JP2020058176A - Motor drive system - Google Patents

Abstract

To identify a short-circuit fault of an arm in a system in which an open winding motor is driven by two inverters.SOLUTION: In a system in which a single open-winding type motor 10 is driven by two inverters 12 and 14, when a short-circuit fault occurs in the inverter 12, all upper and lower arms of the faulty inverter 12 are turned off, and with respect to the inverter 14 that has not failed, all three phases of the upper arm are turned on or all three phases of the lower arm are turned on, a motor 10 is set to the neutral point connection state, and a circulating current is measured. Then, the arm having a short circuit fault is specified on the basis of the measured circulating current. Therefore, according to the specified short-circuit faulty arm, a switching element of the faulty inverter 12 is set to the neutral point connection state of the motor 10, and the motor 10 is driven by the non-faulty inverter 14 to perform the evacuation traveling.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a motor drive system that drives one open winding motor using two inverters.

  Patent Document 1 discloses an electric vehicle, in which, when a one-phase or two-phase short-circuit fault occurs in an inverter, an upper arm and a lower arm of the inverter in which the short-circuit fault has occurred are turned off and a circulating current flowing through each arm To identify the arm that has failed due to a short circuit. Patent Literature 1 discloses that a short-circuited arm is similarly specified in a system having two inverters and motors connected to the respective inverters.

JP 2009-278791 A

  Here, in Patent Document 1, a short-circuited arm is specified by detecting a circulating current flowing based on the free rotation of the motor. This is based on the premise that an AC motor whose neutral point is short-circuited is used. In a system in which a single motor of an open winding type is driven by two inverters, it is assumed in Patent Document 1. No circulating current is generated. For this reason, there is a demand for specifying a short-circuited arm in a system in which a single motor of the open winding type is driven by two inverters.

  A motor drive system according to the present invention includes two inverters each having a plurality of phases of series connection of an upper arm and a lower arm, converting DC power into AC power of a plurality of phases and outputting the AC power, and the two inverters. An open winding type motor connected to both output sides of the two inverters, and a control device for controlling on and off of an upper arm and a lower arm of the two inverters, wherein the control device includes at least one of the two inverters. Upon detecting a short-circuit fault of one upper arm or lower arm, for the inverter including the short-circuited arm, all the arms are turned off, and the upper arm or all phases of all the phases of the inverter not having the short-circuit fault are turned off. Turn on one of the lower arms, detect each phase current value of the motor in this state, and detect a short-circuit fault based on the detected phase current. The and has the arm to identify.

  Further, the motor drive system according to the present invention includes two inverters each having a plurality of phases of an upper arm and a lower arm connected in series, converting DC power into a plurality of phases of AC power, and outputting the converted power. An open-winding type motor connected to both outputs of two inverters; and a control device for controlling on and off of an upper arm and a lower arm of the two inverters, wherein the control device includes the two inverters. Detecting a short-circuit fault in at least one of the upper arm and the lower arm in the above-described method, turns off all the arms for the inverter including the short-circuited arm, and turns off all the phases for the inverter not including the short-circuited arm. The state in which the upper arm is ON and the state in which the lower arms of all phases are ON are alternately switched, and the current value of each phase of the motor in this state is changed. Detecting, identifying the arm has the short fault on the basis of the detected phase currents.

  The duty ratio between the state where the upper arms of all phases are on and the state where the lower arms of all phases are on may be 50%.

  After identifying the short-circuited arm, the control device turns on all of the upper arm or lower arm of the one inverter other than the short-circuited arm and on the same side as the short-circuited arm. It is preferable to drive the motor by turning on and off the upper and lower arms of the other inverter.

  The two inverters may be three-phase inverters, and the motor may be a three-phase motor.

  According to the present invention, in a system in which one open-winding type motor is driven by two inverters, the motor is set to a neutral point connection state, and a circulating current is measured to identify a short-circuited arm. Can be.

It is a figure showing the whole motor drive system composition concerning an embodiment. FIG. 3 is a diagram illustrating a configuration of a control unit. 5 is a flowchart illustrating detection of a short-circuited arm according to the first embodiment. It is a figure which shows the flow of a circulating current, (a) shows the state of a lower arm all ON, (b) shows the state of an upper arm all ON. It is a flow chart explaining detection of an arm with a short circuit fault concerning a 2nd embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment described here.

"System configuration"
FIG. 1 is a diagram illustrating a configuration of a motor drive system according to one embodiment. The motor 10 is a three-phase open winding motor having a permanent magnet rotor, and has three-phase coils 10u, 10v, and 10w. Here, it is assumed that the motor drive system is mounted on a vehicle, and that the motor 10 is a motor generator that generates a driving force for running the vehicle and a regenerative electric power during deceleration. Vehicles on which the system is mounted are, for example, electric vehicles (EV) and hybrid vehicles (HV), and the hybrid vehicle preferably has an engine.

  A first inverter 12 for converting DC power into AC power is connected to one end of the three-phase coils 10u, 10v, 10w, and a second inverter 14 is connected to the other end of the three-phase coils 10u, 10v, 10w. It is connected. A first capacitor 16 and a first power supply 18 are connected in parallel to the first inverter 12, and a second capacitor 20 and a second power supply 22 are connected in parallel to the second inverter 14. As the first and second power supplies 18 and 22, secondary batteries are used, but a power storage device such as a capacitor, a fuel cell, or the like may be used, or a combination of different power supplies may be used.

  The first inverter 12 and the second inverter 14 have the same configuration, have three (three-phase) upper and lower arms in which two switching elements are connected in series, and the midpoint of the upper and lower arms of each phase corresponds to the corresponding phase. Are connected to the coils 10u, 10v, and 10w, respectively. Therefore, at the time of power running, electric power from the first power supply 18 is supplied to the motor 10 via the first inverter 12, and at the time of regeneration (power generation), electric power from the motor 10 is supplied to the first inverter 12 via the first inverter 12. The power is supplied to the power supply 18. Further, the second inverter 14 and the second power supply 22 also exchange power similarly to the motor 10.

  The switching element is a transistor such as an IGBT and a reverse current diode connected in parallel. When the upper transistor is turned on, current flows toward the corresponding coil, and when the lower transistor is turned on, the corresponding phase is turned on. Current is drawn from the coil.

  The control unit 24 is configured by a computer, generates switching signals for the first inverter 12 and the second inverter 14 based on power supply information, motor information, vehicle information, and the like, and controls these switchings. Note that the control unit 24 may separately and separately provide the first inverter 12 and the second inverter 14. Each phase current of the motor 10 is detected by the ammeter 26 and supplied to the control unit 24.

"Configuration of control unit"
FIG. 2 shows the configuration of the control unit 24. The vehicle control unit 30 is supplied with vehicle information on vehicle travel such as the operation amounts of an accelerator pedal and a brake pedal, the vehicle speed, and motor information such as the rotation angle of the motor 10. Power supply information such as the state of charge (SOC1, SOC2) and temperature (T1, T2) of the first power supply 18 and the second power supply 22 and navigation information such as road conditions and destinations are also supplied to the vehicle control unit 30. Good to be.

  The vehicle control unit 30 calculates a torque command for an output request (target output torque) of the motor 10 from an operation amount of an accelerator pedal, a brake pedal, and the like.

  The calculated torque command is supplied to the current command generator 34 of the motor control block 32. The current command generator 34 calculates d-axis and q-axis currents idcom and iqcom, which are target current commands in the vector control of the motor 10, based on the torque command. The three-phase / two-phase converter 36 is supplied with the capacitor voltages VH1, VH2 of the first capacitor 16, the second capacitor 20, the rotor rotation angle θ of the motor 10, and the current phase currents iu, iv, iw. The three-phase / two-phase converter 36 converts the detected phase currents iu, iv, iw into d-axis and q-axis currents id, iq. The target current commands (d-axis and q-axis currents) idcom and iqcom from the current command generator 34 and the current d-axis and q-axis currents id and iq from the three-phase / two-phase converter 36 are controlled by PI. A voltage vector (d-axis excitation voltage command vd, q-axis torque voltage command vq) is calculated. The PI control unit 38 calculates a voltage command (motor voltage vector V (vd, vq)) by feedback control such as P (proportional) control and I (integral) control. Note that feedforward control such as prediction control may be combined.

  The calculated motor voltage vector V (voltage commands vd, vq) is supplied to the distribution unit 40. The distribution unit 40 converts the motor voltage vector V (voltage command vd, vq) into a first inverter voltage vector V (INV1) for the first inverter 12 (voltage command vd1, vq1) and a second It is distributed to the inverter voltage vector V (INV2) (voltage commands vd2, vq2).

  The voltage commands vd1 and vq1 from the distribution unit 40 are supplied to a two-phase / three-phase conversion unit 42, where they are converted into three-phase voltage commands Vu1, Vv1, and Vw1 for the first inverter and output. , Vq2 are supplied to a two-phase / 3-phase converter 44, where they are converted into three-phase voltage commands Vu2, Vv2, Vw2 for the second inverter and output. The motor control block 32 includes a current command generator 34, a three-phase / two-phase converter 36, a PI controller 38, a distributor 40, and two-phase / 3-phase converters 42 and 44.

  The three-phase voltage commands Vu1, Vv1, Vw1 for the first inverter from the two-phase / three-phase conversion unit 42 are supplied to the first inverter control unit 46, and the three-phase voltage commands Vu2, Vv2, for the second inverter. Vw2 is supplied to the second inverter control unit 48. The first inverter control unit 46 is supplied with a rotor rotation angle θ and a first capacitor voltage (first inverter input voltage) VH1. The first inverter control unit 46 compares the PWM carrier (triangular wave) with the voltage commands Vu1, Vv1, and Vw1 to make the first. A switching signal for turning on / off the switching element in the inverter 12 is generated and supplied to the first inverter 12. Similarly, the second inverter control unit 48 generates a switching signal for turning on / off the switching element in the second inverter 14 and supplies the switching signal to the second inverter 14.

  In this way, the switching of the first inverter 12 and the second inverter 14 is controlled by the signal from the control unit 24, and the motor 10 is driven by the current obtained by summing the outputs of these.

"Identification of arm with short-circuit failure"
<First embodiment>
Here, in one of the first and second inverters 12 and 14, detection of a short-circuited arm when a short-circuit failure of a switching element forming the arm occurs will be described with reference to FIG. I do.

  First, it is detected that a short circuit fault has occurred in the switching element (S11). The non-energized state is determined based on a switching signal to a switching element of each arm of the first inverters 12 and 14 and a current value detected by each ammeter. In general, the inverter has a delay in the on-rise characteristic so that the switching elements of the upper and lower arms connected in series are not turned on at the same time. For this reason, at the time of low rotation and when the switching element operates normally, the non-energized state can be detected. On the other hand, when a short-circuit fault occurs, the non-energized state does not occur, and thus the short-circuit fault can be detected.

  When the short-circuit failure of the first inverter 12 is detected, all the switching elements of the upper and lower arms in the first inverter 12 are turned off (S12). The control unit 24 turns off all the arms in the first inverter 12 (issues a command to turn off), but does not turn off the short-circuit arm. Then, all the switching elements of either the upper arm or the lower arm in the second inverter 14 are turned on (S13). Note that all the other switching elements of the upper arm or the lower arm are turned off.

  As a result, the switching elements of the three upper arms or the three lower arms of the second inverter 14 are turned on, the ends of the three-phase coils of the motor are short-circuited by the second inverter 14, and the neutral point is connected. become.

  In this state, an arm having a short-circuit failure (short-circuit arm) is identified by detecting each phase current accompanying free rotation of the motor 10 (S14). That is, by short-circuiting the neutral point of the motor 10, a circulating current flows through the short-circuit arm, and the short-circuited arm can be specified in the same manner as in Patent Document 1. For example, as shown in FIG. 4A, when the switching element of the lower arm of the u-phase of the first inverter 12 is short-circuited and all the lower arms of the second inverter 12 are turned on, the free rotation of the rotor is stopped. Accordingly, the current flowing out of the u phase of the first inverter 12 flows through the u and w phases of the first inverter 12 and the second inverter 14, and finally passes through the lower arm of the u phase of the second inverter 14, and the u phase of the motor 10. A circulating current flows back to. When all the upper arms of the second inverter 14 are turned on, a circulating current flows through the upper arm of the second inverter 14 as shown in FIG. Therefore, since the flow of the circulating current is determined according to the arm having the short-circuit failure, the arm having the short-circuit failure can be specified by measuring the circulating current.

  In addition, when the switching element of the lower arm has a short-circuit failure, a current drawn from the motor 10 flows, and when the switching element of the upper arm has a short-circuit failure, a current flows toward the motor 10. Therefore, it is possible to determine which of the upper and lower arms is short-circuited from the direction of the current. Further, even when the arm of the other phase is short-circuited, the same circulating current flows, so that the short-circuited arm can be similarly specified. The method described in Patent Document 1 can be used as it is to identify the arm having a short-circuit failure due to the circulating current. For example, for a two-phase or three-phase short circuit, the current values of all three phases are constant. , Or the two-phase current value exceeds a certain value, it is possible to identify a short-circuited arm.

  In this way, when the short-circuited arm can be identified, if the short-circuited arm of the first inverter 12 is on the same side, that is, if the short-circuited arm is the upper arm, the other upper arm, the short-circuited arm If the performed arm is the lower arm, all other lower arms are turned on (S15). In this example, since the lower arm of the u-phase of the first inverter 12 is short-circuited, both the lower arms of the v and w phases of the first inverter 12 are turned on. As a result, all the lower arms of the first inverter 12 are turned on, the motor 10 is connected to the neutral point, and the motor 10 can be driven by the switching of the second inverter 14.

  Then, the evacuation traveling is performed using the second inverter 14 (S16). By evacuation, the vehicle moves to the service factory where it is repaired. At this time, since the arm having the short-circuit failure is known, the repair becomes easy.

  In the above description, the case where the short-circuit fault occurs in the first inverter 12 has been described. However, the same processing can be performed when the short-circuit fault occurs in the second inverter 14.

<Second embodiment>
FIG. 5 shows a flowchart in the second embodiment. In the second embodiment, S21 to S22 and S24 to S26 are the same as S11 to S12 and S14 to S16 in the first embodiment. And S23 is different from S13. In S23, the second inverter 14 alternately switches between the upper arm three-phase ON and the lower arm three-phase ON.

  Here, when the three-phase ON of the upper arm and the three-phase ON of the lower arm of the second inverter 14 are switched, the states shown in FIGS. 4A and 4B occur alternately. Accordingly, regarding the circulating current flowing through each phase of the motor 10, there is no difference between the three-phase ON of the upper arm of the second inverter 14 and the three-phase ON of the lower arm. Therefore, even in the state where the switching has been performed, the arm having the short-circuit failure can be identified by the current value of each phase of the motor 10 as in the first embodiment.

  If the temperature of the switching element that turns on the three phases is high in the state before the occurrence of the fault and the switching element is fixed to ON and a circulating current flows, the temperature further rises and the switching element becomes overheated, causing a current to flow. May not be able to continue. In the second embodiment, the amount of current can be reduced, and overheating of the switching element can be suppressed.

  Further, when the switching element is at a high temperature, restrictions are imposed during evacuation traveling, and drivability during evacuation traveling deteriorates. According to the present embodiment, it is possible to improve drivability during limp-home running by preventing overheating of the switching element.

  Here, the duty ratio of the three-phase ON of the upper arm of the second inverter 14 and the three-phase ON of the lower arm may be set to 50%. By setting the duty ratio to 50%, the circulating current flowing through the upper arm and the lower arm can be evenly distributed, and overheating of the switching element can be effectively prevented. That is, the amount of current flowing through each arm of the second inverter 14 is halved, and overheating of the switching element can be prevented.

"Effects of the embodiment"
According to the present embodiment, in a system in which one motor of the open winding type is driven by two inverters, when a short-circuit fault occurs in the inverter, all of the upper and lower arms of the faulty inverter are turned off, and the fault occurs. The circulating current is measured by setting the upper arm all three phases ON or the lower arm all three phases ON for the inverter without the motor and setting the motor to the neutral point connection state. Then, the short-circuited arm is specified based on the measured circulating current. For this reason, according to the specified short-circuit faulty arm, the switching element of the faulty inverter is set to the neutral point connection state of the motor, and the non-faulty inverter drives the motor to perform limp-home travel. it can.

  Further, when the short-circuited arm of the faulty inverter is specified, the switching element through which the circulating current of the non-failure inverter flows is switched, so that the circulating current flows to detect the short-circuited arm. Can be prevented from overheating.

Reference Signs List 10 motor, 10u, 10v, 10w coil, 12 first inverter, 14 second inverter, 16 first capacitor, 18 first power source, 20 second capacitor, 22 second power source, 24 control unit, 26 ammeter, 30 vehicle Control unit, 32 motor control block, 34 current command generation unit, 36 3-phase / 2-phase conversion unit, 38 PI control unit, 40 distribution unit, 42,44 2-phase / 3-phase conversion unit, 46 first inverter control unit, 48 Second inverter control unit.

Claims (5)

Two inverters each having a plurality of phases of series connection of an upper arm and a lower arm, converting DC power into AC power of a plurality of phases and outputting the AC power,
An open winding type motor connected to both outputs of the two inverters,
A control device for controlling on and off of an upper arm and a lower arm of the two inverters;
With
The control device includes:
Upon detecting a short-circuit failure of at least one upper arm or lower arm in the two inverters, turning off all arms for one of the inverters including the short-circuited arm;
Turning on either the upper arm or the lower arm of all phases of the other inverter that is not short-circuited,
Detecting each phase current value of the motor in this state, and identifying a short-circuited arm based on the detected phase currents,
Motor drive system. Two inverters each having a plurality of phases of series connection of an upper arm and a lower arm, converting DC power into AC power of a plurality of phases and outputting the AC power,
An open winding type motor connected to both outputs of the two inverters,
A control device for controlling on and off of an upper arm and a lower arm of the two inverters;
With
The control device includes:
Upon detecting a short-circuit failure of at least one upper arm or lower arm in the two inverters, turning off all arms for one of the inverters including the short-circuited arm;
Regarding the other inverter that does not include the short-circuited arm, the upper arm of all phases is alternately switched on and the lower arm of all phases is alternately switched on,
Detecting each phase current value of the motor in this state, and identifying a short-circuited arm based on the detected phase currents,
Motor drive system. The motor drive system according to claim 2, wherein
The duty ratio between the state where the upper arm of all phases is on and the state where the lower arm of all phases is on is 50%.
Motor drive system. It is a motor drive system according to any one of claims 1 to 3,
The control device includes:
After identifying the short-circuited arm,
The upper arm or lower arm of the phase other than the short-circuited arm of the one inverter, and all the arms on the same side as the short-circuited arm are turned on,
Driving the motor by turning on and off an upper arm and a lower arm of the other inverter;
Motor drive system. The motor drive system according to claim 1, wherein:
The two inverters are three-phase inverters, respectively.
The motor is a three-phase motor;
Motor drive system.

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