Power converter

Abstract

To provide a small-sized power converter with reduced loss, the converter comprising a function of driving a motor, and anther function of quickly charging a battery by DC.SOLUTION: An MG 1 is driven with a battery 2 as a drive power supply. A power conversion unit 4 comprises a series circuit of capacitors 6a, 6b connected to the battery 2 in parallel; upper and lower arm switches 7U to 7W; a capacitor 10 connected to each of arm switches 8, 9 in parallel; and another series circuit of an auxiliary switch 11 and an inductor 12 that are connected between a DC circuit common connection point and an upper and lower arm switch 7 common connection point. Relays S21, S22 are connected between output terminals of the upper and lower arm switches 7U to 7W and the MG 1. There are provided wirings 15U to 15W connecting a commercial AC power supply 17 with the output terminals, and relays S31, S32 connected between a DC quick charger 20 and the capacitor 6b. A control unit 22 switches an operation of the power conversion unit 4 in each of modes of an inverter, a step-up converter, and a three-phase PFC.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conversion device that uses a battery mounted on a vehicle as a driving power source to drive a three-phase motor that drives the vehicle. [Background technology]

[0002] While battery voltages for electric vehicles are increasing to shorten charging times, the current situation is that the spread of high-voltage DC fast chargers has been slow. Charging high-voltage batteries with existing fast chargers requires the use of a boost converter, but boost converters have the drawback of being large and expensive. Furthermore, as battery voltage increases, the input current ripple to the motor / generator (MG) increases, leading to increased losses in the MG.

[0003] In response to the above-mentioned problems, Patent Documents 1 to 3 disclose technologies that take note of the fact that electric vehicles are stopped when charging and do not use MGs or inverters, and that utilize the power elements of the inverter, the windings of the MG, and the reactor to also function as a power converter for charging, thereby reducing the size and cost. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-175363 [Patent Document 2] Patent No. 5601274 [Patent Document 3] Patent No. 6147426 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the use of MG windings may result in poor boost converter efficiency and limited performance. It is also necessary to externally connect the neutral point of the MG. There is no mention of the need to reduce losses in the MG. In Patent Document 2, in addition to using MG windings like in Patent Document 1, it is also necessary to use a separate inverter to control the MG so that it does not rotate during charging. Patent Document 3 also requires the placement of a large relay between the inverter and MG to prevent the MG from rotating during charging.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a small-sized power conversion device that has at least the function of driving a motor and the function of rapidly charging a battery using direct current, and that has little loss in the motor. [Means for solving the problem]

[0007] According to the power conversion device of claim 1, a power conversion unit (4) drives a three-phase motor (1) for driving the vehicle using a battery (2) mounted on the vehicle as a driving power source. The power conversion unit includes a series circuit of two capacitors (6a, 6b) connected in parallel to the battery, upper and lower arm switches (7U to 7V) corresponding to each phase, a capacitor (10) connected in parallel to each arm switch (8, 9), and a series circuit of an auxiliary switch (11) and an inductor (12) connected between a common connection point of the two capacitors and a common connection point of the upper and lower arm switches of each phase.

[0008] The charger relays (S31, S32) are connected between an external DC quick charger (20), one end of the auxiliary switch, and the ground of the power conversion unit to charge the battery. The control unit (22, 32, 34) controls the charger relays and the auxiliary switch to switch the operation mode of the power conversion unit between at least an inverter mode and a boost converter mode. In the inverter mode, the control unit controls the auxiliary switch to perform soft switching of the upper and lower arm switches.

[0009] With this configuration, when the power conversion unit is operated in inverter mode to drive the motor, the auxiliary switch is turned on for the period during which each arm switch is switching on and off. This allows current to flow to the common connection point of the upper and lower arm switches via an inductor, resulting in soft switching operation and reducing switching loss in the upper and lower arm switches.

[0010] Furthermore, when charging the battery using an external DC rapid charger, the charger relay can be turned on and the auxiliary switch can be kept on at all times to operate the power conversion unit in boost converter mode. This allows the battery to be rapidly charged at an appropriate voltage. Furthermore, because this operation does not use the motor windings, there is no need for control to suppress rotor rotation.

[0011] According to the power conversion device of claim 2, the motor relays (S21, S22) are connected between a common connection point of the upper and lower arm switches of any two of the three phases and the two-phase windings of the motor. The AC charging wiring (15U to 15W) connects a commercial AC power supply to a common connection point of the auxiliary switches and inductors of each phase. The control unit (22, 32) also switches the operation mode of the power conversion unit to a three-phase power factor correction mode.

[0012] With this configuration, when charging the battery with an external DC quick charger, the motor relay can be turned off to operate the power conversion unit in boost converter mode. When charging the battery with a commercial AC power source, the charger relay and motor relay can be turned off and the auxiliary switch can be kept on all the time to operate the power conversion unit in three-phase power factor correction mode. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a power conversion device according to a first embodiment. [Figure 2] 10 is a flowchart showing the processing performed by the control unit. [Figure 3]Circuit configuration when operating in inverter mode [Figure 4] Diagram showing the voltage and current of each of the upper and lower arm switches A and B, and auxiliary switches C and D [Figure 5] 5 is an enlarged view of the rectangular area of ​​the load current Iload waveform shown in FIG. 4, and shows the gate signal waveforms of the upper and lower arm switches A and B and the auxiliary switches C and D during soft switching operation. [Figure 6] Circuit configuration when operating in boost converter mode [Figure 7] Circuit configuration diagram for operation in three-phase PFC mode [Figure 8] A diagram showing an example of specific values ​​of each parameter [Figure 9] Diagram showing critical current mode and discontinuous current mode [Figure 10] FIG. 10 is a diagram illustrating a configuration of a power conversion device according to a second embodiment. [Figure 11] 10 is a flowchart showing the processing performed by the control unit. [Figure 12] Circuit configuration when operating in inverter mode [Figure 13] Circuit configuration when operating in boost converter mode [Figure 14] Circuit configuration diagram for operation in three-phase PFC mode [Figure 15] FIG. 10 is a diagram illustrating a configuration of a power conversion device according to a third embodiment. [Figure 16] 10 is a flowchart showing the processing performed by the control unit. [Figure 17] Circuit configuration when operating in inverter mode [Figure 18] Circuit configuration when operating in boost converter mode DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) As shown in Fig. 1, the power conversion device 23 of this embodiment controls an MG1 for driving an electric vehicle (EV) as a vehicle, and also has the function of charging a battery 2 mounted on the EV. The battery 2 has a battery main body 3 and switches S11 and S12 connected to the positive and negative terminals of the battery main body 3, respectively. A power conversion unit 4 is connected to the battery 2 via the switches S11 and S12. An isolated DC-DC converter 5 is connected between the battery main body 3 and the switches S11 and S12.

[0015] The power conversion unit 4 includes a series circuit of capacitors 6a and 6b, and upper and lower arm switches 7U, 7V, and 7W connected in parallel to the capacitors and corresponding to the U, V, and W phases. The upper and lower arm switches 7 include series circuits of MOSFETs 8 and 9 corresponding to the upper and lower arm switches, respectively, and freewheel diodes and capacitors 10 connected in parallel to each of the FETs 8 and 9. The freewheel diodes are parasitic diodes of the FETs. The common connection point of the FETs 8 and 9 is the output terminal of the power conversion unit 4, and the V and W phase output terminals are connected to the phase winding terminals of MG1 via motor relays S21 and S22, respectively.

[0016] A series circuit of an auxiliary switch 11 and an inductor 12 is connected for each phase between the midpoint of the capacitors 6a and 6b and each phase output terminal of the power conversion unit 4. The auxiliary switch 11 is configured with two N-channel MOSFETs 13 and 14 connected with their drains in common. The common connection point of the auxiliary switch 11 and inductor 12 for each phase is connected to a three-phase filter 16 via wiring 15U, 15V, and 15W, respectively. When charging the battery 2 from a three-phase commercial AC power supply 17, the filter 16 is connected to the commercial AC power supply 17 via a cable 18 and a power plug (not shown). In other words, the wiring 15 is a wiring for AC charging.

[0017] Furthermore, in the power conversion device 23, the cable 19 can be connected to a DC rapid charger 20 outside the vehicle to charge the battery 2. For this reason, both ends of the capacitor 6b are connected to the cable 19 via a wiring 21P and a charger relay S31, and via a wiring 21M and a charger relay S32, respectively. The DC rapid charger 20 is a charger that complies with standards such as CHAdeMO (registered trademark). Note that the relays S21, S22, S31, and S32 may be mechanical or may be configured with semiconductor switches.

[0018] The control unit 22 is configured with a microcomputer or the like, and controls the on / off of each switch and relay. The control unit 22 also controls the switching of the upper and lower arm switches 7 of the power conversion unit 4. This allows the drive control of the MG 1 and charging of the battery 2. The above constitutes the power conversion device 23.

[0019] Next, the operation of this embodiment will be described. As shown in Fig. 2, when the EV is in standby mode, the control unit 22 turns off the switches S11 and S12 of the battery 2, and also turns off the motor relays S21 and S22 and the charger relays S31 and S32. Furthermore, it turns off the auxiliary switch 11 (P1). When the power is turned on and the EV starts running (P2; YES), it turns on the motor relays S21 and S22, connecting the power conversion unit 4 to the MG1 (P3). Then, it turns on the switches S11 and S12, connecting the battery main body 3 to the power conversion unit 4 (P4).

[0020] As a result, the control unit 22 operates the power conversion unit 4 in inverter mode (P5), as shown in Fig. 3. In inverter mode, the control unit 22 controls the switching of the three-phase upper and lower arm switches 7U to 7W. In Fig. 3, Fig. 6, and Fig. 7, which correspond to each operation mode, active elements are indicated by bold lines. At this time, the control unit 22 also performs soft switching operation using the auxiliary switch 11 based on the ARCP (Auxiliary Resonant Commutated Pole) method. The soft switching operation will be described below with reference to Figs. 4 and 5.

[0021] Figure 5 shows the load current I load The waveforms of the upper and lower arm switches A and B, and the auxiliary switches C and D during soft switching are shown in the enlarged view of the waveform of the load current I. load Although the waveform of only one phase is shown, the three-phase current waveforms in inverter mode are shifted in phase by 120 degrees.

[0022] When the polarity of the current Ir flowing through the inductor 12 is positive, i.e., to the right in the diagram, the auxiliary switch D is turned on so as to correspond to both the turn-off timing of the lower-arm switch B and the turn-on timing of the upper-arm switch A. In the diagram, periods M1 to M6 are defined as one cycle, and the auxiliary switch D is turned on for periods M2 to M4 of this cycle. As a result, the current Ir flows through the inductor 12 during a period that includes both the start and end of the rise of the drain-source voltage VL of the lower-arm switch B, thereby performing soft switching. Note that when the polarity of the current is negative, the auxiliary switch C is turned on instead of the auxiliary switch D.

[0023] Referring again to Figure 2, when the power is turned off and the EV stops running (P6; YES), switches S11 and S12 are turned off (P7), and motor relays S21 and S22 are turned off (P8). When the EV is stopped (P2; NO) and the controller 22 detects that the cable 21 is connected to the DC rapid charger 20 (P9; YES), the controller 22 turns on the charger relays S31 and S32 (P10). Furthermore, the controller 22 turns on the switches S11 and S12 (P11) to start charging the battery 2 (P12).

[0024] At this time, the control unit 22 operates the power conversion unit 4 in the boost converter mode, as shown in Fig. 6. In the boost converter mode, the auxiliary switches 11 of each phase are always on, and the upper and lower arm switches 7 are switched on and off. When charging is completed (P13; YES), the auxiliary switches 11 are turned off (P14). Furthermore, the switches S11 and S12 are turned off (P15), and the charger relays S31 and S32 are turned off (P17).

[0025] Similarly, when the EV is parked (P2; NO) and the cable 18 is connected to the commercial AC power supply 17 (P17; YES), charging of the battery 2 begins (P18). At this time, the control unit 22 operates the power conversion unit 4 in a three-phase power factor correction mode, a three-phase PFC mode, as shown in FIG. 7. In the three-phase PFC mode, the auxiliary switch 11 is always off, and controls the switching of the upper and lower arm switches 7 of each phase. Because the motor relays S21 and S22 are off, the MG1 is disconnected from the commercial AC power supply 17, and the rotor does not rotate. When charging is completed (P19; YES), the process ends.

[0026] FIG. 8 shows an example of specific values ​​for each parameter. Inductance of inductor 12: 6000 nH, capacitance of capacitor 10: 0.4 nF Battery 2 voltage: 800V Carrier frequency in inverter mode: 100kHz Fast charging voltage in boost converter mode: 400V, charging power: 140kW Operation method in this mode: Critical current mode or discontinuous current mode Carrier frequency: 140kHz or less The critical current mode and discontinuous current mode are shown in Figure 9.

[0027] As described above, according to this embodiment, the power conversion device 23 drives the three-phase MG 1 that drives the EV using the battery 2 mounted on the EV as a driving power source. The power conversion unit 4 includes a series circuit of capacitors 6a and 6b connected in parallel to the battery 2, three-phase upper and lower arm switches 7U to 7W, a capacitor 10 connected in parallel to each of the arm switches 8 and 9, and a series circuit of an auxiliary switch 11 and an inductor 12 connected between a common connection point of the capacitors 6a and 6b and a common connection point of the upper and lower arm switches 7 of each phase.

[0028] Motor relays S21 and S22 are connected between the output terminals of the upper and lower arm switches 7U to 7W and each phase winding terminal of MG1. To charge the battery 2, wiring 15U to 15W connects the commercial AC power supply 17 to the output terminals, and charger relays S31 and S32 are connected between an external DC quick charger 20 and the capacitor 6b. The control unit 22 switches the operation mode of the power conversion unit 4 between an inverter mode, a boost converter mode, and a three-phase PFC mode.

[0029] With this configuration, when the power conversion unit 4 is operated in inverter mode, the auxiliary switch 11 soft-switches the upper and lower arm switches 7 of each phase, thereby suppressing ripple in the current input to MG1 and reducing losses. Also, by operating in boost converter mode when charging the battery 2 with the DC rapid charger 20 and operating in three-phase PFC mode when charging with the commercial AC power supply 17, the power conversion device 23 can be made smaller. Furthermore, because the winding of MG1 is not used when charging the battery 2, control to prevent rotation of MG1 is not required.

[0030] (Second embodiment) Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted, and only different parts will be described. As shown in Fig. 10, the power conversion device 31 of the second embodiment differs from the first embodiment in the connection between the power conversion unit 4 and the rapid charger 20 outside the vehicle. Instead of the wiring 21P and the charger relay S31, wirings 21U to 21W and charger relays S311 to S313, one end of which is connected to one end of each of these wirings 21U to 21W, are provided. The other ends of the charger relays S311 to S313 are commonly connected to the positive terminal of the rapid charger 20. The other ends of the wirings 21U to 21W are respectively connected to a common connection point of the FETs 14 and inductors 12 of each phase. The power conversion device 31 also includes a control unit 32 instead of the control unit 22.

[0031] Next, the operation of the second embodiment will be described. As shown in Fig. 11, in step P21, which replaces step P1, the control unit 32 turns off the relays S11 and S12 of the battery 2, turns off the motor relays S21 and S22, and turns off the charger relays S311 to S313 and S32. The auxiliary switch 11 is also turned off. From this state, when the power conversion unit 4 is operated in inverter mode in step P5, the connection configuration is the same as that of the first embodiment, as shown in Fig. 12.

[0032] If the determination in step P9 is "YES," the control unit 32 turns on the charger relays S311 to S313 and S32 (P22). When the power conversion unit 4 is operated in the boost converter mode in step P12, the connection configuration is different from that in the first embodiment as shown in Fig. 13, but is equivalent in terms of circuitry. Furthermore, when the battery 2 is charged by the commercial AC power supply 17, the configuration is the same as in the first embodiment as shown in Fig. 14.

[0033] (Third embodiment) 15, in a power conversion device 33 of the third embodiment, the DC-DC converter 5, the wiring 15U, 15V, and 15W, and the filter 16 are eliminated, and the device does not support charging of the battery 2 from a commercial AC power source 17. Also, a control unit 34 is provided in place of the control unit 22.

[0034] Next, the operation of the third embodiment will be described. As shown in Fig. 16, in step P31, which replaces step P1, the control unit 34 turns off the relays S11 and S12 of the battery 2 and the charger relays S31 and S32. The auxiliary switch 11 is also turned off. Thereafter, steps P2 to P7 are executed. In the operation in inverter mode in step P5, the connection configuration shown in Fig. 17 is obtained.

[0035] If the answer to step P9 is "YES", steps P10 to P13, P15 and P16 are executed. In the operation in the boost converter mode in step P12, the connection configuration shown in FIG.

[0036] (Other embodiments) The upper and lower arm switches are not limited to MOSFETs, but may be, for example, IGBTs or the like. Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure. [Explanation of symbols]

[0037] In the drawings, 1 is a motor / generator, 2 is a battery, 4 is a power conversion unit, 7 is an upper and lower arm switch, 8 and 9 are MOSFETs, 10 is an inductor, 11 is a capacitor, 12 is wiring, 17 is a commercial AC power supply, 20 is a DC fast charger, 22 is a control unit, 23 is a power conversion device, S21 and S22 are motor relays, and S31 and S32 are charger relays.

Claims

1. a power conversion unit (4) that drives a three-phase motor (1) that drives the vehicle using a battery (2) mounted on the vehicle as a driving power source; The power conversion unit includes a series circuit (6a, 6b) of two capacitors connected in parallel to the battery; Upper and lower arm switches (8, 9) corresponding to each phase; A capacitor (10) connected in parallel to each arm switch; a series circuit of an auxiliary switch (11) and an inductor (12) connected between a common connection point of the two capacitors and a common connection point of the upper and lower arm switches of each phase; a charger relay (S31, S32) connected between a DC quick charger outside the vehicle, one end of the auxiliary switch, and the ground of the power conversion unit in order to charge the battery; a control unit (22, 32, 34) that controls the charger relay and the auxiliary switch to switch the operation mode of the power conversion unit between an inverter mode and a boost converter mode, The control unit controls the auxiliary switch in the inverter mode to cause the upper and lower arm switches to perform soft switching operation.

2. a motor relay (S21, S22) connected between a common connection point of the upper and lower arm switches of any two of the three phases and the two-phase windings of the motor; and AC charging wiring (15U to 15W) connecting a commercial AC power source to a common connection point of the auxiliary switches and inductors of each phase in order to charge the battery; The power conversion device according to claim 1, wherein the control unit (22, 32) also switches the operation mode of the power conversion unit to a three-phase power factor correction mode.

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