WO2024142379A1 - Power control system and hydrogen production system - Google Patents

Abstract

In an electrolyzer system such as a hydrogen production system 1, the conversion efficiency of a power source is reduced and the flexibility of controlling the individual electrolyzers is reduced. The hydrogen production system 1 comprises: a plurality of electrolytic pairs A100A and B100B connected in series with each other, the electrolytic pairs consisting of electrolytic cells 13A and 13B and AC/DC converters 11A and 11B that supply power to the electrolytic cells; a dummy pair 10 that is connected in series with the electrolytic pairs A100A and B100B and consists of a capacitor 12 that can input energy and an AC/DC converter 11 connected to the capacitor 12; and an arithmetic device 14 having an input unit 141 that receives input information including current command values to the electrolytic cells 13A and 13B and electrolytic cell voltages of the plurality of electrolytic cells, a voltage command value calculation unit 142 that uses the input information to calculate a voltage command value that is a voltage correction value for the AC/DC converter 11, and an output unit 143 that outputs the voltage command value to the AC/DC converter 11.

Description

Power control system and hydrogen production system

The present invention relates to electrolysis systems, such as power control systems and hydrogen production systems, that use electrolysis.

Currently, in an effort to realize a low-carbon society, power generation using renewable energy sources such as solar and wind power is becoming more common, replacing thermal power generation using fossil fuels. However, electricity from renewable energy sources fluctuates greatly due to natural phenomena, so it cannot directly replace grid power and can also cause grid instability. As a result, the market for green hydrogen, which uses renewable electricity to convert it into hydrogen using water electrolysis, is expanding rapidly.

　The method of electrolysis using renewable energy power is not limited to the method of directly feeding renewable energy power into an electrolytic cell at the renewable energy site, but also includes a method of first feeding the renewable energy power back into the grid at the site and then feeding the power from the grid at a remote substation or business. In particular, large-capacity electrolysis systems of the 100MW class adopt the latter configuration, and are expected to absorb surplus renewable energy power via the grid and provide adjustment power such as stabilizing the grid frequency. In addition, in large-scale electrolysis systems such as those installed in substations, the system voltage (several tens of kV) is stepped down in several stages using a transformer to a voltage suitable for the electrolytic cell (several hundreds of V). Furthermore, the system is configured to connect to the electrolytic cell via an AC/DC converter. In large-scale electrolysis systems, multiple pairs of electrolysis transformers - AC/DC converters - electrolytic cells have been connected in parallel to scale up.

　The configuration of the electrical circuit of a conventional large-scale electrolysis system as represented by Non-Patent Document 1 is shown in Figure 1A. In Figure 1A, the AC voltage of the system (effective value of several hundred to several tens of kV) is first stepped down to the AC voltage of the distribution level, and then several transformers are further connected to it to step down to several hundred volts. In the configuration shown in Figure 1A, water electrolysis is performed with DC, so power is input to the electrolytic cell through an AC/DC converter consisting of a rectifier that converts AC to DC and a current control circuit. Thus, Figure 1A shows a configuration in which the electrolytic transformer - AC/DC converter - electrolytic cell pair is connected in parallel from the perspective of the distribution transformer. In this configuration of Figure 1A, the equipment of the substation can be utilized up to the distribution stage, but the installation of the electrolytic cell transformer in the second stage requires a large footprint area and is very heavy. This has been a factor in increasing construction costs, including land costs and materials such as transformers.

IEEE Transactions on Industry Applications, vol.57, no.3, pp.3064-3076, May-June 2021, Optimum Design of MMC-Based ES-STATCOM Systems: The Role of the Submodule Reference Voltage

Here, in the large-scale electrolysis system shown in Figure 1A, the electric circuits are connected in parallel, but as shown in Figure 1B, a configuration in which the electric circuits are connected in series is also possible. More specifically, pairs (electrolytic couples) consisting of only an AC/DC converter and an electrolytic cell are used, and the AC sides are connected in series in several tens of stages and directly connected to a distribution transformer in a manner that matches the distribution voltage of several tens of kV. The series connection configuration shown in Figure 1B does not require a dedicated transformer, so it is expected that the problems of footprint area and cost in system installation will be alleviated. Also, in the parallel connection configuration of Figure 1A, the voltage on the system side (distribution side) of the AC/DC converter is common to each electrolytic couple. In contrast, the series connection configuration of Figure 1B differs in that the current on the system side (distribution side) of the AC/DC converter is common to all electrolytic couples and the sum of the voltages is fixed to the system voltage.

In the above configuration, the installation of the electrolytic cell transformer requires a large current, which requires a large footprint and is very heavy, resulting in increased construction costs. It is also possible to connect AC/DC converter-electrolytic cell pairs in series in several dozen stages, so that the system side processes the electricity without passing through the electrolytic cell transformer. In this case, no dedicated transformer is required, which alleviates the issues of footprint area and weight when installing the system.

However, when trying to control each electrolytic cell individually based on an operating policy that takes into account variations in the electrical characteristics of the electrolytic cells and the state of each cell, problems arise, such as a decrease in the power conversion efficiency and reduced flexibility in controlling each individual cell.

In the present invention, to solve the above problem, a dummy pair is provided that connects the DC side of the AC/DC converter to a capacitor. For example, one or more dummy pairs consisting of an AC/DC converter and a capacitor are prepared, and the system sides of these are connected in series to be connected to the system. Then, the voltage command value on the system side of the AC/DC converter of the dummy pair is changed and controlled according to the current command value and voltage of the electrolytic cell, that is, the current command value and voltage of the AC/DC converter connected to the electrolytic cell.

A more specific configuration of the present invention is a power control system for a hydrogen generation system that generates hydrogen from saltwater using a plurality of electrolytic couples connected in series to each other, the electrolytic couples being composed of a plurality of electrolytic cells that store saltwater and a first AC/DC converter that supplies power to the electrolytic cells. The power control system has a dummy couple that is connected in series to the plurality of electrolytic couples and is composed of a capacitor that can input energy and a second AC/DC converter that connects to the capacitor, an input unit that receives input information including a current command value to the plurality of electrolytic cells and the electrolytic cell voltage of the plurality of electrolytic cells, a voltage command value calculation unit that uses the input information to calculate a voltage command value that is a correction value for the second AC/DC converter, and an output unit that outputs the voltage command value to the second AC/DC converter. The present invention also includes a hydrogen production system having the above-mentioned plurality of electrolytic couples and the power control system.

The present invention makes it possible to more appropriately control the power of electrolytic cell systems that use electrolytic cells, such as hydrogen production systems.

FIG. 1 is a diagram showing a configuration (parallel connection configuration) of an electric circuit of a conventional large-scale electrolysis system. FIG. 1 is a diagram showing a configuration in which electric circuits of a large-scale electrolysis system are connected in series (series connection configuration). FIG. 1 is a diagram showing a series connection configuration of a large-scale electrolysis system for illustrating a problem in Example 1. FIG. 1 is a diagram showing current-voltage characteristics, which are typical electrical characteristics of an electrolytic cell 13, for illustrating the problems of Example 1. FIG. 11 is a diagram showing an output voltage and a conversion efficiency for explaining a problem in the first embodiment. FIG. 13 is a diagram showing the relationship between voltage and current when the IV curve of electrolytic cell B13B changes, for illustrating the problem in Example 1. FIG. 11 is a diagram illustrating a relationship between voltage and current when a current command value is reduced, for illustrating a problem in the first embodiment. 1 is a configuration diagram of a hydrogen production system 1 according to a first embodiment. FIG. 2 is a functional block diagram of a calculation device 14 according to the first embodiment. FIG. 1 is a configuration diagram of a hydrogen production system 1 according to a second embodiment. FIG. 11 is a diagram showing an IV curve in Example 2. FIG. 11 is a configuration diagram showing a part of a hydrogen production system 1 according to a third embodiment.

Below, an embodiment of the invention will be described with reference to the drawings. In this embodiment, a hydrogen production system is disclosed that generates hydrogen from seawater, salt water, etc. (hereinafter simply salt water) stored in an electrolytic cell in response to supplied power (electricity). For this purpose, the hydrogen production system has a power supply unit, an electrolytic couple, a dummy couple, and a calculation unit. First, the power supply unit is a source of power for hydrogen production. Furthermore, the electrolytic couple is composed of an electrolytic cell and a plurality of AC/DC converters that supply power, particularly DC power, to the electrolytic cell. Furthermore, the dummy couple is composed of an AC/DC converter and a capacitor. Furthermore, the calculation unit controls the power, particularly the voltage, for hydrogen production. These electrolytic couples and dummy pairs are connected in series. Note that the AC/DC converter that constitutes the electrolytic couple can also be called a first AC/DC converter, and the AC/DC converter that constitutes the dummy pair can also be called a second AC/DC converter.

Here, the arithmetic device creates and outputs control commands for the first AC/DC converter and the second AC/DC converter, and controls them. These control commands include current command values for the first AC/DC converter and the second AC/DC converter. For convenience, the current command value for the second AC/DC converter is referred to as the current command value to the electrolytic cell.

The arithmetic unit also calculates a voltage command value for the second AC/DC converter. At this time, the arithmetic unit calculates a voltage command value for the second AC/DC converter using a current command value for each electrolytic cell and a voltage of each electrolytic cell. More preferably, the arithmetic unit uses a current command value when the first AC/DC converter, that is, the electrolytic cell, is electrically evenly balanced, and an electrolysis voltage value before deterioration (new or rated). More preferable input information will be described in the following embodiment. As described above, the arithmetic unit functions as a power control device. Furthermore, the arithmetic unit and the dummy pairs can be configured as a power control system. Furthermore, it is preferable that the number of dummy pairs satisfies the fluctuation range x number of AC/DC converters connected to the electrolytic cell ≦ V _DM . Here, V _DM is a voltage command value that is a correction value of the voltage for the second AC/DC converter.

The number of electrolytic cells and electrolytic couples formed thereby is not limited and may be singular. Furthermore, the number of first AC/DC converters may vary.

With the above configuration, this embodiment can easily realize power control for hydrogen production. Below, we will explain each example that shows a more specific form of this embodiment.

First, the problems in Example 1 will be explained using Figs. 2A to 4. Fig. 2A is a diagram showing a serial connection configuration of a large-scale electrolysis system (hydrogen production system 1) to explain the problems in Example 1. In Fig. 2A, the hydrogen production system 1, which is a large-scale electrolysis system, is composed of multiple electrolytic couples 100 and a power supply unit 15.

Here, the power supply device 15 supplies AC power for hydrogen generation to each electrolytic couple 100. Note that the power supply device 15 may be an external power plant or substation of an electric power company or the like, or may be a power plant or substation managed by the organization that operates the hydrogen production system 1.

The electrolytic couple 100 also includes electrolytic couple x 100x, electrolytic couple A 100A, and electrolytic couple B 100B. Each electrolytic couple 100 also has AC/DC converters 11x, A, B, which are the first AC/DC converter, and electrolytic cells 13x, A, B. That is, electrolytic cell x 100x has AC/DC converter 11x and electrolytic cell 13x. Similarly, electrolytic cell A 100A has AC/DC converter 11A and electrolytic cell 13A, and electrolytic cell B 100B has AC/DC converter 11B and electrolytic cell 13B.

The AC/DC converters 11x, A, B are connected in series to each other. Each of the AC/DC converters 11x, A, B is connected to a power supply unit 15, that is, it is provided on the system side of the electrolytic cells 13x, A, B, and converts AC supplied from the power supply unit 15 into DC. Each of the electrolytic cells x, A, B stores salt water and generates hydrogen from the salt water according to the power supplied. Note that the AC/DC converters 11x, A, B and the electrolytic cells 13x, A, B only need to have similar functions, but do not necessarily need to achieve the same specifications. The number of converters is not limited to that shown in the figure.

In the hydrogen production system 1 shown in Figure 2A above, when an arbitrary voltage is applied to the electrolytic cell 13, a current flows along the IV curve, and vice versa. Therefore, it is necessary for the AC/DC converter 11, which is the second AC/DC converter, to sense the current flowing through the electrolytic cell 13 and fine-tune the voltage applied to the electrolytic cell 13 so that the error with respect to the external current command value is zero. The specific details of this are explained using Figure 2B.

Fig. 2B is a diagram showing current-voltage characteristics, which are typical electrical characteristics of electrolytic cell 13, to explain the problem of Example 1. As shown in Fig. 2B, assume that equal current command values _iA = _iB are given to electrolytic cell A 100A and electrolytic cell B 100B, which are connected in series. The voltages applied to electrolytic cell A 100A and electrolytic cell B 100B are _vA and _vB , respectively, and if the characteristics are the same, the two voltages will match.

Here, if we assume that the efficiency of AC/DC converters 11A and 11B is 1, the power, which is the product of the voltage and current on the electrolytic cell side of AC/DC converters 11A and 11B, is the same as the product (power) of the AC voltage (effective value V) and AC current (effective value I) on the system side. And since the current is common at I, the voltages _VinA and _VinB on the system side will be the same value. If the same current command value is given to each electrolytic cell 13, not just electrolytic cell A 13A and electrolytic cell B 13B, the input voltage to each AC/DC converter 11 is an evenly divided system voltage. Also, if the number of electrolytic couples 100 is n and the system voltage is V _G , then it is V _G /n.

That is, it can be specified by the following formula.
Power before and after AC/DC converter 11 (assuming conversion efficiency of 100%): V _inA *I = v _A *i _A ... (Equation 1)
System side voltage of AC/DC converter 11 (same conditions for each AC/DC converter): ΣV _IN =V _G , that is, V _IN =V _G /n (Equation 2)
Furthermore, at the stage of designing the hydrogen production system 1, the system side voltage Vin of the AC/DC converter 11 is set so that the maximum conversion efficiency can be realized within a certain range of the output voltage v of the electrolytic cell 13. This state is shown in the graph of FIG. 2C. FIG. 2C is a diagram showing the output voltage and conversion efficiency to explain the problem of the first embodiment. Conversely, after the design specifications of the AC/DC converter 11 and the output voltage of the electrolytic cell 13 are determined, it is necessary to maintain the relationship between _vin and v in FIG. 2C. It must be.

Here, as shown in Fig. 3, if the IV curve of the electrolytic cell B 13B changes due to deterioration or the like, the voltage applied to maintain the same current changes from _vB to _v'B (in the case of deterioration, the voltage often increases). In addition, since the current command value is the same, the increase in the electrolytic voltage also increases the voltage _V'inB on the system side of the corresponding AC/DC converter 11. In addition, if the degree of change in the voltage of the electrolytic cell 13 is β, then β is reflected directly in the system side voltage as shown in the following formula.
When V _inA *I=v _A *i _A and V _inB *I=v' _B *i _B
v' _B = βv _A ... (Equation 3)
Power before and after AC/DC converter (assuming 100% conversion efficiency)
V _inB *I = v' _B *i _B = βV _inA ... (Equation 4)
AC/DC converter voltage after balancing
_V'inA = V _G /(n-1+ β) ... (Equation 5)
_V'inB =βV _G /n (Equation 6)
Here, the total voltage on the system side of the AC/DC converters 11 connected in series is VG, so the other voltages will drop relatively. For example, it is shown by the voltage V' _{in A} on the system side of electrolytic cell A 100A. In this case, if an attempt is made to maintain the current, it may operate near the upper limit of the specifications of the AC/DC converter 11A, or it may exceed the specifications and become unable to perform conversion (see the graph on the left side of Figure 3). In such a case, if the characteristics of one electrolytic cell change among about 10 electrolytic cells 13, the impact is thought to be small, but as the number of electrolytic cells 13 with changing characteristics increases, it cannot be ignored.

Furthermore, if electrolytic cell 13 is driven with a current value different from that of the other electrolytic cells, this will have a greater effect.

FIG. 4 is a diagram showing the relationship between voltage and current when the current command value is lowered to explain the problem of the first embodiment. The left diagram of FIG. 4 shows the relationship between voltage and current in the electrolytic cell A 13A, and the right diagram shows the case where the current command value of the electrolytic cell B 13B is lowered to _i'B . In the right diagram, the (electrolysis) voltage drops from a predetermined value to _v'B according to the IV curve in the electrolytic cell B 13B. The voltage on the system side of the corresponding AC/DC converter 11B drops according to the drop to _v'B . However, since the electrolytic current _i'B also changes and the system side current is common, the voltage _V'inB on the system side drops by a square factor. That is, as shown in the following formula, if the degree of change in the current command value in the electrolytic cell is α, the voltage on the system side is ^α2 .
Let V _inA *I=v _A *i _A and V _inB *I=v' _B *i' _B , then
v' _B = αv _A ... (Equation 7)
Power before and after AC/DC converter (assuming conversion efficiency of 100%)
V _inB *I = v' _B *i' _B = α ² V _inA ... (Equation 8)
AC/DC converter voltage after balancing
_V'inA = V _G /(N-1+ α ² ), _V'inB = α ² V _G /N... (Equation 9)
Then, to compensate for this change, the system side voltage of the other AC/DC converters rises. As a result, conversion operation in the efficient region as shown in the left diagram of Figure 4 cannot be performed. If the characteristics of one of several dozen electrolytic cells 13 change, the impact is thought to be small, but as the number of characteristics that change increases, the change in characteristics cannot be ignored.

In order to reduce the above-mentioned changes in characteristics, the configuration shown in FIG. 5 is adopted in Example 1. FIG. 5 is a configuration diagram of a hydrogen production system 1 in Example 1. As shown in FIG. 5, in Example 1, in addition to electrolytic couple A 100A and electrolytic couple B 100B including AC/DC converter 11A and AC/DC converter 11B connected in series, a dummy pair 10 is provided. The number of dummy pairs 10 may be one or more, and is not limited. The dummy pairs 10 are connected in series with each electrolytic couple.

The hydrogen production system 1 of Example 1 further includes a calculation device 14. That is, the hydrogen production system 1 of Example 1 includes a dummy pair 10, a plurality of electrolytic couples 100, a calculation device 14, and a power supply device 15. First, the dummy pair 10 includes an AC/DC converter 11 and a capacitor 12. Therefore, formally, the hydrogen production system 1 of FIG. 5 is different from the hydrogen production system 1 of FIG. 2A in that the electrolytic couples 100x are replaced with dummy pairs 10, and a calculation device 14 is added. Below, the hydrogen production system 1 of Example 1 will be described, focusing on these differences.

The dummy pair 10 is also intended to compensate and correct the voltage on the system side. For this purpose, the dummy pair 10 has an AC/DC converter 11 and a capacitor 12, which are connected. The AC/DC converter 11 is connected to the power supply unit 15, that is, it is provided on the system side and converts the alternating current supplied from the power supply unit 15 into direct current. The AC/DC converter 11 has the same functions as the AC/DC converters 11A and 11B, but its specifications may be different.

The capacitor 12 is a part that can input energy (e.g., electricity) supplied from the AC/DC converter 11. Here, inputting energy includes storing and consuming energy. Therefore, in addition to a so-called capacitor, a storage battery or a resistor can be used as the capacitor 12.

Furthermore, as described above, the calculation device 14 functions as a power control device. To this end, the calculation device 14 calculates a voltage command value for the AC/DC converter 11 of the dummy pair 10. This voltage command value indicates the voltage fluctuation on the system side of the AC/DC converter 11 of the dummy pair 10 caused by a voltage deviation due to a change in the characteristics of the electrolytic cell 13 and a change in the electrolysis current command value, that is, the correction value of the voltage for the AC/DC converter 11. For this reason, the calculation device 14 calculates a voltage command value for the AC/DC converter 11 using the current command value (i) for each electrolytic cell 13A, B and the voltage (v) of each electrolytic cell 13A, B.

The details of the arithmetic device 14 will be described below. First, the configuration of the arithmetic device 14 will be described. FIG. 6 is a functional block diagram of the arithmetic device 14 in the first embodiment. As shown in FIG. 6, the arithmetic device 14 has an input unit 141, a voltage command value calculation unit 142, an output unit 143, and a storage unit 144. The input unit 141 accepts input information used for calculating a voltage command value in the voltage command value calculation unit 142. The voltage command value calculation unit 142 calculates a voltage command value using the input information. The output unit 143 outputs a control command including a voltage command value to the AC/DC converter 11 of the dummy pair 10. This arithmetic device 14 can be realized by a so-called computer. In this case, it may be realized by dedicated hardware, or the calculation may be performed according to a program that is software. In the latter case, the voltage command value calculation unit 142 can be realized by a processor such as a CPU.

The output unit 143 outputs a control command including the calculated voltage command value to the AC/DC converter 11. The memory unit 144 stores information and programs used to calculate the voltage command value. It is preferable that the voltage command value calculation unit 142 calculates a current command value and an electrolytic cell voltage for the electrolytic cell. These may be calculated in a separate location from the voltage command value calculation unit 142.

Then, the output unit 143 outputs control commands including a current command value and an electrolytic cell voltage to the first AC/DC converter and the second AC/DC converter to control them. Note that the current command value and the electrolytic cell voltage include a current command value i when the operation of the first AC/DC converter satisfies a predetermined condition, for example, when the current command values are evenly balanced.

Here, the voltage of AC/DC converter 11A after balancing is as shown in the following (Equation 10).
_V'inA = V _G /(N-1+ αβ), _V'inB = αβ V _G /N... (Equation 10)
In this (Equation 10), the product of α and β is used instead of ^α2 in (Equation 9). This is because the deviation in the electrolysis voltage caused by the deviation in the electrolysis current value α is a measurable deviation β. Therefore, the calculation device 14 calculates a voltage command value for the AC/DC converter 11, which will be described below.

Next, the processing of the arithmetic unit 14 will be described. The input unit 141 receives, as input information, a current command value i when the first AC/DC converter is evenly balanced and the electrolytic cell voltage v before deterioration. More specifically, the following information is used as the input information: (1) electrolysis current command value when evenly balanced (for example, average current command value): i, (2) electrolysis voltage value before deterioration (new product or rated value): v, (3) individual electrolysis current command value: _iK , and (4) electrolytic cell voltage _vk . Note that (3) and (4) are preferably actual measured values.

Furthermore, the voltage command value calculation unit 142 calculates a voltage command value using the input information. That is, the voltage command value calculation unit 142 calculates the voltage command value _VDM according to the following (Equation 11).
V _DM =ΣΔV _K =(1-α _K β _K )V _G /N... (Equation 11)
where α _K =i _K /i, βK= v _k /v
At least a portion of the input information and α and β may be stored in the storage unit 144 .

Then, output unit 143 outputs the calculated voltage command value _VDM to each of AC/DC converters 11, 11A, 11B to control the output voltage. As a result, the influence of voltage fluctuations in each AC/DC converter can be reduced.

In the above-mentioned first embodiment, of the AC/DC converters configured by connecting in series on the AC side (system side), the DC sides of at least some of the AC/DC converters are connected to a capacitor. The DC sides of the remaining AC/DC converters are connected to an electrolytic cell. In this configuration, a voltage command value for the AC/DC converter connected to the capacitor, that is, the dummy pair of AC/DC converters, is calculated based on the current command value of each electrolytic cell and the voltage of each electrolytic cell. As a result, in the first embodiment, the shift in the input voltage of each AC/DC converter resulting from the deviation of each current command value and the deviation of the voltage is compensated for. In the first embodiment, a hydrogen production system controlled by power control as described above can be provided. This concludes the explanation of the first embodiment.

Next, a second embodiment will be described. FIG. 7A is a configuration diagram of the hydrogen production system 1 in the second embodiment. The circuit configuration in FIG. 7A is almost the same as that in the first embodiment (FIG. 5). However, the processing in the arithmetic device 14 is different. In the second embodiment, in order to enable the shut-down and start-up of the electrolytic cell 13, the arithmetic device 14 executes a calculation. Specifically, the calculation in the arithmetic device 14 enables control to reduce the current for the electrolytic cell B 13B operating at the rated current i. For this purpose, it is necessary to reduce the voltage of the electrolytic cell B 13B to 0 by a voltage command after the current is set to 0. This is because, as shown in the IV curve in FIG. 7B, the voltage remains even when the current is set to 0. If this control operation of the electrolytic voltage is performed, it will affect the grid side voltage of the other electrolytic couples. Therefore, in the second embodiment, the voltage command value calculation unit 142 calculates a voltage command value for the dummy couple 10 so as to be contradictory to the change in the grid side voltage of the electrolytic couple B 13B. That is, the voltage command value calculation unit 142 calculates a voltage command value _{VDM such that the amount of change in the grid side voltage of the dummy pair 10 is the same as, but in the opposite direction to, the amount of change in the grid side voltage of the electrolytic pair B 13B} . Specifically, the voltage command value calculation unit 142 calculates the voltage command value _VDM according to the following (Equation 12) using input information: (1) voltage command value _vk for each electrolytic cell, and (2) electrolysis voltage value before deterioration (new or rated): v.
V _DM = V _G /N/v*(vv _k ) ... (Equation 12)
As described above, in the second embodiment, the voltage command value calculation unit 142 controls the voltage of a predetermined electrolytic cell (e.g., electrolytic cell 13A) among the multiple electrolytic cells 13A and 13B, and calculates a voltage command value for the AC/DC converter 11, which is the second AC/DC converter, using the difference between the voltage command value of each electrolytic cell, which is the electrolytic cell rated voltage, and the electrolysis voltage value, which is the command voltage.
This makes it possible to reduce the change in the grid side voltage of the electrolytic couple B 13B. In other words, it is possible to reduce the impact on other electrolytic couples based on the change in the grid side voltage due to deterioration or the like. In other words, by using the control command including the above-mentioned voltage command value from the computing device 14, it is possible to stop and disconnect the electrolytic couple B 13B while suppressing the impact on other electrolysis operations. The opposite is also true, and it is also possible to newly input and start up an electrolytic couple.

In the above-described second embodiment, when the voltage of a specific electrolytic cell is controlled using an AC/DC converter, the difference between the rated voltage of the electrolytic cell and the command voltage is set as the voltage command value for the second AC/DC converter. This concludes the explanation of the second embodiment.

Next, a third embodiment will be described. Fig. 8 is a configuration diagram showing a part of the hydrogen production system 1 in the third embodiment. In Fig. 8, the illustration of the calculation device 14 is omitted. In the third embodiment, the configuration of the electrolytic couple 100 is different from that in the first and second embodiments. That is, the AC/DC converter, which is the first AC/DC converter constituting the electrolytic couple, and the electrolytic cell are grouped and connected.
Specifically, (1) a plurality of AC/DC converters 11A-1, 11A-2, which are the first AC/DC converters, and AC/DC converters 11B-1, 11B-2 are each connected in series as one group, and (2) electrolytic cells 13A-1, 13A-2 and electrolytic cells 13B-1, 13B-2 are each connected in series as one group, and the electrolytic cells 13 of each group are connected in series. In this way, the electrolytic couple does not need to be configured with a one-to-one AC/DC converter and an electrolytic cell.

In the third embodiment, it is preferable to connect the maximum and minimum voltage ends on the DC side of a group of a plurality of AC/DC converters connected adjacently on the AC side to a group of a plurality of electrolytic cells connected in series. Note that, for the calculation of the voltage command value _VDM in the third embodiment, either of the first and second embodiments can be used.

According to each of the above embodiments, in an electrolytic cell system such as a hydrogen production system, the cost of hydrogen production can be reduced by increasing the efficiency. Although the description of each embodiment is finished here, the present invention is not limited to these embodiments. In particular, the number of AC/DC converters and electrolytic cells, and the number of dummy pairs are not limited to those shown in the drawings. However, as described above, it is desirable that the number of dummy pairs satisfies the fluctuation range of the AC/DC converter connected to the electrolytic cell x the number ≦ V _DM . Furthermore, the calculation device 14 may be configured to be able to execute both the calculation of the voltage command value V _DM in the first and second embodiments. Moreover, the present invention can be applied to electrolytic cell systems other than a hydrogen production system.

1... Hydrogen production system, 10... Dummy pair, 11... AC/DC converter, 12... Capacitor, 13... Electrolytic cell, 14... Calculation device, 15... Power supply device, 100... Electrolytic pair, 141... Input unit, 142... Voltage command value calculation unit, 143... Output unit, 144... Storage unit

Claims (12)

A power control system for a hydrogen generation system that generates hydrogen from saltwater using a plurality of electrolytic couples connected in series to each other, the electrolytic couples being composed of a plurality of electrolytic cells that store saltwater and a first AC/DC converter that supplies power to the electrolytic cells, the system comprising:
A dummy pair is connected in series with the plurality of electrolytic pairs and is composed of a capacitor capable of inputting energy and a second AC/DC converter connected to the capacitor;
A power control system comprising an arithmetic device having an input unit that receives input information including current command values to the plurality of electrolytic cells and electrolytic cell voltages of the plurality of electrolytic cells, a voltage command value calculation unit that uses the input information to calculate a voltage command value that is a correction value of voltage for the second AC/DC converter, and an output unit that outputs the voltage command value to the second AC/DC converter. 2. The power control system according to claim 1,
the current command value is a current command value when the plurality of electrolytic cells are equally balanced,
A power control system in which the electrolytic cell voltages are electrolytic voltage values of the multiple electrolytic cells before deterioration. 3. The power control system according to claim 2,
The power control system, wherein the input information further includes electrolysis current command values and electrolysis cell voltages which are actual measured values in each of the plurality of electrolysis cells. 2. The power control system according to claim 1,
The voltage command value calculation unit calculates the voltage command value using a difference between an electrolysis current command value, which is an actual measured value in each of the plurality of electrolytic cells, and an electrolytic cell voltage. 2. The power control system according to claim 1,
A power control system that groups and connects the plurality of first AC/DC converters and the plurality of electrolytic cells that constitute the plurality of electrolytic couples to each other. 6. The power control system according to claim 5,
A power control system that connects the highest and lowest voltage ends on the DC side of a group of a plurality of first AC/DC converters that are adjacently connected on the AC side to a group of a plurality of electrolyzers connected in series. A hydrogen production system that generates hydrogen from salt water stored in a plurality of electrolyzers,
a plurality of electrolytic couples each including the plurality of electrolytic cells and a first AC/DC converter that supplies power to the electrolytic cells, the electrolytic couples being connected in series with each other;
A dummy pair is connected in series with the plurality of electrolytic pairs and is composed of a capacitor capable of inputting energy and a second AC/DC converter connected to the capacitor;
A hydrogen production system comprising an arithmetic device having an input unit that receives input information including current command values for the plurality of electrolytic cells and electrolytic cell voltages of the plurality of electrolytic cells, a voltage command value calculation unit that uses the input information to calculate a voltage command value that is a correction value for voltage for the second AC/DC converter, and an output unit that outputs the voltage command value to the second AC/DC converter. The hydrogen production system according to claim 7,
the current command value is a current command value when the plurality of electrolytic cells are equally balanced,
A hydrogen production system, wherein the electrolytic cell voltage is an electrolysis voltage value of the plurality of electrolytic cells before deterioration. 9. The hydrogen production system according to claim 8,
The input information further includes an electrolysis current command value and an electrolysis cell voltage, which are actual measured values in each of the plurality of electrolysis cells. The hydrogen production system according to claim 7,
The voltage command value calculation unit calculates the voltage command value using a difference between an electrolysis current command value, which is an actual measured value in each of the plurality of electrolytic cells, and an electrolytic cell voltage. The hydrogen production system according to claim 7,
A hydrogen production system in which a plurality of first AC/DC converters and a plurality of electrolyzers constituting the plurality of electrolytic couples are grouped and connected to each other. The hydrogen production system according to claim 11,
A hydrogen production system comprising: a group of a plurality of first AC/DC converters connected adjacently on the AC side; a highest voltage end and a lowest voltage end on the DC side of the group of a plurality of first AC/DC converters connected adjacently on the AC side; and a group of a plurality of electrolyzers connected in series.

Images