Power conversion system

Abstract

To provide a power conversion system that can prevent reverse current flow from the electrolytic device to the filter capacitor. [Solution] The power conversion system 1 that supplies DC power to the electrolytic device 2 includes a power conversion device 3 that converts power from a power source into DC power, a positive side wiring 5 and a negative side wiring 50 that connect the power conversion device 3 and the electrolytic device 2, a filter capacitor 12 connected between the positive side wiring 5 and the negative side wiring 50, a relay 52 provided on at least one of the positive side wiring 5 and the negative side wiring 50 on the electrolytic device 2 side of the filter capacitor 12, a first voltage detection unit 131, a second voltage detection unit 132, and a control device 4. The control device 4 is configured to control the power conversion device 3 so that when the relay 52 is connected, the first voltage V1 detected by the first voltage detection unit 131 is equal to or greater than the second voltage V2 detected by the second voltage detection unit 132.

Description

Technical Field

[0001] The present invention relates to a power conversion system.

Background Art

[0002] As a power conversion device for a vehicle, one including a converter and an inverter is disclosed in, for example, Patent Document 1. This power conversion device boosts the DC power of a high-voltage battery by the converter, then converts it into AC power by the inverter, and supplies three-phase AC power to a rotating electrical machine. A low-voltage battery is connected to the converter in parallel with the high-voltage battery. After a capacitor connected between a power supply line and a ground line is charged by the low-voltage battery, power is supplied from the high-voltage battery to the power conversion device. This suppresses an inrush current from the high-voltage battery to the power conversion device.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, when an attempt is made to use the power conversion device for power supply to an electrolyzer for hydrogen production, the following problems are a concern. In a system that converts three-phase AC power to DC power and supplies it to an electrolytic device, a power converter is installed between the three-phase AC power source and the electrolytic device. In this case, a filter capacitor is installed between the positive and negative wiring connected to the electrolytic device to suppress current ripple in the DC power supplied to the electrolytic device. Furthermore, to prevent inrush current from the electrolytic device when the power converter is connected to the electrolytic device, it is necessary to charge the filter capacitor before starting power supply to the electrolytic device. However, this charging cannot be performed from the electrolytic device. This is because if current flows from the electrolytic device to the filter capacitor, it may accelerate the deterioration of the electrodes of the electrolytic device.

[0005] This invention has been made in view of the above problems, and aims to provide a power conversion system that can prevent the reverse flow of current from an electrolytic device to a filter capacitor. [Means for solving the problem]

[0006] One aspect of the present invention is a power conversion system (1) that supplies DC power to an electrolytic apparatus (2) that generates hydrogen by electrolyzing a raw material, A power conversion device (3) that converts power from an electrical source into DC power, A positive side wiring (5) and a negative side wiring (50) connect the power converter and the electrolytic device, A filter capacitor (12) is connected between the positive wiring and the negative wiring, A relay (52) is provided on at least one of the positive wiring and the negative wiring on the electrolytic device side of the filter capacitor, On the power converter side of the relay, a first voltage detection unit (131) is connected between the positive wiring and the negative wiring, On the electrolytic device side of the relay, a second voltage detection unit (132) is connected between the positive wiring and the negative wiring, The system includes a control device (4) for controlling the power converter, The control device is part of a power conversion system configured to control the power conversion device such that, when connecting the relay, the first voltage (V1) detected by the first voltage detection unit is equal to or greater than the second voltage (V2) detected by the second voltage detection unit. [Effects of the Invention]

[0007] In the power conversion system described above, the control device controls the power converter so that the first voltage becomes equal to or greater than the second voltage when the relay is connected. This prevents current from flowing back from the electrolytic device to the filter capacitor when the relay is connected.

[0008] As described above, according to the above embodiment, a power conversion system can be provided that can prevent the reverse flow of current from the electrolytic device to the filter capacitor. The reference numerals in parentheses in the claims and the means for solving the problem indicate the correspondence with the specific means described in the embodiments later, and do not limit the technical scope of the present invention. [Brief explanation of the drawing]

[0009] [Figure 1] An explanatory diagram of the power conversion system in Embodiment 1. [Figure 2] Control flow diagram of the power conversion system in Embodiment 1. [Figure 3] An explanatory diagram of the power conversion system in Embodiment 2. [Figure 4] An explanatory diagram of the power conversion system in Embodiment 3. [Figure 5] A diagram illustrating PWM control in Embodiment 3. [Figure 6] An explanatory diagram of the power conversion system in Embodiment 4. [Figure 7] An explanatory diagram of the power conversion system in Embodiment 5. [Modes for carrying out the invention]

[0010] (Embodiment 1) An embodiment of a power conversion system will be described with reference to FIG. 1 and FIG. 2. The power conversion system 1 of the present embodiment is a power conversion system that supplies DC power to an electrolyzer. The electrolyzer 2 is an electrolyzer that electrolyzes a raw material to generate hydrogen.

[0011] As shown in FIG. 1, the power conversion system 1 includes a power converter 3, a positive-side wiring 5, a negative-side wiring 50, a filter capacitor 12, a relay 52, a first voltage detector 131, a second voltage detector 132, and a control device 4.

[0012] The power converter 3 converts power from a power source into DC power. The positive-side wiring 5 and the negative-side wiring 50 connect the power converter 3 and the electrolyzer 2. The filter capacitor 12 is connected between the positive-side wiring 5 and the negative-side wiring 50. The relay 52 is provided on at least one of the positive-side wiring 5 and the negative-side wiring 50 on the electrolyzer 2 side relative to the filter capacitor 12.

[0013] The first voltage detector 131 is connected between the positive-side wiring 5 and the negative-side wiring 50 on the power converter 3 side relative to the relay 52. The second voltage detector 132 is connected between the positive-side wiring 5 and the negative-side wiring 50 on the electrolyzer 2 side relative to the relay 52. The control device 4 controls the power converter 3.

[0014] When closing the relay 52, the control device 4 is configured to control the power converter 3 such that a first voltage V1 detected by the first voltage detector 131 is equal to or higher than a second voltage V2 detected by the second voltage detector 132.

[0015] The power converter 3 of the power conversion system 1 is connected to a three-phase AC power source 11 via a supply wiring 151. The supply wiring 151 is provided with an inductor 154. This suppresses noise such as switching noise from the power converter 3 from entering the three-phase AC power source 11. The three-phase AC power source 11 may be, for example, a power grid.

[0016] In the present embodiment, the power conversion system 1 is connected to the electrolyzer via the positive-side wiring 5 and the negative-side wiring 50. The positive-side wiring 5 is connected to the positive electrode of the electrolyzer 2, and the negative-side wiring 50 is connected to the negative electrode of the electrolyzer 2. The electrolyzer 2 electrolyzes a raw material to generate hydrogen. For example, water vapor is used as the raw material. That is, the electrolyzer 2 can electrolyze water vapor, which is the raw material gas, to generate hydrogen by using the power supplied from the power conversion system 1. The electrolyzer 2 can be, for example, one having an SOEC (i.e., solid oxide electrolysis cell), or one having a PEM (i.e., proton exchange membrane).

[0017] Specific examples of the power converter 3 will be described in Embodiments 3 and 4 later. Further, the power converter 3 can also be used by diverting a vehicle power converter to the power conversion system 1 for supplying power to the electrolyzer 2 for hydrogen production.

[0018] The filter capacitor 12 suppresses current ripple in the DC power supplied to the electrolyzer. Further, the filter capacitor 12 suppresses inrush current to the power converter 3. The filter capacitor 12 can have a capacitance of, for example, about 10 to 100000 μF.

[0019] The relay 52 can be configured by, for example, an electromagnetic relay. The first voltage detection unit 131 and the second voltage detection unit 132 can be configured by, for example, voltage sensors.

[0020] Further, the control device 4 includes a microcomputer provided with a processor, a memory and the like, and peripheral circuits thereof. The control device 4 may be configured from a plurality of microcomputers and peripheral devices thereof.

[0021] The control device 4 controls the operation of the power converter 3. The control device 4 is electrically connected to the first voltage detection unit 131 and the second voltage detection unit 132, and receives detection signals from the first voltage detection unit 131 and the second voltage detection unit 132. As will be described later, the control device 4 controls the power converter 3 based on these detection signals. The control device 4 can also control the opening and closing of the relay 52.

[0022] The control device 4 controls the power converter 3 to convert the three-phase AC power supplied from the three-phase AC power supply 11 into DC power and charge the filter capacitor 12. At this time, the power converter 3 is controlled so that the first voltage V1 detected by the first voltage detection unit 131 is equal to or greater than the second voltage V2 detected by the second voltage detection unit 132. Then, only when the first voltage V1 is equal to or greater than the second voltage V2, the relay 52 is closed (i.e., energized).

[0023] The control flow described above by the control device 4 will be briefly explained using Figure 2. The flow starts with relay 52 in the open state. First, the first voltage V1 and the second voltage V2 are obtained (step S1). Then, the first voltage V1 and the second voltage V2 are compared, and if V1 ≥ V2 is not true, the power converter 3 is controlled based on the first voltage V1 and the second voltage V2, while the filter capacitor 12 is charged (step S3). Then, in step S2, if it is determined that V1 ≥ V2, relay 52 is closed (step S4).

[0024] Next, we will explain the effects and benefits of this embodiment. In the power conversion system 1 described above, the control device 4 controls the power converter 3 so that the first voltage V1 becomes equal to or greater than the second voltage V2 when the relay 52 is connected (i.e., energized). This prevents current from flowing back from the electrolytic device 2 to the filter capacitor 12 when the relay 52 is connected.

[0025] Furthermore, if the relay 52 is connected while the filter capacitor 12 is not charged, there is a risk that an inrush current will flow from the electrolytic device 2 to the power converter 3. In this case, there is a concern that it may cause malfunctions in the electronic components that make up the power converter 3.

[0026] Therefore, when connecting relay 52, it is necessary to charge the filter capacitor 12 in advance. However, it is not possible to charge the filter capacitor 12 from the electrolytic device 2. Therefore, as described above, the filter capacitor 12 is charged from the three-phase AC power supply 11 via the power converter 3. However, even if the filter capacitor 12 is charged in advance, if relay 52 is connected when the first voltage V1 falls below the second voltage V2, current will flow back from the electrolytic device 2 to the filter capacitor 12. This may lead to deterioration of the electrodes of the electrolytic device 2.

[0027] Therefore, as described above, when connecting the relay 52, the control device 4 controls the power converter 3 so that the first voltage V1 becomes equal to or greater than the second voltage V2. Then, when V1 ≥ V2, the relay 52 is connected. This prevents reverse current flow from the electrolytic device to the filter capacitor while enabling charging of the filter capacitor 12.

[0028] As described above, this embodiment provides a power conversion system that can prevent reverse current flow from the electrolytic device to the filter capacitor.

[0029] (Embodiment 2) As shown in Figure 3, this configuration is a power conversion system 1 that converts the DC power of the DC power supply 110 into DC power of a different voltage and supplies it to the electrolytic device 2.

[0030] In other words, while Embodiment 1 showed a configuration in which the power converter 3 of the power conversion system 1 was connected to a three-phase AC power supply 11, in this embodiment, the power converter 3 of the power conversion system 1 is connected to a DC power supply 110. The DC power supplied from the DC power supply 110 is then boosted or stepped down by the power converter 3 and supplied to the electrolytic device 2.

[0031] As the DC power supply 110, for example, a storage battery, fuel cell, solar cell, etc., can be used. Similar to Embodiment 1, the filter capacitor 12 is charged via the power converter 3 so that the first voltage V1 becomes equal to or greater than the second voltage V2 before connecting the relay 52.

[0032] Otherwise, it has the same configuration and effects as Embodiment 1. Note that, among the reference numerals used in Embodiment 2 and later, those that are the same as those used in the previously described embodiments represent the same components, etc., as in the previously described embodiments, unless otherwise specified.

[0033] (Embodiment 3) In this embodiment, as shown in Figure 4, the power conversion device 3 has a first power conversion unit 3A and a second power conversion unit 3B. Note that the control device 4 (see Figure 1) is omitted in Figure 4. The same applies to Figures 6 and 7, which will be described later. The first power conversion unit 3A converts the power supply power into DC power. The second power conversion unit 3B converts the DC power converted by the first power conversion unit 3A into DC power of a different voltage.

[0034] The first power conversion unit 3A and the second power conversion unit 3B are connected by a high-potential side wiring 33H and a low-potential side wiring 33L. A DC link capacitor 361 is connected between the high-potential side wiring 33H and the low-potential side wiring 33L between the first power conversion unit 3A and the second power conversion unit 3B. The control device 4 is configured to charge the DC link capacitor 361 from the power supply by the first power conversion unit 3A, and to charge the filter capacitor 12 from the DC link capacitor 361 by the second power conversion unit 3B.

[0035] The first power conversion unit 3A has a plurality of first legs 341 connected in parallel to each other between the high-potential side wiring 33H and the low-potential side wiring 33L. Each first leg 341 consists of a first upper arm switch 351u connected to the high-potential side wiring 33H and a first lower arm switch 351d connected to the low-potential side wiring 33L, connected in series.

[0036] The connection points between the first upper arm switch 351u and the first lower arm switch 351d in multiple first legs 341 are connected to the input wiring 301 to which power is input. In this configuration, three first legs 341 are connected in parallel.

[0037] The second power conversion unit 3B has a plurality of second legs 342 connected in parallel to each other between the high-potential side wiring 33H and the low-potential side wiring 33L. Each second leg 342 consists of a second upper arm switch 352u connected to the high-potential side wiring 33H and a second lower arm switch 352d connected to the low-potential side wiring 33L, connected in series. In this embodiment, three second legs 342 are connected in parallel.

[0038] One or two of the connection points between the second upper arm switch 352u and the second lower arm switch 352d in the multiple second legs 342 are connected to the positive side wiring 5. The low-potential side wiring 33L is connected to the negative side wiring 50.

[0039] Output wires 363 are connected to the connection points of the second upper arm switch 352u and the second lower arm switch 352d in the three second legs 342. In this configuration, two of these three output wires 363 are connected to the positive side wire 5, which is connected to the positive electrode of the electrolytic device 2, via the reactor 364. The remaining one of the three output wires 363 is idle. Alternatively, one of the three output wires 363 can be connected to the positive side wire 5, and the remaining two can be left idle.

[0040] Furthermore, the low-potential wiring 33L is connected to the negative-side wiring 50, which is connected to the negative electrode of the electrolytic device 2, via the extraction wiring 331L. A filter capacitor 12 is connected between the positive-side wiring 5 and the negative-side wiring 50. Although the extraction wiring 331H is also connected to the high-potential wiring 33H, this extraction wiring 331H is idle wiring.

[0041] The input wiring 301 of the first power conversion unit 3A is connected to the supply wiring 151 of three-phase AC power from the three-phase AC power supply 11. The supply wiring 151 is provided with a precharge circuit 152 and a filter circuit 153. The precharge circuit 152 has, for example, a switch and a resistor to prevent inrush current from flowing from the three-phase AC power supply 11 to the power conversion device 3. The filter circuit 153 has, for example, an inductor and a capacitor to remove noise components from the three-phase AC power supplied from the three-phase AC power supply 11. The three-phase AC power supply 11 can be, for example, a power grid.

[0042] A freewheeling diode is connected in antiparallel to each of the switches: the first upper arm switch 351u, the first lower arm switch 351d, the second upper arm switch 352u, and the second lower arm switch 352d. Each of the switches, the first upper arm switch 351u, the first lower arm switch 351d, the second upper arm switch 352u, and the second lower arm switch 352d, can be constructed using, for example, IGBTs (i.e., insulated gate bipolar transistors), MOSFETs (MOS-type field-effect transistors), etc.

[0043] In the first power conversion unit 3A of the power conversion device 3, the input three-phase AC power is converted to DC power by appropriate switching operations of multiple first upper arm switches 351u and multiple first lower arm switches 351d. This DC power is used to charge the DC link capacitor 361. Then, in the second power conversion unit 3B, this DC power is converted to DC power of an appropriate voltage by appropriate switching operations of the second upper arm switch 352u and the second lower arm switch 352d and output. This output DC power is supplied to the electrolytic device 2. However, the second upper arm switch 352u and the second lower arm switch 352d of the second leg 342 to which the idle output wiring 363 is connected are not switched and are both left open (i.e., disconnected).

[0044] In the following section, an example of control of the power converter 3 by the control device 4 will be explained with reference to Figure 5. First, when charging the DC link capacitor 361 from the three-phase AC power supply 11 via the first power conversion unit 3A, the first upper arm switch 351u and the first lower arm switch 351d of all first legs 341 of the first power conversion unit 3A are turned off. This charges the DC link capacitor 361 until the voltage is equal to that of the three-phase AC power supply 11. When charging the DC link capacitor 361 from the three-phase AC power supply 11, the pre-charge circuit 152 is used to charge the DC link capacitor 361 while suppressing the current in the initial stages of charging, so as not to cause an inrush current.

[0045] Furthermore, after the DC link capacitor 361 has been charged to a voltage equal to that of the three-phase AC power supply 11, the on / off switching of the first upper arm switch 351u and the first lower arm switch 351d in the first power conversion unit 3A is controlled so that the voltage of the DC link capacitor 361 is maintained. That is, while the filter capacitor 12 is being charged via the second power conversion unit 3B, as described below, the first upper arm switch 351u and the first lower arm switch 351d are switched to maintain the voltage of the DC link capacitor 361.

[0046] When charging the filter capacitor 12 from the DC link capacitor 361 using the second power conversion unit 3B, the second power conversion unit 3B is controlled by PWM (i.e., pulse width modulation) as follows: Based on the second voltage V2 detected by the second voltage detection unit 132, a voltage command value for the output voltage to be output from the second power conversion unit 3B is determined. The voltage command value is greater than or equal to the second voltage V2. This voltage command value is compared with the first voltage V1 detected by the first voltage detection unit 131. Then, the duty cycle is calculated from the difference between the voltage command value and the first voltage V1. This duty cycle is compared with the carrier signal to control the on / off state of the second upper arm switch 352u and the second lower arm switch 352d.

[0047] That is, for example, as shown in Figure 5, each gate signal is input to the gate of the second upper arm switch 352u and the gate of the second lower arm switch 352d, respectively. In this embodiment, the second upper arm switch 352u and the second lower arm switch 352d of the two-phase second leg 342 in the second power conversion unit 3B are controlled, and in controlling these, the phases of the carriers may be synchronized with each other or inverted by 180°.

[0048] Otherwise, it is the same as in Embodiment 1. In this embodiment, an example of charging the DC link capacitor 361 through a freewheeling diode is shown, but the DC link capacitor 361 can also be charged by other methods. For example, even without a freewheeling diode, the DC link capacitor 361 can be charged by on / off control of the first upper arm switch 351u and the first lower arm switch 351d.

[0049] In this configuration, three-phase AC power can be easily converted to desired DC power to charge the filter capacitor 12. Furthermore, the power conversion device 3 can be a power conversion device for vehicles such as electric vehicles that has been adapted for use in a hydrogen production system. In other words, a vehicle power conversion device is connected between the vehicle's drive battery and drive motor. By connecting the electrolytic device 2 to the side where the drive battery is connected and the three-phase AC power supply 11 to the side where the drive motor is connected, it can be used as a power conversion device for a hydrogen production system. Furthermore, it has the same effects and advantages as Embodiment 1.

[0050] (Embodiment 4) In this embodiment, the power conversion system 1 differs from that of embodiment 3 in the configuration of the second power conversion unit 3B, as shown in Figure 6.

[0051] In this embodiment, the second power conversion unit 3B has a second leg 342 and a reactor 362 connected between the high-potential side wiring 33H and the low-potential side wiring 33L. The second leg 342 is formed by connecting a second upper arm switch 352u connected to the high-potential side wiring 33H and a second lower arm switch 352d connected to the low-potential side wiring 33L in series.

[0052] Reactor 362 is connected between the connection point between the second upper arm switch 352u and the second lower arm switch 452d in the second leg and the positive side wiring 5. The low-potential side wiring 33L is connected to the negative side wiring 50. Otherwise, it has the same configuration and effects as Embodiment 3.

[0053] (Embodiment 5) As shown in Figure 7, this embodiment is a power conversion system 1 in which the power conversion device 3 further comprises a third power conversion unit 3C in addition to the first power conversion unit 3A and the second power conversion unit 3B. The third power conversion unit 3C converts the DC power input through the positive input line 371 and the negative input line 372 into DC power of different voltages. In this embodiment, the first power conversion unit 3A and the second power conversion unit 3B have the same configuration as those disclosed in Embodiment 3.

[0054] The third power conversion unit 3C has a third leg 343 connected to the high-potential side wiring 33H and the low-potential side wiring 33L between the first power conversion unit 3A and the second power conversion unit 3B, an input side reactor 373, and an input side capacitor 374. The third leg 343 is formed by connecting a third upper arm switch 353u connected to the high-potential side wiring 33H and a third lower arm switch 353d connected to the low-potential side wiring 33L in series.

[0055] The input reactor 373 is connected between the connection point of the third upper arm switch 353u and the third lower arm switch 353d in the third leg 343 and the positive input line 371. The input capacitor 374 is connected between the positive input line 371 and the negative input line 372. The low-potential wiring 33L is connected to the negative wiring 50. In this embodiment, the low-potential wiring 33L is connected to the negative wiring 50 via the negative input line 372.

[0056] The positive input line 371 and the negative input line 372 are connected to a DC power supply 161 via a precharge circuit 162. The DC power supply 161 can be, for example, a storage battery, a fuel cell, a solar cell, etc. The precharge circuit 162 includes, for example, a switch and a resistor to prevent inrush current from flowing from the DC power supply 161 to the power converter 3.

[0057] In this configuration, the power conversion system 1 can supply power to the electrolytic device 2 from both a three-phase AC power supply 11 and a DC power supply 161. When charging the DC link capacitor 361 from the DC power supply 161, the input side capacitor 374 is charged first. Then, the third power conversion unit 3C charges the DC link capacitor 361. The control of the third power conversion unit 3C by the control device 4 at this time is performed, for example, by turning off all switches in the third power conversion unit 3C (i.e., the third upper arm switch 353u and the third lower arm switch 353d). As a result, the DC link capacitor 361 is charged through the freewheeling diode. Otherwise, it has the same configuration and effects as Embodiment 3.

[0058] The present invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit. [Explanation of Symbols]

[0059] 1...Power conversion system, 12...Filter capacitor, 131...First voltage detection unit, 132...Second voltage detection unit, 2...Electrolytic device, 3...Power conversion device, 4...Control device, 5...Positive side wiring, 50...Negative side wiring, 52...Relay, V1...First voltage, V2...Second voltage.

Claims

1. A power conversion system (1) that supplies DC power to an electrolytic device (2) that generates hydrogen by electrolyzing raw materials, A power conversion device (3) that converts power from an electrical source into DC power, A positive side wiring (5) and a negative side wiring (50) connect the power converter and the electrolytic device, A filter capacitor (12) connected between the positive wiring and the negative wiring, A relay (52) is provided on at least one of the positive wiring and the negative wiring on the electrolytic device side of the filter capacitor, On the power converter side of the relay, a first voltage detection unit (131) is connected between the positive wiring and the negative wiring, A second voltage detection unit (132) is connected between the positive wiring and the negative wiring on the electrolytic device side of the relay, The system includes a control device (4) for controlling the power converter, The control device is configured to control the power converter so that, when connecting the relay, the first voltage (V1) detected by the first voltage detection unit is equal to or greater than the second voltage (V2) detected by the second voltage detection unit, in a power conversion system.

2. The power conversion device comprises a first power conversion unit (3A) that converts the power supply power into DC power, and a second power conversion unit (3B) that converts the DC power converted by the first power conversion unit into DC power of a different voltage, the first power conversion unit and the second power conversion unit are connected by a high-potential side wiring (33H) and a low-potential side wiring (33L), a DC link capacitor (361) is connected between the high-potential side wiring and the low-potential side wiring between the first power conversion unit and the second power conversion unit, and the control device is configured to charge the DC link capacitor from the power supply power by the first power conversion unit and to charge the filter capacitor from the DC link capacitor by the second power conversion unit, as described in claim 1.

3. The first power conversion unit has a plurality of first legs (341) connected in parallel to each other between the high-potential side wiring and the low-potential side wiring, and each first leg is made up of a first upper arm switch (351u) connected to the high-potential side wiring and a first lower arm switch (351d) connected to the low-potential side wiring connected in series. The connection points between the first upper arm switch and the first lower arm switch in the multiple first legs are connected to the input wiring (301) into which the power supply is input. The second power conversion unit has a plurality of second legs (342) connected in parallel to each other between the high-potential side wiring and the low-potential side wiring, and each second leg is made up of a second upper arm switch (352u) connected to the high-potential side wiring and a second lower arm switch (352d) connected to the low-potential side wiring connected in series. One or two of the connection points between the second upper arm switch and the second lower arm switch in the multiple second legs are connected to the positive side wiring. The low-potential side wiring is connected to the negative side wiring. The power conversion system according to claim 2.

4. The first power conversion unit has a plurality of first legs (341) connected in parallel to each other between the high-potential side wiring and the low-potential side wiring, and each first leg is made up of a first upper arm switch (351u) connected to the high-potential side wiring and a first lower arm switch (351d) connected to the low-potential side wiring connected in series. The connection points between the first upper arm switch and the first lower arm switch in the multiple first legs are connected to the input wiring (301) into which the power supply is input. The second power conversion unit has a second leg (342) and a reactor (362) connected between the high-potential side wiring and the low-potential side wiring, and the second leg is made up of a second upper arm switch (352u) connected to the high-potential side wiring and a second lower arm switch (352d) connected to the low-potential side wiring connected in series. The reactor is connected between the connection point between the second upper arm switch and the second lower arm switch in the second leg and the positive side wiring. The low-potential side wiring is connected to the negative side wiring. The power conversion system according to claim 2.

5. The system further includes a third power conversion unit (3C) that converts DC power input through the positive input line (371) and the negative input line (372) into DC power of different voltages. The third power conversion unit has a third leg (343) connected to the high-potential side wiring and the low-potential side wiring between the first power conversion unit and the second power conversion unit, an input side reactor (373), and an input side capacitor (374). The third leg is formed by connecting a third upper arm switch (353u) connected to the high-potential side wiring and a third lower arm switch (353d) connected to the low-potential side wiring in series. The input side reactor is connected between the connection point between the third upper arm switch and the third lower arm switch in the third leg and the positive side input line. The input capacitor is connected between the positive input line and the negative input line. The low-potential side wiring is connected to the negative side wiring. The power conversion system according to claim 2.

Images