Power conversion system

Abstract

The problem of improving the system efficiency is solved. In a power conversion system (1), a unidirectional AC / DC converter (2) is connected to a power grid. A bidirectional insulated DC / DC converter (3) is provided with: a first DC input / output terminal (31) and a second DC input / output terminal (32) which are respectively connected to a first DC output terminal (23) and a second DC output terminal (24) of a unidirectional AC / DC converter (2); and a third DC input / output terminal (33) and a fourth DC input / output terminal (34) connected to both ends of a battery (E1) of the electric vehicle. The inverter (4) comprises: a first DC input terminal (41) and a second DC input terminal (42) which are respectively connected to a first DC output terminal (23) and a second DC output terminal (24) of the unidirectional AC / DC converter (2); and a first AC output terminal (43) and a second AC output terminal (44) configured to be connected to the socket (5). The inverter control unit (40) controls the inverter (4).

Description

Technical Field

[0001] The present disclosure generally relates to a power conversion system, and more particularly to a power conversion system to be connected to a battery and a socket of an electric vehicle. Background Art

[0002] Patent Document 1 discloses a power converter included in a vehicle. The power converter is electrically connected to a jack, a socket, and a power storage device (i.e., a battery). The power converter includes a first AC / DC conversion unit, a DC / AC conversion unit, an isolation transformer, and a second AC / DC conversion unit. The power converter is connected to the jack via a first relay. The power converter is connected to the socket via a second relay. Patent Document 1 also discloses a PM-ECU for controlling the power converter, the first relay, and the second relay.

[0003] In some cases, a power conversion system including the power converter disclosed in Patent Document 1 may reduce the system efficiency.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-240241 Summary of the Invention

[0007] An object of the present disclosure is to provide a power conversion system that can increase the system efficiency.

[0008] A power conversion system according to an aspect of the present disclosure includes a unidirectional AC / DC converter, a bidirectional isolated DC / DC converter, an inverter, and an inverter control unit. The unidirectional AC / DC converter has a first AC input terminal, a second AC input terminal, a first DC output terminal, and a second DC output terminal. The unidirectional AC / DC converter is configured to be connected to a power grid. The bidirectional isolated DC / DC converter has: a first DC input / output terminal and a second DC input / output terminal, which are respectively connected to the first DC output terminal and the second DC output terminal of the unidirectional AC / DC converter; and a third DC input / output terminal and a fourth DC input / output terminal, which are configured to be connected to both ends of a battery of an electric vehicle. The inverter has: a first DC input terminal and a second DC input terminal, which are respectively connected to the first DC output terminal and the second DC output terminal of the unidirectional AC / DC converter; and a first AC output terminal and a second AC output terminal, which are configured to be connected to a socket. The inverter control unit controls the inverter. Brief Description of the Drawings

[0009] Figure 1 is a circuit block diagram of a power conversion system according to a first embodiment;

[0010] Figure 2 is the circuit diagram of the power conversion system;

[0011] Figure 3 is the circuit diagram of the power conversion system according to the second embodiment; and

[0012] Figure 4 is the circuit block diagram of the power conversion system according to the third embodiment. Detailed Description of the Invention

[0013] (First Embodiment)

[0014] Reference will be made to Figure 1 and Figure 2 to describe the power conversion system 1 according to the first embodiment.

[0015] (1) Summary

[0016] The power conversion system 1 is provided, for example, for electric vehicles (such as electric cars and hybrid cars, etc.) and is configured to be connected to the battery E1 of the electric vehicle. The battery E1 is a rechargeable battery of the electric vehicle. The power conversion system 1 can be included, for example, in an on-vehicle charger for charging the battery E1.

[0017] As Figure 1 shown, the power conversion system 1 includes a unidirectional AC / DC converter 2, a bidirectional isolated DC / DC converter 3, an inverter 4, and an inverter control unit 40. The unidirectional AC / DC converter 2 is configured to be connected to the power grid. The bidirectional isolated DC / DC converter 3 is configured to be connected to the battery E1 of the electric vehicle. The battery E1 can be, for example, a 400V lithium-ion battery. The inverter 4 is configured to be connected to the socket 5. The socket 5 can be, for example, an AC 100V socket (also called an "accessory socket") installed inside the electric vehicle. For example, the plug of a household appliance is to be connected to the socket 5. The inverter control unit 40 controls the inverter 4. Note that the power conversion system 1 preferably further includes a first AC filter provided between the unidirectional AC / DC converter 2 and the AC power supply Vs of the power grid. In this case, the unidirectional AC / DC converter 2 is connected to the AC power supply Vs via the first AC filter. The first AC filter is a noise filter. The power conversion system 1 preferably further includes a DC filter provided between the bidirectional isolated DC / DC converter 3 and the battery E1. In this case, the bidirectional isolated DC / DC converter 3 is connected to the battery E1 via the DC filter. The DC filter is a noise filter. The power conversion system 1 preferably further includes a second AC filter provided between the inverter 4 and the socket 5. In this case, the inverter 4 is connected to the socket 5 via the second AC filter. The second AC filter is a noise filter.

[0018] The power conversion system 1 further includes a first control unit 20 and a second control unit 30. The first control unit 20 controls the unidirectional AC / DC converter 2. The second control unit 30 controls the bidirectional isolated DC / DC converter 3.

[0019] The power conversion system 1 further includes a first switch unit 61, a second switch unit 62, and a switching control unit 60. The first switch unit 61 and the second switch unit 62 are disposed between the input side of the unidirectional AC / DC converter 2 and the output side of the inverter 4 so that power can be supplied from the power grid to the socket 5. The switching control unit 60 controls the first switch unit 61 and the second switch unit 62.

[0020] The power conversion system 1 further includes a voltage detection circuit 7. The voltage detection circuit 7 detects the input voltage of the unidirectional AC / DC converter 2.

[0021] (2) Details

[0022] Next, reference will be made to Figure 1 and Figure 2 to further describe in detail the power conversion system 1 according to the first embodiment.

[0023] (2.1) Unidirectional AC / DC Converter

[0024] The unidirectional AC / DC converter 2 (hereinafter simply referred to as "AC / DC converter 2") has a first AC input terminal 21, a second AC input terminal 22, a first DC output terminal 23, and a second DC output terminal 24. The unidirectional AC / DC converter 2 is configured to be connected to the power grid (for example, in the Figure 1 illustrated example, the single-phase AC power supply Vs of the power grid). As used herein, "power grid" refers to the overall system that enables a power supply party such as an electric power company to supply power to the power receiving facilities of consumers. The power conversion system 1 is connected to the AC power supply Vs when the charging connector (supply plug) of the external charging control unit is connected to the charging jack (charging port) of the electric vehicle. The AC power supply Vs can be, for example, a commercial power supply. The charging control unit includes, for example, a charging controller, a charging cable, a charging connector, a power supply cable, and a power plug. The charging controller is interposed between one end of the power supply cable and one end of the charging cable to control the charging of the battery E1 of the electric vehicle from an external power source (such as a commercial power supply, etc.). The charging controller includes a charging circuit interruption device (CCID).

[0025] As Figure 2 illustrated, the unidirectional AC / DC converter 2 includes, for example, a diode bridge 27 and a boost chopper circuit 28.

[0026] The diode bridge 27 is formed by bridging four diodes D1, D2, D3, and D4 to perform full-wave rectification of the AC voltage of the AC power supply Vs. In the diode bridge 27, the connection node between the two serially connected diodes D1 and D2 is connected to the first AC input terminal 21, and the connection node between the two serially connected diodes D3 and D4 is connected to the second AC input terminal 22.

[0027] The boost chopper circuit 28 includes two inductors L21, L22, two switching elements Q21, Q22, two diodes D21, D22, and a smoothing capacitor C2. In the boost chopper circuit 28, the first series circuit of the inductor L21 and the switching element Q21 is connected between the output terminals of the diode bridge 27. In addition, in the boost chopper circuit 28, the second series circuit of the inductor L22 and the switching element Q22 is connected between the output terminals of the diode bridge 27. Thus, the second series circuit is connected in parallel with the first series circuit.

[0028] In addition, in the boost chopper circuit 28, the anode of the diode D21 is connected to the connection node between the inductor L21 and the switching element Q21, and the cathode of the diode D21 is connected to the first DC output terminal 23.

[0029] In addition, in the boost chopper circuit 28, the anode of the diode D22 is connected to the connection node between the inductor L22 and the switching element Q22, and the cathode of the diode D22 is connected to the first DC output terminal 23.

[0030] In addition, in the boost chopper circuit 28, the smoothing capacitor C2 is connected between the first DC output terminal 23 and the second DC output terminal 24. The smoothing capacitor C2 can be, for example, an electrolytic capacitor.

[0031] In the boost chopper circuit 28, each of the two switching elements Q21, Q22 can be, for example, a normally OFF type n-channel metal oxide semiconductor field effect transistor (MOSFET). In Figure 2 which, the diodes connected in anti-parallel with the two switching elements Q21, Q22 respectively are parasitic diodes for the n-channel MOSFETs used as the switching elements Q21, Q22. However, this is only an example and should not be construed as restrictive. The diodes can also be external diodes.

[0032] The two switching elements Q21, Q22 of the AC / DC converter 2 are controlled by the first control unit 20.

[0033] The AC / DC converter 2 performs high power factor control for synchronizing the phase of the input current of the AC / DC converter 2 with the phase of the AC voltage of the AC power supply Vs, and is thus called a power factor correction (PFC) circuit.

[0034] (2.2) Bidirectional isolated DC / DC converter

[0035] As Figure 1 shown, the bidirectional isolated DC / DC converter 3 (hereinafter simply referred to as "DC / DC converter 3") has a first DC input / output terminal 31, a second DC input / output terminal 32, a third DC input / output terminal 33, and a fourth DC input / output terminal 34. The first DC input / output terminal 31 of the DC / DC converter 3 is connected to the first DC output terminal 23 of the AC / DC converter 2. The second DC input / output terminal 32 of the DC / DC converter 3 is connected to the second DC output terminal 24 of the AC / DC converter 2. The third DC input / output terminal 33 of the DC / DC converter 3 is configured to be connected to the positive electrode of the battery E1 of the electric vehicle. The fourth DC input / output terminal 34 of the DC / DC converter 3 is configured to be connected to the negative electrode of the battery E1. That is, in the DC / DC converter 3, the battery E1 is connected between the third DC input / output terminal 33 and the fourth DC input / output terminal 34.

[0036] As Figure 2 shown, the DC / DC converter 3 includes, for example, a transformer Tr1, a first capacitor C31, a second capacitor C32, a first bridge circuit 37, and a second bridge circuit 38. The DC / DC converter 3 further includes a third capacitor C33 and a fourth capacitor C35. The transformer Tr1 includes a primary winding N1 and a secondary winding N2. The first capacitor C31 is connected between the first DC input / output terminal 31 and the second DC input / output terminal 32 of the DC / DC converter 3. The second capacitor C32 is connected between the third DC input / output terminal 33 and the fourth DC input / output terminal 34 of the DC / DC converter 3. Each of the first capacitor C31 and the second capacitor C32 may be, for example, an electrolytic capacitor.

[0037] The first bridge circuit 37 is connected between the first terminal and the second terminal of the primary winding N1 of the transformer Tr1 via the third capacitor C33. The first bridge circuit 37 includes four switching elements Q31, Q32, Q33, and Q34 that are connected in a bridge configuration with each other. In the first bridge circuit 37, a series circuit of two switching elements Q31 and Q32 and a series circuit of two switching elements Q33 and Q34 are connected in parallel to the first capacitor C31. Further, in the first bridge circuit 37, the connection node between the two switching elements Q31 and Q32 is connected to the first terminal of the primary winding N1 via the third capacitor C33, and the connection node between the two switching elements Q33 and Q34 is connected to the second terminal of the primary winding N1. In the first bridge circuit 37, each of the four switching elements Q31 to Q34 can be, for example, a normally-off n-channel MOSFET. In Figure 2 , the four diodes that are anti-parallel connected to the four switching elements Q31 to Q34 one-to-one are parasitic diodes for the n-channel MOSFETs used as the four switching elements Q31 to Q34. However, this is only an example and should not be construed as restrictive. The diodes can also be external diodes.

[0038] The second bridge circuit 38 is connected between the first terminal and the second terminal of the secondary winding N2 of the transformer Tr1 via the fourth capacitor C35. The second bridge circuit 38 includes four switching elements Q35, Q36, Q37, and Q38 that are connected in a bridge configuration with each other. In the second bridge circuit 38, a series circuit of two switching elements Q35 and Q36 and a series circuit of two switching elements Q37 and Q38 are connected in parallel to the second capacitor C32. Further, in the second bridge circuit 38, the connection node between the two switching elements Q35 and Q36 is connected to the first terminal of the secondary winding N2 via the fourth capacitor C35, and the connection node between the two switching elements Q37 and Q38 is connected to the second terminal of the secondary winding N2. In the second bridge circuit 38, each of the four switching elements Q35 to Q38 can be, for example, a normally-off n-channel MOSFET. In Figure 2 , the four diodes that are anti-parallel connected to the four switching elements Q35 to Q38 one-to-one are parasitic diodes for the n-channel MOSFETs used as the four switching elements Q35 to Q38. However, this is only an example and should not be construed as restrictive. The diodes can also be external diodes.

[0039] In the transformer Tr1, the turns ratio of the primary winding N1 to the secondary winding N2 can be, for example, 1:1. However, this is only an example and should not be construed as restrictive.

[0040] The DC / DC converter 3 is a bidirectional DC-DC converter, which can, for example, convert voltages bidirectionally between a pair of a first DC input / output terminal 31 and a second DC input / output terminal 32 and a pair of a third DC input / output terminal 33 and a fourth DC input / output terminal 34.

[0041] More specifically, the DC / DC converter 3 can perform a first conversion operation of converting a first input voltage into a first output voltage and a second conversion operation of converting a second input voltage into a second output voltage.

[0042] When performing the first conversion operation, the DC / DC converter 3 uses the voltage between the first DC input / output terminal 31 and the second DC input / output terminal 32 as the first input voltage, and uses the voltage between the third DC input / output terminal 33 and the fourth DC input / output terminal 34 as the first output voltage. That is to say, when performing the first conversion operation, the DC / DC converter 3 converts the first input voltage applied between the first DC input / output terminal 31 and the second DC input / output terminal 32 into a first output voltage having a voltage value different from that of the first input voltage, and delivers the first output voltage between the third DC input / output terminal 33 and the fourth DC input / output terminal 34.

[0043] On the other hand, when performing the second conversion operation, the DC / DC converter 3 uses the voltage between the third DC input / output terminal 33 and the fourth DC input / output terminal 34 as the second input voltage, and uses the voltage between the first DC input / output terminal 31 and the second DC input / output terminal 32 as the second output voltage. That is to say, when performing the second conversion operation, the DC / DC converter 3 converts the second input voltage applied between the third DC input / output terminal 33 and the fourth DC input / output terminal 34 into a second output voltage having a voltage value different from that of the second input voltage, and delivers the second output voltage between the first DC input / output terminal 31 and the second DC input / output terminal 32.

[0044] In the DC / DC converter 3, the first DC output terminal 23 of the AC / DC converter 2 is connected to the first DC input / output terminal 31, and the second DC output terminal 24 of the AC / DC converter 2 is connected to the second DC input / output terminal 32. Thus, the power grid is connected to between the first DC input / output terminal 31 and the second DC input / output terminal 32 of the DC / DC converter 3 via the AC / DC converter 2. In addition, in the DC / DC converter 3, the positive electrode of the battery E1 is connected to the third DC input / output terminal 33, and the negative electrode of the battery E1 is connected to the fourth DC input / output terminal 34.

[0045] Therefore, the first conversion operation performed by the DC / DC converter 3 is a charging operation performed by the DC / DC converter 3 to charge the battery E1. On the other hand, the second conversion operation performed by the DC / DC converter 3 is a discharging operation performed by the DC / DC converter 3 to discharge from the battery E1.

[0046] The eight switching elements Q31 to Q38 of the DC / DC converter 3 are controlled by the second control unit 30.

[0047] When the DC / DC converter 3 performs the first conversion operation, the four switching elements Q35 to Q38 of the second bridge circuit 38 are controlled to the OFF state, and the four switching elements Q31 to Q34 of the first bridge circuit 37 are switched. That is, when the DC / DC converter 3 performs the first conversion operation, the four switching elements Q31 to Q34 of the first bridge circuit 37 become ON and OFF. Note that the switching elements Q35 to Q38 may also become ON only during a part of the period in which current is flowing.

[0048] When the DC / DC converter 3 performs the second conversion operation, the four switching elements Q31 to Q34 of the first bridge circuit 37 are controlled to the OFF state, and the four switching elements Q35 to Q38 of the second bridge circuit 38 are switched. That is, when the DC / DC converter 3 performs the second conversion operation, the four switching elements Q35 to Q38 of the second bridge circuit 38 become ON and OFF. Note that the switching elements Q31 to Q34 may also become ON only during a part of the period in which current is flowing.

[0049] (2.3) Inverter

[0050] As Figure 1 shown, the inverter 4 has a first DC input terminal 41, a second DC input terminal 42, a first AC output terminal 43, and a second AC output terminal 44. The first DC input terminal 41 of the inverter 4 is connected to the first DC output terminal 23 of the AC / DC converter 2. Thus, the first DC input terminal 41 of the inverter 4 is connected to the first DC input / output terminal 31 of the DC / DC converter 3. On the other hand, the second DC input terminal 42 of the inverter 4 is connected to the second DC output terminal 24 of the AC / DC converter 2. Thus, the second DC input terminal 42 of the inverter 4 is connected to the second DC input / output terminal 32 of the DC / DC converter 3. The inverter 4 converts the DC voltage supplied from the DC / DC converter 3 that has converted the output voltage of the battery E1 into an AC voltage and outputs the AC voltage. The inverter 4 is a unidirectional DC / AC converter.

[0051] As Figure 2As shown, the inverter 4 includes a bridge circuit 47, two inductors L41, L42, and two capacitors C41, C42.

[0052] The bridge circuit 47 includes four switching elements Q41, Q42, Q43, Q44. In the bridge circuit 47, a series circuit of two switching elements Q41, Q42 and a series circuit of two switching elements Q43, Q44 are connected in parallel to the capacitor C41. In addition, in the bridge circuit 47, the connection node between the two switching elements Q41, Q42 is connected to the first terminal of the socket 5 via the inductor L41, and the connection node between the two switching elements Q43, Q44 is connected to the second terminal of the socket 5 via the inductor L42. In the bridge circuit 47, each of the four switching elements Q41 to Q44 can be, for example, a normally-off n-channel MOSFET. In Figure 2 it, the four diodes anti-parallel connected to the four switching elements Q41 to Q44 one-to-one are parasitic diodes for the n-channel MOSFETs used as the four switching elements Q41 to Q44. However, this is only an example and should not be construed as restrictive. The diodes can also be external diodes.

[0053] The capacitor C41 is connected between the first DC input terminal 41 and the second DC input terminal 42. The capacitor C42 is connected between the first AC output terminal 43 and the second AC output terminal 44.

[0054] (2.4) First switching unit

[0055] The first switching unit 61 is connected between the first AC input terminal 21 of the unidirectional AC / DC converter 2 and the first AC output terminal 43 of the inverter 4. The first switching unit 61 can be, for example, a mechanical relay. The first switching unit 61 is controlled by the switching control unit 60 to be turned on and off.

[0056] The first switching unit 61 does not necessarily have to be a mechanical relay, but can also be, for example, a semiconductor switching element or a semiconductor relay. The semiconductor switching element can be, for example, a MOSFET, a bipolar transistor, an insulated gate bipolar transistor (IGBT), or a GaN-based gate injection transistor (GIT).

[0057] (2.5) Second switching unit

[0058] The second switching unit 62 is connected between the second AC input terminal 22 of the unidirectional AC / DC converter 2 and the second AC output terminal 44 of the inverter 4. The second switching unit 62 can be, for example, a mechanical relay. The second switching unit 62 is controlled by the switching control unit 60 to be turned on and off.

[0059] The second switching unit 62 does not necessarily have to be a mechanical relay, and for example, it may also be a semiconductor switching element or a semiconductor relay.

[0060] (2.6) Voltage detection circuit

[0061] The voltage detection circuit 7 detects the input voltage of the AC / DC converter 2. More specifically, the voltage detection circuit 7 is connected between the first AC input terminal 21 and the second AC input terminal 22 of the AC / DC converter 2 to detect the voltage between the first AC input terminal 21 and the second AC input terminal 22 as the input voltage of the AC / DC converter 2. The voltage detection circuit 7 may be, for example, a resistive voltage division circuit including a plurality of resistors connected in series.

[0062] (2.7) First control unit, second control unit, inverter control unit, and switching control unit

[0063] The first control unit 20 controls the two switching elements Q21 and Q22 of the AC / DC converter 2. The first control unit 20 generates, for example, two control signals corresponding one-to-one to the two switching elements Q21 and Q22 according to an external command or the input voltage of the AC / DC converter 2, and outputs these two control signals. Each of the two control signals may be, for example, a voltage whose voltage level alternates between a voltage value (e.g., 10V) higher than the gate threshold voltage of the corresponding switching element (MOSFET) among the two switching elements Q21 and Q22 and a voltage value (e.g., 0V) lower than the gate threshold voltage.

[0064] The second control unit 30 controls the four switching elements Q31 to Q34 of the first bridge circuit 37 and the four switching elements Q35 to Q38 of the second bridge circuit 38 of the DC / DC converter 3. The second control unit 30 generates, for example, control signals for the eight switching elements Q31 to Q38 according to an external command, the input voltage of the DC / DC converter 3, or the input current, and outputs these eight control signals.

[0065] If the DC / DC converter 3 is made to perform a first conversion operation, the second control unit 30 repeatedly performs control for a first period to a fourth period in a state where the four switching elements Q35 to Q38 of the second bridge circuit 38 are turned off. Specifically, the first period is a period in which the switching element Q31 is turned off, the switching element Q32 is turned on, the switching element Q33 is turned on, and the switching element Q34 is turned off. The second period is a period in which the switching element Q31 is turned off, the switching element Q32 is turned off, the switching element Q33 is turned off, and the switching element Q34 is turned off (i.e., a dead time period). The third period is a period in which the switching element Q31 is turned on, the switching element Q32 is turned off, the switching element Q33 is turned off, and the switching element Q34 is turned on. The fourth period is a period in which the switching element Q31 is turned off, the switching element Q32 is turned off, the switching element Q33 is turned off, and the switching element Q34 is turned off (i.e., a dead time period).

[0066] If the DC / DC converter 3 is made to perform a second conversion operation, the second control unit 30 repeatedly performs control for a fifth period to an eighth period in a state where the four switching elements Q31 to Q34 of the first bridge circuit 37 are turned off. Specifically, the fifth period is a period in which the switching element Q35 is turned off, the switching element Q36 is turned on, the switching element Q37 is turned on, and the switching element Q38 is turned off. The sixth period is a period in which the switching element Q35 is turned off, the switching element Q36 is turned off, the switching element Q37 is turned off, and the switching element Q38 is turned off (i.e., a dead time period). The seventh period is a period in which the switching element Q35 is turned on, the switching element Q36 is turned off, the switching element Q37 is turned off, and the switching element Q38 is turned on. The eighth period is a period in which the switching element Q35 is turned off, the switching element Q36 is turned off, the switching element Q37 is turned off, and the switching element Q38 is turned off (i.e., a dead time period).

[0067] The inverter control unit 40 controls the four switching elements Q41 to Q44 of the bridge circuit 47 of the inverter 4. The inverter control unit 40 generates, for example, four control signals for the four switching elements Q41 to Q44 according to an external command or the input voltage of the inverter 4, and outputs these four control signals. The inverter control unit 40 performs pulse width modulation (PWM) control on each of the four switching elements Q41 to Q44.

[0068] When the inverter control unit 40 performs the operation of converting the input DC voltage into an AC voltage, it repeatedly performs control for the ninth period to the twelfth period. Specifically, the ninth period is a period in which the switching element Q41 turns off, the switching element Q42 turns on, the switching element Q43 turns on, and the switching element Q44 turns off. The tenth period is a period in which the switching element Q41 turns off, the switching element Q42 turns off, the switching element Q43 turns off, and the switching element Q44 turns off (i.e., the dead time period). The eleventh period is a period in which the switching element Q41 turns on, the switching element Q42 turns off, the switching element Q43 turns off, and the switching element Q44 turns on. The twelfth period is a period in which the switching element Q41 turns off, the switching element Q42 turns off, the switching element Q43 turns off, and the switching element Q44 turns off (i.e., the dead time period).

[0069] The switching control unit 60 controls the first switch unit 61 and the second switch unit 62. When the DC / DC converter 3 is charging the battery E1, the switching control unit 60 controls the first switch unit 61 and the second switch unit 62 to the on state. The switching control unit 60 can determine whether the DC / DC converter 3 is charging the battery E1, for example, based on the voltage detected by the voltage detection circuit 7 or the detection result obtained by the sensor for determining whether the charging connector is connected to the charging socket of the electric vehicle.

[0070] On the other hand, when the DC / DC converter 3 is not charging the battery E1, the switching control unit 60 controls the first switch unit 61 and the second switch unit 62 to the off state. When the DC / DC converter 3 is not charging the battery E1, the inverter control unit 40 controls the inverter 4 so that the DC / DC converter 3 performs voltage conversion on the first DC voltage of the battery E1, and thereby converts the second DC voltage to be output between the first DC input / output terminal 31 and the second DC input / output terminal 32 into the AC voltage used by the socket 5. The AC voltage of the socket 5 can be, for example, AC 100V. However, this is only an example and should not be construed as restrictive.

[0071] In addition, when the DC bus voltage between the first DC output terminal 23 and the second DC output terminal 24 of the AC / DC converter 2 has exceeded the voltage to be obtained from the power grid (for example, in Figure 2In the illustrated example, after the maximum value of the AC voltage supplied by the AC power supply Vs) to the AC / DC converter 2, the inverter 4 is caused to operate. The inverter control unit 40 may detect the maximum value of the AC voltage to be supplied from the power grid to the AC / DC converter 2 based on the detection result obtained by the voltage detection circuit 7, or may pre-store the maximum value of the AC voltage to be supplied from the power grid to the AC / DC converter 2, either of which is appropriate.

[0072] If the plug of a household appliance is connected to the socket 5 while the electric vehicle is running (i.e., the charging pause state), the power conversion system 1 enters the following state: the power conversion system 1 supplies an AC voltage to the socket 5 via a path sequentially passing through the battery E1, the bidirectional isolation type DC / DC converter 3, the inverter 4, and the socket 5. If charging of the battery E1 is started in this state (i.e., the charging pause state), the switching control unit 60 controls to keep the first switching unit 61 and the second switching unit 62 off. Thus, if charging of the battery E1 is started in the charging pause state, the AC voltage is supplied to the socket 5 via a path passing through the AC power supply Vs, the unidirectional AC / DC converter 2, the inverter 4, and the socket 5. On the other hand, if the plug of a household appliance is connected to the socket 5 while the battery E1 is being charged, the switching control unit 60 controls the first switching unit 61 and the second switching unit 62 to the conducting state. Thus, the power conversion system 1 enters the following state: the power conversion system 1 supplies the AC voltage from the AC power supply Vs to the socket 5 via the first switching unit 61 and the second switching unit 62 without passing through the unidirectional AC / DC converter 2 or the inverter 4. If the AC power supply Vs is disconnected in this state, the voltage detected by the voltage detection circuit 7 drops. Therefore, in the power conversion system 1, the switching control unit 60 immediately controls the first switching unit 61 and the second switching unit 62 to the off state based on the detection result using the voltage detection circuit 7, and operates to supply the AC voltage to the socket 5 via a path sequentially passing through the battery E1, the bidirectional isolation type DC / DC converter 3, the inverter 4, and the socket 5.

[0073] Agents that perform the functions of the respective control units (i.e., the first control unit 20, the second control unit 30, the switching control unit 60, and the inverter control unit 40) may include, for example, a computer system. The computer system includes a single or multiple computers. The computer system provided for each of these control units may include a processor and a memory as its main hardware components. The computer system serves as an agent for performing the functions of the control unit according to the present disclosure by causing the processor to execute a program stored in the memory of the computer system. The program may be pre-stored in the memory of the computer system. Alternatively, the program may also be downloaded via a telecommunication line or distributed after being recorded in a non-transitory storage medium such as a memory card, an optical disc, or a hard disk drive (magnetic disk) (any of which is readable by the computer system). The processor of the computer system may be constituted by a single or multiple electronic circuits including semiconductor integrated circuits (ICs) or large-scale integrated circuits (LSIs). These electronic circuits may be integrally formed on a single chip or distributed over multiple chips, either of which is appropriate. These multiple chips may be aggregated together in a single device or distributed over multiple devices, without limitation.

[0074] In the power conversion system 1, at least two selected from the group consisting of the first control unit 20, the second control unit 30, the switching control unit 60, and the inverter control unit 40 may be integrally formed in a single microcomputer.

[0075] External commands for each of the first control unit 20, the second control unit 30, and the inverter control unit 40 may be given, for example, by an external controller. As a communication protocol for communicating the external commands from the controller to the first control unit 20, the second control unit 30, and the inverter control unit 40, for example, MODBUS, Controller Area Network (CAN), or any other serial communication protocol may be used. The controller may be, for example, a controller installed in an electric vehicle. However, this is merely an example and should not be construed as restrictive. Alternatively, the controller may also be an electric vehicle supply equipment (EVSE) or an external controller such as an energy management unit (EMU), either of which is appropriate. Alternatively, the controller may also be another microcomputer mounted on the same substrate as at least one of the first control unit 20, the second control unit 30, and the inverter control unit 40.

[0076] (3) Advantages

[0077] In the power conversion system 1 according to the first embodiment, the unidirectional AC / DC converter 2 is configured to be connected to the power grid. The bidirectional isolated DC / DC converter 3 has: a first DC input / output terminal 31 and a second DC input / output terminal 32, which are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2; and a third DC input / output terminal 33 and a fourth DC input / output terminal 34, which are connected to both ends of the battery E1 of the electric vehicle. The inverter 4 has: a first DC input terminal 41 and a second DC input terminal 42, which are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2; and a first AC output terminal 43 and a second AC output terminal 44, which are configured to be connected to the socket 5. The inverter control unit 40 controls the inverter 4.

[0078] This configuration can increase the system efficiency. More specifically, in the power conversion system 1 according to the first embodiment, when the battery E1 is not being charged, the DC / DC converter 3 can convert the output voltage of the battery E1, the inverter 4 can convert the output voltage into an AC voltage, and then supply the AC voltage to the socket 5, thereby increasing the system efficiency. In short, the power conversion system 1 according to the first embodiment can supply an AC voltage of 100V AC to the socket 5 without passing through the unidirectional AC / DC converter 2, thereby increasing the system efficiency.

[0079] In addition, the power conversion system 1 according to the first embodiment further includes: a first switch unit 61, which is connected between the first AC input terminal 21 of the unidirectional AC / DC converter 2 and the first AC output terminal 43 of the inverter 4; a second switch unit 62, which is connected between the second AC input terminal 22 of the unidirectional AC / DC converter 2 and the second AC output terminal 44 of the inverter 4; and a switching control unit 60 for controlling the first switch unit 61 and the second switch unit 62. This enables the power conversion system 1 of the first embodiment to supply an AC voltage from the power grid to the socket 5 when the battery E1 is not being charged.

[0080] Furthermore, in the power conversion system 1 according to the first embodiment, when the bidirectional isolated DC / DC converter 3 is charging the battery E1, the switching control unit 60 controls the first switch unit 61 and the second switch unit 62 to be in the conducting state. This enables the power conversion system 1 according to the first embodiment to supply an AC voltage from the power grid to the socket 5 when the bidirectional isolated DC / DC converter 3 is charging the battery E1.

[0081] In addition, in the power conversion system 1 according to the first embodiment, when the bidirectional isolation type DC / DC converter 3 is not charging the battery E1, the switching control unit 60 controls the first switching unit 61 and the second switching unit 62 to the off state. When the bidirectional isolation type DC / DC converter 3 is not charging the battery E1, the inverter control unit 40 controls the inverter 4 such that the bidirectional isolation type DC / DC converter 3 performs voltage conversion on the first DC voltage of the battery E1, and thereby converts the second DC voltage to be output between the first DC input / output terminal 31 and the second DC input / output terminal 32 into the AC voltage used by the socket 5. Thus, when the bidirectional isolation type DC / DC converter 3 is not charging the battery E1, the power conversion system 1 according to the first embodiment causes the bidirectional isolation type DC / DC converter 3 to convert the first DC voltage of the battery E1 into the second DC voltage, and causes the inverter 4 to convert the second DC voltage into the AC voltage used by the socket 5 and supply the AC voltage to the socket 5.

[0082] In addition, in the power conversion system 1 according to the first embodiment, after the DC bus voltage between the first DC output terminal 23 and the second DC output terminal 24 has exceeded the maximum value of the AC voltage to be supplied from the power grid to the unidirectional AC / DC converter 2, the inverter control unit 40 causes the inverter 4 to operate. This enables the power conversion system 1 according to the first embodiment to reduce the possibility of reverse current flowing from the power grid to the inverter 4.

[0083] (Second Embodiment)

[0084] Next, the power conversion system 1A according to the second embodiment will be described with reference to Figure 3 . In the following description, any component in the power conversion system 1A according to the second embodiment that has the same function as the corresponding part of the above-described power conversion system 1 according to the first embodiment (refer to Figure 2 ) will be designated by the same reference numeral as that of the corresponding part, and the description thereof will be omitted herein.

[0085] (1) Configuration

[0086] The power conversion system 1A according to the second embodiment includes a unidirectional AC / DC converter 2A instead of the unidirectional AC / DC converter 2 of the power conversion system 1 according to the first embodiment, which is different from the power conversion system 1 according to the first embodiment. The unidirectional AC / DC converter 2A is connected to the bidirectional isolation type DC / DC converter 3.

[0087] In this power conversion system 1A, the single-phase AC / DC converter 2A is connected to a three-phase AC power supply in the power grid, which is composed of three AC power supplies Va, Vb, and Vc that output AC voltages with a 120-degree phase difference from each other.

[0088] The single-phase AC / DC converter 2A has three first AC input terminals 21a, 21b, 21c, a second AC input terminal 22, a first DC output terminal 23, and a second DC output terminal 24. In the single-phase AC / DC converter 2A, the AC power supply Va is connected between the first AC input terminal 21a and the second AC input terminal 22. In addition, in the single-phase AC / DC converter 2A, the AC power supply Vb is connected between the first AC input terminal 21b and the second AC input terminal 22. In addition, in the single-phase AC / DC converter 2A, the AC power supply Vc is connected between the first AC input terminal 21c and the second AC input terminal 22.

[0089] The single-phase AC / DC converter 2A converts the three-phase AC voltage into a DC voltage and outputs this DC voltage between the first DC output terminal 23 and the second DC output terminal 24.

[0090] The single-phase AC / DC converter 2A includes three switching elements Q23 and three switching elements Q24. In this single-phase AC / DC converter 2A, three switching circuits (wherein the three switching elements Q23 are connected to the three switching elements Q24 one-to-one) are connected in parallel with each other. In addition, the single-phase AC / DC converter 2A also includes a series circuit of diodes D23 and D24. In the single-phase AC / DC converter 2A, the three switching elements Q23 are connected to the first DC output terminal 23, and the three switching elements Q24 are connected to the second DC output terminal 24. In addition, the single-phase AC / DC converter 2A also includes three inductors L2. The connection nodes between a pair of switching elements Q23 and Q24 in each of the three switching circuits are connected to the corresponding first AC input terminals among the three first AC input terminals 21a, 21b, 21c via the corresponding inductors in the inductors L2.

[0091] In the single-phase AC / DC converter 2A, each of the three switching elements Q23 and the three switching elements Q24 can be, for example, a normally-off n-channel MOSFET. In Figure 3 it, the diodes connected in anti-parallel with the three switching elements Q23 and the three switching elements Q24 are parasitic diodes for the n-channel MOSFETs used as the three switching elements Q23 and the three switching elements Q24. However, this is only an example and should not be construed as restrictive. The diodes can also be external diodes.

[0092] The three switching elements Q23 and the three switching elements Q24 are controlled by the first control unit 20. In the power conversion system 1A according to the second embodiment, the first control unit 20 generates six control signals for controlling the three switching elements Q23 and the three switching elements Q24, respectively, and outputs these six control signals.

[0093] In the power conversion system 1A, the first AC output terminal 43 of the inverter 4 is connected to the first AC input terminal 21c of the unidirectional AC / DC converter 2A via the first switch unit 61. On the other hand, the second AC output terminal 44 of the inverter 4 is connected to the second AC input terminal 22 of the unidirectional AC / DC converter 2A via the second switch unit 62.

[0094] In addition, in the power conversion system 1A, the voltage detection circuit 7 is connected between the first AC input terminal 21c and the second AC input terminal 22 of the unidirectional AC / DC converter 2A.

[0095] (2) Advantages

[0096] In the power conversion system 1A according to the second embodiment, the unidirectional AC / DC converter 2A is configured to be connected to the power grid. The bidirectional isolated DC / DC converter 3 has: a first DC input / output terminal 31 and a second DC input / output terminal 32, which are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2A; and a third DC input / output terminal 33 and a fourth DC input / output terminal 34, which are configured to be connected to both ends of the battery E1 of the electric vehicle. The inverter 4 has: a first DC input terminal 41 and a second DC input terminal 42, which are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2A; and a first AC output terminal 43 and a second AC output terminal 44, which are configured to be connected to the socket 5. The inverter control unit 40 controls the inverter 4.

[0097] This configuration can increase the system efficiency. More specifically, in the power conversion system 1A according to the second embodiment, when the battery E1 is not being charged, the bidirectional isolated DC / DC converter 3 can convert the output voltage of the battery E1, the inverter 4 can convert the output voltage into an AC voltage, and then supply the AC voltage to the socket 5, thereby increasing the system efficiency. In short, the power conversion system 1A according to the second embodiment can supply an AC voltage of 100V AC to the socket 5 without passing through the unidirectional AC / DC converter 2A, thereby increasing the system efficiency.

[0098] (Third Embodiment)

[0099] Next, with reference to Figure 4To describe the power conversion system 1B according to the third embodiment. In the following description, any component in the power conversion system 1B according to this third embodiment that has the same function as the corresponding part of the above-mentioned power conversion system 1 (refer to Figure 1 and Figure 2 ) will be designated by the same reference numeral as that of the corresponding part, and its description will be omitted herein.

[0100] (1) Configuration

[0101] The power conversion system 1B according to the third embodiment includes three single-phase AC / DC converters 2, three bidirectional isolation type DC / DC converters 3, a first control unit 20, and a second control unit 30 according to the first embodiment, respectively. This is different from the power conversion system 1 according to the first embodiment.

[0102] In this power conversion system 1B, the three single-phase AC / DC converters 2 are connected to a three-phase AC power supply composed of three AC power supplies Va, Vb, and Vc that output AC voltages with a 120-degree phase difference from each other in the power grid. In the following description, the single-phase AC / DC converter 2 connected to both ends of the AC power supply Va will be hereinafter referred to as the "single-phase AC / DC converter 2a", the single-phase AC / DC converter 2 connected to both ends of the AC power supply Vb will be hereinafter referred to as the "single-phase AC / DC converter 2b", and the single-phase AC / DC converter 2 connected to both ends of the AC power supply Vc will be hereinafter referred to as the "single-phase AC / DC converter 2c". In addition, in the following description, the bidirectional isolation type DC / DC converter 3 connected to the single-phase AC / DC converter 2a will be hereinafter referred to as the "bidirectional isolation type DC / DC converter 3a", the bidirectional isolation type DC / DC converter 3 connected to the single-phase AC / DC converter 2b will be hereinafter referred to as the "bidirectional isolation type DC / DC converter 3b", and the bidirectional isolation type DC / DC converter 3 connected to the single-phase AC / DC converter 2c will be hereinafter referred to as the "bidirectional isolation type DC / DC converter 3c".

[0103] In this power conversion system 1B, the first AC output terminal 43 of the inverter 4 is connected to the first AC input terminal 21 of the single-phase AC / DC converter 2c via the first switch unit 61. The second AC output terminal 44 of the inverter 4 is connected to the second AC input terminal 22 of the single-phase AC / DC converter 2c via the second switch unit 62.

[0104] In addition, in this power conversion system 1B, the voltage detection circuit 7 is connected between the first AC input terminal 21 and the second AC input terminal 22 of the single-phase AC / DC converter 2c.

[0105] (2) Advantages

[0106] In the power conversion system 1B according to the third embodiment, the unidirectional AC / DC converter 2c is configured to be connected to the power grid. The bidirectional isolated DC / DC converter 3c has: a first DC input / output terminal 31 and a second DC input / output terminal 32, which are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2c; and a third DC input / output terminal 33 and a fourth DC input / output terminal 34, which are configured to be connected to both ends of the battery E1 of the electric vehicle. The inverter 4 has: a first DC input terminal 41 and a second DC input terminal 42, which are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2c; and a first AC output terminal 43 and a second AC output terminal 44, which are connected to the socket 5. The inverter control unit 40 controls the inverter 4.

[0107] This configuration can increase the system efficiency. More specifically, in the power conversion system 1B according to the third embodiment, when the battery E1 is not being charged, the bidirectional isolated DC / DC converter 3c can convert the output voltage of the battery E1, cause the inverter 4 to convert the output voltage into an AC voltage, and then supply the AC voltage to the socket 5, thereby enabling an increase in system efficiency. In short, the power conversion system 1B according to the third embodiment can supply an AC voltage of AC 100V to the socket 5 without passing through the unidirectional AC / DC converter 2c, thereby enabling an increase in system efficiency.

[0108] In the power conversion system 1B according to the third embodiment, the first DC input terminal 41 and the second DC input terminal 42 of the inverter 4 are respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2c. However, this is merely an example and should not be construed as restrictive. Alternatively, the first DC input terminal 41 and the second DC input terminal 42 of the inverter 4 may also be respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2a, rather than the unidirectional AC / DC converter 2c, or respectively connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converter 2b, whichever is appropriate.

[0109] (Other modification examples)

[0110] Note that the above-described first to third embodiments and their modification examples are merely exemplary embodiments among the various embodiments and their modification examples of the present disclosure and should not be construed as restrictive. On the contrary, without departing from the scope of the present disclosure, the first to third embodiments and their modification examples can be easily modified in various ways according to design choices or any other factors.

[0111] For example, each switching element among the switching elements Q21, Q22, Q23, Q24, Q31 to Q38, and Q41 to Q44 does not necessarily have to be an n-channel MOSFET, but can also be a p-channel MOSFET. In addition, in the above-described embodiment, each switching element among the switching elements Q21, Q22, Q23, Q24, Q31 to Q38, and Q41 to Q44 is a Si-based MOSFET. However, this is merely an example and should not be construed as restrictive. Alternatively, each switching element among these switching elements can also be a SiC-based MOSFET. In addition, each switching element among the switching elements Q21, Q22, Q23, Q24, Q31 to Q38, and Q41 to Q44 does not necessarily have to be a MOSFET, but can also be, for example, a bipolar transistor, an IGBT, or a GaN-based GIT.

[0112] In addition, the circuit configuration of the unidirectional AC / DC converter 2 is not limited to Figure 2 the circuit configuration shown, but can also be any other suitable circuit configuration. For example, the unidirectional AC / DC converter 2 does not necessarily have to have the circuit configuration according to the first embodiment, but can also be, for example, a totem pole PFC circuit or a half-bridge PFC circuit. Similarly, the circuit configuration of the unidirectional AC / DC converter 2A is not limited to Figure 3 the circuit configuration shown, but can also be any other suitable circuit configuration.

[0113] In addition, the circuit configuration of the bidirectional isolated DC / DC converter 3 does not necessarily have to be Figure 2 and Figure 3 the circuit configurations shown, but can also be any other suitable circuit configuration. In the above-described first to third embodiments, a CLLC circuit, which is a bidirectional version of an LLC circuit, is employed. However, this is merely an example and should not be construed as restrictive. Alternatively, any other DC / DC converter can also be employed as long as the DC / DC converter is isolated and can perform a charging operation and a discharging operation. The bidirectional isolated DC / DC converter 3 can be, for example, a DAB converter or an FSFB converter.

[0114] In addition, the battery E1 does not necessarily have to be a lithium-ion battery, but can also be, for example, a solid-state battery.

[0115] In addition, in the above-described embodiment, the power conversion systems 1A and 1B include a first switch unit 61, a second switch unit 62, and a switching control unit 60. Alternatively, the power conversion systems 1A and 1B can also have a configuration without the first switch unit 61, the second switch unit 62, or the switching control unit 60.

[0116] Optionally, the power conversion systems 1A, 1B may include a plurality of inverters 4. In this case, the first DC input terminals 41 and the second DC input terminals 42 of each of the plurality of inverters 4 may be connected to the first DC output terminal 23 and the second DC output terminal 24 of the unidirectional AC / DC converters 2, 2A, respectively.

[0117] (In various aspects)

[0118] The foregoing description provides specific implementations of the following aspects of the present disclosure.

[0119] A power conversion system (1; 1A; 1B) according to a first aspect includes a unidirectional AC / DC converter (2; 2A), a bidirectional isolated DC / DC converter (3), an inverter (4), and an inverter control unit (40). The unidirectional AC / DC converter (2; 2A) has a first AC input terminal (21; 21c), a second AC input terminal (22), a first DC output terminal (23), and a second DC output terminal (24). The unidirectional AC / DC converter (2; 2A) is configured to be connected to a power grid. The bidirectional isolated DC / DC converter (3) has: a first DC input / output terminal (31) and a second DC input / output terminal (32), which are respectively connected to the first DC output terminal (23) and the second DC output terminal (24) of the unidirectional AC / DC converter (2; 2A); and a third DC input / output terminal (33) and a fourth DC input / output terminal (34), which are configured to be connected to both ends of a battery (E1) of an electric vehicle. The inverter (4) has: a first DC input terminal (41) and a second DC input terminal (42), which are respectively connected to the first DC output terminal (23) and the second DC output terminal (24) of the unidirectional AC / DC converter (2; 2A); and a first AC output terminal (43) and a second AC output terminal (44), which are configured to be connected to a socket (5). The inverter control unit (40) controls the inverter (4).

[0120] This aspect allows for an increase in system efficiency.

[0121] A power conversion system (1; 1A; 1B) according to a second aspect, which can be implemented in combination with the first aspect, further includes a first switch unit (61), a second switch unit (62), and a switching control unit (60). The first switch unit (61) is connected between the first AC input terminal (21; 21c) of the unidirectional AC / DC converter (2; 2A) and the first AC output terminal (43) of the inverter (4). The second switch unit (62) is connected between the second AC input terminal (22) of the unidirectional AC / DC converter (2; 2A) and the second AC output terminal (44) of the inverter (4). The switching control unit (60) controls the first switch unit (61) and the second switch unit (62).

[0122] This aspect enables the supply of an AC voltage from the power grid to the socket (5) when the battery (E1) is not being charged.

[0123] In a power conversion system (1; 1A; 1B) according to a third aspect that can be implemented in combination with the second aspect, when the bidirectional isolated DC / DC converter (3) is charging the battery (E1), the switching control unit (60) controls the first switch unit (61) and the second switch unit (62) to the conducting state.

[0124] This aspect enables the supply of an AC voltage from the power grid to the socket (5) when the bidirectional isolated DC / DC converter (3) is charging the battery (E1).

[0125] In a power conversion system (1; 1A; 1B) according to a fourth aspect that can be implemented in combination with the second or third aspect, when the bidirectional isolated DC / DC converter (3) is not charging the battery (E1), the switching control unit (60) controls the first switch unit (61) and the second switch unit (62) to the off state. When the bidirectional isolated DC / DC converter (3) is not charging the battery (E1), the inverter control unit (40) controls the inverter (4) such that the bidirectional isolated DC / DC converter (3) performs voltage conversion on the first DC voltage of the battery (E1), and thereby converts the second DC voltage to be output between the first DC input / output terminal (31) and the second DC input / output terminal (32) into the AC voltage used by the socket (5).

[0126] This aspect enables the bidirectional isolated DC / DC converter (3) to convert the first DC voltage of the battery (E1) into the second DC voltage when the bidirectional isolated DC / DC converter (3) is not charging the battery (E1), and enables the inverter (4) to convert the second DC voltage into the AC voltage used by the socket (5) and supply the AC voltage to the socket (5).

[0127] In a power conversion system (1; 1A; 1B) according to a fifth aspect that can be implemented in combination with any one of the first to fourth aspects, the inverter control unit (40) causes the inverter (4) to operate after the DC bus voltage between the first DC output terminal (23) and the second DC output terminal (24) has exceeded the maximum value of the AC voltage to be supplied from the power grid to the unidirectional AC / DC converter (2; 2A).

[0128] This aspect can reduce the possibility of reverse current flowing from the power grid to the inverter (4).

[0129] Description of Reference Numerals

[0130] 1, 1A, 1B Power Conversion System

[0131] 2, 2A Single-phase AC / DC Converter

[0132] 20 First Control Unit

[0133] 21, 21a, 21b, 21c First AC Input Terminal

[0134] 22 Second AC Input Terminal

[0135] 23 First DC Output Terminal

[0136] 24 Second DC Output Terminal

[0137] 3 Bidirectional Isolated DC / DC Converter

[0138] 30 Second Control Unit

[0139] 31 First DC Input / Output Terminal

[0140] 32 Second DC Input / Output Terminal

[0141] 33 Third DC Input / Output Terminal

[0142] 34 Fourth DC Input / Output Terminal

[0143] 4 Inverter

[0144] 40 Inverter Control Unit

[0145] 41 First DC Input Terminal

[0146] 42 Second DC Input Terminal

[0147] 43 First AC Output Terminal

[0148] 44 Second AC Output Terminal

[0149] 5 Socket

[0150] 60 Switching Control Unit

[0151] 61 First Switching Unit

[0152] 62 Second Switching Unit

[0153] 7 Voltage Detection Circuit

[0154] E1 Battery

[0155] Vs AC Power Supply

[0156] Va, Vb, Vc AC Power Supply

Claims

1. A power conversion system, comprising: a unidirectional AC / DC converter having a first AC input terminal, a second AC input terminal, a first DC output terminal, and a second DC output terminal, and configured to be connected to an electrical grid; a bidirectional isolated DC / DC converter having: a first DC input / output terminal and a second DC input / output terminal respectively connected to the first DC output terminal and the second DC output terminal of the unidirectional AC / DC converter; and a third DC input / output terminal and a fourth DC input / output terminal configured to be connected to both ends of a battery of an electric vehicle; an inverter having: a first DC input terminal and a second DC input terminal respectively connected to the first DC output terminal and the second DC output terminal of the unidirectional AC / DC converter; and a first AC output terminal and a second AC output terminal configured to be connected to a socket; and an inverter control unit configured to control the inverter.

2. The power conversion system according to claim 1, further comprising: a first switch unit connected between the first AC input terminal of the unidirectional AC / DC converter and the first AC output terminal of the inverter; a second switch unit connected between the second AC input terminal of the unidirectional AC / DC converter and the second AC output terminal of the inverter; and a switching control unit configured to control the first switch unit and the second switch unit.

3. The power conversion system according to claim 2, wherein the switching control unit is configured to control the first switch unit and the second switch unit to a conducting state when the bidirectional isolated DC / DC converter is charging the battery.

4. The power conversion system according to claim 2 or 3, wherein the switching control unit is configured to control the first switch unit and the second switch unit to a non-conducting state when the bidirectional isolated DC / DC converter is not charging the battery, and the inverter control unit is configured to control the inverter when the bidirectional isolated DC / DC converter is not charging the battery, such that the bidirectional isolated DC / DC converter performs a voltage conversion on a first DC voltage of the battery, and thereby converts a second DC voltage to be output between the first DC input / output terminal and the second DC input / output terminal into an AC voltage for the socket.

5. The power conversion system according to any one of claims 1 to 4, wherein the inverter control unit is configured to cause the inverter to operate after a DC bus voltage between the first DC output terminal and the second DC output terminal has exceeded a maximum value of an AC voltage to be supplied from the electrical grid to the unidirectional AC / DC converter.

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