JP2011244577A - Inverter circuit failure detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect a failure in a plurality of inverter circuits connected to a common DC power supply circuit.SOLUTION: A failure detection processing is performed by using a detection value of a current detection sensor 30 disposed in power transmission lines U1 and V1 of a first motor generator 16 or a detection value of a current detection sensor 30 disposed in power transmission lines U2 and V2 of a second motor generator 20. When a control unit 22 determines that there is a current measurement value out of a reference range, it controls the first inverter circuit 14 so that an operation point of the first motor generator 16 is changed. Thereafter, when the control unit 22 determines that there is the current measurement value out of the reference range, it generates failure information specifying the inverter circuit having the failure, switching element pair having the failure and IGBT, etc. having the failure and stores the information in a memory which the control unit 22 has.

Description

  The present invention relates to an inverter circuit failure detection device, and more particularly to a device that detects a failure of an inverter circuit based on a current detection value of a power transmission line from an inverter circuit to a motor generator.

  Electric vehicles such as a hybrid vehicle that travels using an engine and a motor generator and an electric vehicle that travels using a motor generator are widely used. The motor generator is connected to an inverter circuit that performs DC / AC conversion. The inverter circuit converts the DC power supplied from the DC power source circuit into AC power, supplies the AC power to the motor generator, converts AC power generated by the motor generator into DC power, and converts the DC power. Is supplied to the DC power source circuit.

  In order to facilitate maintenance, inspection and the like, an electric vehicle is often equipped with a device for detecting a failure such as an inverter circuit or a motor generator. The following patent document describes a technique for detecting a failure of an inverter circuit, a motor generator, or the like for an electric vehicle.

JP 2006-176049 A JP 2005-160190 A JP-A-7-154901 JP 2008-5681 A JP 2005-304229 A

  Generally, an electric vehicle is equipped with a plurality of motor generators and an inverter circuit corresponding to each motor generator. For example, in the case of a hybrid vehicle, a first motor generator that performs engine starting and power generation by engine driving force and a second motor generator that performs traveling driving and regenerative braking are mounted. The inverter circuit corresponding to each motor generator is connected to a common DC power source circuit.

  The control unit that controls the inverter circuit detects a failure of the inverter circuit based on the detected current value of the power transmission line from the inverter circuit to the motor generator. However, when a configuration in which a plurality of inverter circuits are connected to a common DC power source circuit, a failure of one of the plurality of inverter circuits may affect the current flowing through the other inverter circuit. is there. This can make it difficult to determine that the inverter circuit has failed.

  An object of the present invention is to facilitate failure detection of a plurality of inverter circuits connected to a common DC power source circuit.

  The present invention relates to a control unit that controls each inverter circuit in an inverter circuit failure detection device that detects any failure among a plurality of inverter circuits that are connected to a common DC power source circuit and that each perform DC-AC conversion. And current detection means for detecting the current of the AC power transmission line from the inverter circuit to be detected to the motor generator provided corresponding to the inverter circuit, and providing a current detection value to the control unit, The control unit includes: a current abnormality detection unit that determines whether or not an abnormality has occurred in the current detection value; and a determination that an abnormality has occurred by the current abnormality detection unit. So that the rotation state of the motor generator corresponding to any of the inverter circuits changes, When it is determined that an abnormality has occurred by the current abnormality detection means after the rotation state change means for performing the rotation state change control on the inverter circuit and the control by the rotation state change means, Failure determination means for determining that a failure has occurred in the inverter circuit for which the determination has been made.

  Further, in the inverter circuit failure detection device according to the present invention, the rotation state changing means is configured so that a rotational speed difference between a plurality of motor generators provided corresponding to the plurality of inverter circuits is within a predetermined range. In some cases, it is preferable to perform the rotational state control.

   According to the present invention, failure detection can be facilitated for a plurality of inverter circuits connected to a common DC power source circuit.

It is a figure showing composition of a vehicle drive system concerning an embodiment of the present invention. It is a flowchart of the process which a control unit performs in a failure detection process. It is a figure which shows the time waveform of the electric current which flows into the power transmission line V1. It is a figure which shows the time waveform of each measured value when one of two IGBTs of V phase of a 2nd inverter circuit produces an open failure.

  FIG. 1 shows a configuration of a vehicle drive system according to an embodiment of the present invention. The vehicle drive system includes a battery 10, a step-up / down converter circuit 12, a first inverter circuit 14, a second inverter circuit 18, and a control unit 22. The step-up / down converter circuit 12 operates according to the control of the control unit 22. That is, the step-up / down converter circuit 12 boosts the output voltage of the battery 10 and outputs the boosted voltage to the first inverter circuit 14 and the second inverter circuit 18, while stepping down the voltage on the inverter circuit side and reducing the stepped-down voltage to the battery. 10 is output.

  The vehicle drive system also includes a first motor generator (MG1) 16 connected to the first inverter circuit 14 and a second motor generator (MG2) 20 connected to the second inverter circuit 18. The first inverter circuit 14 and the second inverter circuit 18 operate under the control of the control unit 22. That is, the first inverter circuit 14 performs DC / AC conversion between the step-up / step-down converter circuit 12 and the first motor generator 16, and the second inverter circuit 18 is connected between the step-up / down converter circuit 12 and the second motor generator 20. DC / AC conversion between the two.

  As described above, the step-up / down converter circuit 12, the first inverter circuit 14, and the second inverter circuit 18 function as a power conversion circuit that performs voltage step-up / step-down and DC / AC conversion. The battery 10 and the step-up / down converter circuit 12 function as a DC power source circuit that exchanges DC power with the first inverter circuit 14 and the second inverter circuit 18.

  When the vehicle drive system is used in a hybrid vehicle, the shafts of the engine, the first motor generator 16 and the second motor generator 20 are attached to a torque dividing mechanism such as a planetary gear unit. The torque dividing mechanism applies torque between them. Further, a torque transmission mechanism for applying torque to the wheels is attached to the shaft of the second motor generator 20. Moreover, when using a vehicle drive system for an electric vehicle, each shaft of the 1st motor generator 16 and the 2nd motor generator 20 is attached to the torque transmission mechanism which acts a torque between wheels.

  Specific configurations of the first inverter circuit 14 and the second inverter circuit 18 will be described. Each of the first inverter circuit 14 and the second inverter circuit 18 includes three pairs of switching elements 24. Here, the switching element pair means a pair of two IGBTs (Insulated Gate Bipolar Transistors) 26 in which one emitter terminal is connected to the other collector terminal. A diode 28 is connected between the collector terminal and the emitter terminal of each IGBT 26 so that the anode terminal is connected to the emitter terminal.

  The collector terminals of the IGBTs on the upper side of the circuit diagram of the three pairs of switching elements 24 provided in each of the first inverter circuit 14 and the second inverter circuit 18 are connected in common, and the common connection terminal is a booster of the buck-boost converter circuit 12 It is connected to the positive terminal on the output side. The emitter terminals of the IGBTs on the lower side of the circuit diagram of the three pairs of switching elements 24 are also connected in common, and the common connection end is connected to the negative terminal on the boost output side of the buck-boost converter circuit 12.

  The three pairs of switching elements 24 provided in the first inverter circuit 14 correspond to the three-phase power transmission lines U 1, V 1, and W 1 that reach the first motor generator 16. That is, a corresponding power transmission line is connected to a connection node between the upper IGBT and the lower IGBT in each switching element pair 24.

  Similarly, the three pairs of switching elements 24 included in the second inverter circuit 18 correspond to the three-phase power transmission lines U 2, V 2, and W 2 that reach the second motor generator 20. That is, a corresponding power transmission line is connected to a connection node between the upper IGBT and the lower IGBT in each switching element pair 24.

  The control unit 22 converts the DC power output from the step-up / step-down converter circuit 12 into three-phase AC power according to a driving operation or the like, and supplies the three-phase AC power to the first motor generator 16 or Each switching element pair 24 included in the first inverter circuit 14 is controlled so that the AC generated power of the first motor generator 16 is converted into DC power and the DC power is supplied to the step-up / down converter circuit 12.

  Further, the control unit 22 converts the DC power output from the step-up / down converter circuit 12 into three-phase AC power according to a driving operation or the like, and supplies the three-phase AC power to the second motor generator 20. Alternatively, each switching element pair 24 included in the second inverter circuit 18 is controlled so that the AC generated power of the second motor generator 20 is converted into DC power and the DC power is supplied to the step-up / step-down converter circuit 12.

  Here, an example in which an IGBT is used as the switching element forming the switching element pair 24 is shown, but other semiconductor elements such as a thyristor, a triac, a bipolar transistor, and a field effect transistor may be used as the switching element. Good.

  Next, failure detection for the first inverter circuit 14 and the second inverter circuit 18 will be described. In the vehicle drive system according to the present invention, it is possible to detect that an IGBT failure has occurred in the first inverter circuit 14 or the second inverter circuit 18. This failure detection processing is performed by detecting the detection value of the current detection sensor 30 provided on the power transmission lines U1 and V1 of the first motor generator 16, or the current detection provided on the power transmission lines U2 and V2 of the second motor generator 20. This is performed using the detection value of the sensor 30. FIG. 2 shows a flowchart of processing executed by the control unit 22 in such failure detection processing.

  Here, a case where it is detected that an IGBT failure has occurred in the first inverter circuit 14 will be described. The control unit 22 acquires current detection values of the power transmission lines U1 and V1, that is, current measurement values Iu1 and Iv1, from the current detection sensors 30 provided on the power transmission lines U1 and V1. Then, the current measurement value Iw1 of the power transmission line W1 is obtained based on the current measurement values Iu1 and Iv1 (S1).

  The control unit 22 obtains a time average value for each of the current measurement values Iu1, Iv1, and Iw1 (S2). Here, the time average value means, for example, a smoothing process for obtaining a time average value with a predetermined time length.

  The control unit 22 determines whether there are any time average values of the current measurement values Iu1, Iv1, and Iw1 that are outside the predetermined reference range (S3). Here, the reference range may be defined as a numerical range between a threshold value −TH and a threshold value TH with respect to a predetermined positive value TH.

  For example, when each IGBT of the first inverter circuit 14 is normal, it is assumed that the current flowing through the power transmission line V1 has a sinusoidal time waveform as shown in FIG. At this time, when one of the two V-phase IGBTs of the first inverter circuit 14 has an open failure, the current flowing through the power transmission line V1 becomes a half-wave rectified waveform as shown in FIG. The time average value is offset to a non-zero value. Further, although an open failure is taken here, the time average value of the current flowing through the power transmission line tends to be offset to a value other than 0 even in the case of other failures.

  Accordingly, if there is a time average value of the current measurement values Iu1, Iv1, and Iw1 that is outside the reference range, the IGBT of the phase corresponding to the current measurement value outside the reference range has a failure such as an open failure. there is a possibility. Therefore, in this embodiment, paying attention to this phenomenon, it is determined whether or not the IGBT is out of order.

  However, as will be described below, when a failure occurs in the second inverter circuit 18, the current flowing through the first inverter circuit 14 is affected, and the time average value of any one of the current measurement values Iu1, Iv1, and Iw1 May be outside the reference range. Therefore, if it is simply determined that the IGBT of the phase corresponding to the current measurement value outside the reference range has failed, a determination error may occur.

  4 shows the measured current value Iv2 of the power transmission line V2 of the second motor generator 20 and the first motor generator 16 when one of the two V-phase IGBTs of the second inverter circuit 18 has an open fault. The measured current value Iv1 of the power transmission line V1, the rotational speed R2 of the second motor generator 20, and the rotational speed R1 of the first motor generator 16 are shown. Here, at time tc, one of the two V-phase IGBTs of the second inverter circuit 18 is forcibly opened.

  FIG. 4A shows a case where the difference between the rotational speed R1 of the first motor generator 16 and the rotational speed R2 of the second motor generator 20 is 5000 [rpm] or more, and FIG. The case where the difference between the rotational speed of the motor generator 16 and the rotational speed of the second motor generator 20 is 1000 [rpm] or less is shown.

  In FIG. 4A, after time tc, the time average value of the current measurement value Iv1 on the side where no failure has occurred is close to 0 and within the reference range. On the other hand, in FIG. 4B, after the time tc, the time average value of the current measurement value Iv1 on the side where no failure has occurred may be offset from 0 and may be out of the reference range. Therefore, if it is simply determined that the IGBT of the phase corresponding to the current measurement value outside the reference range has failed, a determination error may occur.

  Therefore, in the present embodiment, the processing of steps S4 to S6 described below is executed, the vehicle drive system is set to an operation state that is not easily influenced by the second inverter circuit 18, and the current measurement value outside the reference range is set. It is determined whether or not the corresponding phase IGBT has failed.

  In step S3, if the control unit 22 determines that there is no current measurement value outside the reference range, the control unit 22 returns to the process of step S1. On the other hand, when it is determined that there is a current measurement value outside the reference range, the first inverter circuit 14 is controlled so that the operating point of the first motor generator 16 is changed (S4). Here, the operating point refers to the operating state of the motor generator defined by the rotational speed and torque of the motor generator. The operating point of the first motor generator 16 can be changed by changing the switching state of the first inverter circuit 14 and changing the current flowing through the first inverter circuit 14 and the first motor generator 16.

  Here, the process of changing the operating point of the first motor generator 16 is described, but the process of changing the operating point of the second motor generator 20 may be executed. In this case, the control unit 22 controls the second inverter circuit 18 so that the operating point of the second motor generator 20 is changed.

  The control unit 22 performs the same determination process as in step S3 (S5). Then, when it is determined that there is a current measurement value outside the reference range, fault information that identifies a faulty inverter circuit, faulty switching element pair, faulty IGBT, etc. is generated, It memorize | stores in the memory with which the control unit 22 is provided (S6). The faulty IGBT is identified by specifying the phase corresponding to the current measurement value outside the reference range, thereby specifying the faulty one of the three pairs of switching elements 24, This is done by specifying one of the upper and lower IGBTs that is malfunctioning based on the polarity of the time average value. Instead of storing the failure information, a device that alerts the driver by warning display, sounding a warning sound, or the like may be provided. On the other hand, if the control unit 22 determines that there is no current measurement value outside the reference range, the process ends (S5).

  According to such processing, in step S4, after changing the operating point of the first motor generator 16, it is determined that the phase IGBT corresponding to the current measurement value out of the reference range has failed. The As a result, it is possible to determine whether or not a failure has occurred after setting the vehicle drive system in an operation state that is not easily affected by the first inverter circuit 14.

  The control unit 22 measures the difference between the rotation speed of the first motor generator 16 and the rotation speed of the second motor generator 20 between step S3 and step S4, and the difference is outside the predetermined range. If so, a process of avoiding the process of step S4 and proceeding to the process of step S5 may be executed.

  In the above description, the case where it is detected that an IGBT failure has occurred in the first inverter circuit 14 has been described. In the vehicle drive system according to the present embodiment, the configurations of the second inverter circuit 18 and the second motor generator 20 are the same as the configurations of the first inverter circuit 14 and the first motor generator 16. Therefore, a process for detecting that an IGBT failure has occurred in the second inverter circuit 18 can be executed by a process similar to the process related to the first inverter circuit 14.

  In the above description, the current sensor 30 corresponding to the first motor generator 16 detects the currents of the power transmission lines U1 and V1. However, the current sensor 30 includes the power transmission lines U1, V1, and W1. Of these, any two currents may be detected. Similarly, in the above description, the current sensor 30 corresponding to the second motor generator 20 is configured to detect each current of the power transmission lines U2 and V2. However, the current sensor 30 includes the power transmission lines U2, V2 and Any two currents of W2 may be detected.

  DESCRIPTION OF SYMBOLS 10 Battery, 12 Buck-boost converter circuit, 14 1st inverter circuit, 16 1st motor generator, 18 2nd inverter circuit, 20 2nd motor generator, 22 Control unit, 24 Switching element pair, 26 IGBT, 28 Diode, 30 Current Sensor.

Claims (2)

In an inverter circuit failure detection device that detects any failure among a plurality of inverter circuits that are connected to a common DC power source circuit and each perform DC-AC conversion,
A control unit for controlling each inverter circuit;
Current detection means for detecting a current of an AC power transmission line from a fault detection target inverter circuit to a motor generator provided corresponding to the inverter circuit, and providing a current detection value to the control unit,
The control unit is
Current abnormality detection means for determining whether an abnormality has occurred in the current detection value; and
When it is determined by the current abnormality detection means that an abnormality has occurred, the motor circuit corresponding to any one of the plurality of inverter circuits is rotated so that the rotation state of the motor generator changes. Rotation state changing means for performing state change control;
A failure to determine that a failure has occurred in the inverter circuit for which the determination has been made, when it is determined that an abnormality has occurred by the current abnormality detection unit after the control by the rotation state changing unit has been performed A determination means;
An inverter circuit failure detection device comprising: In the inverter circuit failure detection device according to claim 1,
The rotation state changing means is
The inverter circuit failure detection device, wherein the rotational state control is performed when a difference in rotational speed between a plurality of motor generators provided corresponding to the plurality of inverter circuits is within a predetermined range.

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