Power Conversion Device

Abstract

To provide a power conversion device that continues a safe state by reliably operating a switching element.SOLUTION: A power conversion device 100 includes an inverter circuit 107 that is composed of an upper arm switching element and a lower arm switching element to convert DC power supplied from a DC power supply 200 into AC power, and a drive control unit for drivingly controlling an electric motor 400 connected to the inverter circuit 107 by switching the switching element. When a transition command to a safe state is received, an overvoltage is applied to a gate terminal of the switching element, a short-circuit state of the switching element is continued, and the inverter circuit 107 is three-phase short-circuited or the upper and the lower arms are short-circuited.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] Vehicles such as hybrid vehicles and electric vehicles are equipped with power conversion devices that control electric motors. The power conversion device converts DC power supplied from a DC power source into AC power using an inverter circuit to drive the electric motor. When the electric motor is rotated by an external force, the electric motor functions as a generator and converts AC power into DC power. In vehicles equipped with such power conversion devices, it is necessary to transition the power conversion device to a safe state in the event of a vehicle accident or malfunction.

[0003] For example, when transitioning to a safe state, if the switching elements constituting the inverter circuit are short-circuited in three phases to stop power generation by the motor, it is necessary to secure a power source for controlling the switching elements to short-circuit the three phases.Furthermore, if the switching elements on the high potential side and the low potential side of the inverter circuit are simultaneously turned on to discharge the accumulated charge in the capacitor connected in parallel to the input side of the inverter circuit, it is necessary to secure a power source for controlling the switching elements.

[0004] Patent Document 1 describes a discharge control device that diagnoses whether or not there is an abnormality in the discharge control by a discharge control means that controls the discharge so that the charging voltage of a capacitor is equal to or lower than a specified voltage by operating a power conversion circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-244520 Summary of the Invention [Problem to be solved by the invention]

[0006] The device described in Patent Document 1 has a problem in that it is difficult to reliably operate the switching element and maintain a safe state. [Means for solving the problem]

[0007] The present invention First aspect of The power conversion device according to the present invention includes an inverter circuit that is configured with upper arm switching elements and lower arm switching elements and that converts DC power supplied from a DC power source into AC power, and a drive control unit that switches the switching elements to drive and control an electric motor connected to the inverter circuit, a switch provided between a positive power supply line from the DC power supply and a gate terminal of the switching element; and a short-circuit control circuit that controls on / off of the switch; Equipped with The short circuit control circuit When a command to transition to a safe state is received, When no abnormality is detected in the voltage between the positive power supply line and the negative power supply line from the DC power supply, the switch provided between the gate terminal of the switching element of the upper arm or the lower arm of the inverter circuit and the positive power supply line is turned on for a predetermined time. An overvoltage is applied to the gate terminal of the switching element to maintain the short-circuit state of the switching element, and the inverter circuit is in a three-phase short-circuit state. Entangled Can. A power conversion device according to a second aspect of the present invention comprises an inverter circuit composed of upper arm switching elements and lower arm switching elements, and converting DC power supplied from a DC power supply into AC power; a drive control unit that switches on and off the switching elements to control the drive of an electric motor connected to the inverter circuit; a switch provided between a positive power supply line from the DC power supply and a gate terminal of the switching element; and a short circuit control circuit that controls the on / off of the switch, wherein when a command to transition to a safe state is received and an abnormality is detected in the voltage between the positive power supply line and the negative power supply line from the DC power supply, the short circuit control circuit turns on the switch provided between the positive power supply line and the gate terminal of the switching element of one phase of the upper arm and lower arm of the inverter circuit for a predetermined time to apply an overvoltage to the gate terminal of the switching element, thereby maintaining the short-circuited state of the switching element and short-circuiting the upper and lower arms of the inverter circuit. [Effects of the Invention]

[0008] According to the present invention, it is possible to reliably operate the switching element and maintain a safe state. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a circuit configuration diagram of a power conversion device. [Figure 2] 4 is a flowchart showing the operation of the short circuit control circuit. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0011] The arrangement, range, etc. of each component shown in the drawings may not represent the actual arrangement, range, etc. in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the arrangement, range, etc. disclosed in the drawings.

[0012] Furthermore, in the following description, processing performed by executing a program may be described, but the program is executed by a processor (e.g., a CPU or a GPU) to perform the specified processing while appropriately using storage resources (e.g., a memory) and / or interface devices (e.g., a communication port), and therefore the subject of the processing may be the processor. Similarly, the subject of the processing performed by executing a program may be a controller, device, system, computer, or node having a processor. The subject of the processing performed by executing a program may be any computing unit, and may include a dedicated circuit (e.g., an FPGA or an ASIC) that performs a specific processing.

[0013] A program may be installed on a device such as a computer from a program source. The program source may be, for example, a program distribution server or a computer-readable storage medium. If the program source is a program distribution server, the program distribution server may include a processor and storage resources for storing the program to be distributed, and the processor of the program distribution server may distribute the program to be distributed to other computers. Also, in the following description, two or more programs may be realized as one program, and one program may be realized as two or more programs.

[0014] FIG. 1 is a circuit configuration diagram of a power conversion device 100. As shown in FIG. The power conversion device 100 converts high-voltage DC power supplied from the high-voltage DC power supply 200 into AC power to drive the electric motor 400. Furthermore, when the electric motor 400 is rotated by an external force and functions as a generator, the power conversion device 100 converts the generated AC power into high-voltage DC power to charge the high-voltage DC power supply 200.

[0015] The electric motor 400 is a three-phase synchronous motor having three-phase windings therein. Three-phase AC currents Ui, Vi, and Wi output from the power conversion device 100 flow through the windings of the electric motor 400 in their respective phases.

[0016] The high-voltage DC power supply 200 is, for example, a chargeable and dischargeable battery. The high voltage is, for example, a DC voltage of about 400 V. The low-voltage DC power supply 500 supplies operating power to the drive control circuit 101 and short-circuit control circuit 103 in the power conversion device 100.

[0017] During normal vehicle operation, the external ECU 600 outputs a normal operation command, for example, a torque command, to the power conversion device 100. On the other hand, when it is necessary to transition the vehicle to a safe state, for example, when a vehicle collision detection signal is received from an acceleration sensor, the external ECU 600 outputs a transition command to the power conversion device 100 to transition to the safe state.

[0018] The power conversion device 100 includes a drive control circuit 101 , a short-circuit control circuit 103 , a voltage detector 104 , and an inverter circuit 107 .

[0019] When the drive control circuit 101 receives a normal operation command from the external ECU 600, it controls the operation of the inverter circuit 107 via the gate drive circuit 108, converts the DC power supplied from the high-voltage DC power supply 200 into AC power, and drives and controls the electric motor 400. It also converts the AC power generated by the electric motor 400 into DC power and charges the high-voltage DC power supply 200, thereby performing so-called regenerative control.

[0020] When receiving a command to transition to the safe state from the external ECU 600, the short circuit control circuit 103 refers to the voltage between the positive power supply line P and the negative power supply line N from the DC power supply detected by the voltage detector 104, and implements transition to the safe state. In the safe state, as will be described in detail later, the inverter circuit 107 is short-circuited in a lower arm three-phase or an upper arm three-phase to stop power generation by the electric motor 400. Alternatively, the upper and lower arms of a specific phase of the inverter circuit 107 are short-circuited to discharge power between the positive power supply line P and the negative power supply line N.

[0021] The inverter circuit 107 includes a smoothing capacitor C and six switching elements S1 to S6. The smoothing capacitor C is provided between the positive power line P and the negative power line N. Three-phase switching legs Ru, Rv, and Rw are connected between the positive power line P and the negative power line N. Each of the switching legs Ru, Rv, and Rw includes switching elements S1, S3, and S5 of an upper arm Ua and switching elements S2, S4, and S6 of a lower arm La. The switching elements S1 to S6 include power semiconductor elements and diodes connected in parallel with the power semiconductor elements. The power semiconductor elements are, for example, IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switching elements S1 to S6 perform switching operations in response to gate signals from a gate drive circuit 108. During normal operation, the DC voltage supplied from the positive power line P and the negative power line N is converted into three-phase AC current, and AC currents Ui, Vi, Wi flow to the windings of each phase of the motor 400 from the switching legs Ru, Rv, Rw via the AC output lines of each phase.

[0022] Short-circuit switches M1 to M6 are provided between the gate terminals of the switching elements S1 to S6 and the positive power supply line P. The on / off of each switch M1 to M6 is controlled by a gate signal from a short-circuit control circuit 103. While FIG. 1 illustrates only one gate signal line from the short-circuit control circuit 103 for simplicity's sake, six gate signal lines are actually derived from the short-circuit control circuit 103, one for each of the switches M1 to M6. Although not shown, an isolation circuit may be provided between the six gate signal lines. This isolation circuit is composed of a light-emitting element and a light-receiving element, such as a photocoupler, and transmits signals from the short-circuit control circuit 103 while blocking voltage input from each of the switches M1 to M6 to the short-circuit control circuit 103. Because the switches M1 to M6 pass a high voltage from the high-voltage DC power supply 200, the isolation circuit protects the short-circuit control circuit 103 from the effects of this high voltage. The short circuit control circuit 103 turns off all of the switches M1 to M6 when it has not received a command to transition to a safe state from the external ECU 600. On the other hand, when it has received a command to transition to a safe state from the external ECU 600, the short circuit control circuit 103 controls the switches M1 to M6 to short-circuit the lower arm three-phase or the upper arm three-phase of the inverter circuit 107. Alternatively, the short circuit control circuit 103 controls the switches M1 to M6 to short-circuit the upper and lower arms of a specific phase of the inverter circuit 107.

[0023] In this embodiment, the short circuit control circuit 103 is described as being separate from the drive control circuit 101, but the short circuit control circuit 103 may be configured to include the functions of the short circuit control circuit 103 in the drive control circuit 101. Also, the short circuit control circuit 103 may be configured to be a microcomputer, and to control the switches M1 to M6 without relying on the external ECU 600 when it is necessary to transition the vehicle to a safe state, such as when a vehicle collision detection signal is received from an acceleration sensor.

[0024] The smoothing capacitor C smoothes the current generated by the ON / OFF of the switching elements S1 to S6, and suppresses ripples in the DC current supplied from the high-voltage DC power supply 200 to the power conversion device 100. The smoothing capacitor C is, for example, an electrolytic capacitor or a film capacitor.

[0025] 2 is a flowchart showing the operation of the short circuit control circuit 103. This flowchart shows the processing performed by the short circuit control circuit 103 by executing a program. This flowchart starts operation when the short circuit control circuit 103 receives a command to transition to a safe state from the external ECU 600.

[0026] In step S201, the short circuit control circuit 103 determines whether the voltage between the positive power line P and the negative power line N detected by the voltage detector 104 has dropped below a predetermined voltage. The predetermined voltage is the voltage when the inverter circuit 107 is operating normally to drive and control the electric motor 400. If the voltage has dropped below the predetermined voltage, it is assumed that there is an abnormality in the high voltage DC power supply 200 due to a vehicle collision or the like, and the process proceeds to step S202.

[0027] In step S202, the short circuit control circuit 103 short-circuits the upper and lower arms of a specific phase. Specifically, the switches M1 to M2, the switches M3 to M4, or the switches M5 to M6 are turned on for several milliseconds. For example, when the switches M1 to M2 are turned on, the upper and lower arms of the U phase are short-circuited, and the switching elements S1 to S2 are brought into a conductive state. That is, a DC voltage from the high-voltage DC power supply 200 is applied for several milliseconds to the gate terminals of the switching elements S1 to S2, the gate terminals of the switching elements S3 to S4, or the gate terminals of the switching elements S5 to S6.

[0028] In this case, if the gate rating (recommended operation) of the switching elements S1 to S6 is, for example, approximately 20 V, an overvoltage of approximately 400 V DC voltage from the high-voltage DC power supply 200 is applied to the gate terminals, causing the IGBTs (switching elements S1 to S6) to maintain a short circuit. Note that the time for applying the overvoltage to the gate terminals is set appropriately according to the gate withstand voltage of the IGBTs. In this way, once the switching elements S1 to S6 are short-circuited due to the overvoltage, there is no need to apply a voltage to the gate terminals, and the switching elements S1 to S6 continue to maintain a short circuit state. In other words, the short-circuit state of the switching elements S1 to S2, S3 to S4, or S5 to S6 is maintained. This causes the charge stored in the smoothing capacitor C, etc. to be discharged.

[0029] In step S203, the short circuit control circuit 103 determines whether the voltage between the positive power line P and the negative power line N detected by the voltage detector 104 has fallen below a predetermined voltage. If the voltage is not below the predetermined voltage, the short circuit control circuit 103 waits until the voltage falls below the predetermined voltage. If it is determined that the voltage between the positive power line P and the negative power line N has fallen below the predetermined voltage, the process proceeds to the next step S204. The predetermined voltage is a voltage that is considered safe.

[0030] In step S204, the short circuit control circuit 103 ends the upper and lower arm short circuit of a specific phase. Specifically, the short circuit process of the upper and lower arms is ended, and a notification unit (not shown) is notified that the voltage between the positive power line P and the negative power line N has dropped and a safe state has been reached. The notification from the notification unit allows the user or the like to know that a safe state has been reached.

[0031] In this way, by short-circuiting the upper and lower arms, the switching element can be reliably operated, allowing a safe state to continue until the voltage between the positive power line P and the negative power line N drops to a safe voltage.

[0032] If it is determined in step S201 that the voltage between the positive power line P and the negative power line N has not dropped below the predetermined voltage, the process proceeds to the next step S212.

[0033] In step S212, the short circuit control circuit 103 performs a three-phase short circuit. Specifically, it turns on the switches M1, M3, and M5 or the switches M2, M4, and M6. When the switches M1, M3, and M5 are turned on, a three-phase short circuit is performed on the upper arm, and when the switches M2, M4, and M6 are turned on, a three-phase short circuit is performed on the lower arm. That is, a DC voltage from the high-voltage DC power supply 200 is applied for several milliseconds to the gate terminals of the switching elements S1, S3, and S5 or the gate terminals of the switching elements S2, S4, and S6.

[0034] In this case, if the gate rating (recommended operation) of the switching elements S1 to S6 is, for example, approximately 20 V, an overvoltage of approximately 400 V DC voltage from the high-voltage DC power supply 200 is applied to the gate terminals, causing the IGBTs (switching elements S1 to S6) to be in a short-circuited state. Note that the time for applying the overvoltage to the gate terminals is set appropriately according to the gate withstand voltage of the IGBTs. In this way, once the switching elements S1 to S6 are short-circuited due to the overvoltage, there is no need to apply voltage to the gate terminals thereafter, and the switching elements S1 to S6 continue in a short-circuited state. In other words, the short-circuited state of the switching elements S1, S3, and S5 or the switching elements S2, S4, and S6 is maintained. This stops power generation by the electric motor 400.

[0035] In the next step S213, the short circuit control circuit 103 determines whether the voltage between the positive power line P and the negative power line N detected by the voltage detector 104 has fallen below a predetermined voltage. If the voltage has not fallen below the predetermined voltage, the short circuit control circuit 103 waits until the voltage falls below the predetermined voltage. If it is determined that the voltage between the positive power line P and the negative power line N has fallen below the predetermined voltage, the short circuit control circuit 103 proceeds to the next step S214. The predetermined voltage is a voltage that is considered safe.

[0036] In step S215, the short circuit control circuit 103 ends the three-phase short circuit. Specifically, the three-phase short circuit process is ended, and a notification unit (not shown) is notified that the voltage between the positive power line P and the negative power line N has dropped and a safe state has been reached. The user or the like can know that a safe state has been reached by the notification from the notification unit.

[0037] In this way, the switching element can be reliably operated to maintain a safe state until the voltage between the positive power line P and the negative power line N drops to a safe voltage due to a three-phase short circuit.

[0038] In steps S203 and S213, the voltage between the positive power supply line P and the negative power supply line N is detected, but instead, a voltage detector may be used to detect the voltages of the U-, V-, and W-phase AC output lines from the inverter circuit 107 to the motor 400. Then, the short circuit control circuit 103 determines the value of the detected voltage and waits until the voltage becomes equal to or lower than a predetermined voltage.

[0039] According to this embodiment, a special power supply for maintaining the switching elements S1 to S6 in the upper and lower arm short-circuited state or the three-phase short-circuited state is not required, and the inverter circuit can be reliably maintained in the upper and lower arm short-circuited state or the three-phase short-circuited state by utilizing the voltage between the positive power supply line P and the negative power supply line N, thereby enabling the continuation of a safe state. Also, by applying an overvoltage to the gate terminals of the switching elements S1 to S6 to cause the switching elements S1 to S6 to be in the upper and lower arm short-circuited state or the three-phase short-circuited state, there is no need to apply a voltage to the gate terminals thereafter, and the short-circuited state of the switching elements S1 to S6 continues.

[0040] According to the embodiment described above, the following effects can be obtained. (1) Power conversion device 100 includes inverter circuit 107, which is composed of upper-arm switching elements S1, S3, and S5 and lower-arm switching elements S2, S4, and S6, and converts DC power supplied from high-voltage DC power supply 200 into AC power, and drive control circuit 101 that switches switching elements S1 to S6 to drive and control electric motor 400 connected to inverter circuit 107. When a command to transition to a safe state is received, an overvoltage is applied to the gate terminals of switching elements S1 to S6, maintaining the short-circuit state of switching elements S1 to S6 and causing three-phase short-circuit or upper and lower arm short-circuit of inverter circuit 107. This allows the switching elements to operate reliably, enabling the safe state to be maintained.

[0041] The present invention is not limited to the above-described embodiments, and other forms that can be considered within the scope of the technical idea of ​​the present invention are also included in the scope of the present invention, as long as they do not impair the characteristics of the present invention. [Explanation of symbols]

[0042] 100...power conversion device, 101...drive control circuit, 103...short circuit control circuit, 104...voltage detector, 107...inverter circuit, 108...gate drive circuit, 200...high voltage DC power supply, 400...electric motor, 500...low voltage DC power supply, 600...external ECU, C...smoothing capacitor, S1 to S6...switching elements, M1 to M6...switches, P...positive side power supply line, N...negative side power supply line.

Claims

1. an inverter circuit configured with upper arm switching elements and lower arm switching elements, for converting DC power supplied from a DC power supply into AC power; a drive control unit for switching the switching elements to control the drive of an electric motor connected to the inverter circuit; a switch provided between a positive power supply line from the DC power supply and a gate terminal of the switching element; and a short-circuit control circuit for controlling the on / off of the switch; When a command to transition to a safe state is received and when no abnormality is detected in the voltage between the positive power supply line and the negative power supply line from the DC power supply, the short-circuit control circuit turns on the switch provided between the positive power supply line and the gate terminal of the switching element of the upper arm or the lower arm of the inverter circuit for a predetermined time to apply an overvoltage to the gate terminal of the switching element, thereby maintaining the short-circuit state of the switching element and causing a three-phase short-circuit in the inverter circuit.

2. an inverter circuit configured with upper arm switching elements and lower arm switching elements, for converting DC power supplied from a DC power supply into AC power; a drive control unit for switching the switching elements to control the drive of an electric motor connected to the inverter circuit; a switch provided between a positive power supply line from the DC power supply and a gate terminal of the switching element; and a short-circuit control circuit for controlling the on / off of the switch; When a command to transition to a safe state is received and an abnormality is detected in the voltage between the positive power supply line and the negative power supply line from the DC power supply, the short-circuit control circuit turns on the switches provided between the positive power supply line and the gate terminals of the switching elements of one phase of the upper arm and the lower arm of the inverter circuit for a predetermined time to apply an overvoltage to the gate terminals of the switching elements, thereby maintaining the short-circuit state of the switching elements and short-circuiting the upper and lower arms of the inverter circuit.

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