WO2021090679A1 - Electric power conversion device - Google Patents

Abstract

This electric power conversion device (20) is provided with: power wires (30P, 30N); an inverter (40) which includes switching elements (42) and which is connected to one end of a coil (15); an inverter (50) which includes switching elements (52) and which is connected to the other end of the coil (15); a switch (70) which is disposed between the inverters (40, 50) on the power wire (30P); and a control unit (80) which controls the inverters (40, 50) and the switch (70). In a star connection drive region of a rotating electrical machine (14), the control unit (80) sets the switch (70) to an open state, neutralizes the inverter (50), and controls the inverter (40) in response to a drive request of the rotating electrical machine (14). In an open connection drive region, the control unit (80) sets the switch (70) to a closed state and controls, for each phase, the voltage to be applied to the coil (15). In the open connection drive region, the turn-off rate of the switching elements (52) is slower than that of the switching elements (42).

Description

Power converter Cross-reference of related applications

This application is based on Patent Application No. 2019-201648 filed in Japan on November 6, 2019, and the contents of the basic application are incorporated by reference as a whole.

The disclosure in this specification relates to a power conversion device.

Patent Document 1 discloses a power conversion device. The power conversion device performs power conversion between a DC power supply and a rotating electric machine having a plurality of phases of windings that are independent of each phase. The power conversion device includes a high-potential power supply line connected to the positive electrode side of the DC power supply, a low-potential power supply line connected to the negative electrode side, two inverters, and a switch. The two inverters are connected to the power line. The first inverter is connected to one end of the winding and the second inverter is connected to the other end of the winding. A switch is provided between the first inverter and the second inverter at at least one of the power supply lines. The contents of the prior art document are incorporated by reference as an explanation of the technical elements in this specification.

JP-A-2017-175747

Further improvement is required for the above-mentioned power conversion device.

One purpose to be disclosed is to provide a highly reliable power converter.

The power conversion device disclosed here performs power conversion between a DC power supply and a rotating electric machine having a multi-phase winding that is independent for each phase.

This power converter
A high-potential power supply line connected to the positive electrode side of the DC power supply,
A low-potential power supply line connected to the negative electrode side of the DC power supply,
A first inverter having a first upper and lower arm circuit in which a first switching element is connected in series between a high potential power supply line and a low potential power supply line for each phase and connected to one end of a winding,
A second inverter having a second upper and lower arm circuit in which a second switching element is connected in series between the high potential power supply line and the low potential power supply line for each phase and connected to the other end of the winding,
At least one of the high-potential power supply line and the low-potential power supply line is provided between the connection point of the first inverter and the connection point of the second inverter, and the second inverter and the DC power supply are connected in the closed state and are in the open state. With a switch that cuts off the connection between the second inverter and the DC power supply,
Controls the first inverter, the second inverter, and the switch, opens at least one switch in the first drive region of the rotary electric machine, neutralizes the second inverter, and responds to the drive request of the rotary electric machine. A control unit that performs star connection control that controls the first inverter, closes all switches in the second drive region of the rotary electric machine, and performs open connection control that controls the voltage applied to the windings for each phase. And have.

Then, in at least a part of the second drive region, the second switching speed, which is the switching speed of the second switching element, is slower than the first switching speed, which is the switching speed of the first switching element.

The disclosed power conversion device is equipped with a switch, and is configured to enable star connection control and open connection control. In this configuration, the second inverter is connected to the DC power supply via a switch. Since the switch is provided, the wiring inductance of the energization path via the switch is large. On the other hand, in at least a part of the second drive region, the second switching speed is slower than the first switching speed. Therefore, the surge voltage associated with the switching of the second switching element can be reduced. As a result, it is possible to provide a highly reliable power conversion device.

The other power conversion device disclosed here performs power conversion between a DC power supply and a rotating electric machine having a multi-phase winding that is independent for each phase.

This power converter
A high-potential power supply line connected to the positive electrode side of the DC power supply,
A low-potential power supply line connected to the negative electrode side of the DC power supply,
A first inverter having a first upper and lower arm circuit in which a first switching element is connected in series between a high potential power supply line and a low potential power supply line for each phase and connected to one end of a winding,
A second inverter having a second upper and lower arm circuit in which a second switching element is connected in series between the high potential power supply line and the low potential power supply line for each phase and connected to the other end of the winding,
At least one of the high-potential power supply line and the low-potential power supply line is provided between the connection point of the first inverter and the connection point of the second inverter, and the second inverter and the DC power supply are connected in the closed state and are in the open state. With a switch that cuts off the connection between the second inverter and the DC power supply,
Controls the first inverter, the second inverter, and the switch, opens at least one switch in the first drive region of the rotary electric machine, neutralizes the second inverter, and responds to the drive request of the rotary electric machine. A control unit that performs star connection control that controls the first inverter, closes all switches in the second drive region of the rotary electric machine, and performs open connection control that controls the voltage applied to the windings for each phase. And have.

Then, in the closed state of all switches, the switching speed of the second switching element is set to be a surge voltage that does not exceed the element withstand voltage of the second switching element.

The disclosed power conversion device is equipped with a switch, and is configured to enable star connection control and open connection control. In this configuration, the second inverter is connected to the DC power supply via a switch. Since the switch is provided, the wiring inductance of the energization path via the switch is large. On the other hand, in the closed state of all switches, the second switching speed is set so as to be a surge voltage that does not exceed the element withstand voltage of the second switching element. As a result, it is possible to provide a highly reliable power conversion device.

The plurality of aspects disclosed herein employ different technical means to achieve their respective objectives. The claims and the reference numerals in parentheses described in this section exemplify the correspondence with the parts of the embodiments described later, and are not intended to limit the technical scope. The objectives, features, and effects disclosed herein will be made clearer by reference to the subsequent detailed description and accompanying drawings.

It is a figure which shows the power conversion apparatus which concerns on 1st Embodiment. It is a figure which shows the connection structure of a power line, a switch, and an inverter. The horizontal axis is the number of revolutions and the vertical axis is the torque. It is a figure which shows the star connection control and the open connection control. It is a figure which shows the wiring inductance. It is a figure which shows the drive circuit part. Shows the current, voltage, and loss of each inverter It is a figure which shows the reduction effect of a surge voltage. It is a figure which shows the loss per element. It is a figure which shows the modification. It is a figure which shows the power conversion apparatus which concerns on 2nd Embodiment. It is a figure which shows the drive circuit part. It is a figure which shows the threshold value which switches a turn-off speed. It is a figure which shows the modification.

A plurality of embodiments will be described with reference to the drawings. In a plurality of embodiments, the functionally and / or structurally corresponding parts are assigned the same reference numerals. The power conversion device shown below can be applied to a mobile body driven by a rotary electric machine. The moving body is, for example, an electric vehicle (EV), a hybrid vehicle (HV), an electric vehicle such as a fuel cell vehicle (FCV), a vehicle such as a drone, a ship, a construction machine, or an agricultural machine.

<First Embodiment>
First, a schematic configuration of a drive system to which a power conversion device is applied will be described with reference to FIG.

<Drive system>
As shown in FIG. 1, the mobile drive system 10 includes a DC power supply 12, a rotary electric machine 14, and a power conversion device 20.

The DC power supply 12 is, for example, a rechargeable secondary battery such as a lithium ion battery or a nickel hydrogen battery, a capacitor, or a fuel cell. The DC power supply 12 may convert AC power into DC and output it.

The rotary electric machine 14 is, for example, a permanent magnet synchronous type or an induction type AC rotary electric machine. The rotary electric machine 14 is an open winding type rotary electric machine having a plurality of phases of windings 15 that are independent of each phase. The winding is sometimes referred to as a stator coil. The rotary electric machine 14 of the present embodiment has a three-phase winding 15. Specifically, the winding 15 includes a U-phase winding 15U, a V-phase winding 15V, and a W-phase winding 15W. In the following, the U-phase winding 15U, the V-phase winding 15V, and the W-phase winding 15W may be simply referred to as windings 15U, 15V, and 15W. The windings 15U, 15V and 15W are electrically separated from each other. The windings 15U, 15V, and 15W are not connected to each other, and both ends are open.

When the moving body is, for example, a vehicle, the rotary electric machine 14 functions as a traveling drive source of the vehicle, that is, an electric motor. The rotary electric machine 14 generates torque for driving a drive wheel (not shown). The rotary electric machine 14 may be driven by kinetic energy transmitted from an engine or drive wheels (not shown) and may function as a generator.

The power conversion device 20 performs power conversion between the DC power supply 12 and the rotary electric machine 14. As described above, the drive system 10 is a system of a power supply common system having only one DC power supply 12 and supplying power from a common DC power supply 12 to the two inverters 40 and 50 described later.

<Power converter>
Next, the power conversion device 20 will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the power conversion device 20 includes power supply lines 30P and 30N, inverters 40 and 50 which are power conversion units, a smoothing capacitor 60, a switch 70, and a control unit 80.

The power supply line 30P is a power line on the high potential side. The power supply line 30P is connected to the positive electrode of the DC power supply 12. The power supply line 30N is a power line on the low potential side. The power supply line 30N is connected to the negative electrode of the DC power supply 12. The power supply line 30P corresponds to the high potential power supply line, and the power supply line 30N corresponds to the low potential power supply line. The power lines 30P and 30N are formed by using, for example, a bus bar. The bus bar is a metal plate material made of Cu, a Cu alloy, or the like.

Inverters 40 and 50 are DC-AC converters. The inverter 40 includes an upper and lower arm circuit 41 according to the number of phases of the winding 15 of the rotary electric machine 14. The upper and lower arm circuits 41 have an upper arm 41H and a lower arm 41L, respectively. The upper arm 41H and the lower arm 41L are connected in series between the power supply line 30P and the power supply line 30N with the upper arm 41H on the power supply line 30P side. In the following, the upper arm 41H and the lower arm 41L may be simply referred to as arms 41H and 41L. The inverter 40 of this embodiment is a three-phase inverter having a three-phase upper / lower arm circuit 41.

Each arm 41H and 41L has a switching element 42. The upper and lower arm circuits 41 are configured by connecting switching elements 42 in series between power supply lines 30P and 30N. The switching element 42 is a transistor having a gate, specifically, an IGBT or a MOSFET. The switching element 42 of this embodiment is an n-channel type IGBT.

Each of the arms 41H and 41L has a return diode 43 connected in antiparallel to the switching element 42. The cathode of the diode 43 is connected to the collector of the switching element 42 (IGBT), and the anode is connected to the emitter. The switching element 42 and the diode 43 constituting one arm may be configured as a common semiconductor element (chip) or may be configured as different semiconductor elements. The inverter 40 corresponds to the first inverter, the upper and lower arm circuits 41 correspond to the first upper and lower arm circuits, and the switching element 42 corresponds to the first switching element.

The inverter 50 has the same configuration as the inverter 40. The inverter 50 includes an upper and lower arm circuit 51 according to the number of phases of the winding 15. The upper and lower arm circuits 51 have an upper arm 51H and a lower arm 51L, respectively. In the following, the upper arm 51H and the lower arm 51L may be simply referred to as arms 51H and 51L. The inverter 50 of this embodiment is a three-phase inverter having a three-phase upper / lower arm circuit 51.

Each arm 51H and 51L has a switching element 52. The upper and lower arm circuit 51 is configured by connecting switching elements 52 in series between power supply lines 30P and 30N. The switching element 52 of this embodiment is an n-channel type IGBT. Each of the arms 51H and 51L has a return diode 53 connected in antiparallel to the switching element 52. The cathode of the diode 53 is connected to the collector of the switching element 52 (IGBT), and the anode is connected to the emitter. The inverter 50 corresponds to the second inverter, the upper / lower arm circuit 51 corresponds to the second upper / lower arm circuit, and the switching element 52 corresponds to the second switching element.

In the upper arm 41H of the inverter 40, the collector of the switching element 42 is connected to the power supply line 30P. In the lower arm 41L, the emitter of the switching element 42 is connected to the power supply line 30N. The emitter of the switching element 42 in the upper arm 41H and the collector of the switching element 42 in the lower arm 41L are connected to each other. Similarly, in the upper arm 51H of the inverter 50, the collector of the switching element 52 is connected to the power supply line 30P. In the lower arm 51L, the emitter of the switching element 52 is connected to the power supply line 30N. The emitter of the switching element 52 in the upper arm 51H and the collector of the switching element 52 in the lower arm 51L are connected to each other.

In this way, the power supply terminal (collector terminal), which is the terminal on the high potential side of the upper arms 41H and 51H, is connected to the power supply line 30P. Further, the power supply terminal (emitter terminal), which is a terminal on the low potential side of the lower arms 41L and 51L, is connected to the power supply line 30N. The power supply line 30P is a connection line connecting the positive electrode side of the DC power supply 12, the high potential side of the upper arm 41H of the inverter 40, and the high potential side of the upper arm 51H of the inverter 50. The power supply line 30N is a connection line connecting the negative electrode side of the DC power supply 12, the low potential side of the lower arm 41L of the inverter 40, and the low potential side of the lower arm 51L of the inverter 50.

The node that is the connection point between the upper arm 41H and the lower arm 41L is connected to one end of the winding 15 of the corresponding phase, and the node of the upper arm 51H and the lower arm 51L is the other of the winding 15 of the corresponding phase. Connected to the end. The node U1 of the U-phase upper and lower arm circuit 41 is connected to one end of the U-phase winding 15U, and the node U2 of the U-phase upper and lower arm circuit 51 is connected to the other end of the U-phase winding 15U. The node V1 of the V-phase upper and lower arm circuit 41 is connected to one end of the V-phase winding 15V, and the node V2 of the V-phase upper and lower arm circuit 51 is connected to the other end of the V-phase winding 15V. The node W1 of the W-phase upper and lower arm circuit 41 is connected to one end of the W-phase winding 15W, and the node W2 of the W-phase upper and lower arm circuit 51 is connected to the other end of the W-phase winding 15W.

The smoothing capacitor 60 is connected between the power supply lines 30P and 30N. The smoothing capacitor 60 is provided between the DC power supply 12 and the inverters 40 and 50 which are power conversion units. The smoothing capacitor 60 is connected in parallel to the inverters 40 and 50. The smoothing capacitor 60 smoothes the DC voltage supplied from the DC power supply 12 and stores the electric charge of the DC voltage.

The switch 70 is provided between the connection point of the inverter 40 and the connection point of the inverter 50 at at least one of the power supply lines 30P and 30N. The switch 70 connects the power supply terminal of the inverter 50 and the smoothing capacitor 60 (DC power supply 12) in the closed state, and cuts off the connection between the power supply terminal of the inverter 50 and the smoothing capacitor 60 (DC power supply 12) in the open state. To do. As the switch 70, for example, a mechanical relay or a semiconductor switch can be adopted.

The switch 70 of this embodiment is provided on the power supply line 30P. The switch 70 has a switching element 71 formed on a semiconductor chip. The switch 70 has the same configuration as the arms 41H and 41L, and a diode is connected to the switching element 71 in antiparallel. For example, as shown in FIG. 2, the switch 70 is provided between the bus bars 31P and 32P constituting the power supply line 30P. The switch 70 bridges the bus bars 31P and 32P. A power supply terminal 44 on the high potential side of the upper and lower arm circuits 41 constituting the inverter 40 is connected to the bus bar 31P on the DC power supply 12 side. A power supply terminal 54 on the high potential side of the upper and lower arm circuits 51 constituting the inverter 50 is connected to the bus bar 32P.

The collector of the switching element 71 constituting the switch 70 is connected to the bus bar 31P via the wiring portion 33, and the emitter is connected to the bus bar 32P via the wiring portion 34. The wiring portions 33 and 34 are, for example, an extension portion extending from the main body of the bus bars 31P and 32P, terminals provided by the switch 70, one end connected to the bus bars 31P and 32P, and the other end connected to the switch 70. It is composed of at least one of metal members. The wiring portions 33 and 34 have a smaller cross-sectional area of the energization path than, for example, the bus bars 31P and 32P.

The switch 70 is provided between the connection point of the power supply terminal 44 and the connection point of the power supply terminal 54 on the bus bars 31P and 32P. When the switching element 71 is turned on and the switch 70 is closed, the bus bars 31P and 32P are electrically connected. When the switching element 71 is turned off and the switch 70 is opened, the electrical connection between the bus bars 31P and 32P is cut off. In this way, when the switch 70 is opened, the connection between the inverter 50 and the DC power supply 12 is cut off.

Although not shown, the power supply terminal on the low potential side of the upper and lower arm circuits 41 and the power supply terminal on the low potential side of the upper and lower arm circuits 51 are connected to a common bus bar constituting the power supply line 30N. For example, at least a part of the bus bars constituting the power supply line 30N is arranged to face the bus bars 31P and 31P described above. The output terminals of the upper and lower arm circuits 41 and 51 are connected to the corresponding winding 15. The output terminal is connected to the node of the upper and lower arm circuits.

The control unit 80 has a drive command generation unit 81 and a drive circuit unit 82. The drive command generation unit 81 includes, for example, a microcomputer. The microcomputer is a microcomputer configured to include a CPU, a ROM, a RAM, a register, an I / O port, a bus, and the like. The processing in the drive command generation unit 81 may be software processing in which the CPU executes a program stored in advance in a physical memory device such as a ROM. Further, hardware processing by a dedicated electronic circuit may be used.

The drive command generation unit 81 controls the inverters 40 and 50. The drive command generation unit 81 generates a drive command (command signal) for controlling the on / off of the switching elements 42 and 52, and outputs the drive command (command signal) to the drive circuit unit 82. The drive command generation unit 81 generates a drive command based on a drive request of the rotary electric machine 14 such as a torque command value input from a higher-level ECU (not shown) and signals detected by various sensors. Examples of various sensors include a current sensor, a rotation angle sensor, and a voltage sensor. The current sensor detects the phase current flowing through the winding 15 of each phase. The rotation angle sensor detects the rotation angle of the rotor of the rotary electric machine 14. The voltage sensor detects the voltage across the smoothing capacitor 60. The power conversion device 20 includes these sensors (not shown).

The drive command generation unit 81 controls the switch 70. The drive command generation unit 81 generates a drive command that controls the on / off of the switching element 71. This drive command is a switching command for switching the opening and closing of the switch 70.

The drive circuit unit 82 outputs a drive signal to the gates of the corresponding switching elements 42, 52, and 71 based on the drive command of the drive command generation unit 81. The drive circuit unit 82 may be referred to as a driver. The drive circuit unit 82 outputs a drive signal so as to increase the drive voltage (gate voltage Vge) during the on period of the pulsed drive command and decrease the drive voltage during the off period, for example. The drive circuit unit 82 can independently control the on / off of the six switching elements 42, the six switching elements 52, and the switching element 71, respectively. The drive circuit unit 82 includes a drive circuit for each switching element. For example, the drive circuit unit may be converted into an IC. In this case, the drive circuit unit 82 includes a plurality of driver ICs according to the number of switching elements 42, 52, 71.

<Star connection control and open connection control>
Next, star connection control and open connection control will be described with reference to FIGS. 3 and 4. FIG. 3 is an operating point map of the rotary electric machine 14 in which the horizontal axis is the rotation speed and the vertical axis is the torque. As shown in FIG. 3, the drive region of the rotary electric machine 14 is divided into two regions according to the rotation speed and the torque. One of the drive areas is the star connection drive area. The star connection drive area is a normal area. The other one of the drive areas is the open wiring drive area. The open connection drive region is a region having higher rotation or torque than the star connection drive region. The star connection drive area corresponds to the first drive area, and the open connection drive area corresponds to the second drive area.

The control unit 80 executes star connection control when the operating point is in the star connection drive region. The control unit 80 controls the switching elements 42 and 52 and the switch 70 so that the windings 15U, 15V, and 15W are in a star connection state. Specifically, as shown in FIG. 4, the switch 70 is opened, that is, the switching element 71 is turned off. Further, the switching element 52 of the upper arm 51H of all phases is turned on, and the switching element 52 of the lower arm 51L of all phases is turned off to neutralize the inverter 50. Then, the switching element 42 of the inverter 40 is controlled according to a drive request or the like. Star connections are sometimes referred to as Y connections.

The alternate long and short dash line in the figure shows an example of the current path. FIG. 4 shows a current path when the switching element 42 of the upper arm 41H of the U phase and the switching element 42 of the lower arm 41L of the W phase are turned on. The current is U-phase upper arm 41H → node U1 → U-phase winding 15U → node U2 → U-phase upper arm 51H → W-phase upper arm 51H → node W2 → W-phase winding 15W → node W1 → W-phase. It flows in the order of the lower arm 41L.

The control method of the inverter 40 by the control unit 80 (drive command generation unit 81) is not particularly limited. For example, a PWM control method or an overmodulation PWM control method may be used. In the PWM control method and the overmodulation PWM control method, the drive command generation unit 81 outputs, for example, a triangular wave, a sawtooth wave, or a square wave as a high-frequency carrier (carrier wave). Then, a pulse-shaped drive command is generated by comparing the voltage of the sinusoidal voltage signal as the torque command value with the carrier. For example, a square wave control method may be used. In the rectangular wave control method, the drive command generation unit 81 generates a rectangular wave pulse having a one-to-one on / off period ratio within one control cycle as a drive command from a sinusoidal voltage signal as a torque command value. For example, the control method may be switched according to the rotation speed of the rotary electric machine 14. The square wave control has a higher voltage utilization rate than the PWM control. Of the star connection drive region, the PWM control method may be used in the low to medium rotation range, and the rectangular wave control method may be used in the high rotation range.

The control unit 80 executes open connection control when the operating point is in the open connection drive region. The control unit 80 closes the switch 70, that is, turns on the switching element 71, and opens the neutral point by the inverter 50. By opening the neutral point, an open connection circuit of the U-phase upper and lower arm circuits 41 and 51 is formed via the U-phase winding 15U. Similarly, an open connection circuit of the V-phase upper and lower arm circuits 41 and 51 via the V-phase winding 15V and an open connection circuit of the W-phase upper and lower arm circuits 41 and 51 via the W-phase winding 15W are formed. .. The control unit 80 regards each phase as an independent open connection circuit, and controls the applied voltage for each phase.

The alternate long and short dash line in the figure shows an example of the current path. FIG. 4 shows a current path when the switching element 42 of the lower arm 41L of the V phase and the switching element 52 of the upper arm 51H of the V phase are turned on. The current flows in the order of switch 70 → V-phase upper arm 51H → node V2 → V-phase winding 15V → node V1 → V-phase lower arm 41L. This current path corresponds to an energization path via the switch 70.

The control method of the inverters 40 and 50 by the control unit 80 is not particularly limited. For example, a PWM control method may be used. A square wave control method or an overmodulation PWM control method may be used. The control method may be switched according to the rotation speed of the rotary electric machine 14. As described above, the control unit 80 can independently control each of the six switching elements 42 and the six switching elements 52. Therefore, a current can be passed through the windings 15 of each phase in both the positive direction and the negative direction. The positive direction is the direction from the inverter 40 side to the inverter 50 side, and the negative direction is the direction from the inverter 50 to the inverter 40 side.

For example, while the two switching elements 52 constituting the V-phase upper and lower arm circuits 51 are complementarily turned on and off by PWM control, the switching element 42 of the V-phase upper arm 41H is turned off, and the switching element 42 of the V-phase lower arm 41L is turned off. May be turned on. As a result, a current in the negative direction flows through the V-phase winding 15V. On the other hand, while the two switching elements 42 constituting the V-phase upper and lower arm circuits 41 are complementarily turned on and off by PWM control, the switching element 52 of the V-phase upper arm 51H is turned off, and the switching element of the V-phase lower arm 51L is turned off. 52 may be turned on. As a result, a forward current flows through the V-phase winding 15V.

In the present embodiment, the star connection control and the open connection control can be switched by switching the opening / closing of the switch 70 and changing the on / off control of the switching elements 42 and 52. By executing the open connection control instead of the star connection control, it is possible to output a region on the higher rotation side or a region on the higher torque side.

<Wiring inductance and surge voltage>
Next, the wiring inductance and the surge voltage will be described with reference to FIG. FIG. 5 shows the wiring inductance. In FIG. 5, for convenience, only L1 and L2 are shown as the wiring inductance of the power conversion device 20. L1 is the wiring inductance of the power supply line 30P. L2 is the wiring inductance increased by providing the switch 70. The wiring inductance L2 is the sum of the inductance component of the switch 70 and the inductance of the connection portions (wiring portions 33, 34) between the switch 70 and the power supply lines 30P (bus bars 31P, 32P). In FIG. 5, for convenience, the inductance L2 and the switch 70 are shown together.

As described above, the power conversion device 20 has a wiring inductance in the energization path between the DC power supply 12 and the switching element. Therefore, a surge voltage is generated due to a steep current change when the switching element is turned off. In the case of star connection control, the switch 70 does not intervene in the energization path. The wiring inductance of the energization path with the DC power supply 12 is L1 in the switching element 42 of the upper arm 41H. Therefore, when the switching element 42 of the upper arm 41H is turned off, the surge voltage due to the wiring inductance L1 is superimposed on the power supply voltage of the DC power supply 12, and the potential on the high potential side of the switching element 42 rises. On the other hand, in the case of open connection control, the switch 70 is interposed in the energization path with the DC power supply 12. The wiring inductance of the energization path is L1 + L2 in the switching element 52 of the upper arm 51H. Therefore, when the switching element 52 of the upper arm 51H is turned off, the surge voltage due to the wiring inductance L1 + L2 is superimposed on the power supply voltage of the DC power supply 12, and the potential on the high potential side of the switching element 52 rises.

<Switching speed>
FIG. 6 shows an example of the drive circuit unit 82. In FIG. 6, for convenience, only the drive circuit 83a corresponding to one switching element 42 and the drive circuit 83b corresponding to one switching element 52 are shown. The drive circuit 83a corresponding to the remaining five switching elements 42 has the same configuration as that shown in FIG. The drive circuit 83b corresponding to the remaining five switching elements 52 has the same configuration as that shown in FIG. The drive circuit unit 82 further includes a drive circuit corresponding to the switching element 71. For example, the drive circuits 83a and 83b are made into ICs, respectively. In this way, the drive circuit unit (switching element terminal) may be converted into an IC. The upper and lower arm circuits may be converted into ICs, or the inverters may be converted into ICs.

The drive circuit 83a has an on switch 84a, an off switch 85a, and a drive control unit 86a. In the present embodiment, the on switch 84a is a p-channel MOSFET, and the off switch 85a is an n-channel MOSFET.

The on switch 84a and the off switch 85a are connected in series between the power supply and the ground (GND) with the on switch 84a on the power supply side. The drain of the on switch 84a and the drain of the off switch 85a are connected to each other. The gate of the switching element 42 is connected to the connection point between the on switch 84a and the off switch 85a. A resistor 87a is provided between the connection point and the on switch 84a described above, and a resistor 88a is provided between the connection point and the off switch 85a. The on switch 84a may be referred to as a charging switch. The off switch 85a may be referred to as a discharge switch.

A drive command is input to the drive control unit 86a from the drive command generation unit 81 via an insulating element (not shown) such as a photocoupler. The drive control unit 86a controls the on / off of the on switch 84a and the off switch 85a based on the drive command (command signal). When the drive command is L level, the drive control unit 86a turns on the on switch 84a and turns off the off switch 85a. As a result, a current flows through the gate of the switching element 42 via the on switch 84a and the resistor 87a, and the gate is charged. When the drive command is H level, the drive control unit 86a turns off the on switch 84a and turns on the off switch 85a. As a result, a current flows from the gate of the switching element 42 to the ground via the resistor 88a and the off switch 85a, and the charge of the gate is extracted.

The drive circuit 83b of the switching element 52 constituting the inverter 50 has an on switch 84a, an off switch 85b, a drive control unit 86b, and resistors 87b and 88b. Since the drive circuit 83b has the same configuration as the drive circuit 83a, the description thereof will be omitted.

In the present embodiment, the value of the resistance 88a of the drive circuit 83a and the value of the resistance 88b of the drive circuit 83b are different from each other. Specifically, the value of the resistor 88b is larger than the value of the resistor 88a. As a result, the switching speed when the switching element 52 is turned off is slower than the switching speed when the switching element 42 is turned off. The resistors 88a and 88b are not variable resistors but fixed resistors. The resistors 87a and 87b have values equal to each other. In the following, the switching speed at the time of turning off may be referred to as a turn-off speed.

<Summary of the first embodiment>
FIG. 7 shows the collector current Ic, the voltage Vce, and the loss J of the inverters 40 and 50, respectively. FIG. 8 shows the self-surge voltage of the inverter 50 together with a comparative example. In FIG. 9, the loss per element is shown together with a comparative example. In the figure, the inverter 40 is shown as a first INV, and the inverter 50 is shown as a second INV.

In the present embodiment, as described above, the value of the resistor 88b on the inverter 50 side is larger than the value of the resistor 88a on the inverter 40 side. Therefore, as shown in FIG. 7, the turn-off speeds of all the switching elements 52 constituting the inverter 50 are slower than the turn-off speeds of all the switching elements 42 constituting the inverter 40. As a result, the surge voltage of the inverter 50 can be reduced. As shown in FIG. 8, the surge voltage (self-surge voltage) of the inverter 50 is reduced, and thus the surge voltage is equal to or less than the allowable surge voltage, as compared with the comparative example in which the turn-off speed of the switching element 52 is substantially equal to the turn-off speed of the switching element 42. Can be. As a result, it is possible to provide a highly reliable power conversion device 20. The turn-off speed of the switching element 42 corresponds to the first switching speed, and the turn-off speed of the switching element 52 corresponds to the second switching speed.

On the other hand, since the turn-off speed of the switching element 52 is slow, the turn-off loss of the inverter 50 is larger than the turn-off loss of the inverter 40. However, in the star connection drive region, which is a normal range, the control unit 80 fixes the switching element 52 on or off and switches only the switching element 42. Therefore, even if the turn-off speed of the switching element 52 is slowed down, there is no effect on the loss. In the open connection drive region, the turn-off loss increases only when the switch 70 is included in the energization path. Therefore, the loss per element is as shown in FIG. 9 in a predetermined traveling mode in which the star connection drive region is mainly included and the open connection drive region is also included. The loss per element increases by the increase in the turn-off loss, but it is slight (for example, about several%). By switching between star connection control and open connection control, the loss per element can be reduced by about several tens of percent. Therefore, both reduction of surge voltage and low loss drive can be achieved at the same time.

In the present embodiment, the turn-off speed of the switching element 52 is slower than the turn-off speed of the switching element 42 in the entire drive region of the rotary electric machine 14. There is no need to switch the switching speed. For example, fixed resistors may be used as the resistors 88a and 88b. Therefore, the configuration can be simplified. Even if a fixed resistor is used, since the switching element 52 is fixed on or off in the star connection drive region, an increase in turn-off loss can be suppressed.

In the present embodiment, the turn-off speeds of the switching elements 42 and 52 are set so as to satisfy the following equation.
(Equation 1) L1 × di1 / dt = L3 × di2 / dt
di1 / dt is the turn-off speed of the switching element 42. di2 / dt is the turn-off speed of the switching element 52. As described above, L1 is the wiring inductance of the energization path that does not pass through the switch 70, and L3 is the wiring inductance of the energization path that does not pass through the switch 70 (= L1 + L2).

Specifically, the values of the resistors 88a and 88b are adjusted so that the turn-off speed satisfies Equation 1. According to this, in the inverter 40 and the inverter 50, the surge voltage at the time of turn-off becomes substantially equal to each other. The withstand voltage of the switching elements 42 and 52 can be made substantially equal to each other.

In this embodiment, the switching elements 42 and 52 have a common configuration. For example, the semiconductor elements constituting the arms 41H and 41L of the inverter 40 and the semiconductor elements constituting the arms 51H and 51L of the inverter 50 have a common configuration (parts having the same part number). As described above, by slowing down the turn-off speed of the switching element 52, the surge voltage generated in the inverter 50 can be reduced to the allowable surge voltage. Therefore, even if the configuration of the switching elements 42 and 52 is the same and the withstand voltage of the switching element 52 is the same as that of the switching element 42, it is possible to switch between the star connection control and the open connection control.

As described above, when the DC power supply 12 and the inverter 50 are electrically connected via the switch 70, the wiring inductance of the energization path becomes larger than normally thought, and the surge voltage of the switching element 52 becomes large. I found a new thing to be. That is, it was newly found that the inductance derived from the switch 70 cannot be ignored with respect to the surge voltage. The inductance derived from the switch 70 is a small value, for example, about several nH. In particular, as the switching speed is increased (for example, 10 kA / μs or more), it has become necessary to fully consider the inductance derived from the switch 70.

In the present embodiment, the switching speed of the switching element 52 is set to be a surge voltage that does not exceed the element withstand voltage of the switching element 52 in the closed state of all the switches 70. In the entire open connection drive region, the switching speed of the switching element 52 is set in consideration of the increase in inductance derived from the switch 70. For example, the resistor 88b is selected and the switching speed of the switching element 52 is set so that the surge voltage of the switching element 52 does not exceed the element withstand voltage (see FIG. 8). Therefore, it is possible to prevent the surge voltage of the switching element 52 from exceeding the element withstand voltage even though the switch 70 is provided in the energization path. As a result, it is possible to provide a highly reliable power conversion device 20.

The number of phases of the rotary electric machine 14 and the inverters 40 and 50 is not limited to the above-mentioned three phases. It may be polyphasic. For example, as in the modified example shown in FIG. 10, the application can be applied to a five-phase rotary electric machine 14 and inverters 40 and 50. In FIG. 10, the rotary electric machine 14 has a U-phase winding 15U, a V-phase winding 15V, a W-phase winding 15W, an X-phase winding 15X, and a Y-phase winding 15Y. Nodes X1 and X2 of inverters 40 and 50 are connected to both ends of the X-phase winding 15X. Nodes Y1 and Y2 of the inverters 40 and 50 are connected to both ends of the Y-phase winding 15Y.

<Second Embodiment>
This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the prior embodiment, the resistors 88a and 88b are fixed resistors, and the turn-off speed of the switching element 52 is made slower than the turn-off speed of the switching element 42 in the entire drive region. Instead of this, the turn-off speed may be switched by satisfying a predetermined condition, thereby satisfying the magnitude relationship of the turn-off speed described above.

The power conversion device 20 according to the present embodiment further includes a current detection unit that detects a current energized in the rotary electric machine 14. In the example shown in FIG. 11, a current sensor 90 that detects a phase current is provided as a current detection unit. As the current sensor 90, a sensor including a magnetron conversion element such as a Hall element can be used.

The control unit 80 of the power conversion device 20 has a speed switching unit 89. The speed switching unit 89 switches at least the turn-off speed of the switching element 52 among the switching element 42 and the switching element 52 based on the current detected by the current sensor 90. The speed switching unit 89 of the present embodiment switches the turn-off speed of the switching element 52 based on the detected current. The speed switching unit 89 may be integrally configured with the drive command generation unit 81, or may be integrally configured with the drive circuit unit 82.

The phase current changes over time. The speed switching unit 89 compares the value of the detected current of each phase in a predetermined period with a predetermined threshold value. When the detection current of at least one phase exceeds the threshold value, the speed switching unit 89 outputs a switching signal so that the turn-off speed of the switching element 52 becomes slower than the turn-off speed when the detection current is below the threshold value. The value of the detected current is, for example, the maximum value. The effective value or the average value may be used instead of the maximum value. The speed switching unit 89 may have a calculation function for calculating these as needed. The current sensor 90 may be provided with a calculation function. The predetermined period is, for example, one cycle period of a sinusoidal phase current.

FIG. 12 shows the drive circuit unit 82 of this embodiment. FIG. 12 corresponds to FIG. The drive circuit 83b of the switching element 52 has a variable resistor 188b as a gate resistance on the turn-off side instead of the fixed resistor 88b. The variable resistor 188b is composed of, for example, a digital potentiometer. The resistance value of the variable resistor 188b is set according to the switching signal output from the speed switching unit 89.

The speed switching unit 89 sets the resistance value of the variable resistor 188b to the first resistance value when the detected current is equal to or less than the threshold value. The first resistance value is a value smaller than the second resistance value described later. In the present embodiment, the first resistance value is the same value as the resistance value of the resistor 88a in the drive circuit 83a. Therefore, as shown in FIG. 13, the turn-off speed of the switching element 52 is substantially equal to the turn-off speed of the switching element 42 in the small current region where the detected current is equal to or less than the threshold value. When the detected current is larger than the threshold value, the speed switching unit 89 sets the resistance value of the variable resistor 188b to the second resistance value. The second resistance value is a value larger than the resistance value of the resistor 88a. Therefore, in a large current region where the detected current is larger than the threshold value, the turn-off speed of the switching element 52 is slower than the turn-off speed of the switching element 42.

The broken line shown in FIG. 13 indicates an isocurrent line. The current value A1 is the smallest, and the larger the subscript number, the larger the current value. That is, the current value A8 is the largest. In this embodiment, the current value A3 is used as the threshold value.

The control unit 80 controls the turn-off speed of the switching element 52 to be substantially equal to the turn-off speed of the switching element 42 in the region of the star connection drive region where the current value A3 or less is the threshold value. The control unit 80 controls the turn-off speed of the switching element 52 to be slower than the turn-off speed of the switching element 42 in a region larger than the threshold value in the star connection drive region. The control unit 80 controls the turn-off speed of the switching element 52 to be substantially equal to the turn-off speed of the switching element 42 in the region below the threshold value in the open connection drive region. The control unit 80 controls the turn-off speed of the switching element 52 to be slower than the turn-off speed of the switching element 42 in a region larger than the threshold value in the open connection drive region.

<Summary of the second embodiment>
According to this embodiment, the turn-off speed of the switching element 52 can be switched based on the current applied to the rotary electric machine 14, that is, the drive current of the rotary electric machine 14. In a large current region larger than the threshold value, the turn-off speed of the switching element 52 is made slower than the turn-off speed of the switching element 42. As a result, the turn-off speed of the switching element 52 is slower than the turn-off speed of the switching element 42 in at least a part of the open connection drive region. Therefore, as described in the preceding embodiment, the surge voltage can be reduced. In addition, both reduction of surge voltage and low loss drive can be achieved at the same time.

Further, the turn-off speed of the switching element 52 in the small current region is made faster than the turn-off speed of the switching element 52 in the large current region. Specifically, in the small current region, the turn-off speed of the switching element 52 is made substantially equal to the turn-off speed of the switching element 42. Since the turn-off speed of the switching element 52 is not reduced during low current and high rotation, it is possible to suppress a decrease in system efficiency during high-speed running, for example. That is, the electricity cost can be improved when the low current and high rotation region continues. The low current high rotation region is a low torque high rotation region.

An example of switching the turn-off speed of the switching element 52 by using the variable resistor 188b has been shown, but the present invention is not limited to this. An active gate drive circuit can be applied. For example, the configuration of the gate resistor whose turn-off speed can be switched is not limited to the variable resistor 188b. The configuration also includes a plurality of resistors connected in series to the gate and connected in parallel with each other, and a selector for selecting one resistor connected to the off switch 85b from among the plurality of resistors according to a switching signal. Good. Further, the configuration may include a plurality of resistors forming a series circuit connected to the gate, and a selector for selecting a resistor arranged between the gate and the off switch 85b according to a switching signal. The drive circuit unit 82 has a plurality of resistors, and the speed switching unit 89 has a switching signal generation unit and the above-mentioned selector.

An example is shown in which the turn-off speed of the switching element 52 is slowed down when the threshold value is exceeded in both the star connection drive region and the open connection drive region, but the present invention is not limited to this. As described above, in the star connection drive region, the switching element 52 is not operated for switching in order to neutralize the inverter 50. Therefore, as shown in FIG. 14, the turn-off speed of the switching element 52 may be slowed down when the threshold value is exceeded only in the open connection drive region. In FIG. 14, for clarification, hatching is performed in a region where the turn-off speed of the switching element 52 is slower than the turn-off speed of the switching element 42. The speed switching unit 89 slows down the turn-off speed of the switching element 52 when the operating point of the rotary electric machine 14 is larger than the threshold value in the open connection drive region.

An example of switching the turn-off speed of the switching element 52 based on the phase current has been shown, but the present invention is not limited to this. For example, the current flowing through the switching elements 42 and 52 may be detected and the turn-off speed may be switched based on the detected current. In this case, a sense element may be provided in each of the switching elements 42 and 52, and a current detection resistor may be connected in series to the sense element.

The current flowing through the switch 70 may be detected and the turn-off speed may be switched based on the detected current. For example, the switching element 71 may be provided with a sense element, and the sense element may be connected in series with a current detection resistor. When the operating point changes from the star connection drive region to the open connection drive region, the switch 70 changes from the open state to the closed state, and a current flows through the switch 70. Therefore, as shown in FIG. 14, it is suitable for a configuration in which the turn-off speed of the switching element 52 is slowed down when the threshold value is exceeded only in the open connection drive region.

<Other Embodiments>
Disclosure in this specification, drawings and the like is not limited to the illustrated embodiments. The disclosure includes exemplary embodiments and modifications by those skilled in the art based on them. For example, disclosure is not limited to the parts and / or element combinations shown in the embodiments. Disclosure can be carried out in various combinations. The disclosure can have additional parts that can be added to the embodiment. The disclosure includes those in which the parts and / or elements of the embodiment are omitted. Disclosures include replacement or combination of parts and / or elements between one embodiment and another. The technical scope disclosed is not limited to the description of the embodiments. Some technical scopes disclosed are indicated by the claims description and should be understood to include all modifications within the meaning and scope equivalent to the claims statement.

Disclosure in specifications, drawings, etc. is not limited by the description of the scope of claims. The disclosure in the specification, drawings, etc. includes the technical ideas described in the claims, and further covers a wider variety of technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure of the specification, drawings, etc. without being bound by the description of the claims.

The control unit 80 is provided by a control system including at least one computer. The control system includes at least one processor (hardware processor) which is hardware. The hardware processor can be provided by the following (i), (ii), or (iii).

(I) The hardware processor may be a hardware logic circuit. In this case, the computer is provided by a digital circuit that includes a large number of programmed logic units (gate circuits). Digital circuits may include memory for storing programs and / or data. Computers may be provided by analog circuits. Computers may be provided by a combination of digital and analog circuits.

(Ii) The hardware processor may be at least one processor core that executes a program stored in at least one memory. In this case, the computer is provided by at least one memory and at least one processor core. The processor core is referred to as, for example, a CPU. The memory is also referred to as a storage medium. A memory is a non-transitional and substantive storage medium that non-temporarily stores "programs and / or data" that can be read by a processor.

(Iii) The hardware processor may be a combination of the above (i) and the above (ii). (I) and (ii) are arranged on different chips or on a common chip.

That is, the means and / or functions provided by the control unit 80 can be provided by hardware only, software only, or a combination thereof.

An example is shown in which the turn-off speed of the switching element 52 is slower than the turn-off speed of the switching element 42 in the entire star connection drive region and the entire open connection drive region. On the other hand, the turn-off speed of the switching element 52 may be slower than the turn-off speed of the switching element 42 only in the entire open connection drive region. That is, the turn-off speed of the switching element 52 may be reduced in the entire area of the star connection drive region, and the turn-off speed of the switching element 52 may be reduced in the entire area of the open connection drive region. For example, instead of the speed switching unit 89, the resistance value of the variable resistor 188b may be switched according to the drive signal of the switch 70 (switching element 71). The resistance value of the variable resistor 188b becomes a value larger than the value at the time of the drive signal for opening the switch 70 due to the drive signal for closing the switch 70.

An example of providing the switch 70 on the power supply line 30P has been shown, but the present invention is not limited to this. It may be provided between the inverters 40 and 50 on at least one of the power supply line 30P and the power supply line 30N. For example, the switch 70 may be provided only on the power supply line 30N. In this case, in the star connection drive region, the lower arm 51L of the inverter 50 is turned on and the upper arm 51H is turned off. A switch 70 may be provided on each of the power lines 30P and 30N. In this case, in the star connection drive region, one of the arms 51H and 51L of the inverter 50 is turned on, the other is turned off, and at least the switch 70 on the turned-on side is opened. In the open connection drive region, all the switches 70 are closed.

An example of dividing the gate resistance (resistors 87a, 87b, 88a, 88b) between the turn-on side and the turn-off side in the drive circuit unit 82 is shown. However, the gate resistance may be common between the turn-on side and the turn-off side. For example, the drains of the on switch 84b and the off switch 85b may be connected to each other, and a common gate resistor may be provided between the connection point and the gate of the switching element 52.

Claims (7)

A power conversion device that performs power conversion between a DC power supply (12) and a rotating electric machine (14) having a plurality of phases of windings (15) that are independent of each phase.
A high potential power supply line (30P) connected to the positive electrode side of the DC power supply, and
A low potential power supply line (30N) connected to the negative electrode side of the DC power supply, and
Each phase has a first upper and lower arm circuit (41) in which a first switching element (42) is connected in series between the high potential power supply line and the low potential power supply line, and is connected to one end of the winding. The first inverter (40) to be used and
A second upper and lower arm circuit (51) in which a second switching element (52) is connected in series between the high-potential power supply line and the low-potential power supply line is provided for each phase, and is provided at the other end of the winding. The second inverter (50) to be connected and
In at least one of the high-potential power supply line and the low-potential power supply line, the second inverter and the DC power supply are provided between the connection point of the first inverter and the connection point of the second inverter in a closed state. A switch (70) that connects the second inverter and cuts off the connection between the second inverter and the DC power supply in the open state.
The first inverter, the second inverter, and the switch are controlled, at least one switch is opened in the first drive region of the rotary electric machine, the second inverter is neutralized, and the second inverter is neutralized. Star connection control is performed to control the first inverter in response to the drive request of the rotary electric machine, all the switches are closed in the second drive region of the rotary electric machine, and the voltage applied to the winding is applied to the phase. A control unit (80) that performs open connection control that controls each unit,
With
A power conversion device in which the second switching speed, which is the switching speed of the second switching element, is slower than the first switching speed, which is the switching speed of the first switching element, in at least a part of the second drive region. The power conversion device according to claim 1, wherein the second switching speed is slower than the first switching speed in the entire area of the second drive region. The power conversion device according to claim 2, wherein the second switching speed is slower than the first switching speed in the entire drive region of the rotary electric machine including the first drive region and the second drive region. Assuming that the first switching speed is di1 / dt, the second switching speed is di2 / dt, the wiring inductance of the energization path not via the switch is L1, and the wiring inductance of the energization path via the switch is L3.
L1 x di1 / dt = L3 x di2 / dt
The power conversion device according to any one of claims 1 to 3, wherein the second switching speed is set so as to satisfy the above conditions. A current detection unit (90) for detecting the current energized in the rotary electric machine is further provided.
The control unit includes at least a speed switching unit (89) for switching the second switching speed among the first switching speed and the second switching speed.
The power according to claim 1, wherein the speed switching unit slows the second switching speed when the current detected by the current detection unit is larger than a predetermined value, as compared with the case where the detected current is equal to or less than the predetermined value. Conversion device. The power conversion device according to any one of claims 1 to 5, wherein the first switching element and the second switching element are semiconductor elements having a common configuration. A power conversion device that performs power conversion between a DC power supply (12) and a rotating electric machine (14) having a plurality of phases of windings (15) that are independent of each phase.
A high potential power supply line (30P) connected to the positive electrode side of the DC power supply, and
A low potential power supply line (30N) connected to the negative electrode side of the DC power supply, and
Each phase has a first upper and lower arm circuit (41) in which a first switching element (42) is connected in series between the high potential power supply line and the low potential power supply line, and is connected to one end of the winding. The first inverter (40) to be used and
A second upper and lower arm circuit (51) in which a second switching element (52) is connected in series between the high-potential power supply line and the low-potential power supply line is provided for each phase, and is provided at the other end of the winding. The second inverter (50) to be connected and
In at least one of the high-potential power supply line and the low-potential power supply line, the second inverter and the DC power supply are provided between the connection point of the first inverter and the connection point of the second inverter in a closed state. A switch (70) that connects the second inverter and cuts off the connection between the second inverter and the DC power supply in the open state.
The first inverter, the second inverter, and the switch are controlled, at least one switch is opened in the first drive region of the rotary electric machine, the second inverter is neutralized, and the second inverter is neutralized. Star connection control is performed to control the first inverter in response to the drive request of the rotary electric machine, all the switches are closed in the second drive region of the rotary electric machine, and the voltage applied to the winding is applied to the phase. A control unit (80) that performs open connection control that controls each unit,
With
A power conversion device in which the switching speed of the second switching element is set to a surge voltage that does not exceed the element withstand voltage of the second switching element in the closed state of all the switches.

Images