Power conversion device

Abstract

To provide a compact power conversion device that has the functions of rapid charging using DC and normal charging using AC, and has low MG loss.SOLUTION: A power conversion device 20 uses a battery 2 installed in an EV as a driving power source to drive a three-phase MG1 that drives the EV. A power conversion unit 4 includes three-phase converter circuits 7U to 7W. First relays S21 to S23 are connected between output terminals of the converter circuits 7U to 7W and respective phase winding terminals of the MG 1. To charge the battery 2, the power conversion unit 4 includes wires 12U to 12W that connect the output terminals to a commercial AC power source 14, a DC quick charger 17 outside the vehicle, and second relays S31 and S32 that are connected between the output terminal of the converter circuit 7U and the ground of the converter circuit 7. A control unit 19 switches an operation mode of the power conversion unit 4 among an inverter mode, a boost converter mode, and a three-phase PFC mode.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] For electric vehicles that require batteries, the battery voltage is being increased to shorten charging times, but the spread of DC quick chargers that are compatible with high voltages is lagging behind.(1) In order to charge high-voltage batteries with existing quick chargers, a boost converter is required, but boost converters have the problem of being large and expensive.

[0003] (2) Furthermore, for ordinary AC chargers, high output is also required to shorten charging times, and the trend is toward three-phase rather than single-phase, but three-phase PFC converters also have the problem of being large in size and expensive. (3) Furthermore, as the battery voltage increases, the input current ripple to the motor / generator (hereinafter referred to as MG) increases, which increases losses in the MG.

[0004] In response to the above problems (1) and (2), Patent Documents 1 to 3 disclose technologies that take into account the fact that electric vehicles are stopped when charging and do not use MGs or inverters, and that utilize the inverter's power elements, MG windings, and reactors to also function as a power converter for charging, thereby reducing size and costs. [Prior art documents] [Patent documents]

[0005] [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]

[0006] 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.

[0007] The present invention has been made in view of the above circumstances, and its object is to provide a small-sized power conversion device that has the functions of rapid charging using DC and normal charging using AC, and that has little MG loss. [Means for solving the problem]

[0008] According to the power conversion device of claim 1, a three-phase motor (1) for propelling the vehicle is driven using a battery (2) mounted on the vehicle as a driving power source. The power conversion unit (4, 22) includes a three-phase converter circuit (7U-7W, 23U-23W) having a series circuit of an inductor (10) and a capacitor (11) connected in parallel to upper and lower arm switches (8, 9) and a lower arm switch (9). First relays (S21-S23) are connected between output terminals of the converter circuit and winding terminals of each phase of the motor. To charge the battery, the power conversion device includes AC charging wiring (12U-12W) connecting a commercial AC power source (14) and the output terminals, and second relays (S31, S32) connected between an external DC quick charger (17), one of the phases of the output terminals, and the ground of the converter circuit. The control unit (19, 24) switches the operation mode of the power conversion unit between an inverter mode, a boost converter mode, and a three-phase power factor correction mode.

[0009] The common connection point of the upper and lower arm switches is equipped with a series circuit of an inductor and a capacitor, i.e., an LC series circuit, which suppresses ripple in the current input to the motor and reduces losses when the power conversion unit operates in inverter mode. Furthermore, the device can be made more compact by operating in boost converter mode when charging the battery with an external DC quick charger, and in three-phase power factor correction mode when charging with a commercial AC power source. Furthermore, because the motor windings are not used when charging the battery, there is no need for control to prevent the motor from rotating.

[0010] According to a power conversion device of claim 2, the power conversion unit (22) includes n parallel converter circuits for each phase. The control unit (24) controls the switching of the n parallel converter circuits when operating in inverter mode, controls the switching of one or i parallel converter circuits when operating in boost converter mode, and controls the switching of one or j parallel converter circuits when operating in three-phase power factor correction mode. The first relay is connected corresponding to the converter circuit operated in the three-phase power factor correction mode.

[0011] In inverter mode, by controlling the switching of n parallel converter circuits, it is possible to further suppress ripple in the current input to the motor and reduce losses. In boost converter mode and three-phase power factor correction mode, for example, by selecting one of i parallel converter circuits and controlling its switching, it is possible to independently determine the operating frequency and control method. In addition, it is possible to set the characteristics of the upper and lower arm switches and the L and C constants for each converter circuit.

[0012] In addition, when the battery is charged using a commercial AC power source, the first relay for preventing the motor from rotating is connected to the converter circuit that operates in three-phase power factor correction mode, thereby preventing the battery from increasing in size. [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] Circuit configuration when operating in boost converter mode [Figure 5] Circuit configuration diagram for operation in three-phase PFC mode [Figure 6] FIG. 10 is a diagram illustrating a configuration of a power conversion device according to a second embodiment. [Figure 7] 10 is a flowchart showing the processing performed by the control unit. [Figure 8] Circuit configuration when operating in inverter mode [Figure 9] FIG. 10 is a diagram showing currents I1 to I4 output from each converter circuit. [Figure 10] A diagram showing the current waveforms output from each converter circuit [Figure 11] 11 is an enlarged view of a portion of the current waveform shown in FIG. 10, and shows a composite current when currents I1 to I4 are in phase. [Figure 12] 11 is an enlarged view of a portion of the current waveform shown in FIG. 10, and shows a composite current when a phase difference of 90 degrees is applied between currents I1 to I4. [Figure 13] Circuit configuration when operating in boost converter mode [Figure 14] Circuit configuration diagram for operation in three-phase PFC mode [Figure 15] Diagram showing various current control methods for switching a converter circuit [Figure 16] 11 is a diagram showing the third embodiment, in which a part of the current waveform shown in FIG. 10 is enlarged, and shows the currents I1 to I4 and their combined current. [Figure 17] 11 is a diagram showing the fourth embodiment, in which a part of the current waveform shown in FIG. 10 is enlarged, and shows the currents I1 to I4 and their combined current. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) As shown in Fig. 1, a power conversion device 20 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 capacitor 6 and converter circuits 7U, 7V, and 7W connected in parallel to the capacitor and corresponding to the U, V, and W phases. The converter circuit 7 includes a series circuit of MOSFETs 8 and 9 corresponding to the upper and lower arm switches, respectively, and a series circuit of an inductor 10 and a capacitor 11 connected in parallel to the FET 9. The common connection point of the inductor 10 and the capacitor 11 is the output terminal of the converter circuit 7, and the U, V, and W phase output terminals are connected to the phase winding terminals of MG1 via first relays S21, S22, and S23, respectively.

[0016] The phase output terminals are connected to a three-phase filter 13 via wiring 12U, 12V, and 12W, respectively. When charging the battery 2 from a three-phase commercial AC power supply 14, the filter 13 is connected to the commercial AC power supply 14 via a cable 15 and a power plug (not shown). In other words, the wiring 12 is a wiring for AC charging.

[0017] Furthermore, in the power conversion device 20, the cable 16 can be connected to a DC rapid charger 17 outside the vehicle to charge the battery 2. For this reason, the output terminal of the converter circuit 7U is connected to the cable 16 via a first relay S21, a wiring 18P, and a second relay S31, and the ground of the converter circuit 7U is connected to the cable 16 via a wiring 18M and a second relay S32. The DC rapid charger 17 is a charger that complies with standards such as CHAdeMO (registered trademark). Note that the relays S21 to S23 and S31 and S32 may be mechanical or may be configured with semiconductor switches.

[0018] The control unit 19 is configured with a microcomputer or the like, and controls the on / off of each switch and relay. The control unit 19 also controls the switching of the converter circuit 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 20.

[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 19 turns off the switches S11 and S12 of the battery 2, and also turns off the first relays S21 to S23 and the second relays S31 and S32 (P1). When the power is turned on and the EV starts running (P2; YES), the control unit 19 turns on the first relays S21 to S23, connecting the power conversion unit 4 to the MG1 (P3). Then, the control unit 19 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 19 operates the power conversion unit 4 in inverter mode (P5), as shown in Fig. 3. In inverter mode, it controls the switching of the three-phase converter circuits 7U to 7W. In Figs. 3 to 5, which correspond to each operation mode, active elements are indicated by bold lines. When the power is turned off and the EV stops running (P6; YES), the switches S11 and S12 are turned off (P7), and the first relays S21 to S23 are turned off (P8).

[0021] When the EV is stopped (P2; NO) and the controller 19 detects that the cable 16 is connected to the DC rapid charger 17 (P9; YES), the controller 19 turns on the first relay S21 (P10) and turns on the second relays S31 and S32 (P11). Furthermore, the controller 19 turns on the switches S11 and S12 (P12) to start charging the battery 2 (P13).

[0022] At this time, the control unit 19 operates the power conversion unit 4 in the boost converter mode (P14), as shown in Fig. 4. In the boost converter mode, only the converter circuit 7U is switched. When charging is completed (P15; YES), the switches S11 and S12 are turned off (P16), the second relays S31 and S32 are turned off (P17), and the first relay S21 is turned off (P18).

[0023] Similarly, when the EV is parked (P2; NO) and the cable 15 is connected to the commercial AC power supply 14 (P19; YES), charging of the battery 2 begins (P20). At this time, the control unit 19 operates the power conversion unit 4 in a three-phase power factor correction mode, a three-phase PFC mode, as shown in FIG. 5 (P21). In the three-phase PFC mode, the control unit 19 controls the switching of the converter circuits 7U to 7W. Because the first relays S21 to S23 are off, the MG1 is disconnected from the commercial AC power supply 14, and the rotor does not rotate. When charging is completed (P22; YES), the process ends.

[0024] As described above, according to this embodiment, the power conversion device 20 drives the three-phase MG1 that drives the EV using the battery 2 installed in the EV as a driving power source. The power conversion unit 4 includes three-phase converter circuits 7U to 7W. First relays S21 to S23 are connected between the output terminals of the converter circuits 7U to 7W and the winding terminals of each phase of the MG1. To charge the battery 2, the power conversion unit 4 includes wiring 12U to 12W that connects the output terminals of the converter circuits 7U to 7W, and second relays S31 and S32 that are connected between the commercial AC power source 14 and the output terminals, an external DC quick charger 17, and the output terminal of the converter circuit 7U and the ground of the converter circuit 7. The control unit 19 switches the operation mode of the power conversion unit 4 among inverter mode, boost converter mode, and three-phase PFC mode.

[0025] Converter circuit 7 includes a series circuit of inductor 10 and capacitor 11, and an LC series circuit, so that when power conversion unit 4 is operated in inverter mode, ripple in the current input to MG1 can be suppressed and loss can be reduced. Furthermore, by operating in boost converter mode when charging battery 2 with DC rapid charger 17, and operating in three-phase PFC mode when charging with commercial AC power supply 14, power conversion device 20 can be made smaller. Furthermore, because the winding of MG1 is not used when charging battery 2, control to prevent MG1 from rotating is not required.

[0026] (Second embodiment) Hereinafter, the same parts as those in the first embodiment will be assigned the same reference numerals and explanations thereof will be omitted, and only different parts will be explained. As shown in Fig. 6, a power conversion device 21 of the second embodiment includes a power conversion unit 22 instead of the power conversion unit 4. The power conversion unit 22 is made up of three-phase converter units 23U to 23W, and the converter unit 23 is configured by connecting four converter circuits 7 of the first embodiment in parallel. These are referred to as converter circuits 7(1) to 7(4). That is, n=4.

[0027] For example, converter circuit 7(1) is used in inverter mode and three-phase PFC mode, and converter circuits 7(2) and 7(3) are used only in inverter mode. Converter circuit 7(4) is used in inverter mode and boost converter mode. First relays S21 to S23 are connected to the output terminal of converter circuit 7(1), and the output terminals of converter circuits 7(2) to 7(4) are directly connected to the respective phase windings of MG1 without passing through first relays S21 to S23.

[0028] Further, second relays S311, S312, and S313 are provided in place of the second relay S31, and the positive terminal of the DC quick charger 17 is connected to each phase winding of MG1 via the second relays S311, S312, and S313. Furthermore, a control unit 24 is provided in place of the control unit 19.

[0029] Next, the operation of the second embodiment will be described. As shown in Fig. 7, when the power conversion unit 22 is operated in inverter mode in step P23 instead of step P5, the converter circuits 7(1) to 7(4) are controlled in parallel as shown in Fig. 8. As shown in Fig. 9, when the converter circuits 7(1) to 7(4) are switched and controlled, the currents flowing through the respective LC series circuits are designated I1 to I4. Figs. 11 and 12 show enlarged views of the framed portion of the output current waveform due to the continuous current operation shown in Fig. 10.

[0030] The output current of converter unit 23 is a combination of currents I1 to I4. Therefore, as shown in Fig. 11, if the switching control of converter circuits 7(1) to 7(4) is performed in phase, the ripple in the output current of converter unit 23 will be large. In contrast, as shown in Fig. 12, if the above switching control is performed with a phase difference of 90 degrees, the ripple in the output current can be suppressed.

[0031] When the power conversion unit 22 is operated in the boost converter mode, the second relays S311 to S313 and S32 are turned on in step P24, which replaces step P10. This results in the connection state shown in FIG. 13. In step P25, which replaces step P14, the converter circuits 7(1) of the converter units 23U, 23V, and 23W are switched and controlled. That is, since three converter circuits 7 are used in parallel, i=3. At this time, the same voltage is applied to each phase winding of MG1, so the rotor does not rotate.

[0032] In the boost converter mode, the efficiency of the boost converter can be optimized by changing the number of converter circuits 7 to be operated depending on the number of second relays S311 to S313 to be turned on. For example, when the load is heavy, the losses generated in the FETs 8 and 9 and the inductor 10 can be reduced by using three converter circuits 7 in parallel as described above. Also, when the load is light, the losses generated in the FETs 8 and 9 can be reduced by using two converter circuits 7 in parallel or only one converter circuit 7.

[0033] 14, the converter circuits 7(1) of the converter units 23U, 23V, and 23W operate in the same manner as in the first embodiment. In the three-phase PFC mode, two to four converter circuits 7 may also be operated in parallel. However, accordingly, first relays corresponding to the first relays S21 to S23 must be arranged according to the converter circuits 7 used in parallel.

[0034] As described above, according to the second embodiment, the power conversion unit 22 includes four converter circuits 7 connected in parallel for each phase. When operating in inverter mode, the control unit 24 controls the switching of the four parallel converter circuits, and when operating in boost converter mode, the control unit 24 controls the switching of, for example, three parallel converter circuits 7. When operating in three-phase PFC mode, the control unit 24 controls the switching of, for example, one converter circuit 7 for each phase. The first relays S21 to S23 are connected corresponding to the converter circuit 7(1) operated in three-phase PFC mode.

[0035] As a result, in inverter mode, ripple in the current input to the motor 1 can be further suppressed, reducing losses. In boost converter mode and three-phase PFC mode, for example, by selecting one of the i parallel converter circuits 7 and controlling its switching, the operating frequency and control method can be determined independently. In addition, the characteristics of the FETs 8 and 9 and the constants of the inductor 10 and capacitor 11 can be set for each converter circuit 7.

[0036] In addition, when the battery 2 is charged by a commercial AC power supply, the first relays S21 to S23 for preventing the rotation of the motor 1 are connected in correspondence with the converter circuit 7(1) that operates in three-phase PFC mode, thereby suppressing an increase in the physical size.

[0037] (Third and fourth embodiments) The third and fourth embodiments shown in Figs. 15 to 17 show modified examples of switching control when the configuration of the second embodiment is operated in inverter mode. Fig. 15 shows a number of current control methods when switching the converter circuit 7. The current continuous operation method is the same as that shown in Fig. 10. The current discontinuous operation method is a method in which the current ΔI L is set to zero level every time it is switched, and the switching frequency f sw The current boundary operation method is a method of fixing the switching frequency f sw This is a method of controlling the current by varying the on-time of the FET.

[0038] 16, the output currents are synthesized by setting the control of each of the converter circuits 7(1) to 7(4) as follows: The average values ​​of the current amplitudes are all relative values ​​of "1". Converter circuit 7(1): Continuous current operation, relatively high switching frequency. Converter circuit 7(2): Discontinuous current operation, switching frequency is relatively low. Converter circuit 7(3): Similar to converter circuit 7(2), it reverses the phase of the current waveform. Converter circuit 7(4): Similar to converter circuit 7(1), it reverses the phase of the current waveform. As a result of combining these controls, the ripple of the output current (I1+I2+I3+I4) is reduced.

[0039] 17, the output currents are combined by setting the control of each of the converter circuits 7(1) to 7(4) as follows: All of the converter circuits operate continuously and have the same switching frequency. Converter circuit 7(1): Average current amplitude = 0.6 Converter circuit 7(2): Average current amplitude = 1.5 Converter circuit 7(3): average current amplitude = 1.5, The current waveform is made to be in the opposite phase to that of the converter circuit 7(2). Converter circuit 7(4): average current amplitude = 0.4, The current waveform is made to be in the opposite phase to that of the converter circuit 7(1). As a result of combining these controls, the ripple of the output current (I1+I2+I3+I4) is reduced, similar to the third embodiment.

[0040] (Other embodiments) The number of converter circuits connected in parallel may be three or less or five or more. The converter circuit is not limited to a step-down type, but may be a step-up type or a step-up / step-down type. The converter circuit may be either a non-insulated type or an isolated type. The upper and lower arm switches are not limited to MOSFETs, but may be, for example, IGBTs or the like.

[0041] 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]

[0042] In the drawings, 1 indicates a motor / generator, 2 indicates a battery, 4 indicates a power conversion unit, 7 indicates a converter circuit, 8 and 9 indicate MOSFETs, 10 indicates an inductor, 11 indicates a capacitor, 12 indicates wiring, 14 indicates a commercial AC power supply, 17 indicates a DC fast charger, 19 indicates a control unit, 21 indicates a power conversion device, S21 to S23 indicate first relays, and S31 and S32 indicate second relays.

Claims

1. A three-phase motor (1) that drives the vehicle is driven by a battery (2) mounted on the vehicle as a driving power source, a power conversion unit (4, 22) including a three-phase converter circuit (7U to 7W, 23U to 23W) having upper and lower arm switches (8, 9) for each phase, and a series circuit of an inductor (10) and a capacitor (11) connected in parallel to the lower arm switch, with a common connection point of the inductor and the capacitor serving as an output terminal for each phase; a first relay (S21 to S23) connected between the output terminal and each phase winding terminal of the motor; AC charging wiring (12U to 12W) connecting a commercial AC power source (14) and the output terminals to charge the battery; a second relay (S31, S32) connected between an external DC quick charger (17) for charging the battery, one of the phases of the output terminal, and the ground of the converter circuit; a control unit (19, 24) that switches the operation mode of the power conversion unit between an inverter mode, a boost converter mode, and a three-phase power factor correction mode.

2. The power conversion unit (22) includes n converter circuits connected in parallel for each phase, When the control unit (24) is operated in the inverter mode, it controls the switching of the n parallel converter circuits, When operating in the boost converter mode, one or i (i<n) parallel converter circuits are switched and controlled; When operating in the three-phase power factor correction mode, one or j (j<n) parallel converter circuits are switched and controlled; The power conversion device according to claim 1 , wherein the first relay is connected to correspond to a converter circuit that is to be operated in the three-phase power factor correction mode.

3. 3. The power conversion device according to claim 2, wherein, when the control unit operates in the inverter mode, the control unit controls switching of the n parallel converter circuits by imparting a phase difference to each of the n parallel converter circuits.

4. 4. The power conversion device according to claim 2 or 3, wherein when the control unit operates the power conversion unit in the inverter mode, the control unit controls the i converter circuits operated in the boost converter mode, the j (j<n and (i+j)<n} converter circuits operated in the three-phase power factor correction mode, and the {n-(i+j)} converter circuits operated only in the inverter mode so that one or more of an output current, a switching frequency, and a current control method are different for each of them.

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