Power conversion device and control method for power conversion device

Abstract

To appropriately implement protection processing of a power conversion device and a connected apparatus by making shutdown based on detecting overcurrent compatible with stop of power conversion by phase short-circuiting processing.SOLUTION: A power conversion device comprises: a power conversion circuit including a plurality of legs provided with positive electrode side and negative electrode side switching elements and an external connection point which connects the switching elements in series and from which AC output is derived; a phase current detector; and a control device including a switching element drive section, an overcurrent protection section and a phase short-circuit function section by which, when stopping the AC output of the power conversion circuit, a phase short-circuit signal is outputted for turning on all the positive electrode side switching elements and turning off all the negative electrode side switching elements or turning on all the negative electrode side switching elements and turning off all the positive electrode side switching elements. In a case where the phase short-circuit function section starts outputting the phase short-circuit signal, the control device invalidates output of an overcurrent cutoff signal by the overcurrent protection section during an inhibition period.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device and a control method for a power conversion device. [Background technology]

[0002] Electric vehicles using a rotating electric machine as a driving force source have been known for some time. In these electric vehicles, the rotating electric machine is operated in power running mode to generate driving torque during travel, and in regenerative running mode to generate regenerative braking torque during braking. The term "rotating electric machine" is a general term for electric motors and generators, and electric motors that have the ability to generate electricity through regenerative operation are widely used as rotating electric machines. Rotating electric machines that are driven by a combination of a rotor equipped with permanent magnets and a stator equipped with coils are often used.

[0003] A power conversion device is used to drive a rotating electric machine. The power conversion device converts DC power from a DC power source mounted on an electric vehicle into AC power using an inverter, and adjusts the torque and rotation speed of the rotating electric machine. Depending on the operating conditions, the rotating electric machine can function as a generator, and the power conversion device converts regenerative power generated by the power generation into DC power using an inverter, and charges the DC power source.

[0004] The inverter has legs, each of which has a positive-side switching element and a negative-side switching element connected in series and an external connection point from which AC output is derived, for each phase of the coil of the rotating electric machine. The inverter converts DC power and AC power mutually by turning on and off multiple semiconductor switches at a predetermined switching frequency.

[0005] A power conversion device is provided with a phase current detector that detects the phase current flowing through a rotating electric machine connected to an inverter. If the phase current becomes excessive, an overcurrent is occurring in the switching elements, and power conversion must be stopped immediately. When an overcurrent is detected, the power conversion device performs an overcurrent protection process (shutdown) to stop power conversion by turning off all switching elements. However, there are also cases where power conversion needs to be stopped for other reasons by performing a phase short-circuit process. A technology has been disclosed (for example, Patent Document 1) that performs a phase short-circuit process to stop power conversion while protecting the power conversion device and peripheral devices, by turning on all of the inverter's positive-side switching elements and turning off all of the inverter's negative-side switching elements, or by turning on all of the inverter's negative-side switching elements and turning off all of the inverter's positive-side switching elements. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-47055 Summary of the Invention [Problem to be solved by the invention]

[0007] In the technology described in Patent Document 1, if a malfunction occurs in which a switch (contactor) supplying DC power from a DC power source to an inverter circuit opens while the electric vehicle is running, a phase short-circuit process is performed to stop the power supply from the inverter to the motor. This prevents performance degradation of the power conversion device and connected equipment caused by excessive regenerative power when the rotating electric machine is rotating at high speed. In addition, the overcurrent protection process (shutdown) can prevent abrupt regenerative braking that would otherwise occur and cause the vehicle to brake suddenly.

[0008] However, Patent Document 1 does not describe a case where both overcurrent protection processing (shutdown) against overcurrent and phase short-circuit processing for stopping the inverter are performed. When a phase short-circuit is performed while a rotating electric machine is running, the current that had been steadily flowing through each phase to drive the rotating electric machine until then suddenly increases due to the power stored in the stator coil of the rotating electric machine. After a predetermined period has elapsed, the current converges to the steady-state current at the time of the phase short-circuit.

[0009] When the phase short-circuit processing is performed, a transient current behavior occurs, and an overcurrent may be detected due to a suddenly increasing phase current, causing the overcurrent protection unit 63 to perform overcurrent protection processing (shutdown). That is, even though it is desired to protect the power conversion device and connected devices by the phase short-circuit processing, the overcurrent protection processing (shutdown) is performed due to the overcurrent protection, which poses a problem that the protection processing of the power conversion device and connected devices by the phase short-circuit processing cannot be performed.

[0010] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a power conversion device and a control method for the power conversion device that can appropriately perform protection processing for the power conversion device and connected devices by performing both overcurrent protection processing (shutdown) by detecting an overcurrent and stopping power conversion by performing phase short-circuit processing. [Means for solving the problem]

[0011] The power conversion device according to the present disclosure comprises: a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to a positive electrode of a DC power supply, a negative-side switching element connected to a negative electrode of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and from which an AC output is derived; a phase current detector for detecting a phase current flowing between an external connection point of the power conversion circuit and the AC output; a control device including: a switching element drive unit that outputs a control signal for controlling the on / off of a switching element; an overcurrent protection unit that outputs an overcurrent interruption signal to the switching element drive unit when a phase current detected by a phase current detector is greater than a predetermined overcurrent threshold; and a phase short-circuit function unit that outputs a phase short-circuit signal to the switching element drive unit to turn on all positive side switching elements and turn off all negative side switching elements, or to turn on all negative side switching elements and turn off all positive side switching elements, when stopping AC output of the power conversion circuit; When the phase short-circuiting function unit starts outputting the phase short-circuiting signal, the control device disables the output of the overcurrent interruption signal by the overcurrent protection unit for a predetermined prohibition period.

[0012] A control method for a power conversion device according to the present disclosure includes: A control method for a power conversion device including a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to the positive electrode of a DC power supply, a negative-side switching element connected to the negative electrode of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and from which an AC output is derived, a phase current detector detecting a phase current flowing between the external connection point of the power conversion circuit and the AC output, and a switching element driver outputting a control signal for controlling on / off of the switching element, an overcurrent protection step of outputting an overcurrent interrupt signal to a switching element driver when the phase current detected by the phase current detector is greater than a predetermined overcurrent threshold; a phase short-circuiting function step of outputting a phase short-circuiting signal to the switching element drive unit to turn on all of the positive-side switching elements and turn off all of the negative-side switching elements or to turn on all of the negative-side switching elements and turn off all of the positive-side switching elements when stopping the AC output of the power conversion circuit, In the phase short-circuit function step, it is determined whether the output of the phase short-circuit signal has started and whether it is within a predetermined prohibition period since the start of the output, and if it is within the prohibition period, the overcurrent interruption signal is disabled; If the phase short-circuit signal is not output, or if the prohibition period has elapsed since the start of output of the phase short-circuit signal, the overcurrent interruption signal is made valid. [Effects of the Invention]

[0013] The power conversion device and the control method for the power conversion device according to the present disclosure can perform both overcurrent protection processing by detecting an overcurrent and stopping power conversion by processing a phase short circuit, thereby appropriately protecting the power conversion device and connected devices, thereby preventing performance degradation of the power conversion device and connected devices and contributing to improved reliability. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a configuration diagram of a power conversion device according to a first embodiment. [Figure 2] 2 is a hardware configuration diagram of a control device of the power conversion device according to the first embodiment. FIG. [Figure 3] 4 is a time chart showing waveforms of currents flowing through each phase after execution of phase short-circuit processing according to the first embodiment. [Figure 4] 10 is a time chart showing waveforms of currents flowing through each phase when overcurrent protection processing is performed by detecting an overcurrent after execution of phase short-circuit processing according to a comparative example. [Figure 5] 4 is a flowchart illustrating processing by a control device of the power conversion device according to the first embodiment. [Figure 6] FIG. 10 is a configuration diagram of a power conversion device according to a second embodiment. [Figure 7] 10 is a flowchart illustrating processing by a control device of a power conversion device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] A drive system for an electric vehicle is composed of a DC power supply consisting of a secondary battery such as a lithium-ion battery, an inverter consisting of a capacitor and multiple semiconductor switches connected to the DC power supply, and a rotating electric machine connected to the inverter as a load. The inverter converts DC power from the DC power supply into predetermined AC power by turning the multiple semiconductor switches on and off at a predetermined switching frequency, thereby adjusting the torque and rotation speed of the rotating electric machine (the load). The rotating electric machine also functions as a generator depending on the operating conditions, charging the DC power supply with regenerative power generated by the generator. Note that efficient permanent magnet three-phase synchronous rotating electric machines are often used as rotating electric machines for electric vehicles. While a three-phase synchronous rotating electric machine will be used as an example here, the AC output of the rotating electric machine and power conversion device is not limited to three phases. This technology can also be applied to power conversion devices with three or more phases.

[0016] The inverter is provided with legs for each phase of the coil of the rotating electric machine, each leg having a positive-side switching element and a negative-side switching element connected in series and an external connection point from which AC output is derived. By sequentially turning on and off the switching elements provided for each phase of the inverter, AC power with a phase difference of 120 degrees is supplied to each phase of the three-phase synchronous rotating electric machine, thereby driving the three-phase synchronous rotating electric machine. Unless otherwise specified, the rotating electric machine below refers to a three-phase synchronous rotating electric machine. The operating principle of the inverter is widely known and will not be described here.

[0017] Preferred embodiments of a power conversion device according to the present disclosure will be described below with reference to the drawings. The same or corresponding parts in each drawing will be designated by the same reference numerals. Generally, electric motors, also called motors, convert electric power into driving force for power running. However, they can also reversely convert driving force back into electric power for regenerative operation with their original structure. Furthermore, electric generators, also called generators, convert driving force into electric power for regenerative operation. However, they can also reversely convert electric power back into driving force for power running with their original structure. In other words, electric motors and generators have basically the same structure, and both are capable of power running and regenerative operation. Therefore, in this specification, both electric motors and generators are referred to as rotating electric machines.

[0018] 1. First Embodiment <Configuration of power conversion device> Fig. 1 is a configuration diagram of a power conversion device 80 according to embodiment 1. Fig. 1 illustrates a DC power supply 75, such as a battery, that supplies DC power to an inverter circuit 20 and is charged with regenerative power, and a three-phase rotating electric machine 10 to be controlled.

[0019] 1, power conversion device 80 is connected to DC power supply 75 by DC buses 1a and 1b via switch 70, and exchanges driving power and regenerative power with DC power supply 75. Power conversion device 80 is also connected to rotating electric machine 10 by AC bus 2a, and exchanges driving power and regenerative power with rotating electric machine 10.

[0020] The rotating electric machine 10 is also provided with a rotation angle sensor 30 that detects the rotation angle of the rotating electric machine. The rotating electric machine 10 is a rotating electric machine that rotates a load and is capable of regenerating the rotational energy of the load as electrical energy, and for example, a permanent magnet three-phase AC synchronous motor or a three-phase brushless motor is used. These motors are not limited to three phases, and may be electric motors with three or more phases.

[0021] The power conversion device 80 is composed of an inverter circuit 20 and a control device 60. The inverter circuit 20 is provided with a capacitor 21, a voltage detector 24, a power conversion circuit 25, and a phase current detector 26.

[0022] <Voltage detector> The voltage detector 24 is connected between the DC buses 1a and 1b on the power supply input side to detect the DC bus voltage. The voltage detector 24 divides the DC bus voltage using a voltage dividing resistor or the like to a voltage that can be read by the control device 60, and outputs DC bus voltage information to the control device 60.

[0023] <Phase current detector> The phase current detector 26 detects the phase current of the rotating electric machine 10 that flows through the AC bus 2a. The phase current detector 26 converts the current into a voltage and outputs phase current information to the control device 60. FIG. 1 shows a configuration in which the current is detected using a shunt resistor. Note that the phase current detector 26 may also be a current sensor that uses a Hall element or the like.

[0024] <Capacitor> The capacitor 21 has a function of suppressing ripples in the DC bus voltage. The capacitor 21 also has a function of lowering the power supply impedance of the inverter circuit 20 to improve the AC current driving capability of the inverter circuit 20. The capacitor 21 also has a function of absorbing surge voltages.

[0025] <Power conversion circuit> Power conversion circuit 25 is composed of switching elements 31 to 36 and performs DC / AC power conversion. Power conversion circuit 25 is a commonly known inverter in which six switching elements are connected in a full bridge configuration. That is, as shown in FIG. 1 , switching elements 31 and 32, switching elements 33 and 34, and switching elements 35 and 36 are connected in series to each other to form three legs. Each leg is connected in parallel to DC power supply 75.

[0026] The midpoints of the switching elements 31 and 32 are connected to the U-phase input of the rotating electric machine 10. The midpoints of the switching elements 33 and 34 are connected to the V-phase input of the rotating electric machine 10. The midpoints of the switching elements 35 and 36 are connected to the W-phase input of the rotating electric machine 10.

[0027] Here, the switching elements 31, 33, and 35 connected to the positive side of the DC power supply 75, i.e., the DC bus 1a, are referred to as positive side switching elements, and the switching elements 32, 34, and 36 connected to the negative side of the DC power supply, i.e., the DC bus 1b, are referred to as negative side switching elements.

[0028] <Switching element> Power transistors are often used as switching elements, which are power semiconductor switching elements that can operate at high switching frequencies. Figure 1 shows an example in which a power transistor, a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), is used as the switching element.

[0029] A free wheel diode (FWD) is provided in parallel to each MOSFET of the switching element, with the forward direction being the direction from the negative side to the positive side of the DC power supply 75. As the power transistor, an IGBT (Insulated Gate Bipolar Transistor) or the like is used in addition to a MOSFET.

[0030] <Switch> The switch 70 controls the exchange of power between the DC power source 75 and the power conversion device 80. The switch 70 is controlled to an open state by a higher-level system (not shown) in the event of an abnormality.

[0031] An abnormality may be, for example, when the voltage of the DC power supply 75 exceeds a set value during regenerative operation of the rotating electric machine 10. An abnormality may also be when the voltage of the DC power supply 75 falls below a set value due to wear and tear on the DC power supply 75. An abnormality may also be when the current flowing through the DC power supply 75 exceeds a set value. An abnormality may also be when a vehicle malfunction or collision is detected. The switch 70 may be configured to be controlled by the control device 60.

[0032] <Rotation angle sensor> The rotation angle sensor 30 detects the rotor rotation angle of the rotary electric machine 10 by using a resolver, an encoder, etc. The rotor rotation angle detected by the rotation angle sensor 30 is output to the control device 60.

[0033] <Control device hardware configuration> 2 is a hardware configuration diagram of the control device 60 of the power conversion device 80 according to the first embodiment. In this embodiment, each function of the control device 60 is realized by a processing circuit included in the control device 60. Specifically, as shown in FIG. 2, the control device 60 includes, as processing circuits, an arithmetic processing device 90 (computer) such as a CPU (Central Processing Unit), a storage device 91 that exchanges data with the arithmetic processing device 90, an input circuit 92 that inputs external signals to the arithmetic processing device 90, and an output circuit 93 that outputs signals from the arithmetic processing device 90 to the outside. Each piece of hardware, such as the arithmetic processing device 90, the storage device 91, the input circuit 92, and the output circuit 93, is connected to one another via a wired network such as a bus or a wireless network.

[0034] The arithmetic processing device 90 may include an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), various logic circuits, various signal processing circuits, etc. Furthermore, a plurality of the same or different types of arithmetic processing devices 90 may be provided, with each device performing a different process. The storage device 91 may include a RAM (Random Access Memory) configured to be able to read and write data from the arithmetic processing device 90, a ROM (Read Only Memory) configured to be able to read data from the arithmetic processing device 90, a flash memory, etc. The input circuit 92 is connected to various sensors and switches, such as the voltage detector 24, the phase current detector 26, and the rotation angle sensor 30, and includes an A / D converter (Analog / Digital Converter) that inputs output signals from these sensors and switches to the arithmetic processing device 90. The output circuit 93 is connected to electrical loads such as the switching elements 31 to 36, and includes a drive circuit, a communication circuit, and the like that converts and outputs control signals from the arithmetic processing unit 90 to these electrical loads.

[0035] Each function of the control device 60 is realized by the arithmetic processing device 90 executing software (programs) stored in a storage device 91 such as a ROM, and cooperating with other hardware of the control device 60, such as the storage device 91, an input circuit 92, and an output circuit 93. Setting data such as thresholds and judgment values ​​used by the control device 60 is stored in the storage device 91 such as a ROM as part of the software (program). Each function of the control device 60 may be configured as a software module, or may be configured as a combination of software and hardware.

[0036] <Controller function> The control device 60 controls the power conversion device 80 and outputs switching drive signals to the switching elements 31 to 36 to control the on / off operations of the switching elements 31 to 36. As shown in FIG. 1 , the control device 60 has a switching element drive unit 61, a control command signal calculation unit 62, a phase short-circuit function unit 64, an overcurrent protection unit 63, and an abnormality detection unit 65.

[0037] <Control command signal calculation section> The control command signal calculation unit 62 calculates a switching control signal for driving the inverter circuit. The target torque and target current of the rotating electric machine 10 are input to the control command signal calculation unit 62 from another control device such as an on-board ECU (Electronic Control Unit) (not shown) via a network such as a CAN (Control Area Network) (registered trademark).

[0038] A control command signal calculation unit 62 executes current feedback control using DC bus voltage information input from the voltage detector 24, rotation angle information of the rotating electric machine 10 input from the rotation angle sensor 30, and phase current information input from the phase current detector 26. Then, the control command signal calculation unit 62 calculates an on / off control signal for each switching element of the power conversion circuit 25 so that the target torque and target current of the rotating electric machine 10 are obtained.

[0039] Then, the control command signal calculation unit 62 outputs an ON / OFF control signal command to the switching element drive unit 61. Note that current feedback control is well known, and therefore a detailed description thereof will be omitted here.

[0040] <Anomaly detection section> The abnormality detection unit 65 detects abnormalities in the power conversion device 80 or in the system including the power conversion device 80, other than detecting an overcurrent in the phase current output from the inverter circuit. If an abnormality is detected, an abnormality detection signal is output to the phase short-circuit function unit 64.

[0041] The abnormality detection unit 65 may output an abnormality detection signal when it detects a circuit failure in the voltage detector 24, or an open failure or a short failure in any of the switching elements 31 to 36. Furthermore, the abnormality detection unit 65 may determine that an over-rotation has occurred and output an abnormality detection signal when the rotation angular velocity calculated from the rotation angle detected by the rotation angle sensor is equal to or greater than a predetermined number of rotations.

[0042] The abnormality detection unit 65 may be configured to determine that a DC bus voltage detected by the voltage detector 24 is a low voltage when it is equal to or lower than a predetermined voltage, and output an abnormality detection signal. Conversely, the abnormality detection unit 65 may be configured to determine that a DC bus voltage is an overvoltage when it is equal to or higher than the predetermined voltage, and output an abnormality detection signal. The abnormality detection unit 65 may be configured to determine that a system abnormality has occurred and output an abnormality detection signal when it detects an open fault in the switch 70, a fault in the rotation angle sensor, or a break in the connection harness.

[0043] <Phase short-circuit function section> Based on the abnormality detection signal input from the abnormality detection unit 65, the phase short-circuiting function unit 64 outputs to the switching element drive unit 61 a phase short-circuiting signal (phase short-circuiting command) for performing phase short-circuiting processing (phase short-circuiting drive) that turns on all of the positive side switching elements of the power conversion circuit 25 and turns off all of the negative side switching elements. Alternatively, the phase short-circuiting function unit 64 outputs to the switching element drive unit 61 a phase short-circuiting signal (phase short-circuiting command) for performing phase short-circuiting processing (phase short-circuiting drive) that turns on all of the negative side switching elements and turns off all of the positive side switching elements.

[0044] <Overcurrent protection section> The overcurrent protection unit 63 detects an overcurrent in the output current based on the phase current information input from the phase current detector 26, and when an overcurrent is detected, determines to perform an overcurrent protection process to turn off all switching elements constituting the inverter circuit in order to deal with the problem as quickly as possible. Then, the overcurrent protection unit 63 outputs an overcurrent cutoff signal (shutdown command) to the switching element drive unit 61 to perform the overcurrent protection process (shutdown). This suppresses deterioration of the components constituting the inverter circuit 20, including the switching elements 31 to 36.

[0045] <Switching element drive unit> The switching element driver 61 controls the switching elements 31 to 36 based on an on / off control signal command input from a control command signal calculator 62, a phase short-circuit signal input from a phase short-circuit function unit 64, and an overcurrent interruption signal input from an overcurrent protection unit 63. The switching element driver 61 outputs a switching drive signal to the switching elements 31 to 36 to control the on / off of the multiple switching elements that make up the power conversion circuit 25.

[0046] The switching elements 31 to 36 are each turned on and off by a switching drive signal from the switching element drive unit 61, converting DC power into AC power and supplying it to the rotating electric machine 10. At the same time, the switching elements 31 to 36 are turned on and off, converting regenerative power generated by the rotating electric machine 10 in a regenerative state into DC power and charging the DC power supply 75.

[0047] Here, a feature of the power conversion device 80 according to the first embodiment is that, in the control device 60, when the phase short-circuiting function unit 64 outputs a phase short-circuiting signal and performs phase short-circuiting processing, the overcurrent protection unit 63 disables the overcurrent interruption signal (shutdown command) for a predetermined prohibition period Tm after the phase short-circuiting function unit 64 starts outputting the phase short-circuiting signal, and then enables the overcurrent interruption signal from the overcurrent protection unit 63 after the prohibition period has elapsed. This configuration prevents the overcurrent protection unit 63 from operating due to a sudden current rise transiently generated by the phase short-circuit when phase short-circuiting is performed, thereby preventing unintended execution of overcurrent protection processing (shutdown), and ensures continued phase short-circuiting. Furthermore, since the overcurrent interruption signal from the overcurrent protection unit 63 is enabled after the prohibition period Tm has elapsed during phase short-circuiting driving, if an overcurrent actually occurs after the prohibition period Tm has elapsed, the power conversion device can be quickly protected by the overcurrent protection processing (shutdown).

[0048] In the above description, the prohibited period Tm is the time after the phase short-circuiting function unit 64 starts to output the phase short-circuiting signal, but it may also be the time after the switching element drive unit 61 actually starts the phase short-circuiting process (phase short-circuiting drive). Also, it may be the time after the switching elements 31 to 36 transition to a phase short-circuited state.

[0049] Here, a case has been described in which the overcurrent interruption signal from the overcurrent protection unit 63 is disabled for a predetermined prohibited period Tm after the phase short-circuiting function unit 64 starts the phase short-circuiting process. However, it is also possible to prohibit the overcurrent protection unit 63 from outputting the overcurrent interruption signal for a predetermined prohibited period Tm after the phase short-circuiting function unit 64 starts the phase short-circuiting process without determining whether the overcurrent interruption signal from the overcurrent protection unit 63 is enabled or disabled. The switching element driver 61 may then prioritize overcurrent protection processing (shutdown) when it receives an overcurrent interruption signal. In this case, the switching element driver 61 does not need to determine whether the received overcurrent interruption signal is enabled or disabled. In this way, the switching element driver 61 always performs overcurrent protection processing (shutdown) when it receives an overcurrent interruption signal, thereby enabling rapid protection of the power conversion device.

[0050] <Phase current waveform> 3 is a time chart showing waveforms of currents flowing through each phase after the phase short-circuiting process is executed by the phase short-circuiting function unit 64 according to the first embodiment. The horizontal axis represents time, and the vertical axis represents current. A sudden current rise that occurs transiently due to a three-phase short-circuit is shown. The phase current flowing through the U phase is indicated by iu, the phase current flowing through the V phase by iv, and the phase current flowing through the W phase by iw.

[0051] As described above, when a phase short circuit is performed while a rotating electric machine is being driven, the currents that have been flowing through each phase to drive the rotating electric machine suddenly increase immediately after the phase short circuit due to the power stored in the stator coil of the rotating electric machine, and then, after a predetermined period of time, a transient current behavior occurs in which the currents converge to the steady-state current of a three-phase short circuit.

[0052] 3, waveforms of phase currents based on switching control signals for driving a general inverter circuit are shown up to time T1. Based on the switching control signals calculated and output by the control command signal calculation unit 62, the switching elements are controlled to be turned on and off by the switching element drive unit 61, and the rotating electric machine 10 is in a driving state.

[0053] This figure shows the waveforms when a phase short-circuit is performed at time T1. As shown in FIG. 3, immediately after time T1 when the phase short-circuit is performed, the current flowing through each phase increases rapidly in both the positive and negative directions. After that, at time T2, after a predetermined time has elapsed, the current waveform converges to a predetermined waveform. This convergent current is called the phase short-circuit steady-state current. In practice, for example, the effective value of the phase short-circuit steady-state current is calculated, and a predetermined allowable threshold is added to the phase short-circuit steady-state current threshold. When the effective current value calculated from the detected phase current information is equal to or less than this, it may be determined that the phase short-circuit steady-state current has converged.

[0054] Note that Fig. 3 also illustrates the overcurrent threshold value at which the overcurrent protection unit 63 detects an overcurrent. The waveforms in Fig. 3 show waveforms in the case where the overcurrent interruption signal output by the overcurrent protection unit 63 is disabled for the current flowing through each phase after a phase short circuit is performed.

[0055] FIG. 4 is a time chart showing waveforms of currents flowing in each phase when overcurrent protection processing (shutdown) is performed due to overcurrent detection after phase short-circuit processing is performed by the phase short-circuit function unit 64 in a power conversion device according to a comparative example. The behavior when a phase short-circuit is performed while the rotating electric machine is in operation will be explained. This shows a case where a phase short-circuit is performed at time T1 while the rotating electric machine is in operation. After the phase short-circuit is initiated at time T1, the current of each phase rises rapidly and exceeds the overcurrent threshold. Therefore, at time T3, the overcurrent protection unit 63 detects an overcurrent. The overcurrent protection unit 63 outputs an overcurrent interrupt signal and performs overcurrent protection processing (shutdown).

[0056] Normally, if a phase short circuit continues, the current will rise as a temporary transient current as shown in Figure 3, but then converge to the phase short circuit steady current. Since the overcurrent is a temporary occurrence and disappears in a short time, no overcurrent protection process (shutdown) is required.

[0057] 4 shows the waveform of the phase current when the overcurrent protection process (shutdown) is activated unintentionally. As described above, this behavior causes a so-called regenerative operation in which an induced current flows to the DC power supply 75 side due to the back electromotive force of the rotating electric machine 10, which raises concerns about deterioration of the performance of the power conversion device 80 and devices connected to the power conversion device 80. Furthermore, there is a concern that abrupt regenerative braking by the rotating electric machine 10 may suddenly cause the electric vehicle to brake suddenly, which is undesirable.

[0058] Therefore, in the power conversion device 80 according to the first embodiment, when the phase short-circuiting function unit 64 generates a phase short-circuiting signal and performs phase short-circuiting processing in the control device 60, the overcurrent interruption signal from the overcurrent protection unit 63 is disabled for a predetermined prohibited period Tm after the start of the phase short-circuiting processing. Then, after the prohibited period Tm has elapsed, the overcurrent interruption signal from the overcurrent protection unit 63 is enabled.

[0059] Here, when an overcurrent is detected, priority is given to overcurrent protection processing (shutdown) for overcurrent protection, and by quickly performing shutdown, performance degradation of the power conversion device 80 can be suppressed. An exception to the priority of overcurrent protection processing is during phase short-circuit processing, during which the overcurrent interrupt signal from the overcurrent protection unit 63 is disabled from the start of output of the phase short-circuit signal (phase short-circuit command) until the elapse of the prohibition period Tm. This prevents overcurrent protection processing from being performed due to a transient current at the start of phase short-circuit processing. This allows the phase short-circuit processing to continue without interruption.

[0060] More specifically, the switching element drive unit 61 executes processing according to the flowchart shown in Fig. 5 based on the on / off control signal command input from the control command signal calculation unit 62, the phase short-circuit signal input from the phase short-circuit function unit 64, and the overcurrent interruption signal input from the overcurrent protection unit 63. The switching element drive unit 61 is configured to appropriately drive the switching elements 31 to 36.

[0061] <Processing in the control device> 5 is a flowchart illustrating a process for achieving both phase short-circuit processing and overcurrent protection processing by the control device 60 of the power conversion device 80 according to the first embodiment. This process is executed by the arithmetic unit of the control device 60. This process may be executed at predetermined time intervals (for example, every 1 ms). Instead of at predetermined time intervals, this process may be executed in response to an event, such as a signal received from the rotation angle sensor 30 as a trigger.

[0062] 5 starts, and in step S101, the switching element driving unit 61 determines whether a phase short-circuit signal is being output from the phase short-circuit function unit 64. If a phase short-circuit signal is being output (determination is YES), the process proceeds to step S105. If a phase short-circuit signal is not being output (determination is NO), the process proceeds to step S102.

[0063] In step S102, the switching element drive unit 61 determines whether an overcurrent interruption signal is being output from the overcurrent protection unit 63. If an overcurrent interruption signal is being output (determination is YES), the process proceeds to step S104. If an overcurrent interruption signal is not being output (determination is NO), the process proceeds to step S103.

[0064] In step S103, the switching element drive unit 61 continues to control the on / off of the switching elements 31 to 36 based on the on / off control signal command output from the control command signal calculation unit 62, and continues to drive the rotating electric machine 10. Thereafter, the process ends.

[0065] In step S104, the switching element drive unit 61 performs overcurrent protection processing (shutdown) based on the overcurrent cutoff signal output from the overcurrent protection unit 63. Specifically, it turns off all switching elements, and then ends the processing.

[0066] In step S105, the switching element drive unit 61 determines whether or not the prohibition period Tm has elapsed since the phase short-circuiting signal began to be output from the phase short-circuiting function unit 64 (prohibition period Tm is not shown). If the prohibition period Tm has elapsed since the phase short-circuiting signal began to be output (determination is YES), the process proceeds to step S107. If the prohibition period Tm has not elapsed since the phase short-circuiting signal began to be output (determination is NO), the process proceeds to step S106.

[0067] In step S107, the switching element driving unit 61 determines whether an overcurrent interruption signal is being output from the overcurrent protection unit 63. If an overcurrent interruption signal is being output (determination is YES), the process proceeds to step S109. If an overcurrent interruption signal is not being output (determination is NO), the process proceeds to step S108.

[0068] In step S106, the switching element drive unit 61 performs phase short-circuit processing based on the phase short-circuit signal output from the phase short-circuit function unit 64. Specifically, all of the positive side switching elements are turned on and all of the negative side switching elements are turned off, or all of the negative side switching elements are turned on and all of the positive side switching elements are turned off. Then, the processing ends.

[0069] In step S108, the switching element driving unit 61 performs a phase short-circuiting process based on the phase short-circuiting signal output from the phase short-circuiting function unit 64. Thereafter, the process ends.

[0070] In step S109, the switching element driving unit 61 performs overcurrent protection processing (shutdown) based on the overcurrent cutoff signal output from the overcurrent protection unit 63. Thereafter, the processing ends.

[0071] The above shows a control method for power conversion device 80, which includes an overcurrent protection step (steps S104, S109) of outputting an overcurrent interruption signal to switching element drive unit 61 when the phase current detected by phase current detector 26 is greater than the overcurrent threshold, and a phase short-circuiting function step (steps S106, S108) of outputting a phase short-circuiting signal to switching element drive unit 61 to turn on all positive-side switching elements and turn off all negative-side switching elements or turn on all negative-side switching elements and turn off all positive-side switching elements when stopping AC output of power conversion circuit 25. In the phase short-circuiting function step, it is determined whether output of the phase short-circuiting signal has started and whether it is within a prohibited period since the start of output (step S105), and if it is within the prohibited period, the overcurrent interruption signal is disabled (NO in step S105), and if it is not outputting a phase short-circuiting signal (NO in step S101) or if the prohibited period has elapsed since output of the phase short-circuiting signal started (YES in step S105), the overcurrent interruption signal is enabled.

[0072] Here, when performing phase short-circuiting processing by the phase short-circuiting function unit 64, the predetermined prohibition period Tm for disabling the overcurrent interruption signal after the start of phase short-circuiting processing may be set based on the transient period until the current of each phase, which temporarily increases immediately after the start of phase short-circuiting drive, settles to a steady state. Specifically, the prohibition period Tm can be set to a time period equivalent to the period T4 between time T1 and time T2 shown in FIG. 3.

[0073] The inhibition period Tm may be increased or decreased based on the magnitude of the phase current before the onset of a phase short circuit. Specifically, the inhibition period Tm may be adjusted to be longer as the effective value of the phase current before the onset of a phase short circuit increases. This is because the larger the phase current before the onset of a phase short circuit, the larger the current immediately after the onset of the phase short circuit tends to be, and therefore the longer the period during which the phase current immediately after the onset of the phase short circuit exceeds the overcurrent threshold. Therefore, the inhibition period Tm may be adjusted to be longer as the effective value of the phase current before the onset of a phase short circuit increases. This allows for an appropriate inhibition period Tm to be set in accordance with the actual behavior of the transient current after a phase short circuit, thereby appropriately disabling the overcurrent trip signal. The magnitude of the phase current before the onset of a phase short circuit may be determined by the magnitude of the target current input to the control command signal calculation unit 62. Alternatively, the magnitude of the phase current before the onset of a phase short circuit may be determined from the maximum value of the phase current during a predetermined period.

[0074] As described above, according to the power conversion device 80 and the control method thereof according to the first embodiment, the power conversion device including the output current overcurrent protection unit 63 is configured such that, when phase short-circuit driving is performed by outputting a phase short-circuit signal (phase short-circuit command) from the phase short-circuit function unit 64, the overcurrent interrupt signal output by the overcurrent protection unit 63 is disabled during the prohibited period Tm after the start of output of the phase short-circuit signal, and the overcurrent interrupt signal output by the overcurrent protection unit 63 is enabled after the prohibited period Tm has elapsed. With this configuration, when phase short-circuit driving is performed, it is possible to prevent the overcurrent protection unit 63 from operating due to a sudden current rise that occurs transiently due to a phase short-circuit, and to prevent unintended overcurrent protection processing (shutdown). This makes it possible to reliably perform phase short-circuit driving.

[0075] Furthermore, the overcurrent interrupt signal output by the overcurrent protection unit 63 is enabled after the prohibition period Tm has elapsed since the start of output of the phase short-circuit signal. Therefore, if an overcurrent actually occurs in the output current after the prohibition period Tm has elapsed during phase short-circuit driving, the overcurrent protection unit 63 can also protect the power conversion device. In this way, it is possible to provide a power conversion device 80 that can accurately perform protective operations appropriate for the respective abnormal states when an overcurrent abnormality and other abnormalities occur.

[0076] In the first embodiment, the phase short-circuiting function unit 64 is configured to output a phase short-circuiting signal to the switching element driving unit 61 based on the abnormality detection signal input from the abnormality detection unit 65. However, as another configuration, a phase short-circuiting signal may be output to the switching element driving unit 61 when the on / off control of the switching elements of the inverter circuit is stopped to stop the conversion from DC power to AC power. The command to stop the on / off control may be input from another control device such as an on-board ECU (not shown) via a network such as a CAN.

[0077] Any type of element may be used for the switching elements 31 to 36 of the power conversion circuit 25. Semiconductors using silicon (Si) are often used as the material for the switching elements. However, in recent years, materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond have been attracting attention. Switching elements made of these wide bandgap semiconductor materials have lower resistance in the on-state compared to conventional switching elements using silicon, which can reduce power loss. Furthermore, they have high electron saturation velocities, allowing for fast switching between the on and off states.

[0078] In inverter circuit 20 configured with SiC-MOSFET, which is such a wide bandgap semiconductor, when overcurrent protection processing (shutdown) is performed by overcurrent protection unit 63, the current flowing through rotating electrical machine 10 flows to DC power supply 75 via the body diode of the SiC-MOSFET. However, there is a concern that a large current flowing through the body diode may cause deterioration of the SiC-MOSFET.

[0079] Therefore, in a power conversion device 80 using an inverter circuit 20 configured with SiC-MOSFETs, there is a greater concern that the overcurrent protection process (shutdown) by the overcurrent protection unit 63 will be activated due to a current increase when a phase short circuit occurs, which may damage the power conversion device 80, compared to a power conversion device 80 using an inverter circuit 20 configured with conventional switching elements formed of silicon (Si). For this reason, it is necessary to more accurately prevent unintended overcurrent protection process (shutdown) by the overcurrent protection unit 63. Therefore, it is more preferable to apply the technology of the first embodiment to a power conversion device 80 using such an inverter circuit 20 configured with SiC-MOSFETs.

[0080] 2. Second Embodiment <Configuration of power conversion device> 6 is a configuration diagram of a power conversion device 80 according to embodiment 2. In the power conversion device 80 according to embodiment 1, when the phase short-circuiting function unit 64 outputs a phase short-circuiting signal in the control device 60 to perform phase short-circuiting processing, the overcurrent interruption signal output by the overcurrent protection unit 63 is disabled for a predetermined prohibited period after the start of the phase short-circuiting processing, and the overcurrent interruption signal output by the overcurrent protection unit 63 is enabled after the prohibited period has elapsed. In this method, the power conversion device 80 according to embodiment 2 differs from embodiment 1 in the method for setting the prohibited period.

[0081] A power conversion device 80 according to the second embodiment will be described, focusing on the differences from the first embodiment. In Fig. 6, the power conversion device 80 is configured with an inverter circuit 20 and a control device 60, similar to the first embodiment described above. However, a switching element drive unit 61b of the control device 60 according to the second embodiment is different from the switching element drive unit 61 according to the first embodiment. Note that other configurations are the same as those in Fig. 1 of the first embodiment, and therefore, in the figure, parts that are the same as or equivalent to those in Fig. 1 are designated by the same reference numerals and description thereof will be omitted.

[0082] The control device 60 controls the power conversion device 80 and is composed of an arithmetic processing unit, a drive circuit, a logic circuit, etc., and outputs switching drive signals to the switching elements 31 to 36 to control the on / off operation of the switching elements 31 to 36. The control device 60 has a switching element drive unit 61b, a control command signal calculation unit 62, a phase short-circuit function unit 64, an overcurrent protection unit 63, and an abnormality detection unit 65.

[0083] The switching element drive unit 61b determines the output based on the on / off control signal command input from the control command signal calculation unit 62, the phase short-circuit signal input from the phase short-circuit function unit 64, and the overcurrent interruption signal input from the overcurrent protection unit 63. The switching element drive unit 61b outputs a switching drive signal to the switching elements 31 to 36 for controlling the on / off of the multiple switching elements that make up the power conversion circuit 25 by a method that will be described later.

[0084] Here, a feature of the power conversion device 80 according to the second embodiment is that in the control device 60, when a phase short-circuit signal is output by the phase short-circuit function unit 64 and phase short-circuit processing is performed, the overcurrent interruption signal output by the overcurrent protection unit 63 is disabled during a prohibited period after the start of output of the phase short-circuit signal, and the overcurrent interruption signal output by the overcurrent protection unit 63 is enabled after the prohibited period has elapsed; in particular, the determination of whether the prohibited period has elapsed differs from that of the first embodiment.

[0085] More specifically, the switching element drive unit 61b is configured to output switching drive signals to the switching elements 31 to 36 in accordance with the logic shown in Figure 7 based on the on / off control signal command input from the control command signal calculation unit 62, the three-phase short-circuit signal input from the phase short-circuit function unit 64, and the overcurrent interruption signal input from the overcurrent protection unit 63.

[0086] <Processing in the control device> 7 is a flowchart illustrating a process for achieving both phase short-circuit processing and overcurrent protection processing by the control device 60 of the power conversion device 80 according to the second embodiment. This process is executed by the arithmetic unit of the control device 60. This process may be executed at predetermined time intervals (for example, every 1 ms). Instead of at predetermined time intervals, this process may be executed in response to an event, such as a signal received from the rotation angle sensor 30 as a trigger.

[0087] 7 differs from the flowchart of FIG. 5 according to the second embodiment in that step S105 has been changed to step S205. The rest of the process is the same, so only the differences will be explained.

[0088] In step S105, the switching element driver 61 determines whether the prohibition period Tm has elapsed since the phase short-circuiting signal began to be output from the phase short-circuiting function unit 64. In contrast, in step S205, the switching element driver 61b determines whether the phase current has converged to the phase short-circuiting steady-state current since the phase short-circuiting signal began to be output from the phase short-circuiting function unit 64. When it is determined that the phase current has converged, it is considered that the prohibition period Tm has elapsed.

[0089] Therefore, step S205 may also be originally described as the switching element drive unit 61b determining whether the prohibition period Tm has elapsed since the phase short-circuiting signal started to be output from the phase short-circuiting function unit 64. Step S205 in Fig. 7 is described as "Has the phase current converged after the phase short-circuiting?" in order to emphasize the difference from the first embodiment and to clarify the content of the processing.

[0090] In the switching element drive unit 61b, the determination of whether a predetermined period has elapsed since the phase short-circuit signal was input (processing of step S205) is made by determining whether the output current after the start of phase short-circuit drive has converged to a phase short-circuit steady-state current. This is a difference from the first embodiment, and the method for this will be described in detail below.

[0091] First, we will explain the current value of a three-phase short-circuit steady-state current in a power conversion device 80 that drives a three-phase rotating electric machine 10. In a dq-axis coordinate system in which the magnetic flux direction of the permanent magnet of the three-phase rotating electric machine is the d-axis and the direction electrically perpendicular to the d-axis is the q-axis, the voltage equation of the three-phase rotating electric machine is expressed as the following equation (1), where Vd is the d-axis voltage, Vq is the d-axis current, Id is the q-axis current, Iq is the armature winding resistance of the three-phase converter, R is the d-axis inductance, Ld is the d-axis inductance of the three-phase rotating electric machine, Lq is the d-axis armature flux linkage number, Φm is the number of flux linkages in the three-phase rotating electric machine, and ω is the rotational speed of the three-phase rotating electric machine.

[0092]

number

[0093] The steady state after the three-phase short circuit process is performed is a state in which the d-axis voltage Vd and the q-axis voltage Vq are 0 in the above equation (1), and is expressed as shown in the following equation (2) using the d-axis current value Id3ps and the q-axis current value Iq3ps in the steady state after the three-phase short circuit process is performed.

[0094]

number

[0095] From the above equation (2), the d-axis current value Id3ps and the q-axis current value Iq3ps in the steady state after the three-phase short circuit process is performed are expressed by the following equations (3) and (4).

[0096]

number

[0097]

number

[0098] Using the d-axis current value Id3ps and the q-axis current value Iq3ps, the effective value I3ps of the three-phase short-circuit steady-state current of each phase in the steady state after the three-phase short-circuit process is performed is calculated using the following equation (5).

[0099]

number

[0100] As described above, the three-phase short-circuit steady-state current is expressed by the above equations (3), (4), and (5), and can be calculated using the armature winding resistance R of the rotating electric machine 10, the d-axis inductance Ld of the rotating electric machine, the q-axis inductance Lq of the rotating electric machine, the d-axis armature flux linkage number Φm of the rotating electric machine, and the rotational speed ω of the rotating electric machine.

[0101] The armature winding resistance R of the rotating electric machine 10, the d-axis inductance Ld of the rotating electric machine, the q-axis inductance Lq of the rotating electric machine, and the d-axis armature flux linkage number Φm of the rotating electric machine are known values ​​determined by the rotating electric machine 10. The rotation speed ω of the rotating electric machine 10 is calculated from rotation angle information of the rotating electric machine 10 detected by the rotation angle sensor 30.

[0102] Therefore, the switching element driver 61b determines that the output current after the start of three-phase short-circuit driving has converged to the three-phase short-circuit steady-state current when the effective current values ​​of each phase calculated from the phase current information input from the phase current detector 26 approximately match the effective value I3ps of the three-phase short-circuit steady-state current, and determines that the prohibition period has elapsed since the input of the three-phase short-circuit signal. Here, "approximately match" refers to being within a predetermined tolerance range. That is, convergence to the three-phase short-circuit steady-state current can be determined when the effective current value calculated from the detected phase current information is equal to or less than the phase short-circuit steady-state current threshold value obtained by adding a predetermined tolerance threshold to the calculated effective value I3ps of the three-phase short-circuit steady-state current. The tolerance threshold can be determined by experiment or simulation, taking into account calculation errors and detection errors. The tolerance threshold may be set so that it can be determined when the phase currents, which transiently increased after the start of phase short-circuiting processing, have converged to a level where they no longer exceed the overcurrent threshold.

[0103] By using the above-described method, after the start of three-phase driving, the overcurrent interruption signal output by the overcurrent protection unit 63 can be disabled until it is confirmed that the output current after the start of three-phase short circuit driving has actually converged to a steady state, and the overcurrent interruption signal output by the overcurrent protection unit 63 can be enabled after it is confirmed that the output current after the start of three-phase short circuit driving has actually converged to a steady state.

[0104] According to the second embodiment, in a power conversion device 80 including an overcurrent protection unit 63, when phase short-circuit processing is performed by the phase short-circuit function unit 64, the prohibition time Tm is not elapsed until it is confirmed that the output current after the start of phase short-circuit driving has actually converged to a steady state, and the overcurrent interruption signal output by the overcurrent protection unit 63 is disabled. Then, after it is confirmed that the output current after the start of phase short-circuit driving has actually converged to a steady state, the prohibition time Tm is considered to have elapsed and the overcurrent interruption signal output by the overcurrent protection unit 63 is enabled. This configuration prevents the overcurrent protection unit 63 from operating due to a sudden current rise transiently caused by a phase short circuit, and thus prevents unintended overcurrent protection processing (shutdown), when phase short-circuit processing is performed by the phase short-circuit function unit 64. Furthermore, because the overcurrent interruption signal output by the overcurrent protection unit 63 is enabled after the current has converged to a steady state after the start of phase short-circuit driving, the power conversion device can also be protected by the overcurrent protection unit 63 if an overcurrent actually occurs in the output current during phase short-circuit driving.

[0105] Furthermore, in the second embodiment, the overcurrent interrupt signal output by the overcurrent protection unit 63 is enabled or disabled after it is confirmed whether the current after the phase short-circuit drive has actually converged to the phase short-circuit steady-state current. Therefore, the overcurrent interrupt signal output by the overcurrent protection unit 63 can be enabled or disabled at an appropriate timing according to the actual behavior of the transient current in the phase short-circuit process by the phase short-circuit function unit 64. This makes it possible to provide a power conversion device that can more reliably and accurately perform protective operations appropriate for each abnormal state.

[0106] In the second embodiment, after the start of phase short-circuit processing by the phase short-circuit function unit 64, if the effective current value of each phase calculated from the phase current information input from the phase current detector 26 substantially matches the effective value I3ps of the three-phase short-circuit steady-state current, it is determined that the output current after the start of three-phase short-circuit drive has converged to the three-phase short-circuit steady-state current, and that the prohibition period Tm has elapsed since the input of the three-phase short-circuit signal. Alternatively, if the d-axis current calculated from the phase current information input from the phase current detector 26 substantially matches the d-axis current value Id3ps in the three-phase short-circuit steady state, or if the q-axis current calculated from the phase current information input from the phase current detector 26 substantially matches the q-axis current value Iq3ps in the three-phase short-circuit steady state, or if both of these conditions are met, it may be determined that the output current after the start of three-phase short-circuit drive has converged to the three-phase short-circuit steady-state current, and that the prohibition period Tm has elapsed since the input of the three-phase short-circuit signal. "Substantially matching" refers to being within a predetermined tolerance range. In other words, when the phase short-circuit steady-state current threshold value obtained by adding a predetermined allowable threshold value to the calculated three-phase short-circuit steady-state current effective value I3ps is equal to or less than this, it can be determined that the three-phase short-circuit steady-state current has converged.

[0107] In addition, in the second embodiment, a method for calculating the phase short-circuit steady-state current using the above equations (3), (4), and (5) based on the armature winding resistance R of the rotating electric machine, the d-axis inductance Ld of the rotating electric machine, the q-axis inductance Lq of the rotating electric machine, the d-axis armature flux linkage number Φm of the rotating electric machine, and the rotation speed ω of the rotating electric machine has been described. However, the power conversion device 80 according to the second embodiment is not limited to such processing, and is not particularly limited to the above equations (3), (4), and (5) as long as an essentially equivalent calculation method is used.

[0108] For example, since the armature winding resistance R of a rotating electric machine is generally so small that it can be ignored, the d-axis current value Id3ps and the q-axis current value Iq3ps in a three-phase short-circuit steady state can be calculated using the following equations (6) and (7), which are approximated by setting the armature winding resistance R in the above equations (3) and (4) to 0.

[0109]

number

[0110]

number

[0111] When such processing is adopted, compared to the method in which the switching element drive unit 61b calculates the three-phase short-circuit steady-state current using the above equations (3), (4), and (5), it is possible to determine that the output current after the start of phase short-circuit driving has converged to the three-phase short-circuit steady-state current and that the prohibited period has elapsed since the three-phase short-circuit signal was input, using a simple process that is calculated based only on the d-axis inductance of the rotating electric machine and the d-axis armature flux linkage number of the rotating electric machine.

[0112] It should be noted that the above-described first and second embodiments are merely examples, and the present disclosure is not limited to the first and second embodiments as long as they are applicable. For example, in the first and second embodiments, the DC power supply 75 and the power conversion device 80 are directly connected. However, a DC / DC converter that steps up and down the voltage may be disposed between the DC power supply 75 and the power conversion device 80. Furthermore, the DC power supply 75 may be connected to the AC power supply via a rectifier or AC / DC converter that converts AC power from the AC power supply into DC power.

[0113] Although the first and second embodiments have been described with reference to an example of application to an electric vehicle, the present disclosure can be applied not only to electric vehicles but also to hybrid vehicles that use both an engine and a rotating electric machine. Furthermore, the application of the power conversion device 80 according to the present disclosure is not limited to vehicles.

[0114] As described above, the present disclosure is not limited to embodiments 1 and 2, and various design modifications are possible. Within the scope of the disclosed technology, embodiments 1 and 2 can be freely combined, or embodiments 1 and 2 can be modified or omitted as appropriate.

[0115] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this disclosure specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0116] Various aspects of the present disclosure are summarized below as appendices.

[0117] (Appendix 1) a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to a positive electrode of a DC power supply, a negative-side switching element connected to a negative electrode of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and from which an AC output is derived; a phase current detector for detecting a phase current flowing between the external connection point of the power conversion circuit and the AC output; and a control device including: a switching element drive unit that outputs a control signal for controlling the on / off of the switching elements; an overcurrent protection unit that outputs an overcurrent interruption signal to the switching element drive unit when the phase current detected by the phase current detector is greater than a predetermined overcurrent threshold; and a phase short-circuiting function unit that outputs a phase short-circuiting signal to the switching element drive unit to turn on all of the positive electrode side switching elements and turn off all of the negative electrode side switching elements, or to turn on all of the negative electrode side switching elements and turn off all of the positive electrode side switching elements, when stopping AC output of the power conversion circuit; The control device is a power conversion device that, when the phase short-circuiting function unit starts outputting the phase short-circuiting signal, disables the output of the overcurrent interruption signal by the overcurrent protection unit for a predetermined prohibited period. (Appendix 2) The power conversion device according to claim 1, wherein the overcurrent protection unit of the control device outputs a signal to the switching element drive unit as the overcurrent interruption signal, the signal turning off all of the positive-side switching elements and the negative-side switching elements. (Appendix 3) 3. The power conversion device according to claim 1, wherein the inhibited period of the control device is set based on a transient period from when the phase short-circuiting function unit starts outputting the phase short-circuiting signal until when the phase current detected by the phase current detector changes to a steady state after temporarily increasing. (Appendix 4) The power conversion device according to claim 3, wherein the control device determines that a steady state has been reached when the effective value of the phase current detected by the phase current detector becomes equal to or less than a predetermined phase short-circuit steady-state current threshold. (Appendix 5) 3. The power conversion device according to claim 1, wherein the prohibited period of the control device is determined based on the value of the phase current detected by the phase current detector before the phase short-circuiting function unit starts outputting the phase short-circuiting signal. (Appendix 6) 6. The power conversion device according to claim 5, wherein the prohibited period of the control device is extended as the value of the phase current before the phase short-circuiting function unit starts outputting the phase short-circuiting signal increases. (Appendix 7) A power conversion device as described in Appendix 6, wherein the value of the phase current before starting to output the phase short-circuit signal is determined by the effective value of the phase current, the magnitude of the target current given to the control device, or the maximum value of the phase current during a predetermined period. (Appendix 8) The power conversion device according to claim 1 or 2, wherein the control device determines that the prohibition period has elapsed when a maximum value of the phase current detected by the phase current detector for each predetermined period after the phase short-circuiting function unit starts outputting the phase short-circuiting signal becomes smaller than a predetermined current threshold value. (Appendix 9) an external connection point of the power conversion circuit is connected to a coil of a rotating electric machine having a permanent magnet and a coil; The control device determines the phase short-circuit steady-state current threshold by calculating the magnitude of the phase current after the phase short-circuit function unit starts outputting the phase short-circuit signal and the phase current has changed to a steady state, based on the d-axis inductance and d-axis armature flux linkage number of the rotating electric machine on a dq coordinate system, where the magnetic flux direction of the permanent magnet of the rotating electric machine is the d-axis and the direction electrically perpendicular to the d-axis is the q-axis. (Appendix 10) an external connection point of the power conversion circuit is connected to a coil of a rotating electric machine having a permanent magnet and a coil; The control device of the power conversion device described in Appendix 4 determines the phase short-circuit steady-state current threshold by calculating the magnitude of the phase current after the phase short-circuit function unit starts outputting the phase short-circuit signal and the phase current has changed to a steady state, based on the d-axis inductance, q-axis inductance, and d-axis armature flux linkage number of the rotating electric machine on a dq coordinate system, where the magnetic flux direction of the permanent magnet of the rotating electric machine is the d-axis and the direction electrically perpendicular to the d-axis is the q-axis, as well as the armature winding resistance value and rotational speed of the rotating electric machine. (Appendix 11) a voltage detector that detects the voltage of the DC power supply; a rotation angle sensor for detecting a rotation angle of a rotating electric machine connected to an external connection point of the power conversion circuit; and a switch that connects and disconnects the DC power supply and the power conversion circuit, The control device has an abnormality detection unit that detects at least one of an abnormality in the voltage detector, an abnormality in the switching element, an abnormality in the rotation angle sensor, an abnormality in the switch, a voltage abnormality in the DC power supply detected by the voltage detector, an abnormality in the rotation speed of the rotating electric machine detected by the rotation angle sensor, and a connection abnormality in the power conversion device, and the power conversion device described in any one of Appendices 1 to 10, wherein the phase short-circuiting function unit starts outputting the phase short-circuiting signal when the abnormality detection unit detects an abnormality. (Appendix 12) The power conversion device according to any one of appendices 1 to 10, wherein the control device causes the phase short-circuiting function unit to start outputting the phase short-circuiting signal when the control device stops on / off control of the switching element of the power conversion circuit. (Appendix 13) 13. The power conversion device according to claim 1, wherein the switching elements of the power conversion circuit are made of wide-gap semiconductors. (Appendix 14) A control method for a power conversion device including: a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to the positive electrode of a DC power supply, a negative-side switching element connected to the negative electrode of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and from which an AC output is derived; a phase current detector detecting a phase current flowing between the external connection point of the power conversion circuit and the AC output; and a switching element driver outputting a control signal for controlling on / off of the switching element, an overcurrent protection step of outputting an overcurrent interrupt signal to the switching element driver when the phase current detected by the phase current detector is greater than a predetermined overcurrent threshold; a phase short-circuiting function step of outputting a phase short-circuiting signal to the switching element drive unit to turn on all of the positive electrode side switching elements and turn off all of the negative electrode side switching elements, or to turn on all of the negative electrode side switching elements and turn off all of the positive electrode side switching elements, when stopping the AC output of the power conversion circuit; In the phase short-circuit function step, it is determined whether or not the output of the phase short-circuit signal has started and is within a predetermined prohibition period since the start of the output, and if it is within the prohibition period, the overcurrent interruption signal is disabled; A control method for a power conversion device, which enables the overcurrent interruption signal when the phase short-circuit signal is not output or when the prohibited period has elapsed since the output of the phase short-circuit signal began. [Explanation of symbols]

[0118] 10 rotating electric machine, 24 voltage detector, 26 phase current detector, 30 rotation angle sensor, 31, 32, 33, 34, 35, 36 switching element, 60 control device, 61 switching element drive unit, 63 overcurrent protection unit, 64 phase short circuit function unit, 65 abnormality detection unit, 70 switch, 75 DC power supply, 80 power conversion device

Claims

1. a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to a positive electrode of a DC power supply, a negative-side switching element connected to a negative electrode of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and from which an AC output is derived; a phase current detector for detecting a phase current flowing between the external connection point of the power conversion circuit and the AC output; and a control device including: a switching element drive unit that outputs a control signal for controlling the on / off of the switching elements; an overcurrent protection unit that outputs an overcurrent interruption signal to the switching element drive unit when the phase current detected by the phase current detector is greater than a predetermined overcurrent threshold; and a phase short-circuiting function unit that outputs a phase short-circuiting signal to the switching element drive unit to turn on all of the positive electrode side switching elements and turn off all of the negative electrode side switching elements, or to turn on all of the negative electrode side switching elements and turn off all of the positive electrode side switching elements, when stopping AC output of the power conversion circuit; The control device is a power conversion device that, when the phase short-circuiting function unit starts outputting the phase short-circuiting signal, disables the output of the overcurrent interruption signal by the overcurrent protection unit for a predetermined prohibited period.

2. The power conversion device according to claim 1 , wherein the overcurrent protection unit of the control device outputs a signal to the switching element drive unit as the overcurrent interrupt signal, the signal turning off all of the positive-side switching elements and the negative-side switching elements.

3. 2. The power conversion device according to claim 1, wherein the inhibit period of the control device is set based on a transient period from when the phase short-circuiting function unit starts outputting the phase short-circuiting signal until when the phase current detected by the phase current detector changes to a steady state after temporarily increasing.

4. 4. The power conversion device according to claim 3, wherein the control device determines that the steady state has been reached when an effective value of the phase current detected by the phase current detector becomes equal to or less than a predetermined phase short-circuit steady-state current threshold.

5. 2. The power conversion device according to claim 1, wherein the inhibit period of the control device is determined based on the value of the phase current detected by the phase current detector before the phase short-circuiting function unit starts outputting the phase short-circuiting signal.

6. The power conversion device according to claim 5 , wherein the inhibit period of the control device is extended as the value of the phase current before the phase short-circuiting function unit starts outputting the phase short-circuiting signal increases.

7. The power conversion device according to claim 6, wherein the value of the phase current before starting to output the phase short-circuit signal is determined by the effective value of the phase current, the magnitude of the target current given to the control device, or the maximum value of the phase current during a predetermined period.

8. 2. The power conversion device according to claim 1, wherein the control device determines that the prohibition period has elapsed when a maximum value of the phase current detected by the phase current detector for each predetermined period before the phase short-circuiting function unit starts outputting the phase short-circuiting signal becomes smaller than a predetermined current threshold value.

9. an external connection point of the power conversion circuit is connected to a coil of a rotating electric machine having a permanent magnet and a coil; The control device determines the phase short-circuit steady-state current threshold by calculating the magnitude of the phase current after the phase short-circuit function unit starts outputting the phase short-circuit signal and the phase current that temporarily increases after the phase short-circuit function unit starts outputting the phase short-circuit signal and changes to a steady state based on the d-axis inductance and d-axis armature flux linkage number of the rotating electric machine on a d-q coordinate system, where the magnetic flux direction of the permanent magnet of the rotating electric machine is the d-axis and the direction electrically perpendicular to the d-axis is the q-axis.

10. an external connection point of the power conversion circuit is connected to a coil of a rotating electric machine having a permanent magnet and a coil; The control device determines the phase short-circuit steady-state current threshold by calculating the magnitude of the phase current after the phase short-circuit function unit starts outputting the phase short-circuit signal and the phase current has changed to a steady state, based on the d-axis inductance, q-axis inductance, and d-axis armature flux linkage number of the rotating electric machine on a d-q coordinate system, where the magnetic flux direction of the permanent magnet of the rotating electric machine is the d-axis and the direction electrically perpendicular to the d-axis is the q-axis, as well as the armature winding resistance value and rotational speed of the rotating electric machine.

11. a voltage detector that detects the voltage of the DC power supply; a rotation angle sensor for detecting a rotation angle of a rotating electric machine connected to an external connection point of the power conversion circuit; and a switch that connects and disconnects the DC power supply and the power conversion circuit, 2. The power conversion device according to claim 1, wherein the control device has an abnormality detection unit that detects at least one of an abnormality in the voltage detector, an abnormality in the switching element, an abnormality in the rotation angle sensor, an abnormality in the switch, a voltage abnormality in the DC power supply detected by the voltage detector, an abnormality in the rotation speed of the rotating electric machine detected by the rotation angle sensor, and a connection abnormality in the power conversion device, and when the abnormality detection unit detects an abnormality, the phase short-circuiting function unit starts outputting the phase short-circuiting signal.

12. The power conversion device according to claim 1 , wherein the control device causes the phase short-circuiting function unit to start outputting the phase short-circuiting signal when the control device stops on-off control of the switching elements of the power conversion circuit.

13. 13. The power conversion device according to claim 1, wherein the switching elements of the power conversion circuit are made of wide-gap semiconductors.

14. A control method for a power conversion device including: a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to the positive electrode of a DC power supply, a negative-side switching element connected to the negative electrode of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and from which an AC output is derived; a phase current detector detecting a phase current flowing between the external connection point of the power conversion circuit and the AC output; and a switching element driver outputting a control signal for controlling on / off of the switching element, an overcurrent protection step of outputting an overcurrent interrupt signal to the switching element driver when the phase current detected by the phase current detector is greater than a predetermined overcurrent threshold; a phase short-circuiting function step of outputting a phase short-circuiting signal to the switching element drive unit to turn on all of the positive electrode side switching elements and turn off all of the negative electrode side switching elements, or to turn on all of the negative electrode side switching elements and turn off all of the positive electrode side switching elements, when stopping the AC output of the power conversion circuit; In the phase short-circuit function step, it is determined whether or not the output of the phase short-circuit signal has started and is within a predetermined prohibition period since the start of the output, and if it is within the prohibition period, the overcurrent interruption signal is disabled; A control method for a power conversion device, which enables the overcurrent interruption signal when the phase short-circuit signal is not output or when the prohibited period has elapsed since the output of the phase short-circuit signal began.

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