Power conversion device

Abstract

To provide a power conversion device capable of improving power conversion efficiency.SOLUTION: A power conversion device 4 includes inverters 8, 9, a switch 10, a power supply line 5, and a snubber circuit 11. The inverter 8 is connected to one end of a winding of a rotary electric machine 3, and the inverter 9 is connected to the other end of the winding. The switch 10 includes a changeover switch 101 that connects a DC power supply 2 and the inverter 9 in a closed state and cuts off the connection in an open state. The snubber circuit 11 has a capacitor 11C and is connected in parallel to the inverter 9. The power supply line 5 has: wiring 51 that connects the inverter 8 and the changeover switch 101; and wiring 52 that connects the changeover switch 101 and the inverter 9. Of the wirings 51, 52, the wiring 51 is connected to the snubber circuit 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The disclosure in this specification relates to a power conversion device.

Background Art

[0002] Patent Document 1 discloses a power conversion device including a first inverter connected to one end of a winding of a rotating electrical machine, a second inverter connected to the other end of the winding, and a switching switch. The switching switch is disposed between a DC power supply and the second inverter, connects the DC power supply and the second inverter in a closed state, and cuts off the connection between the DC power supply and the second inverter in an open state. The description of the prior art document is incorporated herein by reference as an explanation of the technical elements in this specification.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For inductance reduction, a configuration in which a snubber circuit is connected in parallel to an inverter can be considered. However, when the switching switch is in an open state, there is a risk that the capacitor of the snubber circuit connected in parallel to the second inverter may charge and discharge. That is, there is a problem of low power conversion efficiency. From the above viewpoints, or from other viewpoints not mentioned, further improvement of the power conversion device is required.

[0005] One disclosed object is to provide a power conversion device capable of improving power conversion efficiency.

Means for Solving the Problems

[0006] One aspect of the disclosure is a power conversion device, A first inverter (8) connected to one end of the winding of the rotating electrical machine (3); A second inverter (9) connected to the other end of the winding; A switch (10) having a changeover switch (101) disposed between the DC power supply (2) and the second inverter, connecting the DC power supply and the second inverter in a closed state, and disconnecting the connection between the DC power supply and the second inverter in an open state; Wiring constituting power lines (5, 6) electrically connected to the DC power supply, including a first wiring (51, 61) connecting the first inverter and the changeover switch, and a second wiring (52, 62) connecting the changeover switch and the second inverter; A snubber circuit (11) having a capacitor (11C) and connected in parallel to the second inverter; Comprising; The snubber circuit is connected to the first wiring among the first wiring and the second wiring.

[0007] According to the disclosed power conversion device, the snubber circuit is connected to the first wiring that connects the first inverter and the changeover switch among the power lines. Thereby, since the voltage across the capacitor of the snubber circuit is clamped to the power supply voltage, the charge and discharge operation of the capacitor in the open state of the changeover switch can be suppressed. Therefore, the power conversion efficiency can be improved.

[0008] The plurality of aspects disclosed in this specification employ different technical means in order to achieve their respective purposes. The reference numerals in parentheses described in the claims and in this section exemplify the correspondence with the parts of the embodiments described later, and are not intended to limit the technical scope. The objects, features, and effects disclosed in this specification will become clearer by referring to the subsequent detailed description and the accompanying drawings.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0010] Hereinafter, a plurality of embodiments will be described with reference to the drawings. In each embodiment, the same reference numerals may be assigned to corresponding components, and redundant descriptions may be omitted. When only a part of the configuration is described in each embodiment, the configuration of other embodiments described previously can be applied to other parts of the said configuration. Further, not only the combinations of configurations explicitly shown in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined with each other as long as there is no problem with the combination.

[0011] The power conversion device of this embodiment is applied to, for example, a moving body having a rotating electrical machine as a drive source. The moving body is, for example, an electric vehicle such as a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a flying body such as an electric vertical take-off and landing aircraft or a drone, a ship, a construction machine, an agricultural machine, etc.

[0012] (First Embodiment) First, based on FIG. 1, the schematic configuration of the drive system of the moving body will be described.

[0013] <Drive System of Moving Body> As shown in FIG. 1, the drive system 1 of the moving body includes a DC power supply 2, a rotating electrical machine 3, and a power conversion device 4.

[0014] The DC power supply 2 may be, for example, a rechargeable secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. The DC power supply 2 may also be one that converts AC power into DC and outputs it.

[0015] The rotating electrical machine 3 is an open-wound three-phase rotating electrical machine with a neutral point released. The rotating electrical machine 3 has a U-phase winding 3U, a V-phase winding 3V, and a W-phase winding 3W. Hereinafter, the U-phase winding 3U, the V-phase winding 3V, and the W-phase winding 3W may be simply denoted as windings 3U, 3V, and 3W.

[0016] The rotating electrical machine 3 functions as, for example, a drive source of the moving body, that is, an electric motor. When the moving body is a vehicle, the rotating electrical machine 3 generates torque for driving drive wheels (not shown). The rotating electrical machine 3 is not limited to an electric motor. The rotating electrical machine 3 may be a motor generator having functions as an electric motor and a generator, or may be a generator.

[0017] The power conversion device 4 performs power conversion between the DC power supply 2 and the rotating electrical machine 3. The drive system 1 is a system of a common power supply method that supplies power from a common DC power supply 2 to two inverters 8 and 9 described later. The drive system 1 may include only one common DC power supply 2 as illustrated in FIG. 1, or may include a plurality of them. The drive system 1 may include a power supply switch (not shown) such as an SMR between the DC power supply 2 and the power conversion device 4. SMR is an abbreviation for System Main Relay. When the power supply switch is turned on, power supply from the DC power supply 2 to the rotating electrical machine 3 becomes possible, and when the power supply switch is turned off, power supply from the DC power supply 2 to the rotating electrical machine 3 is cut off.

[0018] <Power Conversion Device> FIG. 1 shows a circuit configuration of an example of the power conversion device 4. The power conversion device 4 (power conversion circuit) illustrated in FIG. 1 includes power lines 5 and 6, a smoothing capacitor 7, inverters 8 and 9, a switch 10, and snubber circuits 11 and 12.

[0019] The power line 5 is a high-potential-side power line. The power line 5 is connected to the positive electrode of the DC power supply 2. The power line 5 may be referred to as a positive electrode side power line, a P line, etc. The power line 6 is a low-potential-side power line. The power line 6 is connected to the negative electrode of the DC power supply 2. The power line 6 may be referred to as a negative electrode side power line, an N line, etc. The power lines 5 and 6 are configured to include, for example, a bus bar made of a metal plate material.

[0020] The power line 5 has wirings 51 and 52. The wirings 51 and 52 are parts of the wirings constituting the power line 5. The wiring 51 is a wiring that connects the inverter 8 and a switching switch 101 described later among the power line 5. The wiring 52 is a wiring that connects the switching switch 101 and the inverter 9 among the power line 5. The wiring 51 corresponds to the first wiring, and the wiring 52 corresponds to the second wiring.

[0021] The smoothing capacitor 7 mainly smoothes the DC voltage supplied from the DC power supply 2. The smoothing capacitor 7 is provided between the power lines 5 and 6. The positive electrode of the smoothing capacitor 7 is connected to the power line 5 between the DC power supply 2 and the inverters 8 and 9. The negative electrode of the smoothing capacitor 7 is connected to the power line 6 between the DC power supply 2 and the inverters 8 and 9. The smoothing capacitor 7 is connected in parallel to the inverters 8 and 9.

[0022] The inverters 8 and 9 are DC-AC conversion circuits. The inverter 8 corresponds to the first inverter, and the inverter 9 corresponds to the second inverter. The inverter 8 is configured to include upper and lower arm circuits 8HL for three phases. The upper and lower arm circuits 8HL may be referred to as legs. The upper and lower arm circuits 8HL have an upper arm 8H and a lower arm 8L. The upper arm 8H and the lower arm 8L are serially connected between the power lines 5 and 6 with the upper arm 8H on the power line 5 side.

[0023] The connection point between the upper arm 8H and the lower arm 8L is connected to the winding of the corresponding phase in the rotating electrical machine 3 via the output line 13. The inverter 8 has six arms. Each arm is configured with a switching element. The number of switching elements constituting each arm is not particularly limited. It may be one or a plurality. In the case of a plurality, a plurality of switching elements connected in parallel to each other are turned on and off at the same timing by a common gate drive signal (drive voltage).

[0024] In the example shown in FIG. 1, an n-channel type MOSFET 8S is adopted as the switching element constituting each arm. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. In the upper arm 8H, the drain terminal of the MOSFET 8S is connected to the power supply line 5. In the lower arm 8L, the source terminal of the MOSFET 8S is connected to the power supply line 6. The source terminal of the MOSFET 8S in the upper arm 8H and the drain terminal of the MOSFET 8S in the lower arm 8L are connected to each other.

[0025] A freewheeling diode 8D is connected in anti-parallel to each of the MOSFETs 8S. The diode 8D may be a parasitic diode (body diode) of the MOSFET 8S or may be provided separately from the parasitic diode. The anode terminal of the diode 8D is connected to the source terminal of the corresponding MOSFET 8S, and the cathode terminal is connected to the drain terminal.

[0026] The inverter 9 has the same configuration as the inverter 8. The inverter 9 is configured with upper and lower arm circuits 9HL for three phases. The upper and lower arm circuit 9HL has an upper arm 9H and a lower arm 9L. The upper arm 9H and the lower arm 9L are connected in series between the power supply lines 5 and 6 with the upper arm 9H on the power supply line 5 side.

[0027] The connection point between the upper arm 9H and the lower arm 9L is connected to the winding of the corresponding phase in the rotating electrical machine 3 via the output line 14. The inverter 9 also has six arms. Each arm is configured with a switching element. The number of switching elements constituting each arm is not particularly limited. It may be one or a plurality.

[0028] In the example shown in FIG. 1, an n-channel type MOSFET 9S is adopted as the switching element constituting each arm. In the upper arm 9H, the drain terminal of the MOSFET 9S is connected to the power supply line 5. In the lower arm 9L, the source terminal of the MOSFET 9S is connected to the power supply line 6. The source terminal of the MOSFET 9S in the upper arm 9H and the drain terminal of the MOSFET 9S in the lower arm 9L are connected to each other. A freewheeling diode 9D is connected in anti-parallel to each of the MOSFET 9S.

[0029] As described above, the high-potential side terminals (drain terminals) of the upper arms 8H, 9H of the inverters 8, 9 are connected to the power supply line 5. The low-potential side terminals (source terminals) of the lower arms 8L, 9L are connected to the power supply line 6. The node, which is the connection point between the upper arm 8H and the lower arm 8L, is connected to one end of the winding of the corresponding phase via the output line 13, and the node between the upper arm 9H and the lower arm 9L is connected to the other end of the winding of the corresponding phase via the output line 14. Specifically, the node U1 of the upper and lower arm circuit 8HL of the U phase is connected to one end of the U-phase winding 3U, and the node U2 of the upper and lower arm circuit 9HL of the U phase is connected to the other end of the U-phase winding 3U. The node V1 of the upper and lower arm circuit 8HL of the V phase is connected to one end of the V-phase winding 3V, and the node V2 of the upper and lower arm circuit 9HL of the V phase is connected to the other end of the V-phase winding 3V. The node W1 of the upper and lower arm circuit 8HL of the W phase is connected to one end of the W-phase winding 3W, and the node W2 of the upper and lower arm circuit 9HL of the W phase is connected to the other end of the W-phase winding 3W.

[0030] Note that the switching elements constituting the inverters 8 and 9 are not limited to the MOSFETs described above. For example, IGBTs may be employed. IGBT is an abbreviation for Insulated Gate Bipolar Transistor. Also in the case of IGBTs, a diode for commutation is connected in anti-parallel. The types of the switching elements constituting the inverters 8 and 9 may be the same or different. For example, one of the inverters 8 and 9 may be constituted by MOSFETs and the other by IGBTs. The types (materials) of the semiconductor substrates may be different.

[0031] The switch 10 is provided between the inverter 8 and the inverter 9 in at least one of the power lines 5 and 6. The switch 10 is provided on the power line. In the closed state, the switch 10 connects the high-potential side terminal of the upper arm 9H of the inverter 9 to the smoothing capacitor 7 (DC power supply 2). In the open state, the switch 10 cuts off the connection between the high-potential side terminal of the upper arm 9H and the smoothing capacitor 7 (DC power supply 2).

[0032] The switch 10 has at least a switching switch 101. The switching switch 101 is a semiconductor switch, that is, a switching element formed on a semiconductor chip. The switching element is not particularly limited. It may have the same configuration as the switching element constituting at least one of the inverters 8 and 9, or a different configuration. The switching switch 101 illustrated in FIG. 1 is a MOSFET. A wiring 51 is connected to the drain terminal of the switching switch 101 (MOSFET), and a wiring 52 is connected to the source terminal. A diode is connected in anti-parallel to the MOSFET. The diode is, for example, a parasitic diode. When the switching switch 101 is turned on and the switch 10 is in the closed state, the high-potential side terminal of the upper arm 9H is electrically connected to the smoothing capacitor 7. When the switching switch 101 is turned off and the switch 10 is in the open state, the electrical connection between the high-potential side terminal of the upper arm 9H and the smoothing capacitor 7 is cut off.

[0033] The snubber circuit 11 is connected in parallel to the inverter 9, that is, the upper and lower arm circuits 9HL. The snubber circuit 11 shown in FIG. 1 is provided collectively for the three-phase upper and lower arm circuits 9HL. The snubber circuit 11 reduces the inductance of the upper and lower arm circuits 9HL. In other words, the snubber circuit 11 absorbs the transient high voltage that occurs during the switching of the switching elements (MOSFET 9S) that make up the upper and lower arm circuits 9HL, that is, the so-called switching surge. As a result, the inverter 9 can perform high-speed switching.

[0034] The snubber circuit 11 has at least a capacitor 11C. The snubber circuit 11 may be, for example, a C snubber circuit having a capacitor, or an RC snubber circuit having a capacitor and a resistor. It may also be an RCD snubber circuit having a capacitor, a resistor, and a diode. The snubber circuit 11 shown in FIG. 1 is an RC snubber circuit in which the capacitor 11C and the resistor 11R are connected in series. One end of the snubber circuit 11 is connected to the power line 5. One end of the snubber circuit 11 is connected to the wiring 51 among the power lines 5. The other end of the snubber circuit 11 is connected to the power line 6. The snubber circuit 11 is electrically connected to the smoothing capacitor 7 and the DC power supply 2 without passing through the switching switch 101.

[0035] The snubber circuit 12 is connected in parallel to the inverter 8, that is, the upper and lower arm circuits 8HL. The snubber circuit 12 shown in FIG. 1 is provided collectively for the three-phase upper and lower arm circuits 8HL. The snubber circuit 12 reduces the inductance of the upper and lower arm circuits 8HL. As a result, the inverter 8 can perform high-speed switching.

[0036] The snubber circuit 12 has at least a capacitor 12C. The snubber circuit 12 may be, for example, a C snubber circuit, an RC snubber circuit, or an RCD snubber circuit. The snubber circuit 12 shown in FIG. 1 is an RC snubber circuit in which the capacitor 12C and the resistor 12R are connected in series. One end of the snubber circuit 12 is connected to the power line 5. The other end of the snubber circuit 11 is connected to the power line 6.

[0037] As illustrated in FIG. 1, the power conversion device 4 may further include a control unit (CTR) 15. The control unit 15 may be configured to include, for example, a processor, a memory, a storage, etc. The processor executes various processes by accessing the memory. The memory is a rewritable volatile storage medium. The memory is, for example, a RAM. RAM is an abbreviation for Random Access Memory. The storage is, for example, a rewritable non-volatile storage medium. A program executed by the processor is stored in the storage. The program constructs a plurality of functional units by causing the processor to execute a plurality of instructions. The processes executed by the control unit 15 may be realized by software processes in which the processor executes the above-described program, or may be realized by hardware processes by dedicated electronic circuits. They may also be realized by a combination of software processes and hardware processes.

[0038] The control unit 15 may have, for example, a drive command generation unit (not shown) and a drive circuit unit. The drive command generation unit controls the inverters 8 and 9. The drive command generation unit generates a drive command (command signal) for controlling the on / off of the MOSFETs 8S and 9S and outputs it to the drive circuit unit. The drive command generation unit generates a drive command based on drive requirements of the rotating electrical machine 3 such as a torque command value input from an upper ECU (not shown) and signals detected by various sensors. The various sensors may include a current sensor, a rotation angle sensor, a voltage sensor, etc. (not shown). The current sensor detects the phase current flowing through the windings 3U, 3V, and 3W of each phase. The rotation angle sensor detects the rotation angle of the rotor of the rotating electrical machine 3. The voltage sensor detects the voltage across the smoothing capacitor 7.

[0039] The drive command generation unit controls the switch 10. The drive command generation unit generates a drive command for controlling the on / off of the changeover switch 101 that constitutes the switch 10.

[0040] The drive circuit section may be referred to as a driver. The drive circuit section can independently control the on / off states of six MOSFET8Ss, six MOSFET9Ss, and one switching switch 101 based on a drive command. For the sake of simplicity, in FIG. 1, the signal lines for transmitting drive signals from the control unit 15 to each switching element are omitted.

[0041] <Star connection drive and open connection drive> Next, based on FIGS. 2, 3, and 4, the star connection drive and the open connection drive will be described. FIG. 2 shows an example of an operating point map of a rotating electrical machine with the horizontal axis being the rotational speed and the vertical axis being the torque. FIG. 3 is a diagram showing the star connection drive. FIG. 4 is a diagram showing the open connection drive. For the sake of simplicity, in FIGS. 3 and 4, the control unit 15 is omitted.

[0042] As shown in FIG. 2, the drive region of the rotating electrical machine 3 is divided into two regions according to the rotational speed and torque. One of the drive regions is the star connection drive region. The star connection drive region is the normal operating region. The other drive region is the open connection drive region. The open connection drive region is a region with higher rotation or higher torque than the star connection drive region.

[0043] When the operating point is in the star connection drive region, the control unit 15 executes the control of the star connection drive. The star connection drive may be referred to as Y drive. The control unit 15 controls the MOSFET8Ss, 9Ss, and the switching switch 101 so that the windings 3U, 3V, 3W are in a star connection state. Specifically, as shown in FIG. 3, the switch 10 is opened, that is, the switching switch 101 is turned off. Also, the inverter 9 is neutralized. As exemplified in FIG. 3, for example, the MOSFET9Ss of the upper arm 9H of all phases may be turned on and the MOSFET9Ss of the lower arm 9L of all phases may be turned off. The MOSFET9Ss of the upper arm 9H of all phases may be turned off and the MOSFET9Ss of the lower arm 9L of all phases may be turned on. Then, the MOSFET8Ss of the inverter 8 are controlled according to the drive requirement and the like.

[0044] Figure 3 shows one of the energization patterns in star connection drive. The arrow of the dashed line shown in Figure 3 indicates an example of the current path. In Figure 3, it shows the current path when the MOSFET 8S of the upper arm 8H of the U phase and the MOSFET 8S of the lower arm 8L of the W phase are turned on. In the example shown in Figure 3, the upper arm 9H side of the inverter 9 is turned on and the lower arm 9L side is turned off. The current flows in the order of the upper arm 8H of the U phase → node U1 → U phase winding 3U → node U2 → upper arm 9H of the U phase → upper arm 9H of the W phase → node W2 → W phase winding 3W → node W1 → lower arm 8L of the W phase. In this way, the current flows without passing through the changeover switch 101 (switch 10).

[0045] When the operating point is in the open connection drive region, the control unit 15 executes the control of the open connection drive. The open connection drive is sometimes referred to as H drive. The control unit 15 closes the switch 10, that is, turns on the changeover switch 101, and releases the neutral point by the inverter 9. By releasing the neutral point, an open connection circuit of the upper and lower arm circuits 8HL, 9HL of the U phase via the U phase winding 3U is formed. Similarly, an open connection circuit of the upper and lower arm circuits 8HL, 9HL of the V phase via the V phase winding 3V is formed. An open connection circuit of the upper and lower arm circuits 8HL, 9HL of the W phase via the W phase winding 3W is formed. The control unit 15 regards each phase as an independent open connection circuit and controls the applied voltage for each phase.

[0046] Figure 4 shows one of the energization patterns in open connection drive. The arrow of the dashed line shown in Figure 4 indicates an example of the current path. In Figure 4, it shows the current path when the MOSFET 8S of the lower arm 8L of the W phase and the MOSFET 9S of the upper arm 9H of the W phase are turned on. The current flows in the order of the changeover switch 101 → upper arm 9H of the W phase → node W2 → W phase winding 3W → node W1 → lower arm 8L of the W phase. In this way, the current flows through the changeover switch 101 (switch 10).

[0047] As described above, the inverters 8 and 9 can switch between star connection drive and open connection drive. By executing open connection drive instead of star connection drive, it is possible to output in a higher rotation speed region or a higher torque region.

[0048] <Summary of the First Embodiment> FIG. 5 and FIG. 6 show reference examples of the power conversion device. FIG. 5 shows an example of the energization pattern during star connection drive in the reference example. FIG. 6 shows an energization pattern at a timing different from that in FIG. 5 during star connection drive. In the reference example, an "r" is added to the end of the reference numerals of the related elements shown in this embodiment.

[0049] The control unit performs star connection drive while switching between a plurality of energization patterns. For example, the control unit performs star connection drive using the PWM control method. PWM is an abbreviation for Pulse Width Modulation. The plurality of energization patterns include the zero vector energization patterns shown in FIGS. 5 and 6. The energization pattern shown in FIG. 5 is a pattern in which all the upper arms 8Hr of the inverter 8r are turned on and all the lower arms 8Lr are turned off among the zero vectors. The energization pattern shown in FIG. 6 is a pattern in which all the lower arms 8Lr of the inverter 8r are turned on and all the upper arms 8Hr are turned off among the zero vectors.

[0050] As shown in FIGS. 5 and 6, in the power conversion device 4r of the reference example, the snubber circuit 11r connected in parallel to the inverter 9r is connected to the wiring 52r that connects the changeover switch 101r and the inverter 9r among the power supply lines 5r. One end of the snubber circuit 11r is connected to the wiring 52r of the power supply line 5, and the other end is connected to the power supply line 6r. For the sake of convenience, in FIGS. 5 and 6, the smoothing capacitor and the snubber circuit connected in parallel to the inverter 8r are omitted. The other configurations are the same as those of the power conversion device 4 of this embodiment.

[0051] In the examples shown in FIGS. 5 and 6, the inverter 9r is neutralized by turning on all of the three-phase upper arms 9Hr of the inverter 9r. In this state, as shown in FIG. 5, when all of the three-phase upper arms 8Hr of the inverter 8r are turned on, the voltage across the capacitor 11Cr becomes approximately equal to the supply voltage of the DC power supply 2r, that is, the power supply voltage Vdc. Also, as shown in FIG. 6, when all of the three-phase lower arms 8Lr of the inverter 8r are turned on, the voltage across the capacitor 11Cr becomes approximately 0 V (zero volts).

[0052] As described above, in order to perform star connection driving while switching a plurality of energization patterns, during star connection driving, the voltage across the capacitor 11Cr of the snubber circuit 11r fluctuates. The voltage across the capacitor 11Cr fluctuates in the range from 0 V to Vdc. Thus, since the capacitor 11Cr is charged and discharged during star connection driving, the power conversion efficiency is lowered. The resistor 11Rr of the snubber circuit 11r consumes the energy stored in the capacitor 11Cr and generates heat. This heat affects the capacitor 11Cr.

[0053] In the power conversion device 4 of the present embodiment, the snubber circuit 11 connected in parallel with the inverter 9 is connected to the wiring 51 (first wiring) that connects the inverter 8 and the switching switch 101, instead of the wiring 52 (second wiring). Thereby, the voltage across the capacitor 11C of the snubber circuit 11 is clamped to the power supply voltage of the DC power supply 2 (the voltage across the smoothing capacitor 7). Therefore, during the OFF state (open state) of the switching switch 101, that is, during star connection driving, the charging and discharging operation of the capacitor 11C can be suppressed. Thus, the power conversion efficiency can be improved.

[0054] As illustrated, a switching switch 101 may be provided on the power supply line 5 that is electrically connected to the positive electrode of the DC power supply 2. During star connection drive, the switching switch 101 turns off. That is, the switch 10 is in the open state. The switching switch 101 cuts off the connection between the DC power supply 2 (smoothing capacitor 7) and the inverter 9. During open connection drive, the switching switch 101 turns on. That is, the switch 10 is in the closed state. The switching switch 101 connects the DC power supply 2 (smoothing capacitor 7) and the inverter 9.

[0055] In this embodiment, an example in which the power conversion device 4 includes the snubber circuit 12 is shown, but it is not limited to this. A configuration without the snubber circuit 12 may also be used.

[0056] (Second Embodiment) This embodiment is a modification example based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the preceding embodiment, one switching switch 101 and one snubber circuit 11 were provided for the three-phase upper and lower arm circuits 9HL that constitute the inverter 9. Instead of this, the switching switch 101 and the snubber circuit 11 may be provided for each phase with respect to the upper and lower arm circuits 9HL.

[0057] FIG. 7 shows the power conversion device 4 and the drive system 1 according to this embodiment. In the power conversion device 4, the switching switch 101 and the snubber circuit 11 are provided for each phase with respect to the upper and lower arm circuits 9HL. The switch 10 has three switching switches 101. The drain terminal of each switching switch 101 is connected to the wiring 51, and the source terminal is connected to the wiring 52. One of the switching switches 101 is connected in series to the upper and lower arm circuits 9HL of the U phase. Another one of the switching switches 101 is connected in series to the upper and lower arm circuits 9HL of the V phase. Another one of the switching switches 101 is connected in series to the upper and lower arm circuits 9HL of the W phase. The source terminals of the three switching switches 101 are electrically connected to each other by the wiring 52. The source terminals of the three switching switches 101 are commonly connected.

[0058] In addition to the three switching switches 101 described above, the power conversion device 4 includes three snubber circuits 11. In each snubber circuit 11, one of the ends is connected to the wiring 51, and the other of the ends is connected to the power line 6. Each snubber circuit 11 has a capacitor 11C and a resistor 11R. One of the snubber circuits 11 is connected in parallel to the upper and lower arm circuits 9HL of the U phase. Another one of the snubber circuits 11 is connected in parallel to the upper and lower arm circuits 9HL of the V phase. Another one of the snubber circuits 11 is connected in parallel to the upper and lower arm circuits 9HL of the W phase.

[0059] As illustrated in FIG. 7, the power conversion device 4 may include three snubber circuits 12. In each snubber circuit 12, one of the ends is connected to the power line 5, and the other of the ends is connected to the power line 6. Each snubber circuit 12 has a capacitor 12C and a resistor 12R. One of the snubber circuits 12 is connected in parallel to the upper and lower arm circuits 8HL of the U phase. Another one of the snubber circuits 12 is connected in parallel to the upper and lower arm circuits 8HL of the V phase. Another one of the snubber circuits 12 is connected in parallel to the upper and lower arm circuits 8HL of the W phase. Other configurations are the same as those of the power conversion device 4 shown in the previous embodiment.

[0060] <Summary of the Second Embodiment> As illustrated, the switching switch 101 and the snubber circuit 11 may be provided for each phase with respect to the upper and lower arm circuits 9HL constituting the inverter 9. According to this, the area of the current loop formed by the upper and lower arm circuits 9HL and the snubber circuit 11 can be made smaller than the configuration in which a single switching switch 101 and a snubber circuit 11 common to the three phases are provided. Thereby, the wiring inductance of the upper and lower arm circuits 9HL can be reduced, and thus the power conversion efficiency can be improved.

[0061] Note that the total chip area of the three switching switches 101 can be made smaller than the chip area of the single switching switch 101 common to the three phases shown in the previous embodiment. Also, the total capacitance of the capacitors 11C of the three snubber circuits 11 can be made smaller than the capacitance of the single capacitor 11C common to the three phases. Therefore, the size of the power conversion device 4 can be reduced.

[0062] As illustrated, the source terminals (low-potential-side terminals) of the switching switches 101 provided for each phase may be electrically connected to each other. Thereby, for example, even if one of the switching switches 101 fails, another switching switch 101 can be substituted. Note that the source terminals of the switching switches 101 provided for each phase may not be electrically connected to each other. That is, the source terminals of the switching switches 101 may be electrically connected only to the upper and lower arm circuits 9HL of the corresponding phases.

[0063] In this embodiment, an example in which the power conversion device 4 includes the snubber circuit 12 is shown, but the present invention is not limited to this. A configuration without the snubber circuit 12 may be employed.

[0064] (Third Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the preceding embodiment, the switching switch 101 and the snubber circuit 11 are provided for each phase with respect to the upper and lower arm circuits 9HL. Instead of this, the switching switch 101 may be provided for each phase with respect to the upper and lower arm circuits 9HL, and the snubber circuit 11 may be commonly arranged with respect to the upper and lower arm circuits 9HL of the three phases.

[0065] FIG. 8 shows the power conversion device 4 and the drive system 1 according to this embodiment. In the example shown in FIG. 8, the switching switches 101 are provided for each phase with respect to the upper and lower arm circuits 9HL. That is, the switch 10 has three switching switches 101. The source terminals of the three switching switches 101 are electrically connected to each other by the wiring 52. The source terminals of the three switching switches 101 are commonly connected.

[0066] Similar to the previous embodiment, the snubber circuit 11 has a capacitor 11C and a resistor 11R. One end of the snubber circuit 11 is connected to the wiring 51, and the other end is connected to the power line 6. The power conversion device 4 includes a single snubber circuit 11 common to the three-phase upper and lower arm circuits 9HL. The power conversion device 4 includes a single snubber circuit 12 common to the three-phase upper and lower arm circuits 8HL. Other configurations are the same as those of the power conversion device 4 shown in the previous embodiment.

[0067] <Summary of the Third Embodiment> As illustrated, the switching switch 101 may be provided for each phase with respect to the upper and lower arm circuits 9HL, and the snubber circuit 11 may be commonly arranged for each phase of the upper and lower arm circuits 9HL. Even with such a configuration, in star connection drive, the voltage across both ends of the capacitor 11C of the snubber circuit 11 is clamped to the power supply voltage of the DC power supply 2 (the voltage across both ends of the smoothing capacitor 7). Therefore, the same effect as the configuration shown in the previous embodiment, that is, the power conversion efficiency can be improved.

[0068] As illustrated, the source terminals (low potential side terminals) of the switching switches 101 provided for each phase may be electrically connected to each other. Thereby, for example, even if one of the switching switches 101 fails, another switching switch 101 can be substituted. Note that the source terminals of the switching switches 101 provided for each phase may not be electrically connected to each other. That is, the source terminal of the switching switch 101 may be electrically connected only to the upper and lower arm circuits 9HL of the corresponding phase.

[0069] In this embodiment, an example in which the power conversion device 4 includes the snubber circuit 12 is shown, but it is not limited thereto. A configuration without the snubber circuit 12 may also be used.

[0070] (Fourth Embodiment) This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be incorporated. In the preceding embodiment, the changeover switch 101 was provided on the power line 5. Instead of this, or in addition to this, the changeover switch 101 may be provided on the power line 6.

[0071] FIG. 9 shows the power conversion device 4 and the drive system 1 according to this embodiment. In the power conversion device 4, the switch 10 has a changeover switch 101 provided on the power line 6. The power line 6 has a wiring 61 connecting the inverter 8 and the changeover switch 101, and a wiring 62 connecting the changeover switch 101 and the inverter 9. The wiring 61 corresponds to the first wiring, and the wiring 62 corresponds to the second wiring.

[0072] The changeover switch 101 has a MOSFET and a diode, as in the preceding embodiment. The source terminal of the changeover switch 101 is connected to the wiring 61, and the drain terminal is connected to the wiring 62. The lower arm 9L (source terminal) of the upper and lower arm circuits 9HL of each phase is connected to the wiring 62. One end of the snubber circuit 11 is connected to the power line 5, and the other end is connected to the wiring 61. The other configurations are the same as those of the power conversion device 4 (see FIG. 1) shown in the preceding embodiment.

[0073] <Summary of the Fourth Embodiment> As illustrated, a changeover switch 101 may be provided in the power supply line 6 that is electrically connected to the negative electrode of the DC power supply 2. During star connection drive, the changeover switch 101 is turned off. That is, the switch 10 is in the open state. The changeover switch 101 cuts off the connection between the DC power supply 2 (smoothing capacitor 7) and the inverter 9. During open connection drive, the changeover switch 101 is turned on. That is, the switch 10 is in the closed state. The changeover switch 101 connects the DC power supply 2 (smoothing capacitor 7) and the inverter 9. Also, a snubber circuit 11 connected in parallel to the inverter 9 is connected to a wiring 61 (first wiring) that connects the inverter 8 and the changeover switch 101, rather than to a wiring 62 (second wiring). Thereby, the voltage across both ends of the capacitor 11C of the snubber circuit 11 is clamped to the power supply voltage of the DC power supply 2 (voltage across both ends of the smoothing capacitor 7). Therefore, when the changeover switch 101 is off (open state), that is, during star connection drive, the charge and discharge operation of the capacitor 11C can be suppressed, and the power conversion efficiency can be improved.

[0074] In this embodiment, an example in which the power conversion device 4 includes the snubber circuit 12 is shown, but it is not limited thereto. A configuration without the snubber circuit 12 may also be used.

[0075] The configuration of the switch 10 including the changeover switch 101 and the snubber circuit 11 is not limited to the example shown in FIG. 9. A configuration similar to the configurations shown in the second embodiment and the third embodiment realized in the power supply line 5 may be realized in the power supply line 6.

[0076] An example in which the switch 10 having the changeover switch 101 is provided only in the power supply line 6 is shown, but it is not limited thereto. The configuration shown in this embodiment and the configuration shown in the previous embodiment may be combined. That is, the switch 10 may have the changeover switch 101 provided in the power supply line 5 and the changeover switch 101 provided in the power supply line 6. In this configuration, one end of the snubber circuit 11 may be connected to the wiring 51 and the other end may be connected to the wiring 61.

[0077] (Other embodiments) The disclosure in this specification, drawings, etc. is not limited to the illustrated embodiments. The disclosure includes the illustrated embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of components and / or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes those in which the components and / or elements of the embodiments are omitted. The disclosure includes the replacement or combination of components and / or elements between one embodiment and another. The disclosed technical scope is not limited to the description of the embodiments. Some of the disclosed technical scopes are indicated by the description of the claims and should be construed to include all changes within the meaning and scope equivalent to the description of the claims.

[0078] The disclosure in the specification, drawings, etc. is not limited by the description of the claims. The disclosure in the specification, drawings, etc. includes the technical idea described in the claims and extends to more diverse and extensive technical ideas than the technical idea described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification, drawings, etc. without being restricted by the description of the claims.

[0079] When an element or layer is referred to as "above," "connected to," "attached to," or "coupled to," it may be directly above, connected to, attached to, or coupled to another element or layer, and there may also be intervening elements or intervening layers. In contrast, when an element is referred to as "directly above," "directly connected to," "directly attached to," or "directly coupled to" another element or layer, there are no intervening elements or intervening layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used in this specification, the term "and / or" includes any combination and all combinations of one or more of the associated listed items. That is, the description of A and / or B means at least one of A and B, and may include only A, only B, or both A and B.

[0080] Spatially relative terms such as "inside," "outside," "beneath," "below," "lower," "above," "upper," etc. are used herein to facilitate the description of the relationship of one element or feature to another element or feature as illustrated. Spatially relative terms can be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figure is turned over, an element described as "below" or "directly below" another element or feature will be oriented "above" the other element or feature. Thus, the term "below" can encompass both the up and down orientations. The device may be oriented in other directions (rotated 90 degrees or other orientations), and the spatially relative descriptors used in this specification will be interpreted accordingly.

[0081] (Disclosure of Technical Idea) This specification discloses a plurality of technical ideas described in a plurality of clauses listed below. Some clauses may be described in a multiple dependent form that alternatively quotes a preceding clause in subsequent clauses. Further, some clauses may be described in a multiple dependent form that quotes a clause in another multiple dependent form. The clauses described in these multiple dependent forms define a plurality of technical ideas.

[0082] <Technical Idea 1> A first inverter (8) connected to one end of the winding of the rotating electrical machine (3), A second inverter (9) connected to the other end of the winding, A switch (10) having a switching switch (101) disposed between the DC power supply (2) and the second inverter, connecting the DC power supply and the second inverter in a closed state, and disconnecting the connection between the DC power supply and the second inverter in an open state, Wiring constituting a power line (5, 6) electrically connected to the DC power supply, including a first wiring (51, 61) connecting the first inverter and the switching switch, and a second wiring (52, 62) connecting the switching switch and the second inverter, A snubber circuit (11) having a capacitor (11C) and connected in parallel to the second inverter, Comprising, The snubber circuit is a power conversion device connected to the first wiring among the first wiring and the second wiring.

[0083] <Technical Idea 2> The second inverter has a three-phase upper and lower arm circuit (9HL), The switching switch and the snubber circuit are provided for each phase with respect to the upper and lower arm circuits, and are the power conversion devices described in Technical Idea 1.

[0084] <Technical Idea 3> The second inverter has a three-phase upper and lower arm circuit (9HL), The switching switch is provided for each phase with respect to the upper and lower arm circuit, The snubber circuit is commonly arranged for the upper and lower arm circuits of each phase, and the power conversion device according to Technical Idea 1.

[0085] <Technical Idea 4> The low-potential side terminals of the switching switches provided for each phase are electrically connected to each other, and the power conversion device according to Technical Idea 2 or Technical Idea 3.

[0086] <Technical Idea 5> The power supply line includes a positive electrode side power supply line electrically connected to the positive electrode of the DC power supply, and the power conversion device according to any one of Technical Ideas 1 to 4.

[0087] <Technical Idea 6> The power supply line includes a negative electrode side power supply line electrically connected to the negative electrode of the DC power supply, and the power conversion device according to any one of Technical Ideas 1 to 5.

Explanation of Reference Numerals

[0088] 1... drive system, 2... DC power supply, 3... rotating electrical machine, 3U, 3V, 3W... windings, 4... power conversion device, 5, 6... power supply lines, 51, 52, 61, 62... wirings, 7... smoothing capacitor, 8, 9... inverters, 8HL, 9HL... upper and lower arm circuits, 8D, 9D... diodes, 8H, 9H... upper arms, 8L, 9L... lower arms, 8S, 9S... MOSFETs, 10... switch, 101... switching switch, 11, 12... snubber circuits, 11C, 12C... capacitors, 11R, 12R... resistors, 13, 14... output lines, 15... control unit

Claims

1. A first inverter (8) connected to one end of the winding of a rotating electrical machine (3); A second inverter (9) connected to the other end of the winding; A switch (10) having a changeover switch (101) disposed between a DC power supply (2) and the second inverter, connecting the DC power supply and the second inverter in a closed state, and disconnecting the connection between the DC power supply and the second inverter in an open state; Wiring constituting power supply lines (5, 6) electrically connected to the DC power supply, including first wiring (51, 61) connecting the first inverter and the changeover switch, and second wiring (52, 62) connecting the changeover switch and the second inverter; A snubber circuit (11) having a capacitor (11C) and connected in parallel to the second inverter; Comprising; The snubber circuit is a power conversion device connected to the first wiring among the first wiring and the second wiring.

2. The second inverter has three-phase upper and lower arm circuits (9HL); The power conversion device according to claim 1, wherein the changeover switch and the snubber circuit are provided for each phase with respect to the upper and lower arm circuits.

3. The second inverter has three-phase upper and lower arm circuits (9HL); The changeover switch is provided for each phase with respect to the upper and lower arm circuits; The power conversion device according to claim 1, wherein the snubber circuit is commonly arranged for the upper and lower arm circuits of each phase.

4. The power conversion device according to claim 2 or claim 3, wherein the low-potential side terminals of the changeover switches provided for each phase are electrically connected to each other.

5. The power conversion device according to any one of claims 1 to 3, wherein the power supply lines include a positive electrode side power supply line electrically connected to the positive electrode of the DC power supply.

6. The power conversion device according to any one of claims 1 to 3, wherein the power supply lines include a negative electrode side power supply line electrically connected to the negative electrode of the DC power supply.

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