Power conversion device and drive system

Abstract

A power conversion device 1 comprises: a converter 4 configured to be capable of selectively executing an operation for stepping up or stepping down DC power and outputting the DC power to an inverter, and an operation for outputting DC power to the inverter; the inverter 5 for converting the DC power input from the converter 4 into AC power and outputting the AC power to a rotary machine 3; a converter operation determination unit B1 for, according to an operation point of the rotary machine 3, determining an operation of the converter on the basis of each of a loss of the converter, a loss of the inverter 5, and a loss of the rotary machine 3 at the operation point; and a converter operation control unit B2 for controlling an operation of the converter 4 according to the determination of the converter operation determination unit B1.

Description

Power conversion device and drive system

[0001] The present disclosure relates to a power conversion device and a drive system.

[0002] Conventionally, electric vehicles are driven by rotating machines powered by AC power, which is obtained by converting DC power input from a DC power source such as a lithium-ion battery into AC power using an inverter. Rotating machines in electric vehicles are required to operate in a wide range of torque and rotational speeds to accommodate various driving modes. This wide range of torque and rotational speed requirements also includes driving the rotating machine at high rotation speeds and high torque. Because the back electromotive force increases with increasing rotational speed, driving a rotating machine at high rotation speeds and high torque requires the rotating machine to be driven at a high voltage, which may be higher than the output voltage of the power source. Furthermore, to extend the driving range of electric vehicles after charging the DC power source, it is necessary to reduce the energy consumption of the electric vehicle, which requires the rotating machine to operate efficiently. The combination of input voltage and current that efficiently drives a rotating machine varies depending on the operating point. When the input voltage to a rotating machine is lower than the input voltage that can efficiently drive the rotating machine, the current input to the rotating machine increases, resulting in increased copper loss in the rotating machine. Furthermore, if the input voltage to the rotating machine is higher than the input voltage that can drive the rotating machine efficiently, losses may increase due to iron loss occurring in the rotating machine or due to switching loss in the inverter.

[0003] As described above, there are cases where the voltage required to realize high torque at high rotational speeds required for a rotating machine is higher than the output voltage of a DC power supply, or where the voltage required to efficiently drive a rotating machine is higher or lower than the output voltage of the DC power supply. For this reason, Patent Document 1 proposes a power conversion device including a converter that performs a boost operation to boost the output power of the DC power supply and output it to an inverter at a desired voltage, a buck operation to lower the output power of the DC power supply and output it to the inverter at a desired voltage, and a direct-coupled operation to output the output power of the DC power supply directly to the inverter. The power output from the converter is converted by the inverter into AC power and output to the rotating machine. This power conversion device calculates an inverter input voltage at which the rotating machine is efficiently driven based on a torque command value and the rotational speed of the rotating machine, and controls the converter operation so that the converter output voltage becomes the calculated inverter input voltage, thereby ensuring torque at high rotational speeds of the rotating machine and efficiently driving the rotating machine.

[0004] International Publication No. 2003 / 015254

[0005] In the conventional power conversion device described above, the converter operation is controlled so that the converter outputs an inverter input voltage that efficiently drives the rotating machine. In a power conversion device that performs such control, for example, when the inverter input voltage that efficiently drives the rotating machine is slightly higher than the output voltage of the DC power supply, the converter is caused to perform a boost operation to increase the inverter input voltage. However, the boost operation of the converter generates switching losses, and the inverter switching losses increase with the increase in input voltage. In such a situation, by operating the converter directly rather than performing a boost operation, the combined loss of the rotating machine and the power conversion device may be reduced by suppressing the switching losses of the converter and inverter, even if the increase in input current slightly increases the loss of the rotating machine. Similarly, in a conventional power conversion device, when the inverter input voltage that efficiently drives the rotating machine is slightly lower than the output voltage of the DC power supply, the converter is caused to perform a buck operation to lower the inverter input voltage. However, the buck operation of the converter generates switching losses. In such a situation, by operating the converter in direct connection rather than stepping down, it may be possible to reduce the combined loss of the rotating machine and the loss of the power conversion device by suppressing the switching loss of the converter, even if the loss of the rotating machine or the loss of the inverter increases slightly due to the high inverter input voltage.

[0006] As described above, in the conventional power conversion device described above, the operation of the converter is controlled so that the converter outputs an inverter input voltage that drives the rotating machine efficiently. Therefore, even if the loss in the rotating machine is suppressed, the loss in the power conversion device increases, and the combined loss of the rotating machine and the loss in the power conversion device may become large, resulting in a problem that the rotating machine may not be driven efficiently.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a power conversion device and a drive system that can operate in a manner that suppresses the combined power loss of the rotating machine and the power loss of the power conversion device, in a power conversion device that converts DC power input from a DC power source into AC power and supplies it to a rotating machine.

[0008] The power conversion device according to the present disclosure includes a converter configured to be able to selectively perform an operation of stepping up or stepping down DC power input from a DC power source and outputting the DC power to an inverter, and an operation of outputting DC power input from the DC power source to the inverter; an inverter that converts the DC power input from the converter into AC power and outputs it to a rotating machine; an operation determination unit that determines the operation of the converter based on the loss of the converter, the loss of the inverter, and the loss of the rotating machine at an operating point of the rotating machine; and an operation control unit that controls the operation of the converter in accordance with the determination of the operation determination unit.

[0009] According to the present disclosure, the power conversion device is provided with an operation determination unit that determines the operation of the converter based on the converter losses, inverter losses, and rotating machine losses that occur at the operating point of the rotating machine, depending on the operating point of the rotating machine, and an operation control unit that controls the operation of the converter in accordance with the determination of the operation determination unit.Since the operation control unit can cause the converter to operate in a way that suppresses the total losses of the converter, inverter, and rotating machine, it is possible to obtain a power conversion device that can operate the converter to suppress power losses.

[0010] Schematic diagram showing a vehicle equipped with a power conversion device and a drive system according to the first embodiment. Configuration diagram showing the configuration of the drive system according to the first embodiment. Configuration diagram showing the hardware configuration of an ECU according to the first embodiment. Control block diagram of a power controller according to the first embodiment. Characteristic diagram showing the efficiency characteristics when the converter according to the first embodiment performs a step-up operation or a direct-coupled operation. Characteristic diagram showing the efficiency characteristics when the converter according to the first embodiment performs a step-down operation. Characteristic diagram showing the combined efficiency characteristics of the inverter and the rotating machine when the inverter input voltage is 200 V in the drive system according to the first embodiment. Characteristic diagram showing the combined efficiency characteristics of the inverter and the rotating machine when the inverter input voltage is 300 V in the drive system according to the first embodiment. a characteristic diagram showing the efficiency characteristics combined with the rotating machine; a schematic diagram showing a converter operation map according to the first embodiment; a flowchart showing the operation of the power conversion device according to the first embodiment; a flowchart showing the operation of the converter operation determination unit according to the first embodiment; a control block diagram of a power controller according to the second embodiment; a flowchart showing the operation of the converter operation determination unit according to the second embodiment; a control block diagram of a power controller according to the third embodiment; a flowchart showing the operation of the converter operation determination unit according to the third embodiment; a control block diagram of a power controller according to the fourth embodiment; a flowchart showing the operation of the converter operation determination unit according to the fourth embodiment; a schematic diagram showing a vehicle equipped with a power conversion device and a drive system according to the fifth embodiment; a configuration diagram showing the configuration of a drive system according to the fifth embodiment; and a flowchart showing the operation of the power conversion device according to the fifth embodiment.

[0011] Embodiment 1. The following describes the configuration of a power conversion device 1 according to Embodiment 1 and a drive system 100 using the power conversion device 1. Fig. 1 is a schematic diagram showing a vehicle 200, such as an electric vehicle, a hybrid electric vehicle, or a fuel cell vehicle, equipped with the power conversion device 1 and the drive system 100 according to Embodiment 1. The vehicle 200 includes a vehicle controller 300 that controls the running of the vehicle 200, and a drive system 100 that drives or brakes wheels 201 in accordance with a drive command 301 input from the vehicle controller 300. The drive system 100 drives or brakes the wheels 201 in accordance with the drive command 301 input from the vehicle controller 300, causing the vehicle 200 to run or brake. The drive system 100 includes a DC power source 2, a power conversion device 1 that converts DC power input from the DC power source 2 into AC power in accordance with the drive command 301 input from the vehicle controller 300 and outputs the converted power, and a rotating machine 3 that is drive-controlled by the AC power input from the power conversion device 1 and transmits power or braking force to the wheels 201.

[0012] 2 is a configuration diagram showing the configuration of a drive system 100 using the power conversion device 1. The DC power supply 2 is a secondary battery formed from a lithium-ion battery, a nickel-metal hydride battery, a supercapacitor, or the like. DC power output from the DC power supply 2 is input to the power conversion device 1. The rotating machine 3 is a permanent magnet synchronous machine and includes a rotation angle sensor 31 and a rotating machine temperature sensor 32. The rotation angle sensor 31 detects the rotation angle of a rotor (not shown) of the rotating machine 3 and outputs a rotation angle sensor signal 63a indicating the detected rotation angle. The rotating machine temperature sensor 32 detects the temperature of a stator (not shown) of the rotating machine 3 and outputs a rotating machine temperature sensor signal 63b indicating the detected temperature.

[0013] The power conversion device 1 converts DC power input from the DC power source 2 into AC power according to a drive command 301 input from the vehicle controller 300 and outputs the AC power to the rotating machine 3, thereby powering the rotating machine 3 and transmitting power to the wheels 201, thereby driving the wheels 201. The power conversion device 1 also charges the DC power source 2 by converting AC power input from the rotating machine 3 to DC power and outputting the DC power to the DC power source 2, while causing the rotating machine 3 to regenerate and transmitting braking force to the wheels 201, thereby braking the wheels 201.

[0014] The power conversion device 1 includes a power supply voltage sensor 7 and an input power smoothing capacitor 8 connected in parallel to the DC power supply 2, a converter 4 connected in parallel to the power supply voltage sensor 7 and the input power smoothing capacitor 8 and having power supply side connection terminals 40a connected to the positive and negative electrodes of the DC power supply 2, an intermediate power smoothing capacitor 9 and an intermediate voltage sensor 10 connected in parallel to an inverter side connection terminal 40b of the converter 4, an inverter 5 connected in parallel to the intermediate power smoothing capacitor 9 and the intermediate voltage sensor 10 and connected to the inverter side connection terminal 40b of the converter 4, current sensors 11u, 11v, and 11w connected to output terminals of the inverter 5 for the U phase, V phase, and W phase, respectively, and a power controller 6 that controls the operation of the converter 4 and the inverter 5 in accordance with a drive command 301 input from a vehicle controller 300. The power supply voltage sensor 7 detects the voltage of the DC power output from the DC power supply 2 and outputs a power supply voltage sensor signal 63c indicating the detected voltage to the power controller 6. Furthermore, intermediate voltage sensor 10 detects the voltage of DC power input to inverter 5, and outputs an intermediate voltage sensor signal 63d indicating the detected voltage to power controller 6. Current sensors 11u, 11v, and 11w detect the current values ​​of the AC power of the corresponding phases output from inverter 5, and output a current sensor signal 63e indicating the detected current values ​​to power controller 6.

[0015] Converter 4 is a bidirectional DC-DC converter, and its operation is controlled by power controller 6. When power conversion device 1 powers rotating machine 3, converter 4 performs a boost operation to boost DC power input from DC power supply 2 and output it at a desired voltage, a buck operation to lower DC power input from DC power supply 2 and output it at a desired voltage, and a direct-coupled operation to output the DC power input from DC power supply 2 as is. When power conversion device 1 powers rotating machine 3, converter 4 performs a boost operation to boost DC power input from inverter 5 and output it at a desired voltage, a buck operation to lower DC power input from inverter 5 and output it at a desired voltage, and a direct-coupled operation to output the DC power input from inverter 5 as is.

[0016] Converter 4 is a non-insulated converter including semiconductor switching elements 41a, 41b, 41c, and 41d configured in a full bridge configuration and a reactor 42 for voltage conversion. The semiconductor switching elements may be semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors) having three types of electrodes: gate, collector, and emitter. Semiconductor switching elements 41a to 41d in the first embodiment are generally configured using wide bandgap semiconductors such as SiC-MOSFETs, which generally have lower switching losses during switching operations than other semiconductor switching elements.

[0017] Specifically, inside the converter 4, a full bridge is configured in which a first arm 43a in which a semiconductor switching element 41a connected to the positive electrode of the DC power supply 2 and a semiconductor switching element 41b connected to the negative electrode of the DC power supply 2 are connected in series is connected, and a second arm 43b in which a semiconductor switching element 41c and a semiconductor switching element 41d connected to the negative electrode of the DC power supply 2 are connected in series is connected. The semiconductor switching elements 41a to 41d are provided with temperature sensors 47a to 47d that detect the temperatures of the respective semiconductor switching elements. The temperature sensors 47a to 47d output a temperature sensor signal 63f indicating the detected temperatures to the power controller 6.

[0018] Furthermore, reactor 42 of converter 4 has one end connected to the midpoint of the direct connection of first arm 43a, and the other end connected via current sensor 46 to the midpoint of the direct connection of second arm 43b. Current sensor 46 detects the current value of reactor 42, and outputs a current sensor signal 63g indicating the detected current value to power controller 6. Furthermore, reactor 42 is provided with temperature sensor 48 that detects the temperature of reactor 42, and temperature sensor 48 outputs a temperature sensor signal 63h indicating the detected temperature to power controller 6.

[0019] The inverter 5 converts DC power input from the converter 4 into AC power and outputs it. The inverter 5 has a half-bridge configuration in which a U-phase arm 52u in which semiconductor switching elements 51a and 51b are connected in series, a V-phase arm 52v in which semiconductor switching elements 51c and 51d are connected in series, and a W-phase arm 52w in which semiconductor switching elements 51e and 51f are connected in series are connected in parallel. The semiconductor switching elements included in the inverter 5 are semiconductor elements such as MOSFETs or IGBTs. In the first embodiment, the semiconductor switching elements 51a to 51f are generally configured as low-cost IGBTs. The U-phase arm 52u, the V-phase arm 52v, and the W-phase arm 52w are each connected in parallel to the inverter-side connection end 40b of the converter 4. The midpoint of the series connection of U-phase arm 52u, V-phase arm 52v, and W-phase arm 52w of inverter 5 is connected via current sensors 11u, 11v, and 11w to the coils (not shown) of the corresponding phases of rotating machine 3. Semiconductor switching elements 51a to 51f are provided with temperature sensors 54a to 54f that detect the temperatures of the respective semiconductor switching elements, and temperature sensors 54a to 54f output a temperature sensor signal 63j indicating the detected temperatures to power controller 6.

[0020] The power controller 6 controls the operation of the converter 4 and the inverter 5 in response to a drive command 301 input from the vehicle controller 300. The configuration of the power controller 6 will be described with reference to FIGS. 2, 3, and 4. The power controller 6 includes a drive circuit 61 and an ECU 62. The ECU 62 receives a rotation angle sensor signal 63a, a rotating machine temperature sensor signal 63b, a power supply voltage sensor signal 63c, an intermediate voltage sensor signal 63d, a current sensor signal 63e, a temperature sensor signal 63f, a current sensor signal 63g, a temperature sensor signal 63h, and a temperature sensor signal 63j. The ECU 62 generates and outputs a converter gate drive signal 63k that controls the operation of the converter 4. The converter gate drive signal 63k is amplified by the drive circuit 61 and then applied to the gates of the semiconductor switching elements 41a to 41d. The ECU 62 also generates and outputs an inverter gate drive signal 63m that controls the operation of the inverter 5, and this inverter gate drive signal 63m is amplified by the drive circuit 61 and then applied to the gates of the semiconductor switching elements 51a to 51f.

[0021] 3 is a configuration diagram showing the hardware configuration of the ECU 62 of the power controller 6. The ECU 62 includes a processor 64 and a storage device 65. The storage device 65 includes a volatile storage device 66 such as a random access memory, and a non-volatile auxiliary storage device 67 such as a flash memory. The processor 64 executes a program input from the auxiliary storage device 67 via the volatile storage device 66. The processor 64 outputs data such as calculation results to the volatile storage device 66 of the storage device 65. The processor 64 may also store data in the auxiliary storage device 67 via the volatile storage device 66.

[0022] 4 is a control block diagram showing the configuration of the power controller 6. A drive command 301 indicating a torque command value for the rotating machine 3 determined in response to accelerator work or brake work by the driver of the vehicle 200 is input from the vehicle controller 300 to the power controller 6. A rotation angle sensor signal 63a is also input from the rotating machine 3 to the power controller 6. The power controller 6 includes a rotation speed calculation unit B0 that calculates the rotation speed of the rotating machine 3, a converter operation determination unit B1 that determines the operation of the converter 4 in response to the drive command 301, a converter operation control unit B2 that controls the converter 4 in response to the determination by the converter operation determination unit B1, an inverter current command determination unit B3 that determines the current value and frequency of AC power output by the inverter 5 in response to the drive command 301, and an inverter operation control unit B4 that controls the inverter 5 in response to the determination by the inverter current command determination unit B3. In the first embodiment, the operation of converter 4 determined by converter operation determination unit B1 is a converter operation mode indicating any one of a boost operation in which DC power input from DC power supply 2 is boosted and output at a desired voltage, a buck operation in which DC power input from DC power supply 2 is reduced and output at a desired voltage, and a direct-coupled operation in which DC power input from DC power supply 2 is output as is, and a duty ratio when the converter operation mode is the boost operation or the buck operation.

[0023] A rotation angle sensor signal 63a output from the rotation angle sensor 31 is input to the rotation speed calculation unit B0. The rotation speed calculation unit B0 calculates the rotation speed of the rotating machine 3 based on the rotation angle indicated by the input rotation angle sensor signal 63a, and outputs a rotation speed signal 63n indicating the calculated rotation speed. This rotation speed signal 63n is input to the converter operation determination unit B1 and the inverter current command determination unit B3.

[0024] Converter operation determination unit B1 also receives as input a drive command 301 output from vehicle controller 300 and a power supply voltage sensor signal 63c output from power supply voltage sensor 7. Converter operation determination unit B1 determines a converter operation mode and duty ratio as the operation of converter 4 from the torque command value indicated in drive command 301, the rotation speed indicated in rotation speed signal 63n, and the power supply voltage, which is the output voltage of DC power supply 2, indicated in power supply voltage sensor signal 63c, and outputs a converter operation command 63p indicating the determined converter operation mode and duty ratio. This converter operation command 63p is input to converter operation control unit B2. Here, the converter operation mode is one of a first mode in which the voltage at the inverter side connection end 40b is higher than that at the power supply side connection end 40a, a second mode in which the voltage at the inverter side connection end 40b is lower than that at the power supply side connection end 40a, and a third mode in which the voltages at the power supply side connection end 40a and the inverter side connection end 40b are equal. When the power conversion device 1 powers the rotating machine 3, the first mode is step-up operation, the second mode is step-down operation, and the third mode is direct-coupled operation. When the power conversion device 1 powers the rotating machine 3, the first mode is step-down operation, the second mode is step-up operation, and the third mode is direct-coupled operation. Also, a current sensor signal 63g output from the current sensor 46 and an intermediate voltage sensor signal 63d output from the intermediate voltage sensor 10 are input to the converter operation control unit B2. The converter operation control unit B2 generates and outputs a converter gate drive signal 63k for controlling the operation of the converter 4, based on the converter operation mode and duty ratio indicated in the converter operation command 63p, the current value of the reactor 42 indicated in the current sensor signal 63g, and the inverter input voltage indicated in the intermediate voltage sensor signal 63d. This converter gate drive signal 63k is output to the converter 4.

[0025] The inverter current command determiner B3 receives a drive command 301 output from the vehicle controller 300 and an intermediate voltage sensor signal 63d output from the intermediate voltage sensor 10. The inverter current command determiner B3 determines the current value and frequency of the AC power output by the inverter 5 based on the torque command value indicated in the drive command 301, the rotational speed indicated in the rotational speed signal 63n, and the inverter input voltage indicated in the intermediate voltage sensor signal 63d, and outputs an inverter current command 63q indicating the determined current value and frequency. The inverter current command 63q is also input to the inverter operation controller B4. The inverter operation controller B4 also receives a current sensor signal 63e output from the current sensors 11u, 11v, and 11w. The inverter operation controller B4 generates and outputs an inverter gate drive signal 63m based on the current value and frequency indicated in the inverter current command 63q and the output current values ​​of each phase of the inverter 5 indicated in the current sensor signal 63e. This inverter gate drive signal 63 m is input to the inverter 5 .

[0026] Here, a configuration for the converter operation determination unit B1 to determine the operation of the converter 4 will be described. The auxiliary storage device 67 stores a drive lower limit voltage map M1. The drive lower limit voltage map M1 is a lookup table showing the correspondence between an operating point specified by a torque command value and a rotational speed and a lower limit value of the inverter input voltage required to drive the rotating machine 3 at that operating point. The auxiliary storage device 67 also stores a converter operation map M2. The converter operation map M2 is a lookup table showing the correspondence between an operating point specified by a power supply voltage, a torque command value, and a rotational speed, a converter operation mode indicating step-up operation, step-down operation, or direct-coupled operation corresponding to that operating point and power supply voltage, and a duty ratio for the step-up operation or step-down operation. The converter operation mode and duty ratio in the converter operation map M2 are the converter operation mode and duty ratio for step-up operation or step-down operation that minimizes the total loss of the rotating machine 3, the converter 4, and the inverter 5 at each operating point and power supply voltage.

[0027] Here, a method for determining the converter operation mode and duty ratio in the converter operation map M2 will be described with reference to FIGS. 5 to 10 . FIG. 5 shows the efficiency characteristics of converter 4 when converter 4 is in direct-connection operation and when converter 4 is in step-up operation in drive system 100 according to the first embodiment when the power supply voltage is 300 V. FIG. 6 shows the efficiency characteristics of converter 4 when converter 4 is in step-down operation when the power supply voltage is 300 V. In FIGS. 5 and 6 , the vertical axis of the graph represents the efficiency of converter 4, and the horizontal axis represents the input power input to converter 4 from DC power supply 2. As shown in FIGS. 5 and 6 , converter 4 is less efficient and experiences increased losses during step-up and step-down operation than during direct-connection operation. This increase in loss is due to switching losses caused by the switching operations of semiconductor switching elements 41 a to 41 d during step-up and step-down operation. Regarding losses in converter 4, switching losses increase as the switching voltage increases, and conduction losses increase as the current value increases. For this reason, in the step-up operation and step-down operation of converter 4, in the region where the output power is low, the current value is small and the effect of switching loss on efficiency is large, so switching at a low voltage increases the efficiency of converter 4. Conversely, in the region where the output power is high, in the step-up operation and step-down operation of converter 4, the current value is large and the effect of conduction loss on efficiency is large, so switching at a high voltage increases the efficiency of converter 4 because the current value can be reduced.

[0028] 7, 8, and 9 show the combined efficiency characteristics of the inverter 5 and the rotating machine 3 in the drive system 100 according to the first embodiment when the inverter input voltage is 200 V, 300 V, and 400 V, respectively. As shown in FIGS. 7 to 9, the higher the inverter input voltage, the higher the combined efficiency of the inverter 5 and the rotating machine 3 at a high-torque, high-rotation-speed operating point. This is because flux weakening is no longer necessary to suppress the induced voltage in the rotating machine 3, which increases as the rotation speed increases, and the current value flowing through the inverter 5 and the rotating machine 3 can be reduced. Conversely, at an operating point with low torque and low rotation speed, the effects of switching loss in the switching operation of the semiconductor switching elements 51a to 51f of the inverter 5 and iron loss in the rotating machine 3 become significant. Therefore, at a low-torque, low-rotation-speed operating point, the higher the inverter input voltage, the higher the switching loss in the inverter 5 and iron loss in the rotating machine 3, and the lower the combined efficiency of the inverter 5 and the rotating machine 3.

[0029] The efficiency characteristics of the converter 4 shown in FIGS. 5 and 6 and the efficiency characteristics of the inverter 5 and the rotating machine 3 shown in FIGS. 7 to 9 are obtained by simulation or experiments using a drive system with the same specifications. From the efficiency characteristics of the converter 4 shown in FIGS. 5 and 6 and the efficiency characteristics of the inverter 5 and the rotating machine 3 shown in FIGS. 7 to 9, the losses generated in the converter 4, the inverter 5, and the rotating machine 3 at each inverter input voltage are obtained by varying the converter operation mode and duty ratio of the converter 4 for each combination of torque command value, rotational speed, and power supply voltage. The converter operation map M2 is a table created from the losses obtained in this manner, which shows which converter operation mode and duty ratio are suitable for driving the rotating machine 3 in the drive system 100 by minimizing the total losses in the converter 4, the inverter 5, and the rotating machine 3 for each combination of torque command value, rotational speed, and power supply voltage. This converter operation map M2 is stored in the auxiliary storage device 67.

[0030] An overview of the converter operation map M2 thus obtained is shown in FIG. 10 . FIG. 10 shows which converter operation mode and duty ratio are suitable for a combination of an operating point, i.e., a torque command value and a rotational speed, when the power supply voltage is set to a predetermined value. In FIG. 10 , the region where the torque command value is positive indicates the case where the rotating machine 3 is powered, and the region where the torque command value is negative indicates the case where the rotating machine 3 is regenerated. For example, when the power conversion device 1 powers the rotating machine 3, if a point specified by the torque command value and the rotational speed is located in the second mode region M2c, selecting the second mode (step-down operation) as the converter operation mode and the duty ratio at that point indicates that the total loss of the converter 4, the inverter 5, and the rotating machine 3 is smaller than that of the first mode (step-up operation), the third mode (direct-coupled operation), or the second mode (step-down operation) at another duty ratio. Here, FIG. 5 shows converter operation modes and duty ratios corresponding to a predetermined power supply voltage, but the converter operation map M2 also contains a table of converter operation modes and duty ratios corresponding to a plurality of different power supply voltage values.

[0031] Next, an operation of the drive system 100 of the first embodiment configured as described above when the power conversion device 1 powers or regenerates the rotating machine 3 will be described with reference to Fig. 11 . When the power conversion device 1 powers the rotating machine 3, the power conversion device 1 converts DC power output from the DC power supply 2 into AC power of a desired voltage and outputs the AC power to the rotating machine 3, thereby powering the rotating machine 3. When the power conversion device 1 powers the rotating machine 3, the power conversion device 1 converts AC power input from the rotating machine 3 into DC power of a desired voltage and outputs the DC power to the DC power supply 2, thereby causing the rotating machine 3 to regenerate and charging the DC power supply 2.

[0032] FIG. 11 is a flowchart illustrating the operation of the power conversion device 1 in the drive system 100 according to the first embodiment when the power conversion device 1 powers or regenerates the rotating machine 3. When the power conversion device 1 starts powering or regenerating the rotating machine 3, the vehicle controller 300 first inputs a torque command value as a drive command 301 to the rotating machine 3 (step S01). Here, the drive command 301 is a drive command for powering the rotating machine 3 when the torque command value is positive, and conversely, is a drive command for regenerating the rotating machine 3 when the torque command value is negative. Next, the rotational speed calculation unit B0 calculates the rotational speed of the rotating machine 3 (step S02). Next, the converter operation determination unit B1 determines the operation of the converter 4 (step S03). Next, the converter 4 is controlled by the converter operation control unit B2 according to the operation of the converter 4 determined in step S02 (step S04). Next, the inverter current command determination unit B3 determines a current command for the inverter 5 (step S05). Next, the inverter operation control unit B4 controls the inverter 5 in accordance with the current command determined in step S05 (step S06).

[0033] The operation of this flowchart causes the rotating machine 3 to perform power running or regeneration. Next, the operation of each step will be described in detail. FIG. 12 is a flowchart showing the operation of the converter operation determination unit B1 in step S03 to determine the operation of the converter 4. The processing of FIG. 12 is executed periodically. When the operation to determine the operation of the converter 4 is started, first, a torque command value for the rotating machine 3 is input from the vehicle controller 300 to the converter operation determination unit B1 (step S07). Next, the rotation speed of the rotating machine 3 is input from the rotation speed calculation unit B0 to the converter operation determination unit B1 (step S08). Next, the converter operation determination unit B1 refers to a drive lower limit voltage map M1 and determines a drive lower limit voltage V corresponding to the torque command value and rotation speed input in steps S07 and S08. ｍｉｎ Next, the power supply voltage V, which is the output voltage of the DC power supply 2, is read from the power supply voltage sensor 7 (step S09). BNext, the converter operation determination unit B1 refers to the converter operation map M2 and determines the torque command value, the rotation speed, and the power supply voltage V B and reads out the converter operation mode corresponding to the duty ratio D when the converter operation mode is the step-up operation or the step-down operation. ｃｎｖ (Step S11). Here, the duty ratio D ｃｎｖ is the power supply voltage V applied to the power supply side connection terminal 40a of the converter 4. B The inverter input voltage V applied to the inverter side connection terminal 40b of the converter 4, ｉｎｖ The ratio (V ｉｎｖ / V B Next, the converter operation determination unit B1 determines the power supply voltage and the converter operation mode, and further determines the duty ratio D ｃｎｖ From the target voltage V ｃｎｖ Next, the converter operation determination unit B1 calculates the target voltage V ｃｎｖ and the driving lower limit voltage V ｍｉｎ and the target voltage V ｃｎｖ is the driving lower limit voltage V ｍｉｎ It is determined whether the target voltage V ｃｎｖ is the driving lower limit voltage V ｍｉｎ If it is equal to or greater than this (step S13: YES), the inverter input voltage V ｉｎｖ is the target voltage V ｃｎｖ After step S14, the converter operation determination unit B1 determines the converter operation mode and duty ratio D ｃｎｖ is output as a converter operation command 63p to the converter operation control unit B2 (step S16). ｃｎｖ is the driving lower limit voltage V ｍｉｎ If it is determined that the voltage is not equal to or greater than the target voltage V ｃｎｖ is the driving lower limit voltage V ｍｉｎ When the inverter input voltage V ｉｎｖ is the driving voltage lower limit V ｍｉｎAfter step S15, the converter operation determination unit B1 determines the driving lower limit voltage V ｍｉｎ The inverter input voltage V ｉｎｖ Duty ratio D according to ｃｎｖ power supply voltage V B The calculated duty ratio D ｃｎｖ Then, the converter operation determination unit B1 reselects the converter operation mode corresponding to the converter operation mode and the duty ratio D ｃｎｖ is output as a converter operation command 63p to the converter operation control section B2 (step S17).

[0034] Next, the control of the converter 4 executed by the converter operation control unit B2 in step S04 will be described.

[0035] The operation of the converter operation control unit B2 when the converter operation mode determined by the operation of determining the operation of the converter 4 (step S03) is the first mode will be described. Here, the ratio of the ON time to the switching period of the semiconductor switching element 41a is set to D Ｂ and the ratio of the ON time to the switching period of the semiconductor switching element 41d is D Ｆ When the converter operation mode is the first mode, D Ｂ = 1, the semiconductor switching element 41a is kept in the ON state, the semiconductor switching element 41b is kept in the OFF state, and the duty ratio D ｃｎｖ Depending on D Ｆ and causes the semiconductor switching elements 41c and 41d to turn on and off, thereby operating the converter 4. Ｆ is the duty ratio D ｃｎｖ and D Ｆ It is calculated from the formula (1) which shows the relationship:

[0036] The converter operation control unit B2 determines the duty ratio D ｃｎｖ is applied to equation (1), and the duty ratio D ｃｎｖ D for converter 4 to operate ＦThe converter 4 is controlled by generating and outputting a converter gate drive signal 63k.

[0037] In this case, in the converter 4, the semiconductor switching element 41a is held in the ON state, the semiconductor switching element 41b is held in the OFF state, and the semiconductor switching elements 41c and 41d perform ON / OFF operation. By this ON / OFF operation, when the rotating machine 3 is powered by using the energy held in the reactor 42, the DC power input from the DC power supply 2 is boosted and output to the inverter 5. When the rotating machine 3 is to be regenerated, the DC power input from the inverter 5 is reduced and output to the DC power supply 2. Here, the input power smoothing capacitor 8 and the intermediate power smoothing capacitor 9 smooth the current ripple generated by the ON / OFF operation of the semiconductor switching elements 41c and 41d, respectively.

[0038] Next, the operation of the converter operation control unit B2 when the converter operation mode is the second mode will be described. Ｆ = 0, the semiconductor switching element 41c is kept in the ON state, the semiconductor switching element 41d is kept in the OFF state, and the duty ratio D ｃｎｖ Depending on D Ｂ and turns on and off the semiconductor switching elements 41a and 41b to operate the converter 4. Ｂ is the duty ratio D ｃｎｖ and D Ｂ It is calculated from the formula (2) which shows the relationship:

[0039] The converter operation control unit B2 determines the duty ratio D ｃｎｖ is applied to equation (2), and the duty ratio D ｃｎｖ D for converter 4 to operate Ｂ The converter 4 is controlled by generating and outputting a converter gate drive signal 63k.

[0040] In this case, in converter 4, semiconductor switching element 41c is held in the ON state, semiconductor switching element 41d is held in the OFF state, and semiconductor switching elements 41a and 41b perform ON / OFF operation. By this ON / OFF operation, when powering rotating machine 3 using energy held in reactor 42, DC power input from DC power supply 2 is stepped down and output to inverter 5. When powering rotating machine 3, DC power input from inverter 5 is stepped up and output to DC power supply 2. Here, input power smoothing capacitor 8 and intermediate power smoothing capacitor 9 smooth current ripples generated by the ON / OFF operation of semiconductor switching elements 41a and 41b, respectively.

[0041] Next, the operation of the converter operation control unit B2 when the converter operation mode is the third mode will be described. Ｂ = 1, the semiconductor switching element 41a is kept in the ON state, and the semiconductor switching element 41b is kept in the OFF state. Ｆ = 0, so that the semiconductor switching element 41c is kept in the ON state and the semiconductor switching element 41d is kept in the OFF state. In this case, the converter 4 outputs the DC power input from the DC power supply 2 as is to the inverter 5 when the DC power from the DC power supply 2 is to power the rotating machine 3 via the semiconductor switching element 41a in the ON state, the reactor 42, and the semiconductor switching element 41c in the ON state, and outputs the DC power input from the inverter 5 as is to the DC power supply 2 when the rotating machine 3 is to be regenerated.

[0042] The operation of the inverter current command determination unit B3 to determine the current command for the inverter 5 in step S05 and the operation of the inverter operation control unit B4 to control the inverter 5 in step S06 are vector control of a typical permanent magnet synchronous machine.

[0043] As described above, the power conversion device 1 according to the first embodiment includes a converter operation determination unit B1 that determines the operation of the converter 4 based on the loss of the converter 4, the loss of the inverter 5, and the loss of the rotating machine 3 that occur at an operating point of the rotating machine 3, and a converter operation control unit B2 that controls the operation of the converter 4 in accordance with the determination by the converter operation determination unit B1, so that the converter operation control unit B2 can cause the converter 4 to operate in a manner that suppresses the total loss of the converter 4, the inverter 5, and the rotating machine 3. Furthermore, in the power conversion device 1 according to the first embodiment, the power controller 6 holds a converter operation map M2 that indicates a converter operation mode and a duty ratio appropriate for driving the rotating machine 3 based on the losses of the converter 4, the inverter 5, and the rotating machine 3 that correspond to the power supply voltage and the operating point, which have been obtained in advance by simulation or experiment, and the power controller 6 refers to this converter operation map M2 using the converter operation determination unit B1 to determine a converter operation mode and a duty ratio that will reduce the total loss of the converter 4, the inverter 5, and the rotating machine 3 at the operating point when driving the rotating machine 3, and causes the converter 4 to operate in that converter operation mode and duty ratio. This reduces the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, compared to when only the loss of the rotating machine 3 is considered, and makes it possible to suppress the loss generated in the drive system 100 when the rotating machine 3 is powered or regenerated. Here, the converter operation mode and duty ratio shown in the converter operation map M2 can be most effective in suppressing the loss generated in the drive system 100 when the power conversion device 1 powers or regenerates the rotating machine 3, when the converter operation mode and duty ratio at the corresponding operating point and power supply voltage are such that the total loss generated in the converter 4, the inverter 5, and the rotating machine 3 is minimized at that operating point and power supply voltage.

[0044] Furthermore, the converter operation determination unit B1 determines the converter operation mode and duty ratio according to the power supply voltage and operating point by referring to the converter operation map M2, which is a lookup table that shows the converter operation mode and duty ratio appropriate for driving the rotating machine 3 based on the losses in the converter 4, inverter 5, and rotating machine 3 corresponding to the power supply voltage and operating point, so the processing load for the operation of determining the operation of the converter 4 can be reduced compared to when the converter operation mode and duty ratio are determined by inputting the power supply voltage and operating point into a calculation formula. Furthermore, even for drive systems with different specifications, the process of determining the operation of the converter 4 can be executed by the same program by referring to the converter operation map M2 tailored to the drive system, so the cost of changing the program for the process of determining the operation of the converter 4 to suit the specifications of the drive system can be reduced.

[0045] Furthermore, since the drive system 100 according to the first embodiment is mounted on the vehicle 200, the power conversion device 1 according to the first embodiment can suppress losses that occur when driving the rotating machine 3, and can reduce consumption of the power charged in the DC power source 2, thereby extending the cruising range of the vehicle 200.

[0046] Furthermore, converter 4 is a bidirectional DC-DC converter, and when power conversion device 1 causes rotating machine 3 to regenerate, the voltage input to power conversion device 1 from rotating machine 3 can be input to DC power supply 2 at a desired voltage to charge DC power supply 2. In power conversion device 1 according to embodiment 1, even when causing rotating machine 3 to regenerate, power controller 6 uses converter operation determination unit B1 to refer to converter operation map M2, determines a converter operation mode and duty ratio that reduce the total loss of converter 4, inverter 5, and rotating machine 3 at that operating point, and operates converter 4 at that converter operation mode and duty ratio, thereby suppressing losses generated in drive system 100 when rotating machine 3 is caused to regenerate, and enabling efficient charging of DC power supply 2.

[0047] Furthermore, because the DC power supply 2 is a secondary battery, the voltage of the DC power it outputs varies depending on the state of charge. For example, if the DC power supply 2 is a lithium-ion battery, the voltage varies depending on the state of charge, with the voltage range being 2.7 V to 4.2 V per cell. For this reason, if the power supply voltage is directly converted into AC power and output to the rotating machine 3, the upper limit of the output when driving the rotating machine 3 may decrease depending on the state of charge. Furthermore, the power supply voltage may vary depending on the state of charge, causing the inverter 5 and the rotating machine 3 to be driven at a voltage different from the voltage suitable for operating the inverter 5 or driving the rotating machine 3, which may result in increased losses when driving the rotating machine 3. However, in the power conversion device 1 according to the first embodiment, the converter 4 performs any one of a boost operation in which the converter 4 boosts the DC power input from the DC power supply 2 and outputs it at a desired voltage, a step-down operation in which the converter 4 steps down the DC power input from the DC power supply 2 and outputs it at a desired voltage, and a direct-coupled operation in which the converter 4 outputs the DC power input from the DC power supply 2 as is, thereby making it possible to output AC power of a desired voltage to the rotating machine 3. Therefore, even if the power supply voltage of the DC power supply 2 fluctuates, the output of the rotating machine 3 can be ensured, the rotating machine 3 can be driven at high rotation speed and high torque, and an increase in loss occurring in the drive system 100 due to fluctuations in the power supply voltage can be suppressed. Therefore, in the drive system 100 according to the first embodiment mounted on the vehicle 200, the rotating machine 3 can be driven at high rotation speed and high torque, and the vehicle 200 can be driven in various driving modes.

[0048] Furthermore, the semiconductor switching elements 41a to 41d included in the converter 4 of the power conversion device 1 according to the first embodiment are configured with wide bandgap semiconductors. Wide bandgap semiconductors such as SiC-MOSFETs are generally able to suppress switching losses during switching operations compared to other semiconductor switching elements. This allows for suppression of losses that occur when the converter 4 performs step-up or step-down operations. Furthermore, the semiconductor switching elements 51a to 51f included in the inverter 5 of the power conversion device 1 according to the first embodiment are configured with IGBTs. IGBTs are generally low-cost, but have larger switching losses due to switching operations compared to other semiconductor elements such as MOSFETs or wide bandgap semiconductors. Therefore, when the semiconductor switching elements 51a to 51f are configured with IGBTs, the deterioration of losses in the inverter 5 associated with an increase in the inverter input voltage becomes greater compared to when the semiconductor switching elements 51a to 51f are configured with other semiconductor elements such as MOSFETs or wide bandgap semiconductors. However, in the power conversion device 1 of the first embodiment, the converter operation determination unit B1 determines a converter operation that reduces the total loss of the converter 4, the inverter 5, and the rotating machine 3, and the converter 4 is controlled in accordance with the determination to output an inverter input voltage appropriate for driving the rotating machine 3, thereby suppressing losses that occur in the drive system 100 when driving the rotating machine 3. Therefore, even if the semiconductor switching elements 51a to 51f are configured with IGBTs, losses that occur in the drive system 100 when driving the rotating machine 3 can be suppressed, thereby reducing the manufacturing cost of the power conversion device 1. As described above, when the semiconductor switching elements 51a to 51f are configured with IGBTs, the influence of the inverter input voltage on losses in the inverter 5 becomes greater, and therefore the power conversion device 1 according to the first embodiment can more effectively suppress losses that occur in the drive system 100 when the rotating machine 3 is powered or regenerated.

[0049] In the first embodiment, the semiconductor switching elements 41a to 41d included in the converter 4 are configured using wide bandgap semiconductors. However, the semiconductor switching elements 41a to 41d may be configured using IGBTs. When the semiconductor switching elements 41a to 41d are configured using IGBTs, the manufacturing cost of the power conversion device 1 can be reduced compared to when the semiconductor switching elements 41a to 41d are configured using MOSFETs or wide bandgap semiconductors. However, the switching loss due to the switching operation when the converter 4 performs step-up or step-down operation increases. However, in the power conversion device 1 of the first embodiment, the converter operation determination unit B1 determines a converter operation that reduces the total loss of the converter 4, the inverter 5, and the rotating machine 3. The converter 4 is controlled in accordance with the determination, thereby reducing the loss generated in the drive system 100 when driving the rotating machine 3. Therefore, even when the semiconductor switching elements 41a to 41d are configured using IGBTs, the loss generated in the drive system 100 when driving the rotating machine 3 can be reduced. Therefore, the manufacturing cost of the power conversion device 1 can be reduced by using IGBTs for the semiconductor switching elements 41a to 41d.

[0050] Embodiment 2 In Embodiment 1, converter operation determination unit B1 determines the operation of converter 4 in accordance with an operating point indicated by the power supply voltage, torque command value, and rotation speed so as to reduce the total loss in converter 4, inverter 5, and rotating machine 3 at the power supply voltage and operating point. In contrast, converter operation determination unit B1 may be input with temperature information of converter 4, temperature information of inverter 5, and temperature information of rotating machine 3 in addition to the power supply voltage, operating point indicated by the torque command value, and rotation speed, so that converter operation determination unit B1 determines the operation of converter 4 in accordance with the power supply voltage, operating point, temperature information of converter 4, temperature information of inverter 5, and temperature information of rotating machine 3 so as to reduce the total loss in converter 4, inverter 5, and rotating machine 3.

[0051] 13 is a control block diagram showing the configuration of a power conversion device 1 according to the second embodiment. In the power conversion device 1 according to the second embodiment, a power supply voltage sensor signal 63c indicating the power supply voltage, a rotational speed signal 63n indicating the rotational speed, and a drive command 301 indicating a torque command value are input to a converter operation determination unit B1. Further, a rotating machine temperature sensor signal 63b indicating the stator temperature of the rotating machine 3 from the rotating machine temperature sensor 32, a temperature sensor signal 63h indicating the reactor temperature of the reactor 42 from the temperature sensor 43, a temperature sensor signal 63f indicating the converter element temperatures of the semiconductor switching elements 41a to 41d from the temperature sensors 47a to 47d, and a temperature sensor signal 63j indicating the temperatures of the semiconductor switching elements 51a to 51f from the temperature sensors 54a to 54f are input to the converter operation determination unit B1.

[0052] A converter operation map M3 is stored in the auxiliary storage device 67 of the power controller 6. The converter operation map M3 is a lookup table showing the correspondence between the operating point indicated by the torque command value and the rotational speed, the power supply voltage, and each temperature information, and the converter operation mode and duty ratio. The converter operation mode and duty ratio in this converter operation map M3 are the converter operation mode and duty ratio in voltage step-up operation or voltage step-down operation that minimizes the total loss of the rotating machine 3, the converter 4, and the inverter 5 for each operating point, power supply voltage, and temperature information. Like the converter operation map M2 in the first embodiment, the converter operation map M3 is obtained in advance by simulation or experiment using a drive system with the same specifications. Other configurations are the same as those of the power conversion device 1 according to the first embodiment shown in FIG. 4.

[0053] An operation of the power conversion device 1 of the second embodiment configured as described above to power or regenerate the rotating machine 3 will be described. Fig. 14 is a flowchart showing an operation of the converter operation determination unit B1 of the second embodiment to determine the operation of the converter 4 in step S03. In the power conversion device 1 of the second embodiment, when the operation of determining the operation of the converter 4 by the converter operation determination unit B1 is started, a torque command value and a rotation speed are input to the converter operation determination unit B1 as in the first embodiment (steps S18 and S19), and then the converter operation determination unit B1 determines the driving lower limit voltage V from the driving lower limit voltage map M1. ｍｉｎ (step S20), and the power supply voltage is input to the converter operation determination unit B1 (step S21). Then, the stator temperature, converter element temperature, reactor temperature, and inverter element temperature are further input to the converter operation determination unit B1 (step S22). Then, the converter operation determination unit B1 refers to the converter operation map M3 and reads out the converter operation mode and duty ratio corresponding to the power supply voltage, operating point, and each piece of temperature information input in step S22 (step S23). Regarding the processing after step S23 in the second embodiment, the converter operation determination unit B1 performs the same processing as in the first embodiment, and determines the converter operation mode and duty ratio D that indicate the operation of the converter 4. ｃｎｖ to the converter operation control unit B2 (steps S24 to S29). The power conversion device 1 in the second embodiment performs the same operations as the power conversion device 1 in the first embodiment, except for the operation of determining the operation of the converter 4 (step S03).

[0054] In this case, as in the first embodiment, the converter operation control unit B2 can cause the converter 4 to operate in such a way as to reduce the total loss of the converter 4, the inverter 5, and the rotating machine 3. Furthermore, by reducing the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, it is possible to reduce the loss generated in the drive system 100 when driving the rotating machine 3. Furthermore, the efficiency characteristics of the converter 4 vary depending on the temperature of the semiconductor switching elements 41a to 41d of the converter 4. Furthermore, the efficiency characteristics of the converter 4 vary depending on the temperature of the reactor 42. The efficiency characteristics of the inverter 5 vary depending on the temperature of the semiconductor switching elements 51a to 51f. Furthermore, the efficiency characteristics of the rotating machine 3 vary depending on the temperature of the stator of the rotating machine 3. For this reason, in the power conversion device 1 according to the second embodiment, the converter operation determination unit B1 determines the operation of the converter 4 that will reduce the total of the losses of the converter 4, the inverter 5, and the rotating machine 3 at the power supply voltage, operating point, and each temperature, based on the temperatures of the semiconductor switching elements 41a to 41d, the temperature of the reactor 42, the temperatures of the semiconductor switching elements 51a to 51f, and the temperature of the stator of the rotating machine 3, in addition to the power supply voltage and operating point, and the converter operation control unit controls the converter 4 to perform this operation, thereby making it possible to further reduce the losses that occur in the drive system 100 when driving the rotating machine 3, compared to when the operation of the converter 4 is determined without referring to the temperature information.

[0055] In the power conversion device 1 in the above-described second embodiment, the converter operation determination unit B1 determines the operation of the converter 4 so as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3, in accordance with the temperature information of the converter 4, the temperature information of the inverter 5, and the temperature information of the rotating machine 3, in addition to the power supply voltage and the operating point. However, the converter operation determination unit B1 may determine the operation of the converter 4 in accordance with the temperature information of one or more of the temperature information of the converter 4, the inverter 5, and the rotating machine 3, in addition to the power supply voltage and the operating point. In this case, the parts of the rotating machine 3 whose efficiency characteristics are significantly affected by temperature are confirmed in advance by simulation or an experiment using a drive system with the same specifications, and the converter operation determination unit B1 determines the operation of the converter 4 so as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3, in accordance with the temperature information of the parts whose efficiency characteristics are significantly affected by temperature, confirmed as above, in addition to the power supply voltage and the operating point.

[0056] Embodiment 3 In Embodiment 1, the converter operation determination unit B1 determines the operation of the converter 4 so as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3 at the power supply voltage and operating point indicated by the torque command value and the rotational speed, by referring to the converter operation map M2, which is a lookup table indicating the converter operation mode and duty ratio corresponding to the power supply voltage and operating point. In contrast, the converter operation determination unit B1 may determine the operation of the converter 4 so as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3 by referring to a lookup table indicating the loss in the converter 4, the loss in the inverter 5, and the loss in the rotating machine 3 corresponding to the operating point indicated by the torque command value and the rotational speed, the power supply voltage, and the converter operation mode and duty ratio indicating the operation of the converter 4.

[0057] FIG. 15 is a control block diagram showing the configuration of the power conversion device 1 according to the third embodiment. A converter loss map M4a, an inverter loss map M4b, and a rotating machine loss map M4c are stored in the auxiliary storage device 67 of the power controller 6. The converter loss map M4a is a lookup table showing the correspondence between the power supply voltage, the operating point indicated by the torque command value and the rotational speed, and the converter loss. The converter loss in this converter loss map M4a is the loss generated in the converter 4 when the rotating machine 3 is driven at each operating point and power supply voltage. Similarly, the inverter loss map M4b is a lookup table showing the correspondence between the power supply voltage and operating point and the inverter loss generated in the inverter 5, and the rotating machine loss map M4c is a lookup table showing the correspondence between the power supply voltage and operating point and the rotating machine loss generated in the rotating machine 3. As with the converter operation map M2 according to the first embodiment, the converter loss map M4a, the inverter loss map M4b, and the rotating machine loss map M4c are obtained in advance by simulation or experiments using a drive system with the same specifications. The converter loss map M4a, the inverter loss map M4b, and the rotating machine loss map M4c can also be obtained from experiments using a converter, an inverter, and a rotating machine having the same specifications as the converter 4, the inverter 5, and the rotating machine 3, respectively. The configuration other than these configurations is the same as that of the power conversion device 1 according to the first embodiment shown in FIG.

[0058] An operation of the power conversion device 1 in the third embodiment configured as described above to power or regenerate the rotating machine 3 will be described. Fig. 16 is a flowchart showing an operation of the converter operation determination unit B1 in the third embodiment to determine the operation of the converter 4 in step S03. In the power conversion device 1 in the third embodiment, when the operation of determining the operation of the converter 4 by the converter operation determination unit B1 is started, a torque command value and a rotation speed are input to the converter operation determination unit B1 as in the first embodiment (steps S30 and S31), and then the converter operation determination unit B1 determines the driving lower limit voltage V from the driving lower limit voltage map M1. ｍｉｎ(Step S32), and the power supply voltage is input to the converter operation determination unit B1 (Step S33). Next, the converter operation determination unit B1 determines whether the voltage of the DC power to be output is equal to or lower than the driving lower limit voltage V ｍｉｎ Then, the converter operation determination unit B1 determines the range of the converter operation mode and duty ratio so that the converter loss L is equal to or greater than the above range (step S34). Then, the converter operation determination unit B1 determines the converter loss L by referring to the converter loss map M4a for each point of the converter operation mode and duty ratio within the range set in step S34. ｃｎｖ , and calculate the inverter loss L ｉｎｖ is calculated by referring to the rotating machine loss map M4c. ｍｏｔ (Step S35), and the converter loss L corresponding to each point is read out. ｃｎｖ , inverter loss L ｉｎｖ , rotating machine loss L ｍｏｔ The total loss L ｔｏｔａｌ (Step S36). Next, the loss L calculated in step S36 ｔｏｔａｌ The point at which is the smallest is selected, and the converter operation mode and duty ratio D ｃｎｖ to the converter operation control unit B2 as a converter operation command 63p (step S37). The power conversion device 1 in the third embodiment performs the same operations as the power conversion device 1 in the first embodiment except for the operation of determining the operation of the converter 4 (step S03).

[0059] In this case, as in the first embodiment, a converter operation determination unit B1 is provided which determines the operation of the converter 4 based on the loss of the converter 4, the loss of the inverter 5, and the loss of the rotating machine 3 which occur at the operating point of the rotating machine 3, and a converter operation control unit B2 which controls the operation of the converter 4 in accordance with the determination by the converter operation determination unit B1. Therefore, the converter operation control unit B2 can cause the converter 4 to operate in such a way as to suppress the total loss of the converter 4, the inverter 5, and the rotating machine 3. ｍｉｎFor each point of the converter operation mode and duty ratio that results in an output voltage within the range set by the above, the converter loss map M4a, inverter loss map M4b, and rotating machine loss map M4c are referenced to calculate the total of the converter loss, inverter loss, and rotating machine loss that occurs when the converter 4 is operated at the converter operation mode and duty ratio at each point. The converter operation determination unit B1 then determines the converter operation mode and duty ratio at the point that results in the minimum total loss as the operation of the converter 4, and the converter operation control unit B2 controls the converter 4 in accordance with the determined operation, thereby determining the inverter input voltage V ｉｎｖ is the driving lower limit voltage V ｍｉｎ Within the above range, the converter 4 can be caused to operate in such a way that the loss in the drive system 100 is reduced. Therefore, the power conversion device 1 in the third embodiment can suppress the loss that occurs in the drive system 100 when the rotating machine 3 is driven.

[0060] Furthermore, the converter loss map M4a, inverter loss map M4b, and rotating machine loss map M4c in the third embodiment are determined in advance based on the efficiency characteristics of the converter 4, inverter 5, and rotating machine 3, respectively. As a result, each loss map can be determined without performing a large-scale simulation using traction system 100 as a model or a large-scale experiment using a system with the same specifications as traction system 100, and manufacturing costs can be reduced compared to when a loss map of the entire traction system 100 is referenced.

[0061] Embodiment 4 In the embodiment 3, the converter operation determination unit B1 determines the driving lower limit voltage V ｍｉｎ The converter operation determination unit B1 determines the operation of the converter 4 by referring to the converter loss map M4a, inverter loss map M4b, and rotating machine loss map M4c for each point of the converter operation mode and duty ratio that results in an output voltage within the range set by the above. ｍｉｎThe operation of the converter 4 may be determined by referring to the converter loss map M4a, the inverter loss map M4b, and the rotating machine loss map M4c for each point of the converter operation mode and duty ratio at which the output voltage falls within a range set based on the temperature information of the converter 4, the temperature information of the inverter 5, and the temperature information of the rotating machine 3 input to the converter operation determination unit B1 and depending on whether the temperature of each unit is equal to or higher than the respective threshold value.

[0062] 17 is a control block diagram showing the configuration of a power conversion device 1 according to the fourth embodiment. In the power conversion device 1 according to the fourth embodiment, a power supply voltage sensor signal 63c indicating the power supply voltage, a rotational speed signal 63n indicating the rotational speed, and a drive command 301 indicating a torque command value are input to a converter operation determination unit B1. Furthermore, a rotating machine temperature sensor signal 63b indicating the stator temperature of the rotating machine 3 from the rotating machine temperature sensor 32, a temperature sensor signal 63h indicating the reactor temperature of the reactor 42 from the temperature sensor 43, a temperature sensor signal 63f indicating the converter element temperatures of the semiconductor switching elements 41a to 41d from the temperature sensors 47a to 47d, and a temperature sensor signal 63j indicating the inverter element temperatures of the semiconductor switching elements 51a to 51f from the temperature sensors 54a to 54f are input to the converter operation determination unit B1. Other than these components, the configuration is the same as that of the power conversion device 1 according to the third embodiment.

[0063] An operation of the power conversion device 1 in the fourth embodiment configured as described above to power or regenerate the rotating machine 3 will be described. Fig. 18 is a flowchart showing an operation of the converter operation determination unit B1 in the fourth embodiment to determine the operation of the converter 4 in step S03. In the power conversion device 1 in the fourth embodiment, when the operation of determining the operation of the converter 4 by the converter operation determination unit B1 is started, a torque command value and a rotation speed are input to the converter operation determination unit B1 as in the first embodiment (steps S38 and S39), and then the converter operation determination unit B1 determines the driving lower limit voltage V from the driving lower limit voltage map M1. ｍｉｎ (Step S40), and the power supply voltage is input to the converter operation determination unit B1 (Step S41).ｍｏｔ , converter element temperature T ｃｎｖ１ , reactor temperature T ｃｎｖ２ , inverter element temperature T ｉｎｖ is input to the converter operation determination unit B1 (step S41). ｍｏｔ is a preset stator temperature threshold T ｍｏｔ＿ｔｈ (Step S42), and determine whether the stator temperature T ｍｏｔ is the stator temperature threshold T ｍｏｔ＿ｔｈ is not less than (step S42: NO), that is, the stator temperature T ｍｏｔ is the stator temperature threshold T ｍｏｔ＿ｔｈ If the stator temperature threshold T is equal to or greater than the predetermined value, the converter operation mode and the range of the duty ratio are set so that the rotor loss in the rotor loss map M4c does not exceed the predetermined value (step S43). ｍｏｔ＿ｔｈ is set in advance based on the heat resistance temperature of components such as coils provided in the stator of the rotating machine 3. Next, the converter operation determination unit B1 determines the inverter element temperature T ｉｎｖ is the preset inverter element temperature threshold T ｉｎｖ＿ｔｈ (Step S44), and the inverter element temperature T ｉｎｖ is the inverter element temperature threshold T ｉｎｖ＿ｔｈ is not less than (step S44: NO), that is, the inverter element temperature T ｉｎｖ is the inverter element temperature threshold T ｉｎｖ＿ｔｈ If the inverter element temperature threshold T is equal to or greater than the predetermined value, the converter operation mode and the range of the duty ratio are set so that the inverter loss in the inverter loss map M4b does not exceed the predetermined value (step S45). ｉｎｖ＿ｔｈ is set in advance based on the heat resistance temperature of the semiconductor switching elements 51a to 51f of the inverter 5. Next, the converter operation determination unit B1 determines the converter element temperature T ｃｎｖ１ is the preset converter element temperature threshold T ｃｎｖ１＿ｔｈ (Step S46), and the converter element temperature T ｃｎｖ１ is the converter element temperature threshold T ｃｎｖ１＿ｔｈis not less than (step S46: NO), that is, the converter element temperature T ｃｎｖ１ is the converter element temperature threshold T ｃｎｖ１＿ｔｈ If the converter element temperature threshold T is equal to or greater than the predetermined value, the converter operation mode and the range of the duty ratio are set so that the loss in the converter loss map M4a does not exceed the predetermined value of the converter loss (step S47). ｃｎｖ１＿ｔｈ is set in advance based on the heat resistance temperature of the semiconductor switching elements 41a to 41d of the converter 4. Next, the converter operation determination unit B1 determines the reactor temperature T ｃｎｖ２ is the preset reactor temperature threshold T ｃｎｖ２＿ｔｈ (Step S48), and the reactor temperature T ｃｎｖ２ is the reactor temperature threshold T ｃｎｖ２＿ｔｈ is not less than the reactor temperature T ｃｎｖ２ is the reactor temperature threshold T ｃｎｖ２＿ｔｈ If the reactor temperature threshold T is equal to or greater than the predetermined value, the converter operation mode and the range of the duty ratio are set so that the loss in the converter loss map M4a does not exceed the predetermined value of the converter loss (step S49). ｃｎｖ２＿ｔｈ is set in advance based on the heat resistance temperature of components such as the coil of the reactor 42 of the converter 4. Here, the respective predetermined losses used to set the ranges in steps S43, S45, S47, and S49 are determined in advance in accordance with the temperature conditions in the corresponding steps S42, S44, S46, and S48, respectively, through simulations, experiments using a drive system with the same specifications, or experiments using a converter, inverter, and rotating machine with the same specifications as the converter 4, inverter 5, and rotating machine 3, respectively. Each predetermined loss is a loss that occurs when the rotating machine 3 is driven so as not to raise the temperature of the corresponding part. Next, the converter operation determination unit B1 determines whether the voltage of the DC power to be output is lower than the driving lower limit voltage V ｍｉｎIf the range is set in steps S43, S45, S47, and S49, the converter operation determination unit B1 sets the range of the converter operation mode and duty ratio so that they fall within the range (step S50). Then, for each point of the converter operation mode and duty ratio within the range set in step S50, the converter operation determination unit B1 refers to the converter loss map M4a to calculate the converter loss L ｃｎｖ , and calculate the inverter loss L ｉｎｖ is calculated by referring to the rotating machine loss map M4c. ｍｏｔ (Step S51), and the converter loss L corresponding to each point is read out. ｃｎｖ , inverter loss L ｉｎｖ , rotating machine loss L ｍｏｔ The total loss L ｔｏｔａｌ (Step S52). Next, the loss L calculated in step S52 ｔｏｔａｌ The point at which is the smallest is selected, and the converter operation mode and duty ratio D ｃｎｖ to the converter operation control unit B2 as a converter operation command 63p (step S53). The power conversion device 1 in the fourth embodiment performs the same operations as the power conversion device 1 in the first embodiment except for the operation of determining the operation of the converter 4 (step S03).

[0064] In this case, as in the third embodiment, the converter operation control unit B2 can cause the converter 4 to operate in such a way as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3. Furthermore, by reducing the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, it is possible to reduce the loss generated in the traction system 100 when driving the rotating machine 3, and further, since each loss map can be obtained without performing a large-scale simulation using the traction system 100 as a model or a large-scale experiment using a system with the same specifications as the traction system 100, manufacturing costs can be reduced.

[0065] Furthermore, in step S50, the converter operation determination unit B1 of the power conversion device 1 in the fourth embodiment determines the driving lower limit voltage Vｍｉｎ In addition, the stator temperature T ｍｏｔ , inverter element temperature T ｉｎｖ , converter element temperature T ｃｎｖ１ , reactor temperature T ｃｎｖ２ When the temperatures are equal to or higher than the thresholds, the converter operation mode and duty ratio range are set so that the loss is equal to or lower than a predetermined value, and the operation of the converter 4 is determined. Therefore, when the rotating machine 3 is driven, overheating of the stator of the rotating machine 3, the semiconductor switching elements 51a to 51f of the inverter 5, the semiconductor switching elements 41a to 41d of the converter 4, and the reactor 42 can be suppressed.

[0066] In the power conversion device 1 according to the fourth embodiment, the converter operation determination unit B1 determines the driving lower limit voltage V ｍｉｎ In addition, the stator temperature T ｍｏｔ , inverter element temperature T ｉｎｖ , converter element temperature T ｃｎｖ１ , reactor temperature T ｃｎｖ２ When the respective temperatures are equal to or higher than the thresholds, the converter operation determination unit B1 determines the operation of the converter 4 by setting a converter operation mode and a range of duty ratios that will result in a predetermined loss or less so that a rise in the temperature is suppressed. However, the converter operation determination unit B1 may also determine the operation of the converter 4 by further setting a converter operation mode and a range of duty ratios that will result in a predetermined loss or less so that a rise in the magnet temperature, which is the temperature of the permanent magnet provided in the rotor (not shown) of the rotating machine 3, is suppressed when the magnet temperature is equal to or higher than the thresholds.

[0067] In this case, the converter operation determination unit B1 determines the input stator temperature T ｍｏｔBased on this, the magnet temperature is estimated using a thermal network stored in advance in the auxiliary storage device 67. Regarding the magnet temperature, the converter operation determination unit B1 can provide a voltage sensor at the rotating machine-side connection terminal of each phase of the inverter and estimate the magnet temperature from the induced voltage of the rotating machine 3 detected by the voltage sensor. Alternatively, the converter operation determination unit B1 can provide magnet temperature information by providing a temperature sensor in the rotor of the rotating machine 3 and inputting the magnet temperature detected by the temperature sensor. If the estimated magnet temperature is equal to or higher than a preset threshold, the converter operation determination unit B1 sets a converter operation mode and a duty ratio range that prevents the rotating machine loss in the rotating machine loss map M4c from exceeding a predetermined value so as to suppress an increase in magnet temperature. In step S50, the converter operation determination unit B1 sets a converter operation mode and a duty ratio range that reflects this range. The magnet temperature threshold is set in advance based on characteristics such as the heat resistance temperature of the permanent magnet of the rotating machine 3 or changes in performance due to temperature.

[0068] In this case, when the magnet temperature is above a threshold, the converter operation determination unit B1 determines the operation of the converter 4 so as to suppress the rise in magnet temperature, thereby suppressing overheating of the permanent magnets provided in the rotor of the rotating machine 3.

[0069] In the above third and fourth embodiments, the converter operation determination unit B1 determines the operation of the converter 4 by referring to each loss map, which is a lookup table showing the correspondence between the power supply voltage, the operating point indicated by the torque command value and the rotational speed, and the loss generated in the converter 4, the inverter 5, or the rotating machine 3 when the rotating machine 3 is driven at that power supply voltage and operating point. Alternatively, in addition to the power supply voltage and operating point, any one or more of temperature information of the converter 4, temperature information of the inverter 5, and temperature information of the rotating machine 3 may be input to the converter operation determination unit B1, and the converter operation determination unit B1 may determine the operation of the converter 4 so as to reduce the total loss of the converter 4, the inverter 5, and the rotating machine 3, by referring to each loss map set based on the power supply voltage, operating point, and temperature information of each part, in accordance with the power supply voltage, operating point, and input temperature information. In this case, each loss map is a lookup table showing the correspondence between the power supply voltage, operating point, and temperature information of each part, and the loss generated in the converter 4, the inverter 5, or the rotating machine 3 when the rotating machine 3 is driven at that power supply voltage, operating point, and temperature of each part.

[0070] In this case, as in the third and fourth embodiments, the converter operation control unit B2 can cause the converter 4 to operate in a manner that reduces the total loss of the converter 4, the inverter 5, and the rotating machine 3. Furthermore, by reducing the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, it is possible to reduce the loss generated in the drive system 100 when driving the rotating machine 3. Furthermore, the efficiency characteristics of the converter 4 vary depending on the temperature of the semiconductor switching elements 41a to 41d of the converter 4. Furthermore, the efficiency characteristics of the converter 4 vary depending on the temperature of the reactor 42. Furthermore, the efficiency characteristics of the inverter 5 vary depending on the temperature of the semiconductor switching elements 51a to 51f. Furthermore, the efficiency characteristics of the rotating machine 3 vary depending on the temperature of the stator of the rotating machine 3. Therefore, compared to when the operation of the converter 4 is determined without reference to temperature information, it is possible to further reduce the loss generated in the drive system 100 when driving the rotating machine 3.

[0071] Fifth Embodiment. Fig. 19 is a schematic diagram showing a vehicle 200, such as an electric vehicle, a hybrid electric vehicle, or a fuel cell vehicle, equipped with a power conversion device 1 and a drive system 100 according to a fifth embodiment. In the fifth embodiment, the vehicle 200 includes a power receiving connection unit 12 connected to an external power source 400. While the vehicle 200 is traveling or stopped, the vehicle 200 receives a supply of power from the external power source 400, such as a power grid, via the power receiving connection unit 12 and the power feeding connection unit 13 connected to the external power source 400. Here, power feeding via the power receiving connection unit 12 and the power feeding connection unit 13 may be achieved by contact feeding using an overhead line or contactless feeding using a magnetic resonance system. In the case of contact feeding using an overhead line, the power receiving connection unit 12 is a pantograph or the like, and the power feeding connection unit 13 is an overhead line. In the case of contactless feeding using a magnetic resonance system, the power receiving connection unit 12 is a power receiving coil mounted on the vehicle 200, and the power feeding connection unit 13 is a power feeding coil connected to the external power source 400.

[0072] 20 is a configuration diagram showing the configuration of a drive system 100 using a power conversion device 1 according to embodiment 5. Power conversion device 1 according to embodiment 5 includes a high-voltage terminal 15a on a high-voltage side connection line 14a that connects an inverter-side connection end 40b of converter 4 to inverter 5, and a low-voltage terminal 15b on a low-voltage side connection line 14b. High-voltage terminal 15a and low-voltage terminal 15b are connected to a power receiving connection unit 12 included in vehicle 200. A high-voltage section 401a of an external power supply 400 is connected to high-voltage terminal 15a via power receiving connection unit 12 and power feeding connection unit 13, and the low-voltage section 401b of external power supply 400 is connected to low-voltage terminal 15b, thereby supplying power from external power supply 400 to power conversion device 1. A drive command 301 indicating a drive permission and a torque command value for the rotating machine 3, which are determined in response to accelerator work, brake work, or the like, of the driver of the vehicle 200, is input from the vehicle controller 300 to the ECU 62 of the power controller 6. Here, the drive permission is input to the ECU 62 as a flag, and when TRUE, indicates that the rotating machine 3 is to be driven, and when FALSE, indicates that the rotating machine 3 is not to be driven. Furthermore, a power control command 302 indicating a charge / discharge power range, which is a range of power that can be charged to the DC power supply 2 and a range of power that can be discharged from the DC power supply 2, calculated in response to the power supply voltage and temperature information of the DC power supply 2, which is a secondary battery, is input to the power controller 6 from the vehicle controller 300. Other configurations than these are the same as those of the drive system 100 and the power conversion device 1 in any of the first to fourth embodiments.

[0073] 21 is a flowchart showing the operation of the power conversion device 1 when the power conversion device 1 receives power supply from the external power source 400 in the drive system 100 of the fifth embodiment. When the power receiving connection unit 12 and the power supply connection unit 13 are connected and power supply from the external power source 400 begins, the vehicle controller 300 first inputs a drive permission and a torque command value to the rotating machine 3 as a drive command 301 to the rotating machine 3 (step S501). Next, the vehicle controller 300 inputs the charge / discharge power range of the DC power source 2 as a power control command 302 to the rotating machine 3 (step S502). Next, the rotational speed calculation unit B0 calculates the rotational speed of the rotating machine 3 (step S503). Next, the power controller 6 receives the power supply voltage from the power supply voltage sensor 7 and the intermediate voltage from the intermediate voltage sensor 10 (step S504). At this time, the intermediate voltage is the external power supply voltage, which is the voltage applied to the high-voltage terminal 15a and the low-voltage terminal 15b by the external power source 400. Next, in the power controller 6, the converter operation determination unit B1 determines whether the drive permission is TRUE or FALSE, i.e., whether the power input from the external power source 400 to the power conversion device 1 is to be input to the rotating machine 3 to drive the rotating machine 3, or whether the power input from the external power source 400 to the power conversion device 1 is to be input to the DC power source 2 without being input to the rotating machine 3 (step S505). If the drive permission is TRUE (step S505: YES), i.e., if the power input from the external power source 400 to the power conversion device 1 is to be input to the rotating machine 3 to drive the rotating machine 3, the converter operation determination unit B1 determines the drive power P ｍｏｔ , and the external power supply power P ｉｎ After step S506, the converter operation determination unit B1 calculates the external power supply power P ｉｎ is the driving power P ｍｏｔ (step S507), and the external power supply power P ｉｎ is the driving power P ｍｏｔ If it is greater than the external power supply power P ｉｎ, the excess power not required for driving the rotating machine 3 is output to the DC power supply 2 so that the DC power supply 2 is charged. ｍｏｔ , external power supply P ｉｎ In step S507, the operation of the converter 4 is determined based on the external power supply power P ｉｎ is the driving power P ｍｏｔ If it is determined that the external power supply power P ｉｎ is the driving power P ｍｏｔ If the condition is the same as or lower than the condition above, the converter operation determination unit B1 determines the operation of the converter 4 so as to compensate for the power shortage by discharging the DC power supply 2 (step S509). Then, the converter operation control unit B2 controls the converter 4 in accordance with the operation of the converter 4 determined in step S508 or step S509 (step S510). Next, the inverter current command determination unit B3 determines a current command for the inverter 5 (step S511). Next, the inverter operation control unit B4 controls the inverter 5 in accordance with the current command determined in step S511 (step S512). The operation of the inverter current command determination unit B3 to determine the current command for the inverter 5 in step S511 and the operation of the inverter operation control unit B4 to control the inverter 5 in step S512 are vector control of a general permanent magnet synchronous machine, similar to the operation of the power conversion device 1 according to the first embodiment.

[0074] If the drive permission is FALSE in step S505 (step S505: NO), that is, if the power conversion device 1 inputs the power input from the external power source 400 to the DC power source 2 without inputting it to the rotating machine 3, the converter operation determination unit B1 determines the value of the power to be charged to the DC power source 2 for the power source voltage and intermediate voltage in accordance with the power source voltage, the intermediate voltage, and the charge / discharge power range (step S513), and determines the operation of the converter 4 so that the converter 4 inputs the determined power value to the DC power source 2 (step S514). Then, the converter operation control unit B2 controls the converter 4 in accordance with the operation of the converter 4 determined in step S514 (step S515). Next, the inverter current command determination unit B3 determines each current value to 0 as a current command for the inverter 5 to turn off each of the semiconductor switching elements 51a to 51f (step S516). Next, the inverter operation control unit B4 controls the inverter 5 to turn off each of the semiconductor switching elements 51a to 51f in accordance with the current command determined in step S516 (step S517).

[0075] In embodiment 5, when the power conversion device 1 powers or regenerates the rotating machine 3 without receiving power supply from the external power source 400, the power conversion device 1 performs the same operation as the power conversion device 1 in any of embodiments 1 to 4.

[0076] In this case, too, when power conversion device 1 powers or regenerates rotating machine 3 without receiving power supply from external power supply 400, power conversion device 1 operates in the same manner as power conversion device 1 in any of the first to fourth embodiments, and therefore, similarly to the first to fourth embodiments, converter operation control unit B2 can cause converter 4 to operate to reduce the total loss of converter 4, inverter 5, and rotating machine 3. Furthermore, by reducing the total loss generated in converter 4, inverter 5, and rotating machine 3, it is possible to reduce loss generated in drive system 100 when driving rotating machine 3. Furthermore, in power conversion device 1 according to the fifth embodiment, power is input from external power supply 400 via high-voltage terminal 15a and low-voltage terminal 15b connected to power receiving connection unit 12, and thereby it is possible to drive rotating machine 3 or charge DC power supply 2 with power from external power supply 400.

[0077] Furthermore, the voltages applied by converter 4 to the positive and negative electrodes of DC power supply 2 must be higher than the power supply voltage of DC power supply 2 when power is input to DC power supply 2 to charge it, and must be lower than the power supply voltage when DC power supply 2 is discharged to output power. Furthermore, because DC power supply 2 is a secondary battery, the power supply voltage fluctuates depending on the state of charge. Therefore, in order to enable charging and discharging regardless of the state of charge of DC power supply 2, it is preferable that converter 4 be able to output power to DC power supply 2 at a voltage that is wider in both lower and upper limits than the range of the power supply voltage of DC power supply 2. Therefore, when an external power supply voltage, which is a voltage applied to high-voltage terminal 15 a and low-voltage terminal 15 b by external power supply 400, is converted by a converter that can only step down the voltage and output the converted power to DC power supply 2, the external power supply voltage is required to be higher than the upper limit of the power supply voltage of DC power supply 2. Conversely, when the power of the external power supply 400 is converted by a converter that can only boost the voltage and output to the DC power supply 2, the external power supply voltage is required to be lower than the lower limit of the power supply voltage of the DC power supply 2. However, when the rotating machine 3 is driven by power input from the external power supply 400, the voltage applied to the inverter 5 and the rotating machine 3 is the external power supply voltage, and therefore, if the external power supply voltage is limited as described above, the range of torque and rotation speed for driving the rotating machine 3 may be limited, the inverter 5 or the rotating machine 3 may be increased in size to accommodate an unnecessarily high voltage, or the rotating machine 3 may be driven at an inefficient voltage, making it impossible to drive the rotating machine 3 efficiently.

[0078] The power conversion device 1 according to the fifth embodiment includes the converter 4, which is a bidirectional DC-DC converter capable of stepping up or down the external power supply voltage to a desired voltage, and determines the operation of the converter 4 based on an intermediate voltage indicating the external power supply voltage and the power supply voltage of the DC power supply 2. The converter operation control unit B2 controls the converter 4 so that the determined operation is performed. Therefore, the external power supply voltage can be converted to a voltage corresponding to the power supply voltage of the DC power supply 2 to charge the DC power supply 2. Therefore, in the power conversion device 1 according to the fifth embodiment, when the rotating machine 3 is driven while the DC power supply 2 is being charged with power input from the external power supply 400, the DC power supply 2 can be charged without being limited by the state of charge of the DC power supply 2, which is a secondary battery, or the external power supply voltage, and an increase in loss when the rotating machine 3 is driven can be prevented. Furthermore, the inverter 5 and the rotating machine 3 can be prevented from becoming larger.

[0079] In the power conversion device 1 according to the fifth embodiment, when the rotating machine 3 is driven by the power input from the external power supply 400, the converter operation determination unit B1 determines whether the external power supply power P ｉｎ and driving power P which is the power required to drive the rotating machine 3. ｍｏｔ The operation of the converter 4 is determined based on the above. Therefore, excessive power can be prevented from being input to the components of the power conversion device 1, the DC power supply 2, or the power receiving connection unit 12, thereby preventing damage to the components.

[0080] Furthermore, the external power supply voltage may fluctuate depending on the connection state of the power receiving connection part 12 and the power supply connection part 13. Furthermore, the power supply voltage of the DC power supply 2 fluctuates depending on the charging state. If there is a portion where the range between the upper and lower limit values ​​of the external power supply voltage overlaps with the range between the upper and lower limit values ​​of the power supply voltage of the DC power supply 2, and if the converter does not step up or down the external power supply voltage, or if a converter that can only step down or step up only steps up or down the voltage, then in that overlapping range, charging or discharging of the DC power supply 2 may not be possible depending on the magnitude relationship between the external power supply voltage and the power supply voltage of the DC power supply 2. In contrast, the power conversion device 1 according to the fifth embodiment includes the converter 4, which is a bidirectional DC-DC converter that can boost or buck the power input from the external power supply 400 to a desired voltage and output the power to the DC power supply 2, and converts the external power supply voltage to a voltage corresponding to the power supply voltage of the DC power supply 2 to charge or discharge the DC power supply 2. Therefore, even if there is a portion where the range between the upper and lower limit values ​​of the external power supply voltage overlaps with the range between the upper and lower limit values ​​of the power supply voltage of the DC power supply 2, it is possible to prevent the DC power supply 2 from becoming unable to charge or discharge. Therefore, when the power conversion device 1 receives power from the external power supply 400 while the vehicle 200 is traveling, even if the connection state of the power receiving connection unit 12 and the power supply connection unit 13 fluctuates depending on the traveling state of the vehicle 200, causing the voltage of the power input from the external power supply 400 to fluctuate, it is possible to prevent the DC power supply 2 from becoming unable to charge or discharge.

[0081] In all of the above embodiments, the converter operation determination unit B1 determines the converter operation mode and duty ratio as indicating the operation of the converter 4, and outputs the determined converter operation mode and duty ratio to the converter operation control unit B2. However, the converter operation determination unit B1 may also determine an inverter input voltage suitable for driving a rotating machine as indicating the operation of the converter 4, and output the determined inverter input voltage as the power supply voltage to the converter operation control unit B2.

[0082] In this case, as in embodiments 1 and 2, when the converter operation determination unit B1 determines the operation of the converter 4 by referring to the converter operation map M2 or the converter operation map M3, the converter operation map M2 or the converter operation map M3 indicates the correspondence between the conditions indicated by the operating point and the power supply voltage, or the operating point, the power supply voltage and the temperature information of each part, and the inverter input voltage that reduces the total of the losses generated in the converter 4, the inverter 5, and the rotating machine 3 when the rotating machine is driven under those conditions.

[0083] On the other hand, when converter operation determination unit B1 determines the operation of converter 4 by referring to each loss map, namely, converter loss map M4a, inverter loss map M4b, and rotating machine loss map M4c, as in embodiments 3 and 4, converter loss map M4a shows the correspondence between conditions indicated by the operating point, power supply voltage, and inverter input voltage, or the operating point, power supply voltage, temperature information of each part, and inverter input voltage, and losses generated in converter 4 when the rotating machine is driven under those conditions. Similarly, inverter loss map M4b shows the correspondence between conditions and losses generated in inverter 5 when the rotating machine is driven under those conditions, and rotating machine loss map M4c shows the correspondence between conditions and losses generated in rotating machine 3 when the rotating machine is driven under those conditions. Like the converter operation maps M2 and M3 and each loss map of each embodiment, these converter operation maps M2 and M3 and each loss map are also obtained in advance by simulation or experiment using a drive system with the same specifications. When the converter operation determination unit B1 determines the inverter input voltage as an indication of the operation of the converter 4, the converter operation determination unit B1 inputs the inverter input voltage and power supply voltage to the converter operation control unit B2 as the determined operation of the converter 4. The converter operation control unit B2 calculates a duty ratio from the input inverter input voltage and power supply voltage, selects a converter operation mode corresponding to the calculated duty ratio, and generates a converter gate drive signal 63k corresponding to the converter operation mode and duty ratio and outputs it to the converter 4.

[0084] In this case, as in the first embodiment, the converter operation control unit B2 can cause the converter 4 to operate in such a way as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3. Furthermore, by reducing the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, it is possible to reduce the loss generated in the drive system 100 when driving the rotating machine 3.

[0085] In both of the first and second embodiments, the converter operation determination unit B1 determines the operation of the converter 4 so as to minimize the total loss in the converter 4, the inverter 5, and the rotating machine 3 at an operating point indicated by the power supply voltage, the torque command value, and the rotational speed by referring to the converter operation map M2 or M3, which is a lookup table indicating the converter operation mode and duty ratio corresponding to the power supply voltage and operating point. However, the converter operation determination unit B1 may determine the operation of the converter 4 by calling a converter operation function that takes the operating point indicated by the power supply voltage, the torque command value, and the rotational speed as arguments and returns the converter operation mode and duty ratio corresponding to the power supply voltage and operating point. The converter operation function stores a formula for calculating a duty ratio appropriate for driving the rotating machine from the torque command value, the rotational speed, the power supply voltage, temperature information of each part, etc. In this case, in the operation in which the converter operation determination unit B1 in embodiments 1 and 2 determines the operation of the converter 4, instead of the step in which the converter operation determination unit B1 reads out the converter operation mode and duty ratio from the converter operation map M2 or the converter operation map M3, the converter operation determination unit B1 executes a step in which it calls the above-mentioned converter operation function, thereby determining the converter operation mode and duty ratio appropriate for driving the rotating machine 3 according to the power supply voltage and operating point.

[0086] In this case, as in the first and second embodiments, the converter operation control unit B2 can cause the converter 4 to operate in such a way as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3. Furthermore, by reducing the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, it is possible to reduce the loss generated in the drive system 100 when driving the rotating machine 3.

[0087] Furthermore, in both of the above-described third and fourth embodiments, the converter operation determination unit B1 determines the operation of the converter 4 that reduces the total loss of the converter 4, the inverter 5, and the rotating machine 3 by referring to a lookup table that indicates the loss of the converter 4, the loss of the inverter 5, and the loss of the rotating machine 3, corresponding to the operating point indicated by the torque command value and the rotational speed, the power supply voltage, and the converter operating mode and duty ratio that indicate the operation of the converter. However, the converter operation determination unit B1 may determine the operation of the converter 4 that reduces the total loss of the converter 4, the inverter 5, and the rotating machine 3 by calling a loss function that uses the operating point indicated by the torque command value and the rotational speed, the power supply voltage, and the converter operating mode and duty ratio that indicate the operation of the converter as arguments, and returns the total loss of the converter 4, the loss of the inverter 5, and the loss of the rotating machine 3. The loss function stores a calculation formula for calculating the loss of the converter 4, the loss of the inverter 5, and the loss of the rotating machine 3 that occurs when the rotating machine 3 is driven from the torque command value, the rotational speed, the power supply voltage, temperature information of each part, etc. In this case, in the operation in which the converter operation determination unit B1 according to the third and fourth embodiments determines the operation of the converter 4, the converter operation determination unit B1 refers to the converter loss map M4a for each point of the converter operation mode and duty ratio to determine the converter loss L ｃｎｖ , and calculate the inverter loss L ｉｎｖ is calculated by referring to the rotating machine loss map M4c. ｍｏｔ and the converter loss L corresponding to each point ｃｎｖ , inverter loss L ｉｎｖ , rotating machine loss L ｍｏｔ The total loss L ｔｏｔａｌInstead of the step of calculating the loss function, the converter operation determination unit B1 executes a step of calling the loss function, thereby determining a converter operation mode and duty ratio appropriate for driving the rotating machine 3 according to the power supply voltage and operating point.

[0088] In this case, as in the third and fourth embodiments, the converter operation control unit B2 can cause the converter 4 to operate in such a way as to reduce the total loss in the converter 4, the inverter 5, and the rotating machine 3. Furthermore, by reducing the total loss generated in the converter 4, the inverter 5, and the rotating machine 3, it is possible to reduce the loss generated in the drive system 100 when driving the rotating machine 3.

[0089] Furthermore, while the above embodiments have all described power conversion devices and drive systems that are mounted on vehicles, the power conversion device of the present disclosure is not limited to those that are mounted on vehicles, and in cases where power from a DC power source is converted into AC power by the power conversion device and the AC power is output to a rotating machine to drive the rotating machine, the power conversion device is provided with a converter operation determination unit that determines the operation of the converter based on the converter losses, inverter losses, and rotating machine losses that occur at the operating point of the rotating machine, and a converter operation control unit that controls the operation of the converter in accordance with the determination of the converter operation determination unit, thereby achieving the effect that the converter operation control unit can cause the converter to operate in a way that suppresses the total loss of the converter, inverter, and rotating machine.

[0090] Furthermore, in all of the above embodiments, the configuration has been described where the rotating machine 3 is a permanent magnet synchronous rotating machine. However, even if the rotating machine 3 is configured as another rotating machine such as an induction rotating machine or a wound-field synchronous rotating machine, when power from a DC power source is converted into AC power by a power conversion device and the AC power is output to the rotating machine to drive it, the system is provided with a converter operation determination unit that determines the operation of the converter based on the converter loss, inverter loss, and rotating machine loss that occur at the operating point of the rotating machine, and a converter operation control unit that controls the operation of the converter in accordance with the determination by the converter operation determination unit, thereby achieving the effect that the converter operation control unit can cause the converter to operate in a way that suppresses the total loss of the converter, inverter, and rotating machine.

[0091] It should be noted that appropriate combinations, modifications, and omissions of the respective embodiments are also included within the scope of the technical ideas shown in the embodiments.

[0092] Various aspects of the present disclosure are collectively described below as appendices. (Appendix 1) A power conversion device comprising: a converter configured to selectively perform an operation of stepping up or stepping down DC power input from a DC power source and outputting the DC power to an inverter, and an operation of outputting the DC power input from the DC power source to the inverter; an inverter that converts the DC power input from the converter into AC power and outputs the AC power to a rotating machine; an operation determination unit that determines an operation of the converter based on a loss of the converter, a loss of the inverter, and a loss of the rotating machine at an operating point of the rotating machine; and an operation control unit that controls the operation of the converter in accordance with the determination by the operation determination unit. (Appendix 2) The power conversion device according to Appendices 1 or 2, wherein the converter is a bidirectional DC-DC converter. (Appendix 3) The power conversion device according to Appendices 1 or 2, wherein the converter is a bidirectional DC-DC converter. (Appendix 4) The power conversion device according to any one of Appendices 1 to 3, wherein the DC power source is a secondary battery. (Supplementary Note 5) The power conversion device according to any one of Supplements 1 to 4, further comprising a converter operation map indicating a correspondence between an operating point of the rotating machine, the operating point being set in advance based on a loss of the converter, a loss of the inverter, and a loss of the rotating machine, and an operation of the converter suitable for driving the rotating machine at that operating point, wherein the operation determination unit determines the operation of the converter by referring to the converter operation map. (Supplementary Note 6) The power conversion device according to Supplementary Note 5, wherein the converter operation map indicates a correspondence between an operating point of the rotating machine and an operation of the converter that minimizes a total of losses generated in the converter, the inverter, and the rotating machine when the rotating machine is driven at that operating point. (Supplementary Note 7) The power conversion device according to any one of Supplements 1 to 6, wherein the operation determination unit determines the operation of the converter based on one or more of rotating machine temperature information of the rotating machine, inverter temperature information of the inverter, and converter temperature information of the converter.(Supplementary Note 8) The power conversion device according to any one of Supplementary Notes 1 to 7, further comprising a converter loss map, an inverter loss map, and a rotating machine loss map, which respectively indicate a correspondence between an operating point of the rotating machine and an operation of the converter, and a converter loss, an inverter loss, and a rotating machine loss that occur in the converter, the inverter, and the rotating machine when the rotating machine 3 is driven at the operating point and the operation, wherein the operation determination unit sets a range of operation of the converter that can drive the rotating machine at the operating point according to the operating point of the rotating machine, reads out the converter loss, inverter loss, and rotating machine loss that occur when the rotating machine is driven at each of a plurality of points within the range for the operation by referring to the converter loss map, the inverter loss map, and the rotating machine loss map, calculates a total value of the converter loss, inverter loss, and rotating machine loss for each of the points, and outputs the operation at the point at which the calculated total value is minimum to the operation control unit. (Supplementary Note 9) The power conversion device according to Supplementary Note 8, wherein the operation determination unit sets the range according to one or more of temperature information of the converter, temperature information of the inverter, and temperature information of the rotating machine. (Supplementary Note 10) The power conversion device according to Supplementary Note 9, wherein the operation determination unit determines the range so that loss in the converter does not rise above a predetermined value when the temperature of the converter is equal to or higher than a predetermined threshold. (Supplementary Note 11) The power conversion device according to Supplementary Note 9 or 10, wherein the operation determination unit determines the range so that loss in the inverter does not rise above a predetermined value when the temperature of the inverter is equal to or higher than a predetermined threshold. (Supplementary Note 12) The power conversion device according to any one of Supplements 9 to 11, wherein the operation determination unit determines the range so that loss in the rotating machine does not rise above a predetermined value when the temperature of the rotating machine is equal to or higher than a predetermined threshold. (Supplementary Note 13) The power conversion device according to any one of Supplements 1 to 12, wherein the converter includes a semiconductor switching element, and the semiconductor switching element is made of a wide bandgap semiconductor.(Supplementary Note 14) The power conversion device according to any one of Supplements 1 to 13, comprising: a high-voltage terminal provided on a high-voltage line section connecting the converter and the inverter, the high-voltage terminal being connected to a high-voltage section of an external power supply; and a low-voltage terminal provided on a low-voltage line section connecting the converter and the inverter, the low-voltage terminal being connected to a low-voltage section of the external power supply, wherein power is input from the external power supply via the high-voltage terminal and the low-voltage terminal. (Supplementary Note 15) The power conversion device according to Supplementary Note 14, wherein, when power is input from the external power supply via the high-voltage terminal and the low-voltage terminal, the operation determination unit determines the operation of the converter based on a voltage of the power input from the external power supply and a voltage of the DC power supply. (Supplementary Note 16) The power conversion device according to Supplementary Note 14 or 15, wherein, when power is input from the external power supply via the high-voltage terminal and the low-voltage terminal, the operation determination unit determines the operation of the converter based on a value of the power input from the external power supply and a value of power required to drive the rotating machine. (Supplementary Note 17) The power conversion device according to any one of Supplementary Notes 14 to 16, wherein the DC power supply is a secondary battery whose voltage varies depending on a state of charge, and wherein a voltage range between an upper limit and a lower limit of the voltage of the power input from the external power supply overlaps with a power supply voltage range between an upper limit and a lower limit of the voltage of the DC power supply. (Supplementary Note 18) A drive system comprising: the power conversion device according to any one of Supplementary Notes 1 to 17; a DC power supply that inputs DC power to the power conversion device as the DC power supply; and a rotating machine that is driven by AC power input from the power conversion device as the rotating machine. (Supplementary Note 19) The drive system according to Supplementary Note 18, which is mounted on a vehicle.

[0093] REFERENCE SIGNS LIST 100 Drive system 200 Vehicle 300 Vehicle controller 301 Drive command 302 Power control command 400 External power supply 1 Power conversion device 2 DC power supply 3 Rotating machine 31 Rotation angle sensor 32 Rotating machine temperature sensor 4 Converter 41a to 41d Semiconductor switching element 42 Reactor 47a to 47d Temperature sensor 5 Inverter 51a to 51f Semiconductor switching element 54a to 54f Temperature sensor 6 Power controller 61 Drive circuit 62 ECU 64 Processor 65 Storage device 66 Volatile storage device 67 Auxiliary storage device 7 Power supply voltage sensor 8 Input power smoothing capacitor 9 Intermediate power smoothing capacitor 10 Intermediate voltage sensor 11u, 11v, 11w Current sensor B0 Rotational speed calculation unit B1 Converter operation determination unit B2 Converter operation control unit B3 Inverter current command determination unit B4 Inverter operation control unit M1 Drive lower limit voltage map M2, M3 Converter operation map M4a Converter loss map M4b Inverter loss map M4c Rotating machine loss map 12 Power receiving connection part 13 Power supply connection part 15a High voltage terminal 15b Low voltage terminal

Claims

1. A power conversion device comprising: a converter configured to be able to selectively perform an operation of stepping up or stepping down DC power input from a DC power source and outputting the DC power to an inverter, and an operation of outputting DC power input from the DC power source to the inverter; an inverter that converts the DC power input from the converter into AC power and outputs the AC power to a rotating machine; an operation determination unit that determines the operation of the converter based on the losses of the converter, the losses of the inverter, and the losses of the rotating machine at an operating point of the rotating machine; and an operation control unit that controls the operation of the converter in accordance with the determination of the operation determination unit.

2. The power conversion device according to claim 1, wherein the operation determination unit determines the operation of the converter depending on the voltage of the DC power supply.

3. The power conversion device according to claim 1, wherein the converter is a bidirectional DC-DC converter.

4. The power conversion device according to claim 1, wherein the DC power source is a secondary battery.

5. A power conversion device according to claim 1, further comprising a converter operation map indicating a correspondence between an operating point of the rotating machine, which is set in advance based on the losses of the converter, the losses of the inverter, and the losses of the rotating machine, and the operation of the converter suitable for driving the rotating machine at that operating point, and wherein the operation determination unit determines the operation of the converter by referring to the converter operation map.

6. The power conversion device according to claim 5, wherein the converter operation map indicates the correspondence between the operating point of the rotating machine and the operation of the converter that minimizes the total of losses generated in the converter, the inverter, and the rotating machine when the rotating machine is driven at that operating point.

7. The power conversion device according to claim 1, wherein the operation determination unit determines the operation of the converter based on one or more of rotating machine temperature information of the rotating machine, inverter temperature information of the inverter, and converter temperature information of the converter.

8. The power conversion device according to claim 1, further comprising a converter loss map, an inverter loss map, and a rotating machine loss map, which respectively indicate a correspondence between an operating point of the rotating machine and an operation of the converter, and a converter loss, an inverter loss, and a rotating machine loss that occur in the converter, the inverter, and the rotating machine when the rotating machine 3 is driven at that operating point and that operation, wherein the operation determination unit sets a range of operation of the converter that can drive the rotating machine at that operating point according to the operating point of the rotating machine, reads out the converter loss, inverter loss, and rotating machine loss that occur when the rotating machine is driven at each of the operations at a plurality of points within that range by referring to the converter loss map, the inverter loss map, and the rotating machine loss map, calculates a total value of the converter loss, inverter loss, and rotating machine loss for each of the points, and outputs the operation at the point at which the calculated total value is smallest to the operation control unit.

9. The power conversion device according to claim 8, wherein the operation determination unit sets the range in accordance with one or more of temperature information of the converter, temperature information of the inverter, and temperature information of the rotating machine.

10. The power conversion device according to claim 9, wherein the operation determination unit determines the range so that loss in the converter does not exceed a predetermined value when the temperature of the converter is equal to or higher than a preset threshold value.

11. The power conversion device according to claim 9, wherein the operation determination unit determines the range so that loss in the inverter does not exceed a predetermined value when the temperature of the inverter is equal to or higher than a preset threshold value.

12. The power conversion device according to claim 9, wherein the operation determination unit determines the range so that loss in the rotating machine does not exceed a predetermined value when the temperature of the rotating machine is equal to or higher than a preset threshold value.

13. The power conversion device according to claim 1, wherein the converter includes a semiconductor switching element, and the semiconductor switching element is made of a wide bandgap semiconductor.

14. The power conversion device according to claim 1, comprising: a high-voltage terminal provided on a high-voltage line section connecting the converter and the inverter and connected to a high-voltage section of an external power supply; and a low-voltage terminal provided on a low-voltage line section connecting the converter and the inverter and connected to a low-voltage section of the external power supply, wherein power is input from the external power supply via the high-voltage terminal and the low-voltage terminal.

15. The power conversion device according to claim 14, wherein, when power is input from the external power supply via the high voltage terminal and the low voltage terminal, the operation determination unit determines the operation of the converter based on the voltage of the power input from the external power supply and the voltage of the DC power supply.

16. The power conversion device according to claim 14, wherein, when power is input from the external power supply via the high-voltage terminal and the low-voltage terminal, the operation determination unit determines the operation of the converter based on the value of the power input from the external power supply and the value of the power required to drive the rotating machine.

17. The power conversion device according to claim 14, wherein the DC power supply is a secondary battery whose voltage fluctuates depending on the state of charge, and the voltage range between the upper and lower limit values ​​of the voltage of the power input from the external power supply overlaps with the power supply voltage range between the upper and lower limit values ​​of the voltage of the DC power supply.

18. A drive system comprising: a power conversion device according to any one of claims 1 to 17; a DC power supply that inputs DC power to said power conversion device as said DC power supply; and a rotating machine that is driven by AC power input from said power conversion device as said rotating machine.

19. The drive system of claim 18 mounted on a vehicle.