respectively similar to the steps S1, S2, and S3 to S7 in the electrolytic current control process of the first embodiment (see Fig. 4). Therefore, detailed description of these steps will be omitted here, and only the steps from S12 onwards will be described.

[0088] If, in the process of S12, the current control unit 22 determines that no voltage drop (abnormality) has occurred in the commercial power supply 5 (if S12 is determined as No), the current control unit 22 determines whether or not the current operation period is a recovery operation period (S16), in the same manner as the process of S4 in Fig. 4 (first embodiment) described above. Then, from S16 onwards, the current control unit 22 performs the processes of S17 to S19, in the same manner as the processes of S5 to S7 in Fig. 4 (first embodiment) described above, and ends the electrolysis current control process.

[0089] On the other hand, in the processing of S12, if the current control unit 22 determines that a voltage drop (abnormality) has occurred in the commercial power source 5 (if S12 is determined to be Yes), the current control unit 22 determines whether the duration of operation at the abnormal voltage value (hereinafter referred to as the "drop period") is less than a specific period (dth in Figures 5 and 6) (S13).

[0090] If the current control unit 22 determines in the process of S13 that the decrease period is less than the specific period (if S13 is determined as Yes), the current control unit 22 performs a process of setting the minimum current operation (S15) in the same manner as the process of S3 in Fig. 4 (first embodiment) described above. After the process of S15, the current control unit 22 performs an electrolytic current control process of S19 in the same manner as the process of S7 in Fig. 4 (first embodiment) described above, and ends the electrolytic current control process.

[0091] On the other hand, if the current control unit 22 determines in the process of S13 that the decrease period is not less than the specific period (if the determination in S13 is No), the current control unit 22 outputs a parallel-off command to the power conversion unit 21 (S14). In this process, the current control unit 22 outputs an output command including an electrolysis current command value set to 0 (A) as the parallel-off command to the power conversion unit 21. As a result, the hydrogen production system 1 is parallel-off from the commercial power source 5.

[0092] After the hydrogen production system 1 is disconnected, the current control unit 22 monitors the commercial power supply voltage and waits until an increase in the commercial power supply voltage (resolution of the abnormality) is detected. If an increase in the commercial power supply voltage (resolution of the abnormality) is detected, the current control unit 22 shifts the process to the recovery operation setting process of S17 and performs the processes from S17 onwards. However, in this embodiment, while the hydrogen production system 1 is operating, the above-mentioned electrolysis current control process (processes of S11 to S19) by the power conditioner 20 is constantly and repeatedly executed.

[0093] [Various effects] As described above, in this embodiment, similar to the first embodiment, when an abnormality occurs in the commercial power supply 5 (external power supply), the hydrogen production system 1 is not disconnected, but the electrolysis current value is reduced to the minimum electrolysis current value and operation is continued. Furthermore, in this embodiment, after the abnormality in the commercial power supply 5 (external power supply) is resolved, the electrolysis current value is not immediately restored to the rated operating value, but is restored by increasing the electrolysis current value in steps. Therefore, this embodiment also provides the same effects as the first embodiment.

[0094] Furthermore, in this embodiment, if the period of operation at an abnormal voltage value of the commercial power source 5 (period of operation during an abnormality) exceeds a specific period, the hydrogen production system 1 is temporarily disconnected from the commercial power source 5. Therefore, in this embodiment, deterioration of the water electrolysis stack in the hydrogen production device 10 can be further prevented.

[0095] 3. Third embodiment Next, a hydrogen production system according to a third embodiment of the present invention and a method for controlling an electrolytic current output to a hydrogen production device will be described. In the third embodiment, a configuration will be described in which a commercial power source and a renewable energy power generation system (hereinafter referred to as "renewable energy power generation system") are used as external power sources for the hydrogen production system.

[0096] When an external power supply having such a configuration is employed, for example, a known operation mode is one in which the hydrogen production device consumes the variable power included in the output power of the renewable energy power generation system to produce hydrogen. Another known operation mode is a grid-connected operation mode in which the hydrogen production device consumes the output power from the renewable energy power generation system and replenishes any shortfall in power from a commercial power source. In this embodiment, an example is described in which the hydrogen production system is operated in the grid-connected operation mode described below.

[0097] [Configuration of hydrogen production system] 8 is a schematic diagram of a hydrogen production system according to a third embodiment of the present invention. For the sake of simplicity, only components related to control of electrolytic current in the hydrogen production system are shown. In the following description, the same reference numerals are used to designate devices and components having the same functions as those in the first and second embodiments, and detailed descriptions of the functions and operations of the devices and components will be omitted.

[0098] 8, the hydrogen production system 2 includes a hydrogen production device 10, a first storage tank 11, a first gas-liquid separator 12, a second gas-liquid separator 13, a liquid junction 14, a second storage tank 15, and a third storage tank 16. The hydrogen production system 2 also includes a power conditioner 20 (power supply device), which has a power conversion unit 21 and a current control unit 22. The hydrogen production system 2 also includes a renewable energy power conditioner 30, which has a renewable energy power conversion unit 31 and a renewable energy current control unit 32.

[0099] 8 , in this embodiment, the power conversion unit 21 in the power conditioner 20 is electrically connected in parallel to the commercial power supply 5 provided outside the hydrogen production system 2 and the renewable energy power conversion unit 31 in the renewable energy power conditioner 30. Furthermore, the renewable energy power conversion unit 31 in the renewable energy power conditioner 30 is electrically connected to the renewable energy current control unit 32 and a renewable energy power generation system 6 provided outside the hydrogen production system 2. That is, in this embodiment, the power conversion unit 21 in the power conditioner 20 is electrically connected to the renewable energy power generation system 6 via the renewable energy power conversion unit 31. Therefore, the hydrogen production device 10 is essentially electrically connected in parallel to the commercial power supply 5 and the renewable energy power conditioner 30.

[0100] Note that the connection modes between components other than the connection mode between the renewable energy power conditioner 30 and other components are the same as those of the hydrogen production system 1 of the first embodiment described above, and therefore explanation of those connection modes will be omitted here.

[0101] [Configuration and operation of each part] In the hydrogen production system 2 of this embodiment, the configurations of the components other than the renewable energy power conditioner 30 are the same as those of the hydrogen production system 1 of the first embodiment described above, and therefore, description of these components will be omitted here.

[0102] The renewable energy power conversion unit 31 includes a power conversion element, converts DC power supplied (input) from the renewable energy power generation system 6 into AC power (three-phase AC power), and supplies (outputs) the converted AC power to the power conversion unit 21 in the power conditioner 20. Although not shown, the renewable energy power conversion unit 31 is provided with a renewable energy voltmeter for monitoring the voltage of the renewable energy power generation system 6. In this embodiment, the voltage value (output voltage value) of the renewable energy power generation system 6 detected by the renewable energy voltmeter is output to the renewable energy current control unit 32 and also to the current control unit 22 in the power conditioner 20.

[0103] The renewable energy current control unit 32 controls the DC / AC conversion operation of power in the renewable energy power conversion unit 31. Although not shown, the renewable energy current control unit 32 can be configured with a microprocessor, similar to the current control unit 22 of the power conditioner 20, and has various functions such as a calculation function and a communication function.

[0104] In this embodiment, the renewable energy power generation system 6 may be configured with multiple types of renewable energy power generation systems, such as solar power generation and wind power generation, or may be configured with a single type of renewable energy power generation system.

[0105] [Power conditioner control overview] In this embodiment, when a voltage drop (abnormality) in the renewable energy power generation system 6 is detected, the current control unit 22 controls the electrolysis current value output from the power conditioner 20 to the hydrogen production device 10 to be the minimum electrolysis current value, regardless of whether there is a voltage fluctuation in the commercial power source 5. In other words, also in this embodiment, when a voltage drop (abnormality) in the renewable energy power generation system 6 is detected, the hydrogen production system 2 is not disconnected from the external power source, and the hydrogen production device 10 continues to operate at the minimum electrolysis current value.

[0106] However, in a configuration in which the hydrogen production device 10 is interconnected between the renewable energy power generation system 6 and the commercial power source 5, as in this embodiment, when a voltage drop (abnormality) occurs in the renewable energy power generation system 6, the abnormality may spread to the commercial power source 5, potentially causing adverse effects such as a voltage drop. Therefore, in this embodiment, when a voltage drop (abnormality) occurs in the renewable energy power generation system 6, it is necessary to perform minimum current operation and recovery operation, taking into account voltage fluctuations in the commercial power source 5, and to control the abnormality so that it does not spread to the commercial power source 5.

[0107] Therefore, in this embodiment, first, the current control unit 22 monitors the voltage of the renewable energy power generation system 6, and when a voltage drop (abnormality) of the renewable energy power generation system 6 is detected, the current control unit 22 reduces the electrolysis current value to the minimum electrolysis current value regardless of whether there is a voltage fluctuation in the commercial power supply 5. Thereafter, the current control unit 22 monitors the voltage of the commercial power supply 5, and if a voltage drop (abnormality) of the commercial power supply 5 is not detected by the time the abnormality of the renewable energy power generation system 6 is resolved, the current control unit 22 restores the electrolysis current value from the minimum electrolysis current value to the rated electrolysis current value when the abnormality of the renewable energy power generation system 6 is resolved.

[0108] However, if a voltage drop (abnormality) in the commercial power supply 5 is detected after a voltage drop (abnormality) in the renewable energy power generation system 6 is detected and before the abnormality is resolved, the current control unit 22 continues operation at the minimum electrolysis current value until the abnormality in the commercial power supply 5 is resolved, rather than until the abnormality in the renewable energy power generation system 6 is resolved. Then, after the abnormality in the commercial power supply 5 is resolved, the electrolysis current value is restored from the minimum electrolysis current value to the rated electrolysis current value.

[0109] Furthermore, in this embodiment, similar to the second embodiment, when the external power supply continues to operate at an abnormal voltage value for a specific period, the hydrogen production system 2 is temporarily disconnected to prevent deterioration of the water electrolysis stack. Note that the disconnection operation of the hydrogen production system 2 in this embodiment differs depending on the type of abnormality (voltage drop) occurring in the external power supply (commercial power supply 5 and / or renewable energy power generation system 6).

[0110] If a voltage drop (abnormality) occurs only in the renewable energy power generation system 6, the hydrogen production system 2 is temporarily disconnected from the external power supply once the renewable energy power generation system 6 has continued to operate at an abnormal voltage value for a specific period of time. Also, if a voltage drop (abnormality) occurs only in the commercial power supply 5, the hydrogen production system 2 is temporarily disconnected from the external power supply once the commercial power supply 5 has continued to operate at an abnormal voltage value for a specific period of time.

[0111] Furthermore, if a voltage drop (abnormality) occurs in the commercial power supply 5 as a result of a voltage drop (abnormality) occurring in the renewable energy power generation system 6, the commercial power supply 5 will also start operating at the abnormal voltage value after the renewable energy power generation system 6 starts operating at the abnormal voltage value. In this operating mode, the period from when the renewable energy power generation system 6 starts operating at the abnormal voltage value to when a voltage rise (abnormality detection) is detected in the commercial power supply 5 is the duration of operation at the abnormal voltage value of the external power supply. In this embodiment, when the duration of operation at the abnormal voltage value of the external power supply reaches a specific period, the hydrogen production system 2 is disconnected.

[0112] Furthermore, the control mode during recovery operation in this embodiment is similar to that in the first and second embodiments, and the electrolysis current is increased (recovered) from the minimum electrolysis current value or 0 (A) to the rated electrolysis current value in a predetermined step increase or sweep increase mode.

[0113] [Example of power conditioner control operation] Next, with reference to Figures 9 and 10, a specific example of the control operation of the electrolysis current in this embodiment when a voltage drop (abnormality) in the renewable energy power generation system 6 spreads to the commercial power source 5, causing a voltage drop in the commercial power source 5 will be described.

[0114] (1) Example of control when the voltage drop of the commercial power supply is within a specified tolerance range Fig. 9 is a diagram showing the relationship between the change characteristics of the voltage value of the renewable energy power generation system 6 (hereinafter referred to as "renewable energy power source voltage value"), the change characteristics of the commercial power source voltage value, and the change characteristics of the electrolysis current command value when a voltage drop (abnormality) in the renewable energy power generation system 6 also occurs in the commercial power source 5. The horizontal axis of each change characteristic in Fig. 9 represents time, the vertical axis of each change characteristic of the renewable energy power source voltage value and the commercial power source voltage represents voltage value, and the vertical axis of the change characteristic of the electrolysis current command value represents current value. Note that the example shown in Fig. 9 explains an example in which only one intermediate electrolysis current value is provided for step increase during the recovery operation period.

[0115] In the example shown in FIG. 9, consider the following case where a voltage drop (abnormality) occurs in the renewable energy power generation system 6. First, during normal operation at the rated value Vr of the renewable energy power supply voltage, a drop (abnormality) in the renewable energy power supply voltage value is detected at time t21. Thereafter, the renewable energy power supply voltage value drops to the abnormal voltage value Vrm (for example, 20% of the rated value Vr: hereinafter referred to as the "abnormal renewable energy power supply voltage value"), and the state of the abnormal renewable energy power supply voltage value Vrm continues until time t25. Then, at time t25, an increase in the renewable energy power supply voltage value (abnormality resolution) is detected, and thereafter the renewable energy power supply voltage value increases from the abnormal renewable energy power supply voltage value Vrm to the rated value Vr. That is, in the example shown in FIG. 9, the period before time t21 is a pre-abnormality period of the renewable energy power generation system 6, the period from time t21 to time t25 is a voltage drop (abnormality) period of the renewable energy power generation system 6, and the period from time t25 onwards is a post-abnormality resolution period of the renewable energy power generation system 6. In the example shown in FIG. 9, the time t25 when operation at the renewable energy power supply abnormal voltage value Vrm ends is set to a time before the time te when parallel-off execution starts.

[0116] In the example shown in FIG. 9, a case is considered in which the following voltage fluctuation occurs in the commercial power supply 5 due to a voltage drop (abnormality) in the renewable energy power generation system 6 described above.

[0117] First, during normal operation at the rated value Vc of the commercial power supply voltage, at time t21, a voltage drop (abnormality) occurs in the commercial power supply 5 due to a voltage drop in the renewable energy power generation system 6. However, in the example shown in FIG. 9 , the amount of voltage drop (Vc-Vcm) of the commercial power supply 5 at this time is set to, for example, a value within a predetermined allowable range stipulated in the grid interconnection rules of the electric power company. In this case, the voltage value of the commercial power supply 5 returns to the rated value Vc in a relatively short period of time, and the abnormality is resolved. In the example shown in FIG. 9 , the commercial power supply voltage rises at time t23, which is earlier than time t25 when the renewable energy power supply voltage rises (the abnormality is resolved), and then increases (recovers) to the rated value Vc. Thereafter, the commercial power supply voltage does not fluctuate, and the rated value Vc is maintained. That is, in the example shown in FIG. 9 , the period before time t21 is a pre-abnormality period of the commercial power supply 5, the period from time t21 to time t23 is a voltage drop (abnormality) period of the commercial power supply 5, and the period from time t23 onwards is a post-abnormality resolution period of the commercial power supply 5.

[0118] In the above-described example of abnormality occurring in the renewable energy power generation system 6 and the commercial power supply 5, the current control unit 22 performs the following control process of the electrolysis current.

[0119] First, at time t21, when the current control unit 22 detects a drop (abnormality) in the voltage value of the renewable energy power source, the current control unit 22 starts processing to reduce the electrolysis current value to the minimum electrolysis current value. Specifically, at time t22, the current control unit 22 starts processing to reduce the electrolysis current command value output to the power conversion unit 21 from the rated electrolysis current command value Ic to the minimum electrolysis current command value Icm. As a result, at time t22, control of normal operation ends and control of minimum current operation starts.

[0120] 9 corresponds to a minute time difference in processing from the detection of a voltage drop in the renewable energy power supply voltage value by the current control unit 22 to the output of an electrolysis current command value (output command) at the start of minimum current operation. Therefore, from a macroscopic perspective, the time t22 when minimum current operation starts is approximately the same time as the time t21 when a drop in the renewable energy power supply voltage value is detected.

[0121] After time t22, the current control unit 22 reduces the electrolysis current command value to the minimum electrolysis current command value Icm, and thereafter maintains the electrolysis current command value at the minimum electrolysis current value Icm until an increase in the commercial power supply voltage value (elimination of the abnormality) is detected.

[0122] Thereafter, at time t23, when the current control unit 22 detects an increase in the commercial power supply voltage value (abnormality elimination), the current control unit 22 starts processing to step-up the electrolysis current value to its rated value. Specifically, at time t24, the current control unit 22 starts processing to step-up the electrolysis current command value output to the power conversion unit 21 from the minimum electrolysis current command value Icm to the rated electrolysis current command value Ic. As a result, at time t24, control of the minimum current operation ends, and control of the recovery operation starts.

[0123] The time lag between time t23 when the rise in the commercial power supply voltage value is detected and time t24 when the recovery operation starts corresponds to a minute time difference in processing from when the current control unit 22 detects the rise in the voltage of the commercial power supply 5 to when the electrolysis current command value (output command) is output at the start of the recovery operation. Therefore, from a macroscopic perspective, time t24 when the recovery operation starts is approximately the same time as time t23 when the rise in the commercial power supply voltage value is detected.

[0124] After time t24, the current control unit 22 increases the electrolysis current command value up to the rated electrolysis current command value Ic while changing the electrolysis current command value in accordance with the elapsed time in a preset step increase manner.

[0125] 9, after the start of recovery operation, the current control unit 22 first increases the electrolysis current command value to the intermediate electrolysis current command value Ics, and then maintains the electrolysis current command value at the intermediate electrolysis current command value Ics for a certain period of time. Next, after the certain period has elapsed, the current control unit 22 increases the electrolysis current command value to the rated electrolysis current command value Ic, and then maintains the electrolysis current command value at the rated electrolysis current command value Ic for the period until time t26. Then, at time t26, the current control unit 22 ends control of recovery operation, and resumes control of normal operation after time t26.

[0126] 9, the time t25 when the operation of the renewable energy power source at the abnormal voltage value Vrm ends, and the time t23 when the operation of the commercial power source 5 at the abnormal voltage value Vcm ends, are both times before the time te when parallel-out execution starts. Therefore, the duration of operation at the abnormal voltage value of the external power source is less than the specific period dth (time te - time ts), so parallel-out of the hydrogen production system 2 is not performed in the example shown in FIG.

[0127] (2) Example of control when the drop in commercial power supply exceeds the specified allowable range Fig. 10 is a diagram showing the relationship between the change characteristics of the renewable energy power source voltage value, the change characteristics of the commercial power source voltage value, and the change characteristics of the electrolysis current command value when a voltage drop (abnormality) in the renewable energy power generation system 6 also occurs in the commercial power source 5. The horizontal axis of each change characteristic in Fig. 10 represents time, the vertical axis of each change characteristic of the renewable energy power source voltage value and the commercial power source voltage represents the voltage value, and the vertical axis of the change characteristic of the electrolysis current command value represents the current value. Note that the example shown in Fig. 10 explains an example in which only one intermediate electrolysis current value is provided for step increase during the recovery operation period.

[0128] In the example shown in Fig. 10, a case is considered in which a voltage drop (abnormality) occurs in the renewable energy power generation system 6 described in Fig. 9. Therefore, a description of the change characteristics of the renewable energy power supply voltage value will be omitted here.

[0129] 10, consider the following case where a voltage drop (abnormality) in the renewable energy power generation system 6 causes a voltage fluctuation in the commercial power source 5. First, during normal operation at the rated commercial power source voltage Vc, a voltage drop (abnormality) in the commercial power source 5 occurs at time t31 after the renewable energy power source voltage drops to an abnormal renewable energy power source voltage Vrm. The commercial power source voltage then drops to an abnormal voltage Vcm (e.g., 20% of the rated voltage Vc) and remains at the abnormal voltage Vcm until time t32. After time t32, the commercial power source voltage increases (recovers) to the rated voltage Vc. That is, in the example shown in FIG. 10, the period before time t31 corresponds to a pre-abnormality period in the commercial power source 5, the period from time t31 to time t32 corresponds to a voltage drop (abnormality) period in the commercial power source 5, and the period after time t32 corresponds to a post-abnormality period in the commercial power source 5.

[0130] 10, the amount of voltage drop (Vc-Vcm) of the commercial power supply 5 is set to a value that exceeds a predetermined allowable range defined in the interconnection rules of the electric power company. Also, in the example shown in Fig. 10, the time t32 when a voltage increase (abnormality resolution) of the commercial power supply 5 is detected is set to be later than the time t25 when an increase in the renewable energy power supply voltage value (abnormality resolution) is detected and before the time te when parallel-off execution starts.

[0131] In the above-described example of abnormality occurring in the renewable energy power generation system 6 and the commercial power supply 5, the current control unit 22 performs the following control process of the electrolysis current.

[0132] First, at time t21, when the current control unit 22 detects a drop (abnormality) in the voltage value of the renewable energy power source, the current control unit 22 starts processing to reduce the electrolysis current value to the minimum electrolysis current value. Specifically, at time t22, the current control unit 22 starts processing to reduce the electrolysis current command value output to the power conversion unit 21 from the rated electrolysis current command value Ic to the minimum electrolysis current command value Icm. As a result, at time t22, control of normal operation ends and control of minimum current operation starts.

[0133] 10 corresponds to a minute time difference in processing from the detection of a voltage drop in the renewable energy power supply voltage value by the current control unit 22 to the output of an electrolysis current command value (output command) at the start of minimum current operation. Therefore, from a macroscopic perspective, the time t22 when minimum current operation starts is approximately the same time as the time t21 when a drop in the renewable energy power supply voltage value is detected.

[0134] After time t22, the current control unit 22 reduces the electrolysis current command value to the minimum electrolysis current command value Icm, and thereafter maintains the electrolysis current command value at the minimum electrolysis current command value Icm until an increase in the commercial power supply voltage value (resolution of abnormality) is detected. Therefore, in the example shown in Fig. 10, the current control unit 22 maintains the electrolysis current command value at the minimum electrolysis current command value Icm even if an increase in the renewable energy power supply voltage value (resolution of abnormality) is detected at time t25, which is before time t32 when an increase in the commercial power supply voltage value (resolution of abnormality) is detected.

[0135] Thereafter, at time t32, when the current control unit 22 detects an increase in the commercial power supply voltage value (abnormality elimination), the current control unit 22 starts processing to step-up the electrolysis current value to its rated value. Specifically, at time t33, the current control unit 22 starts processing to step-up the electrolysis current command value output to the power conversion unit 21 from the minimum electrolysis current command value Icm to the rated electrolysis current command value Ic. As a result, at time t33, control of the minimum current operation ends, and control of the recovery operation starts.

[0136] 10, the time lag between time t32 when an increase in the commercial power supply voltage value is detected and time t33 when the recovery operation starts corresponds to a minute time difference in the processing from when the current control unit 22 detects an increase in the voltage of the commercial power supply 5 to when the electrolysis current command value (output command) is output at the start of the recovery operation. Therefore, from a macroscopic perspective, time t33 when the recovery operation starts is approximately the same time as time t32 when an increase in the commercial power supply voltage value is detected.

[0137] After time t33, the current control unit 22 increases the electrolysis current command value up to the rated electrolysis current command value Ic while changing the electrolysis current command value in accordance with the elapsed time in a preset step increase manner.

[0138] 10, after the start of recovery operation, the current control unit 22 first increases the electrolysis current command value to the intermediate electrolysis current command value Ics, and then maintains the electrolysis current command value at the intermediate electrolysis current command value Ics for a certain period of time. Next, after the certain period has elapsed, the current control unit 22 increases the electrolysis current command value to the rated electrolysis current command value Ic, and then maintains the electrolysis current command value at the rated electrolysis current command value Ic for the period until time t34. Then, at time t34, the current control unit 22 ends control of recovery operation, and resumes control of normal operation after time t34.

[0139] 10, the time t25 when the operation of the renewable energy power source at the abnormal voltage value Vrm ends, and the time t32 when the operation of the commercial power source 5 at the abnormal voltage value Vcm ends, are both times before the time te when parallel-out execution starts. Therefore, the duration of operation at the abnormal voltage value of the external power source is less than the specific period dth (time te - time ts), so parallel-out of the hydrogen production system 2 is not performed in the example shown in FIG.

[0140] However, in the example of an abnormality shown in Figure 10, for example, if the time t32 when operation of the commercial power source 5 at the abnormal voltage value Vcm ends is later than the time te when the parallel-off execution begins, the hydrogen production system 2 will be temporarily parallel-off from the external power source during the period from time te to time t32, as in the example of an abnormality described in Figure 6.

[0141] [Power conditioner control process flow] Next, the specific contents of the control process of the electrolytic current output to the hydrogen production device 10, which is performed by the power conditioner 20 in this embodiment, will be described with reference to the drawings. Fig. 11 is a flowchart showing the procedure of the control process of the electrolytic current in this embodiment, which is performed by the power conditioner 20. The control process of the electrolytic current described below is executed on software by a CPU (not shown) included in the current control unit 22 of the power conditioner 20.

[0142] First, the current control unit 22 performs a process of monitoring the renewable energy power supply voltage (S21). In this process, the current control unit 22 acquires a renewable energy power supply voltage value measured by a renewable energy voltmeter (not shown) for monitoring the voltage of the renewable energy power generation system 6, which is provided in the renewable energy power conversion unit 31. The current control unit 22 monitors (recognizes) the operating state of the renewable energy power generation system 6 based on the acquired renewable energy power supply voltage value.

[0143] Next, the current control unit 22 determines whether or not a voltage drop (abnormality) has occurred in the renewable energy power generation system 6, based on the renewable energy power supply voltage value acquired in the process of S21 (S22). In this process, the current control unit 22 determines whether or not the renewable energy power generation system 6 is in a voltage drop (abnormal) period (see the change characteristics of the renewable energy power supply voltage value in FIGS. 9 and 10). Therefore, in the period from the detection of a voltage drop (abnormality) in the renewable energy power supply voltage to the detection of a voltage rise (abnormality resolution), the determination result in S22 is a Yes determination, and in other periods (the period before the abnormality in the renewable energy power generation system 6 and the period after the abnormality has been resolved), the determination result in S22 is a No determination.

[0144] In addition, in the detection of a voltage drop (abnormality) and a voltage rise (abnormality resolution) of the renewable energy power generation system 6 performed in the processing of S22, the voltage value to be compared with the current renewable energy power source voltage value may be, for example, the renewable energy power source voltage value from a predetermined time ago (for example, about several seconds). Also, in the processing of S22, for example, the presence or absence of a drop or rise in the renewable energy power source voltage may be determined by comparing an average value of the renewable energy power source voltage value from the current time until a certain time ago with an average value of the renewable energy power source voltage value from a preset time before a certain time ago.

[0145] In the process of S22, if the current control unit 22 determines that a voltage drop (abnormality) has not occurred in the renewable energy power generation system 6 (if the determination in S22 is No), the current control unit 22 performs the process of S24 described below.

[0146] On the other hand, if the current control unit 22 determines in the process of S22 that a voltage drop (abnormality) has occurred in the renewable energy power generation system 6 (if S22 is determined as Yes), the current control unit 22 performs a process of setting the minimum current operation (S23). This process is performed in the same manner as the process of S3 in FIG. 4 (first embodiment) described above. However, in the process of S23, the current control unit 22 stores the value of the dropped renewable energy power supply voltage together with the current time (time when the abnormality occurred) as an abnormal voltage value of the renewable energy power generation system 6 in a RAM (not shown) included in the current control unit 22.

[0147] After the process of S23, or if the determination in S22 is No, the current control unit 22 performs a process of monitoring the commercial power supply voltage (S24) in the same manner as the process of S1 in Fig. 4 (first embodiment) described above. Next, the current control unit 22 determines whether or not a voltage drop (abnormality) has occurred in the commercial power supply 5 in the same manner as the process of S2 in Fig. 4 (first embodiment) described above (S25).

[0148] In the processing of S25, if the current control unit 22 determines that a voltage drop (abnormality) has occurred in the commercial power supply 5 (if S25 is determined as Yes), the current control unit 22 determines whether the drop period (the period during which operation continues at the abnormal voltage value of the external power supply) is less than a specific period (dth in FIGS. 9 and 10) (S26), similar to the processing of S13 in FIG. 7 (second embodiment) described above.

[0149] If the current control unit 22 determines in the process of S26 that the decrease period is not less than the specific period (if S26 is determined to be No), the current control unit 22 outputs a parallel-off command to the power conversion unit 21 (S27), similar to the process of S14 in FIG. 7 (second embodiment) described above. After the hydrogen production system 2 is parallel-off, the current control unit 22 monitors the commercial power supply voltage and waits until an increase in the commercial power supply voltage (resolution of the abnormality) is detected. Then, if an increase in the commercial power supply voltage (resolution of the abnormality) is detected, the current control unit 22 shifts the process to the recovery operation setting process of S31 described below.

[0150] On the other hand, if the current control unit 22 determines in the process of S26 that the decrease period is less than the specific period (if S26 is determined as Yes), the current control unit 22 performs a process of setting the minimum current operation (S28). This process is performed in the same manner as the process of S3 in FIG. 4 (first embodiment) described above. However, in the process of S28, the current control unit 22 stores the value of the decreased commercial power supply voltage together with the current time (time when the abnormality occurred) as an abnormal voltage value of the commercial power supply 5 in a RAM (not shown) included in the current control unit 22. Then, after the process of S28, the current control unit 22 performs a process of S33 described below.

[0151] Returning to the explanation of the processing of S25 again, if the current control unit 22 determines in the processing of S25 that a voltage drop (abnormality) has not occurred in the commercial power supply 5 (if the determination in S25 is No), the current control unit 22 determines whether or not the current operation period is the minimum current operation period (S29). In this processing, if the current time is a time after the start of the minimum current operation and if a voltage rise (abnormality resolution) of the commercial power supply 5 has not been detected at the time of the current processing, the current control unit 22 determines the determination result in S29 as Yes, and otherwise determines the determination result in S29 as No.

[0152] In the process of S29, if the current control unit 22 determines that the current operation period is the minimum current operation period (if S29 is determined to be Yes), the current control unit 22 shifts the process to the process of S26 described above and performs the processes from S26 onwards.

[0153] On the other hand, if the current control unit 22 determines in the process of S29 that the current operation period is not the minimum current operation period (if the determination in S29 is No), the current control unit 22 determines whether the current operation period is the recovery operation period (S30). Note that this process is performed in the same manner as the process of S4 in FIG. 4 (first embodiment) described above.

[0154] In the process of S30, if the current control unit 22 determines that the current operation period is a recovery operation period (if S30 is determined as Yes), the current control unit 22 performs a recovery operation setting process (S31) in the same manner as the process of S5 in Fig. 4 (first embodiment) described above. Then, after the process of S31, the current control unit 22 performs a process of S33 described below.

[0155] On the other hand, if the current control unit 22 determines in the process of S30 that the current operation period is not the recovery operation period (if S30 is determined to be No), the current control unit 22 performs a process of setting the normal operation (S32) in the same manner as the process of S6 in Fig. 4 (first embodiment) described above. Then, after the process of S32, the current control unit 22 performs a process of S33 described later.

[0156] After the process of S28, S31, or S32, the current control unit 22 performs electrolysis current control processing (S33) in the same manner as the process of S7 in Fig. 4 (first embodiment) described above. Then, after the process of S33, the current control unit 22 ends the electrolysis current control processing. However, in this embodiment, while the hydrogen production system 2 is in operation, the above-described electrolysis current control processing (processes of S21 to S33) is constantly and repeatedly performed by the power conditioner 20.

[0157] [Various effects] As described above, in this embodiment, similar to the first embodiment, when an abnormality occurs in the external power supply (renewable energy power generation system 6), first, the hydrogen production system 2 is not disconnected, but the electrolysis current value is reduced to the minimum electrolysis current value and operation is continued. Furthermore, in this embodiment, after the abnormality in the external power supply (commercial power supply 5 or renewable energy power generation system 6) is resolved, the electrolysis current value is not immediately restored to the rated operating value, but is restored by increasing the electrolysis current value in steps. Therefore, even in a configuration in which the commercial power supply 5 and the renewable energy power generation system 6 are interconnected and operated as external power supplies, as in this embodiment, the same effects as in the first embodiment can be obtained.

[0158] Furthermore, in this embodiment, similar to the second embodiment, if the duration of operation at an abnormal voltage value of the external power supply (duration of operation at the minimum electrolysis current value) exceeds a specific period, a function is provided to temporarily disconnect the hydrogen production system 2. Therefore, even in a configuration in which the commercial power supply 5 and the renewable energy power generation system 6 are interconnected as an external power supply, as in this embodiment, the same effects as those of the second embodiment can be obtained.

[0159] Furthermore, the control method (electrolysis current control method) of the hydrogen production device 10 of this embodiment described above can also be used with renewable energy power generation systems 6, which are prone to output fluctuations, making it possible to apply a wide variety of combinations of power systems as external power sources.

[0160] 4. Various Modifications While the hydrogen production systems and power conditioners included therein according to various embodiments of the present invention have been described above, the present invention is not limited thereto. For example, the following various modifications are possible.

[0161] [Variation 1] In the second and third embodiments, the duration of operation at an abnormal voltage value of the external power source (commercial power source 5 and / or renewable energy power generation system 6) is used as a parameter for determining whether or not to temporarily disconnect the hydrogen production system 1 after a voltage drop of the external power source. However, the present invention is not limited to this.

[0162] For example, the duration of operation at the minimum electrolysis current value after the voltage of the external power supply drops may be used as the duration of operation in an abnormal state of the external power supply, which is a parameter for determining whether or not to temporarily disconnect the hydrogen production system 1.

[0163] [Variation 2] In the above second and third embodiments, an example has been described in which a method of paralleling off the hydrogen production system is used in which the current control unit 22 of the power conditioner 20 outputs a parallel-off command (control signal) including an electrolysis current command value set to 0 (A) to the power conversion unit 21. That is, an example has been described in which a method of paralleling off the hydrogen production system is used in which the electrolysis current value supplied to the hydrogen production device 10 is set to 0 (A). However, the present invention is not limited to this.

[0164] For example, the hydrogen production system may be physically disconnected from the external power source by turning on a circuit breaker (shutoff switch) provided between the hydrogen production system and the external power source. However, from the viewpoint of quickly resuming operation of the hydrogen production device 10 after the voltage drop (abnormality) in the external power source is resolved, the method of the above embodiment is advantageous because it allows for parallel-off while the hydrogen production system and the external power source remain electrically connected.

[0165] [Variation 3] In the above-described various embodiments, the configuration example in which the step increase mode of the electrolysis current command value during the recovery operation period is determined in advance has been described, but the present invention is not limited to this.

[0166] For example, the recovery rate of the voltage of the external power supply during the recovery operation period may be monitored based on the voltage value of the external power supply monitored by the current control unit 22 of the power conditioner 20, and the step increase mode of the electrolysis current command value may be appropriately set according to the voltage recovery rate. In this case, optimal parameters for the step increase mode of the electrolysis current command value (e.g., the value and number of intermediate electrolysis current command values, the duration for which each intermediate electrolysis current command value is maintained, etc.) may be constantly set according to, for example, the recovery rate of the voltage of the external power supply during the recovery operation period. Therefore, in this case, deterioration of the water electrolysis stack can be more reliably suppressed.

[0167] [Variation 4] Furthermore, in the various embodiments described above, configuration examples in which one hydrogen production system is connected to an external power supply have been described, but the present invention is not limited to this. The technology of the present invention described above can also be applied to configurations in which multiple hydrogen production systems are connected in parallel to an external power supply. In such configuration examples, when a voltage drop (abnormality) occurs in the external power supply, the electrolysis current control method in the various embodiments described above can be applied to the method of controlling the electrolysis current output from the power conditioner to the hydrogen production device in each hydrogen production system. In this case, the same effects as those of the various embodiments described above can be obtained.

[0168] Furthermore, in such a configuration example, multiple hydrogen production systems constitute one large-scale hydrogen production system, and the installed capacity of the system is also large. In this case, the adverse effects on the power grid (external power source) that may occur when multiple hydrogen production systems are simultaneously disconnected in the event of a voltage drop in the external power source may also be greater due to the larger installed capacity. Therefore, when the electrolysis current control method described in the various embodiments described above is applied to a configuration in which multiple hydrogen production systems are connected in parallel to an external power source, the effect of suppressing the adverse effects of the hydrogen production systems on the external power source and the effect of stabilizing the external power source become more pronounced.

[0169] [Variation 5] In the above-described various embodiments, the electrolysis current value (electrolysis current command value) in the period after the abnormality is resolved (after recovery) is the same as the electrolysis current value (electrolysis current command value) in the period before the abnormality, but the present invention is not limited to this. The electrolysis current value (electrolysis current command value) in the period after the abnormality is resolved may be different from the electrolysis current value (electrolysis current command value) in the period before the abnormality.

[0170] [others] In the various embodiments described above, configuration examples have been described in which the electrolytic current control process by the power conditioner 20 (current control unit 22) is executed on software, but the present invention is not limited to this. For example, part or all of the electrolytic current control process may be implemented by hardware.

[0171] Furthermore, the various embodiments and modifications described above have described the configuration of the device in detail and specifically in order to clearly explain the present invention, and are not necessarily limited to those having all of the described configurations. The position, size, shape, range, etc. of each component shown in the drawings, etc. may not represent the actual position, size, shape, range, etc. in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings, etc. Furthermore, the present invention may have various other applications and modifications as long as they do not deviate from the gist of the present invention described in the claims. [Explanation of symbols]

[0172] 1, 2... Hydrogen production system, 5... Commercial power supply, 6... Renewable energy power generation system, 10... Hydrogen production device, 11... First storage tank, 12... First gas-liquid separator, 13... Second gas-liquid separator, 14... Liquid junction, 15... Second storage tank, 16... Third storage tank, 20... Power conditioner, 21... Power conversion unit, 22... Current control unit, 30... Renewable energy power conditioner, 31... Renewable energy power conversion unit, 32... Renewable energy current control unit

Claims

1. A hydrogen production device; a power supply unit that converts AC power input from an external power source into DC power and outputs the DC current to the hydrogen production device; a control unit that monitors the voltage of the external power supply and controls the DC current output from the power supply unit based on the result of monitoring the voltage, and when a voltage drop of the external power supply is detected, the control unit reduces the value of the DC current output from the power supply unit to a predetermined DC current value greater than 0 to continue operation of the hydrogen production device, and thereafter, when a recovery of the voltage of the external power supply is detected, the control unit increases the value of the DC current to a specific DC current value in a predetermined increasing manner. Hydrogen production system.

2. The predetermined DC current value is the minimum current value at which the hydrogen production device can be operated. The hydrogen production system according to claim 1 .

3. After detecting the recovery of the voltage of the external power supply, the target value of the DC current that is initially set by the control unit is a value that is less than the specific DC current value. The hydrogen production system according to claim 1 .

4. The control unit increases the value of the DC current in a stepwise manner with respect to elapsed time up to the specific DC current value after detecting the recovery of the voltage of the external power supply. The hydrogen production system according to claim 3 .

5. The control unit disconnects the hydrogen production device from the external power source when the operation duration in the voltage drop state of the external power source reaches a specific period after detecting the voltage drop of the external power source. The hydrogen production system according to claim 1 .

6. The control unit disconnects the hydrogen production device from the external power source by setting the value of the direct current output to the hydrogen production device to 0. The hydrogen production system according to claim 5 .

7. The control unit monitors a speed at which the voltage of the external power supply is restored after detecting the voltage restoration of the external power supply, and sets an increase mode of the value of the direct current based on the result of monitoring the speed at which the voltage is restored. The hydrogen production system according to claim 1 .

8. The external power source includes a commercial power source and a renewable energy power generation system; The control unit is electrically connected in parallel to the commercial power supply and the renewable energy power generation system. The hydrogen production system according to claim 1 .

9. The control unit When a voltage drop of the renewable energy power generation system is detected, the value of the DC current output from the power supply unit is reduced to the predetermined DC current value, and operation of the hydrogen production device is continued; When a voltage drop of the commercial power supply is detected due to a voltage drop of the renewable energy power generation system, after detecting a voltage recovery of the commercial power supply, the value of the direct current is increased in a predetermined increasing manner up to the specific direct current value. The hydrogen production system according to claim 8 .

10. a plurality of components including the hydrogen production device, the power supply unit, and the control unit; A plurality of the components are connected in parallel to the external power supply. The hydrogen production system according to claim 1 .

11. a power supply unit that converts AC power input from an external power source into DC power and outputs the DC current to an external device; a control unit that monitors the voltage of the external power supply and controls the DC current output from the power supply unit based on the result of monitoring the voltage, and when a voltage drop of the external power supply is detected, the control unit reduces the value of the DC current output from the power supply unit to a predetermined DC current value greater than 0 to continue operation of the external device, and thereafter, when a recovery of the voltage of the external power supply is detected, the control unit increases the value of the DC current in a predetermined increasing manner to a specific DC current value. Power supply device.

12. A control method for a hydrogen production system including a hydrogen production device, a power supply unit that converts AC power input from an external power source into DC power and outputs DC current to the hydrogen production device, and a control unit that controls the DC current output from the power supply unit, the control unit monitors a voltage of the external power supply; When the control unit detects a voltage drop of the external power supply, the control unit reduces the value of the DC current output from the power supply unit to a predetermined DC current value greater than 0, and continues operation of the hydrogen production apparatus; and when the control unit detects a voltage recovery of the external power supply, increasing the value of the direct current in a predetermined increasing manner up to a specific direct current value. A method for controlling a hydrogen production system.

Images