Power supply unit for electrolytic cells

Abstract

Provided is a power supply device for an electrolytic cell, said power supply device comprising: a first converter that converts AC power supplied from a power grid into rectified power; a second converter that has a conversion circuit for converting the rectified power outputted from the first converter into DC power suited to the electrolytic cell, and supplies the DC power converted by the conversion circuit to the electrolytic cell 2; and a control device that controls the operation of the conversion from the rectified power to the DC power by the conversion circuit. The conversion circuit has a pair of input terminals, a pair of output terminals, a pair of switching elements, a pair of rectifying elements, a pair of charge storage elements, and a pair of reactors. As a result, this power supply device for an electrolytic cell can reduce a ripple component superimposed on the DC current that is supplied to the electrolytic cell.

Description

Technical Field

[0001] Embodiments of the present invention relate to a power supply device for an electrolytic cell.

Background Art

[0002] There is a power supply device for an electrolytic cell that causes electrolysis in the electrolytic cell by supplying direct current power between the anode and cathode of the electrolytic cell. The power supply device for the electrolytic cell is connected to an alternating current power system, converts the alternating current power supplied from the power system into direct current power corresponding to the electrolytic cell, and supplies the converted direct current power between the anode and cathode of the electrolytic cell. The electrolytic cell performs electrolysis in response to the supply of direct current power from the power supply device for the electrolytic cell, and thereby produces products such as hydrogen, for example.

[0003] In such a power supply device for an electrolytic cell, if the component of ripple (pulsation) superimposed on the direct current supplied to the electrolytic cell is large, it may cause a decrease in the efficiency of electrolysis in the electrolytic cell or a reduction in the life of the electrolytic cell. Therefore, in the power supply device for the electrolytic cell, it is desirable to be able to reduce the component of ripple superimposed on the direct current supplied to the electrolytic cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document No. 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Embodiments of the present invention provide a power supply device for an electrolytic cell that can reduce the component of ripple superimposed on the direct current supplied to the electrolytic cell.

Means for Solving the Problems

[0006] According to an embodiment of the present invention, an electrolytic cell power supply device for causing an electrolytic cell to perform electrolysis by supplying DC power between the anode and cathode of the electrolytic cell, comprising: a first converter that converts AC power supplied from a power system into rectified power; and a conversion circuit that converts the rectified power output from the first converter into DC power corresponding to the electrolytic cell, wherein the DC power converted by the conversion circuit is used to perform electrolysis In the tankThe system comprises a second converter that supplies power, and a control device that controls the operation of the conversion circuit from rectified power to DC power. The conversion circuit has a pair of input terminals, a pair of output terminals, a pair of switching elements, a pair of rectifier elements, a pair of charge storage elements, and a pair of reactors. The pair of input terminals receive rectified power input from the first converter, and the pair of output terminals are connected to the electrolytic cell. The pair of switching elements have a pair of main terminals and control terminals, and have an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals is interrupted. One main terminal of one of the pair of switching elements is connected to one of the pair of input terminals, and the other main terminal of one of the switching elements is connected to one end of one of the pair of rectifier elements, and the other end of one of the rectifier elements is connected to one end of the other rectifier element. The end of one reactor is connected to one main terminal of the other switching element of the pair of switching elements, the other main terminal of the other switching element is connected to the other input terminal of the pair of input terminals, the pair of charge storage elements are connected in series between the pair of input terminals, the connection point of the pair of charge storage elements is connected to the connection point of the pair of rectifier elements, one end of one reactor of the pair of reactors is connected to the connection point between one switching element and one rectifier element, the other end of one reactor is connected to one output terminal of the pair of output terminals, one end of the other reactor of the pair of reactors is connected to the connection point between the other rectifier element and the other switching element, the other end of the other reactor is connected to the other output terminal of the pair of output terminals, and the control device controls the operation of the conversion circuit from rectified power to DC power by controlling the switching of the pair of switching elements. The switching of the pair of switching elements is controlled such that, during the period when one switching element is in the ON state, the other switching element is in the OFF state, thereby outputting a DC voltage corresponding to the charge stored in one of the pair of charge storage elements to the pair of output terminals, and during the period when one switching element is in the OFF state, the other switching element is in the ON state, thereby outputting a DC voltage corresponding to the charge stored in the other of the pair of charge storage elements to the pair of output terminals. A power supply unit for the electrolytic cell is provided. [Effects of the Invention]

[0007] According to embodiments of the present invention, a power supply device for an electrolytic cell is provided that can reduce the ripple component superimposed on the DC current supplied to the electrolytic cell. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic block diagram showing a power supply unit for an electrolytic cell according to the embodiment. [Figure 2] This is a block diagram schematically representing an example of a conversion circuit. [Figure 3] Figures 3(a) to 3(c) are timing charts that schematically represent an example of the operation of the conversion circuit. [Figure 4] This is a schematic block diagram showing a modified example of the power supply device for an electrolytic cell according to the embodiment. [Figure 5] This is a schematic block diagram showing a modified example of the second converter according to the embodiment. [Figure 6] This is a schematic block diagram showing a modified example of the power supply device for an electrolytic cell according to the embodiment. [Figure 7] Figures 7(a) to 7(d) are timing charts that schematically represent an example of the operation of the two second transducers. [Modes for carrying out the invention]

[0009] Each embodiment will be described below with reference to the drawings. Please note that the drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of the parts, are not necessarily identical to those of reality. Furthermore, even when representing the same part, the dimensions and ratios may differ between drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0010] Figure 1 is a schematic block diagram showing a power supply unit for an electrolytic cell according to an embodiment. As shown in Figure 1, the electrolytic cell power supply unit 10 comprises a first converter 11, a second converter 12, and a control device 14. The electrolytic cell power supply unit 10 is used with the electrolytic cell 2. The electrolytic cell 2 has an anode 2a and a cathode 2b. The electrolytic cell power supply unit 10 causes the electrolytic cell 2 to perform electrolysis by supplying DC power between the anode 2a and the cathode 2b of the electrolytic cell 2.

[0011] The electrolytic cell 2 performs electrolysis in response to the supply of DC power from the electrolytic cell power supply unit 10, thereby generating products such as hydrogen. The electrolytic cell 2 may further include, for example, an ion exchange membrane (diaphragm) placed between the anode 2a and the cathode 2b. The configuration of the electrolytic cell 2 may be any configuration that has at least an anode 2a and a cathode 2b and is capable of performing electrolysis of an electrolyte or the like by supplying DC power between the anode 2a and the cathode 2b.

[0012] The electrolytic cell power supply unit 10 is connected to the electrolytic cell 2 and also to the power system 4. The power system 4 is an AC power system. The electrolytic cell power supply unit 10 is connected to the power system 4 via, for example, a transformer 6. The power of the power system 4 is, for example, three-phase AC power. However, the power of the power system 4 is not limited to three-phase AC power, but may also be single-phase AC power, etc.

[0013] The first converter 11 is connected to the power system 4. The first converter 11 is connected to the power system 4 via, for example, a transformer 6 or the like. The first converter 11 converts the AC power supplied from the power system 4 into rectified power. The first converter 11 is, for example, a rectifier using rectifying elements such as diodes. The first converter 11 is, for example, a diode bridge circuit. The first converter 11 may also be, for example, a thyristor rectifier using thyristors or a PWM rectifier using switching elements such as IGBTs and FETs. The first converter 11 may further have a function of adjusting the magnitude of the rectified power output. The rectified power output from the first converter 11 is, for example, pulsating DC power. The first converter 11 may further have a function of smoothing the pulsating DC power by, for example, a smoothing capacitor or the like. The rectified power output from the first converter 11 may also be DC power.

[0014] The second converter 12 has a conversion circuit 20 that converts the rectified power output from the first converter 11 into DC power corresponding to the electrolytic cell 2. The second converter 12 supplies the DC power converted by the conversion circuit 20 between the anode 2a and the cathode 2b of the electrolytic cell 2. The second converter 12 (conversion circuit 20) is, for example, a DC-DC converter circuit.

[0015] The control device 14 controls the operation of the second converter 12. The control device 14 controls the operation of converting the rectified power into DC power by the conversion circuit 20.

[0016] FIG. 2 is a block diagram schematically showing an example of the conversion circuit. As shown in FIG. 2, the conversion circuit 20 has a pair of input terminals 20a, 20b, a pair of output terminals 20c, 20d, switching elements 21a to 21d, rectifying elements 22a to 22d, charge storage elements 23a, 23b, and reactors 24a, 24b.

[0017] A pair of input terminals 20a and 20b receive the input of the rectified power from the first converter 11. One input terminal 20a is connected to the high-potential side output terminal of the first converter 11. The other input terminal 20b is connected to the low-potential side output terminal of the first converter 11. Thereby, the rectified power output from the first converter 11 is input to the conversion circuit 20 via the pair of input terminals 20a and 20b.

[0018] A pair of output terminals 20c and 20d are connected to the electrolytic cell 2. One output terminal 20c is connected to the anode 2a of the electrolytic cell 2. The other output terminal 20d is connected to the cathode 2b of the electrolytic cell 2. Thereby, the DC power converted by the conversion circuit 20 is supplied between the anode 2a and the cathode 2b of the electrolytic cell 2.

[0019] The switching elements 21a to 21d have a pair of main terminals and a control terminal. Also, the switching elements 21a to 21d have an on state and an off state. The on state is a state in which a current flows between the pair of main terminals. The off state is a state in which the flow of current between the pair of main terminals is blocked. Each of the switching elements 21a to 21d switches between the on state and the off state according to the voltage between the pair of main terminals and the voltage of the control terminal. Note that the off state does not necessarily mean that no current flows between the pair of main terminals, and a weak current within a range that does not affect the operation of the conversion circuit 20 may flow between the pair of main terminals.

[0020] The switching elements 21a to 21d are, for example, self-excited semiconductor switching elements such as IGBTs and MOSFETs. However, the switching elements 21a to 21d are not limited to this, and any element that can arbitrarily switch between the on state and the off state may be used.

[0021] One main terminal of switching element 21a is connected to input terminal 20a. The other main terminal of switching element 21a is connected to one main terminal of switching element 21b. The other main terminal of switching element 21b is connected to one main terminal of switching element 21c. The other main terminal of switching element 21c is connected to one main terminal of switching element 21d. The other main terminal of switching element 21d is connected to input terminal 20b. In other words, in this example, the four switching elements 21a to 21d are connected in series between a pair of input terminals 20a and 20b.

[0022] Each of the rectifier elements 22a to 22d is connected in antiparallel to each of the switching elements 21a to 21d. The rectifier elements 22a to 22d are, for example, diodes. The anodes of the rectifier elements 22a to 22d are connected to the main terminals on the low-potential side of the switching elements 21a to 21d, and the cathodes of the rectifier elements 22a to 22d are connected to the main terminals on the high-potential side of the switching elements 21a to 21d. The direction of the current flowing through the rectifier elements 22a to 22d (direction of rectification) is opposite to the direction of the current flowing through the switching elements 21a to 21d.

[0023] The charge storage elements 23a and 23b are connected in series between a pair of input terminals 20a and 20b. The charge storage elements 23a and 23b are provided in parallel with the switching elements 21a to 21d. Furthermore, the connection point between charge storage element 23a and charge storage element 23b is connected to the connection point between switching element 21b and switching element 21c. In other words, the series connection of switching elements 21a and 21b is connected in parallel with charge storage element 23a, and the series connection of switching elements 21c and 21d is connected in parallel with charge storage element 23b. The charge storage elements 23a and 23b are, for example, capacitors.

[0024] One end of reactor 24a is connected to the connection point of switching elements 21a and 21b. The other end of reactor 24a is connected to one output terminal 20c. One end of reactor 24b is connected to the connection point of switching elements 21c and 21d. The other end of reactor 24b is connected to the other output terminal 20d.

[0025] In the conversion circuit 20, by controlling the switching of the outer switching elements 21a and 21d while keeping the inner switching elements 21b and 21c in the off state, the rectified power input from the first converter 11 can be converted into DC power corresponding to the electrolytic cell 2 and supplied to the electrolytic cell 2. The conversion circuit 20 converts the rectified power input from the first converter 11 into DC power using the charge storage elements 23a and 23b, and then steps down the converted DC power to DC power corresponding to the electrolytic cell 2 by switching the switching elements 21a and 21d. In this case, the conversion circuit 20 functions as a step-down chopper circuit.

[0026] Furthermore, in the conversion circuit 20, by controlling the switching of the inner switching elements 21b and 21c while keeping the outer switching elements 21a and 21d in the off state, the DC power from the electrolytic cell 2 can be boosted and supplied to the charge storage elements 23a and 23b (the pair of input terminals 20a and 20b). In this case, the conversion circuit 20 functions as a boost chopper circuit.

[0027] Thus, the conversion circuit 20 can convert power from the input terminals 20a and 20b to the output terminals 20c and 20d by switching the switching elements 21a and 21d, and can also convert power from the output terminals 20c and 20d to the input terminals 20a and 20b by switching the switching elements 21b and 21c. The conversion circuit 20 is sometimes called, for example, a double chopper circuit.

[0028] Furthermore, the conversion circuit 20 does not necessarily have to have the function of converting power from the output terminals 20c and 20d to the input terminals 20a and 20b. The conversion circuit 20 may, for example, omit the switching elements 21b and 21c and be configured to include only the rectifier elements 22b and 22c.

[0029] More specifically, the conversion circuit 20 may have a configuration comprising a pair of switching elements 21a and 21d and a pair of rectifier elements 22b and 22c. One main terminal of the switching element 21a is connected to the input terminal 20a. The other main terminal of the switching element 21a is connected to one end of the rectifier element 22b. The other end of the rectifier element 22b is connected to one end of the rectifier element 22c. The other end of the rectifier element 22c is connected to one main terminal of the switching element 21d. The other main terminal of the switching element 21d is connected to the input terminal 20b. The connection point of the charge storage elements 23a and 23b is connected to the connection point of the rectifier elements 22b and 22c. One end of the reactor 24a is connected to the connection point of the switching element 21a and the rectifier element 22b. The other end of the reactor 24a is connected to one of the output terminals 20c. One end of reactor 24b is connected to the connection point between rectifier element 22c and switching element 21d. The other end of reactor 24b is connected to the other output terminal 20d. In this case as well, power can be converted from the input terminals 20a and 20b to the output terminals 20c and 20d by switching the switching elements 21a and 21d.

[0030] The control device 14 controls the operation of the second converter 12 by controlling the switching of the switching elements 21a to 21d. When only power conversion from the input terminals 20a and 20b to the output terminals 20c and 20d is performed, the control device 14 controls the operation of the second converter 12 (the operation of conversion from rectified power to DC power by the conversion circuit 20) by controlling the switching of the pair of switching elements 21a and 21d. The control device 14 is connected to the respective control terminals of the switching elements 21a to 21d, for example, and controls the switching of the switching elements 21a to 21d by inputting control signals (e.g., gate signals) to the respective control terminals of the switching elements 21a to 21d.

[0031] Figures 3(a) to 3(c) are timing charts that schematically represent an example of the operation of the conversion circuit. Figure 3(a) schematically shows an example of a control signal input to the control terminal of the switching element 21a. Figure 3(b) schematically shows an example of a control signal input to the control terminal of the switching element 21d. Figure 3(c) schematically shows an example of the DC voltage output from the conversion circuit 20 (second converter 12).

[0032] Switching elements 21a and 21d are turned on when the voltage at the control terminal is high, and turned off when the voltage at the control terminal is low. However, conversely, switching elements 21a and 21d may be turned on when the voltage at the control terminal is low, and turned off when the voltage at the control terminal is high. The control device 14 controls the switching between the on and off states of switching elements 21a and 21d by changing the voltage at the control terminal (control signal) of the switching elements 21a and 21d.

[0033] As shown in Figure 3(a), the control device 14 alternately switches the switching element 21a between the on and off states. The control device 14 switches the switching element 21a between the on and off states at a predetermined period, for example. The control device 14 switches the switching element 21a between the on and off states at a predetermined period, for example, by pulse width modulation control (PWM). However, the method by which the control device 14 switches the switching element 21a between the on and off states is not limited to PWM control, but may be any method that can appropriately switch the switching element 21a between the on and off states.

[0034] As shown in Figure 3(b), the control device 14, similar to the switching element 21a, alternately switches the switching element 21d between the on and off states.

[0035] When switching element 21a is turned ON and switching elements 21b to 21d are turned OFF, a DC voltage corresponding to the charge stored in charge storage element 23a appears between output terminals 20c and 20d. When switching element 21d is turned ON and switching elements 21a to 21c are turned OFF, a DC voltage corresponding to the charge stored in charge storage element 23b appears between output terminals 20c and 20d.

[0036] If the capacitance of charge storage element 23b is substantially the same as that of charge storage element 23a, the DC voltage corresponding to the charge stored in charge storage element 23a and the DC voltage corresponding to the charge stored in charge storage element 23b will be half the voltage between input terminals 20a and 20b. Therefore, when switching elements 21a and 21d are switched, the DC power (rectified power) supplied from the first converter 11 can be stepped down to the DC power corresponding to the electrolytic cell 2.

[0037] As shown in Figure 3, the control device 14 controls the switching of switching elements 21a and 21d such that switching element 21d is turned off during the period when switching element 21a is turned off, and switching element 21d is turned on during the period when switching element 21a is turned off.

[0038] The control device 14, for example, sets the duty cycle of the PWM control of switching elements 21a and 21d to 50%, and inverts the on and off states of switching elements 21a and 21d. As a result, as shown in Figure 3(c), a DC voltage and DC current with extremely low ripple, which is half the voltage between input terminals 20a and 20b, can be supplied to the electrolytic cell 2.

[0039] Note that the duty cycles of switching elements 21a and 21d do not necessarily have to be 50%. For example, the duty cycle of switching element 21a may be set to 60% and the duty cycle of switching element 21d to 40%. In this case as well, ripple superimposed on the DC voltage and DC current supplied to the electrolytic cell 2 can be suppressed. For example, after setting the duty cycle of switching element 21a to 60% and the duty cycle of switching element 21d to 40%, in the next cycle, the duty cycle of switching element 21a may be set to 40% and the duty cycle of switching element 21d to 60%. This makes it possible to suppress, for example, an imbalance in the consumption of charge stored in charge storage elements 23a and 23b, and an imbalance in the charge (voltage) stored in charge storage elements 23a and 23b.

[0040] The method for controlling the switching of switching elements 21a and 21d is not limited to the above, and any control method is acceptable in which switching element 21d is turned off during the period when switching element 21a is turned on, and switching element 21d is turned on during the period when switching element 21a is turned off. As described above, if the duty cycles of switching elements 21a and 21d are set to 50%, then, for example, the uneven distribution of charge stored in charge storage elements 23a and 23b can be suppressed with simpler control.

[0041] As described above, in the electrolytic cell power supply device 10 according to this embodiment, the rectified power converted by the first converter 11 is converted into DC power corresponding to the electrolytic cell 2 by the conversion circuit 20 of the second converter 12 and supplied to the electrolytic cell 2. The conversion circuit 20 distributes the rectified power converted by the first converter 11 among the charge storage elements 23a and 23b, and converts the DC power stored in the charge storage elements 23a and 23b into DC power corresponding to the electrolytic cell 2 by the switching elements 21a to 21d, the rectifying elements 22a to 22d, and the reactors 24a and 24b. As a result, in the electrolytic cell power supply device 10 according to this embodiment, the ripple component superimposed on the DC current supplied to the electrolytic cell 2 can be reduced compared to the case where the rectified power converted by the first converter 11 is converted to DC by a filter reactor or the like and supplied to the electrolytic cell 2.

[0042] Furthermore, in the power supply unit for the electrolytic cell, it is conceivable to use, for example, a single chopper circuit with two switching elements connected in series as the second converter. However, if a single chopper circuit is used as the second converter, it becomes necessary to increase the switching frequency or increase the inductance of the filter reactor in order to reduce ripple. There are concerns that increasing the switching frequency will increase switching losses. Also, there are concerns that increasing the inductance of the filter reactor will lead to an increase in the size of the filter reactor, as well as the cooling mechanism for cooling the filter reactor, resulting in an increase in the overall size of the power supply unit.

[0043] In contrast, the electrolytic cell power supply device 10 according to this embodiment uses a double chopper circuit configuration in the conversion circuit 20. In the double chopper circuit configuration, for example, as shown in Figure 3, the combined output of the output associated with the switching of switching element 21a and the output associated with the switching of switching element 21d is output to the electrolytic cell 2. Therefore, even when the switching frequencies of switching elements 21a and 21d are the same as those of a single chopper circuit, the ripple component superimposed on the DC current supplied to the electrolytic cell 2 can be reduced compared to a single chopper circuit. This suppresses the need for large inductance in reactors 24a and 24b, and prevents the reactors 24a and 24b from becoming larger.

[0044] Thus, the electrolytic cell power supply device 10 according to this embodiment can suppress an increase in switching frequency and an increase in device size compared to the case where a single chopper circuit is used as the second converter. The electrolytic cell power supply device 10 according to this embodiment can reduce the ripple component superimposed on the DC current supplied to the electrolytic cell 2 while suppressing an increase in switching frequency and an increase in device size. Furthermore, compared to an interleaved method in which single chopper circuits are connected in parallel and the switching timing is shifted to suppress ripple, in the interleaved method, a crosscurrent component is generated where current flows between the parallel circuits due to manufacturing tolerances of the reactor inductance, etc., and the ripple superimposed on the DC current supplied to the electrolytic cell 2 may not be the desired ripple. In contrast, in the conversion circuit 20 with the configuration of a double chopper circuit according to this embodiment, crosscurrent does not occur in principle. Therefore, regardless of, for example, manufacturing tolerances of the reactor inductance, a target low-ripple output can be obtained.

[0045] Furthermore, in the electrolytic cell power supply device 10 according to this embodiment, the control device 14 controls the switching of switching elements 21a and 21d such that the switching element 21d is turned off during the period when the switching element 21a is turned off, and the switching element 21d is turned on during the period when the switching element 21a is turned off. As a result, as described above, a DC voltage and DC current with extremely low ripple can be supplied to the electrolytic cell 2. For example, the inductance required for the reactors 24a and 24b can be further reduced, and the size of the device can be further suppressed.

[0046] In the electrolytic cell power supply device 10 according to this embodiment, the control device 14 sets the duty cycle of the switching elements 21a and 21d to 50%. This makes it possible to suppress the uneven distribution of charge stored in the charge storage elements 23a and 23b with simpler control, for example.

[0047] Figure 4 is a schematic block diagram showing a modified example of the electrolytic cell power supply device according to the embodiment. Furthermore, components that are substantially the same in function and configuration as those in the above embodiments are denoted by the same reference numerals, and detailed descriptions are omitted. As shown in Figure 4, in the electrolytic cell power supply unit 10a, the control device 14 controls the operation of the second converter 12 and also controls the operation of the first converter 11. In the electrolytic cell power supply unit 10a, the first converter 11 has the function of converting AC power supplied from the power system 4 into rectified power and adjusting the magnitude of the rectified power. In the electrolytic cell power supply unit 10a, the first converter 11 is, for example, a thyristor rectifier or a PWM rectifier.

[0048] The control device 14 controls the switching of switching elements 21a and 21d of the second converter 12 (conversion circuit 20) so that switching element 21d is turned off during the period when switching element 21a is turned off, and switching element 21d is turned on during the period when switching element 21a is turned off, similar to the explanation with respect to Figure 3. In this case, a voltage with a magnitude of half the voltage supplied to the conversion circuit 20 is output from the conversion circuit 20. Therefore, the magnitude of the DC power supplied to the electrolytic cell 2 can be adjusted by adjusting the magnitude of the rectified power output from the first converter 11. For example, if the required DC voltage for the electrolytic cell 2 is 400V, the control device 14 controls the operation of the first converter 11 so that a DC voltage of 800V is supplied to the conversion circuit 20.

[0049] Thus, in the electrolytic cell power supply unit 10a, the control device 14 controls the operation of the second converter 12 as well as the operation of the first converter 11. This makes it easier to adjust the amount of DC power supplied to the electrolytic cell 2.

[0050] The magnitude of the DC power supplied to the electrolytic cell 2 may be adjusted, for example, by adjusting the switching duty cycle of the switching elements 21a and 21d. However, as described above, by adjusting the magnitude of the rectified power output from the first converter 11 and controlling the switching of the switching elements 21a and 21d such that the switching element 21d is in the off state when the switching element 21a is on, and the switching element 21d is in the on state when the switching element 21a is off, the magnitude of the DC power supplied to the electrolytic cell 2 can be adjusted while keeping the ripple component superimposed on the DC current supplied to the electrolytic cell 2 extremely small.

[0051] Figure 5 is a block diagram schematically showing a modified example of the second transducer according to the embodiment. As shown in Figure 5, the second converter 12a has two conversion circuits 20 connected in parallel. The input terminal 20a of one conversion circuit 20 is connected to the input terminal 20a of the other conversion circuit 20. The input terminal 20b of one conversion circuit 20 is connected to the input terminal 20b of the other conversion circuit 20. The output terminal 20c of one conversion circuit 20 is connected to the output terminal 20c of the other conversion circuit 20. The output terminal 20d of one conversion circuit 20 is connected to the output terminal 20d of the other conversion circuit 20. In this way, the two conversion circuits 20 are connected in parallel.

[0052] Furthermore, the connection point of the charge storage elements 23a and 23b of one conversion circuit 20 is connected to the connection point of the charge storage elements 23a and 23b of the other conversion circuit 20. This allows, for example, the potential of the neutral point of the series-connected charge storage elements 23a and 23b to be common to both conversion circuits 20, thereby reducing the number of sensors required for control and protection.

[0053] The two parallel-connected conversion circuits 20 each perform the same operation. In other words, the control device 14 controls the operation of the two parallel-connected conversion circuits 20 so that each of them performs the same operation.

[0054] The switching timing of each switching element 21a to 21d in one conversion circuit 20 is substantially the same as the switching timing of each switching element 21a to 21d in the other conversion circuit 20. For example, when the switching element 21a of one conversion circuit 20 is ON, the switching element 21a of the other conversion circuit 20 is also ON, and when the switching element 21a of one conversion circuit 20 is OFF, the switching element 21a of the other conversion circuit 20 is also OFF.

[0055] Thus, the second converter 12a has two conversion circuits 20 connected in parallel. This makes it possible to handle large DC power while suppressing an increase in the allowable current and voltage values ​​required for each element of the conversion circuit 20, such as the switching elements 21a to 21d, the rectifying elements 22a to 22d, the charge storage elements 23a and 23b, and the reactors 24a and 24b. Large DC power can be supplied to the electrolytic cell 2 while suppressing an increase in the allowable values ​​of each element of the conversion circuit 20.

[0056] The number of conversion circuits 20 connected in parallel is not limited to two; it may be three or more. The second converter 12a may have multiple conversion circuits 20 connected in parallel.

[0057] Figure 6 is a schematic block diagram showing a modified example of the electrolytic cell power supply device according to the embodiment. As shown in Figure 6, the electrolytic cell power supply unit 10b has two first converters 11 and two second converters 12. Each of the two first converters 11 is connected to the power system 4 via two correspondingly provided transformers 6. In other words, the two first converters 11 are connected in parallel to the power system 4. In this example, two transformers 6 are provided, each corresponding to one of the two first converters 11. However, it is not limited to this, and for example, a multi-winding transformer having two secondary windings corresponding to each of the two first converters 11 may be used.

[0058] The two second converters 12 are provided in correspondence with the two first converters 11. The input sides of the two second converters 12 are connected to the output sides of the two first converters 11, respectively. The rectified power output from one first converter 11 is input to only one second converter 12. The output sides of the two second converters 12 are connected to the electrolytic cell 2. In other words, the output sides of the two second converters 12 are connected in parallel to the electrolytic cell 2. The control device 14 controls the operation of each of the two second converters 12.

[0059] Thus, the electrolytic cell power supply unit 10b has two first converters 11 and second converters 12 connected in parallel between the power system 4 and the electrolytic cell 2. In this case as well, similar to the example shown in Figure 5, a large amount of DC power can be supplied to the electrolytic cell 2 while suppressing an increase in the allowable value of each element of the conversion circuit 20 of each second converter 12.

[0060] Furthermore, the number of first converters 11 and second converters 12 connected in parallel between the power system 4 and the electrolytic cell 2 is not limited to two, but may be three or more. In other words, the electrolytic cell power supply unit 10b may have multiple first converters 11 and multiple second converters 12 connected in parallel between the power system 4 and the electrolytic cell 2. By increasing the number of parallel connections of the first converters 11 and second converters 12, for example, the allowable values ​​required for each element of the conversion circuit 20 can be further suppressed.

[0061] Furthermore, multiple second converters 12 connected in parallel may be provided, and multiple conversion circuits 20 connected in parallel may be provided for each of the multiple converters 12. This makes it possible to further suppress the tolerance values ​​required for each element of each conversion circuit 20.

[0062] Figures 7(a) to 7(d) are timing charts that schematically represent an example of the operation of the two second transducers. Figures 7(a) to 7(d) schematically illustrate an example of the operation of the electrolytic cell power supply unit 10b. Figure 7(a) schematically shows an example of a control signal input to the control terminal of the switching element 21a of the first stage second converter 12. Figure 7(b) schematically shows an example of a control signal input to the control terminal of the switching element 21d of the first stage second converter 12. Figure 7(c) schematically shows an example of a control signal input to the control terminal of the switching element 21a of the second stage converter 12. Figure 7(d) schematically shows an example of a control signal input to the control terminal of the switching element 21d of the second stage converter 12.

[0063] As shown in Figures 7(a) and 7(c), the control device 14 shifts the period of PWM control of the switching element 21a of the conversion circuit 20 of the second stage second converter 12 by 1 / 2 period relative to the period of PWM control of the switching element 21a of the conversion circuit 20 of the first stage second converter 12. For example, if the duty cycle of the PWM control of the switching element 21a is set to 50%, as shown in Figures 7(a) and 7(c), when the switching element 21a of the first stage second converter 12 is ON, the switching element 21a of the second stage second converter 12 is OFF, and when the switching element 21a of the first stage second converter 12 is OFF, the switching element 21a of the second stage second converter 12 is ON.

[0064] Similarly, as shown in Figures 7(b) and 7(d), the control device 14 shifts the period of PWM control of the switching element 21d of the conversion circuit 20 of the second stage second converter 12 by 1 / 2 period relative to the period of PWM control of the switching element 21d of the conversion circuit 20 of the first stage second converter 12.

[0065] In this way, the control device 14 periodically switches the on and off states of each switching element 21a and 21d of the multiple second converters 12, for example. When the number of multiple second converters 12 is N, the control device 14 shifts the switching period of each switching element 21a of the multiple second converters 12 by 1 / N periods, and also shifts the switching period of each switching element 21d of the multiple second converters 12 by 1 / N periods.

[0066] In this way, by shifting the switching periods of the on and off states of the switching elements 21a and 21d of the multiple parallel-connected second converters 12, the ripple component superimposed on the DC current supplied to the electrolytic cell 2 can be reduced.

[0067] This embodiment includes the following aspects. (Note 1) A power supply device for an electrolytic cell that causes the electrolytic cell to perform electrolysis by supplying DC power between the anode and cathode of the electrolytic cell, A first converter that converts AC power supplied from the power grid into rectified power, A second converter has a conversion circuit that converts the rectified power output from the first converter into DC power corresponding to the electrolytic cell, and supplies the DC power converted by the conversion circuit to the electrolytic cell 2. A control device that controls the operation of the conversion circuit from rectified power to DC power, Equipped with, The conversion circuit has a pair of input terminals, a pair of output terminals, a pair of switching elements, a pair of rectifier elements, a pair of charge storage elements, and a pair of reactors. The pair of input terminals receive rectified power input from the first converter. The pair of output terminals are connected to the electrolytic cell, The pair of switching elements have a pair of main terminals and a control terminal, and have an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals is interrupted. One main terminal of one of the pair of switching elements is connected to one of the pair of input terminals. The other main terminal of the one switching element is connected to one end of one of the pair of rectifier elements. The other end of the one rectifier element is connected to one end of the other rectifier element of the pair of rectifier elements. The other end of the aforementioned rectifier element is connected to one of the main terminals of the other switching element of the pair of switching elements. The other main terminal of the other switching element is connected to the other input terminal of the pair of input terminals. The pair of charge storage elements are connected in series between the pair of input terminals, The connection point of the pair of charge storage elements is connected to the connection point of the pair of rectifier elements. One end of one of the pair of reactors is connected to the connection point between the one switching element and the one rectifying element. The other end of the aforementioned reactor is connected to one of the pair of output terminals, One end of the other reactor of the pair of reactors is connected to the connection point between the other rectifier element and the other switching element. The other end of the other reactor is connected to the other output terminal of the pair of output terminals. The control device is a power supply device for an electrolytic cell that controls the operation of the conversion circuit from rectified power to DC power by controlling the switching of the pair of switching elements.

[0068] (Note 2) The power supply device for an electrolytic cell according to Appendix 1, wherein the control device controls the switching of the pair of switching elements such that the other switching element is in the off state during the period when one switching element is in the on state, and the other switching element is in the on state during the period when one switching element is in the off state.

[0069] (Note 3) The power supply device for an electrolytic cell as described in Appendix 2, wherein the control device switches the on state and the off state of the pair of switching elements at a predetermined period by pulse width modulation control, and sets the duty cycle of each of the pair of switching elements to 50%.

[0070] (Note 4) The first converter has the function of converting AC power supplied from the power system into rectified power and adjusting the magnitude of the rectified power. The control device controls the operation of the second converter and also controls the operation of the first converter, as described in any one of the appendices 1 to 3.

[0071] (Note 5) The second converter is a power supply device for an electrolytic cell according to any one of the appendices 1 to 4, having a plurality of the conversion circuits connected in parallel.

[0072] (Note 6) An electrolytic cell power supply device according to any one of the appendices 1 to 5, comprising a plurality of first converters and a plurality of second converters connected in parallel between the power system and the electrolytic cell.

[0073] (Note 7) The control device periodically switches the ON state and OFF state of each of the pair of switching elements of the plurality of second converters, and when the number of the plurality of second converters is N, the period of switching the ON state and OFF state of one of the switching elements of each of the plurality of second converters is shifted by 1 / N periods, and the period of switching the ON state and OFF state of the other switching element of each of the plurality of second converters is shifted by 1 / N periods, as described in Appendix 6, for an electrolytic cell power supply device.

[0074] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention and in the scope of the invention and its equivalents as described in the claims. [Explanation of Symbols]

[0075] 2…Electrolytic cell, 2a…Anode, 2a…Cathode, 4…Power system, 6…Transformer, 10, 10a, 10b…Power supply unit for electrolytic cell, 11…First converter, 12, 12a…Second converter, 14…Control device, 20…Conversion circuit, 20a, 20b…Input terminals, 20c, 20d…Output terminals, 21a~21d…Switching elements, 22a~22d…Rectifier elements, 23a, 23b…Charge storage elements, 24a, 24b…Reactor

Claims

1. A power supply device for an electrolytic cell that causes the electrolytic cell to perform electrolysis by supplying DC power between the anode and cathode of the electrolytic cell, A first converter that converts AC power supplied from the power grid into rectified power, A second converter has a conversion circuit that converts the rectified power output from the first converter into DC power corresponding to the electrolytic cell, and supplies the DC power converted by the conversion circuit to the electrolytic cell. A control device that controls the operation of the conversion circuit from rectified power to DC power, Equipped with, The conversion circuit has a pair of input terminals, a pair of output terminals, a pair of switching elements, a pair of rectifier elements, a pair of charge storage elements, and a pair of reactors. The pair of input terminals receive rectified power input from the first converter. The pair of output terminals are connected to the electrolytic cell, The pair of switching elements have a pair of main terminals and a control terminal, and have an ON state in which current flows between the pair of main terminals and an OFF state in which the flow of current between the pair of main terminals is interrupted. One main terminal of one of the pair of switching elements is connected to one of the pair of input terminals. The other main terminal of the one switching element is connected to one end of one of the pair of rectifier elements. The other end of the one rectifier element is connected to one end of the other rectifier element of the pair of rectifier elements. The other end of the aforementioned rectifier element is connected to one of the main terminals of the other switching element of the pair of switching elements. The other main terminal of the other switching element is connected to the other input terminal of the pair of input terminals. The pair of charge storage elements are connected in series between the pair of input terminals, The connection point of the pair of charge storage elements is connected to the connection point of the pair of rectifier elements. One end of one of the pair of reactors is connected to the connection point between the one switching element and the one rectifying element. The other end of the aforementioned reactor is connected to one of the pair of output terminals, One end of the other reactor of the pair of reactors is connected to the connection point between the other rectifier element and the other switching element. The other end of the other reactor is connected to the other output terminal of the pair of output terminals. The control device controls the switching of the pair of switching elements to control the operation of the conversion circuit from rectified power to DC power, and controls the switching of the pair of switching elements such that the other switching element is turned off during the period when one switching element is turned on, thereby outputting a DC voltage corresponding to the charge stored in one of the pair of charge storage elements to the pair of output terminals, and the other switching element is turned on during the period when one switching element is turned off, thereby outputting a DC voltage corresponding to the charge stored in the other of the pair of charge storage elements to the pair of output terminals.

2. The power supply device for an electrolytic cell according to claim 1, wherein the control device switches the on state and the off state of the pair of switching elements at a predetermined period by pulse width modulation control, and sets the duty cycle of each of the pair of switching elements to 50%.

3. The first converter has the function of converting AC power supplied from the power system into rectified power and adjusting the magnitude of the rectified power. The electrolytic cell power supply device according to claim 1, wherein the control device controls the operation of the second converter and also controls the operation of the first converter.

4. The electrolytic cell power supply device according to claim 1, wherein the second converter has a plurality of the conversion circuits connected in parallel.

5. The electrolytic cell power supply device according to claim 1, further comprising a plurality of first converters and a plurality of second converters connected in parallel between the power system and the electrolytic cell.

6. The power supply device for an electrolytic cell according to claim 5, wherein the control device periodically switches the ON state and the OFF state of each of the pair of switching elements of the plurality of second converters, and when the number of the plurality of second converters is N, the period of switching the ON state and the OFF state of one of the switching elements of each of the plurality of second converters is shifted by 1 / N periods, and the period of switching the ON state and the OFF state of the other switching element of each of the plurality of second converters is shifted by 1 / N periods.

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