JP2016226132A - Electric power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in a method of discharging voltage of a capacitor by short-circuiting two upper and lower pairs of power elements, a circuit becomes complicated and reliability is reduced.SOLUTION: Current with which a short-circuit of a power element can be detected is energized by simultaneously turning on upper and lower arms. Then, by turning on only the upper arm, presence of a short-circuit alarm is confirmed. When there is no problem, the lower arm is also turned on. When there is no problem, a short-circuit discharge by the next simultaneous turning on operation of the upper and lower arms is permitted.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a power converter, and more particularly to a vehicle power converter.

  FIG. 1 shows the configuration of a motor-driven inverter device that is an example of a power converter. Reference numeral 900 denotes a motor, 200 a power conversion device, 901 a battery, and 902 a contactor for controlling connection between the power conversion device 200 and the battery 901.

  The power conversion device 200 includes, as main components, a voltage smoothing capacitor 500 that smoothes a DC voltage input to the power conversion device 200, a power semiconductor module 300 in which a power semiconductor element is modularized, a gate driver circuit 100b, a motor And a control controller 100a. A host controller (not shown) gives a command for driving the motor, such as a torque or rotation command, to the motor control controller 100a, and the motor control controller 100a gives a PWM signal corresponding to the command to the gate driver circuit 100b. The circuit 100b has a function of switching the power semiconductor module 300 according to the PWM signal and converting a DC voltage from the battery 901 into an AC voltage for driving the motor 900.

  In addition, there are a voltage sensor 60, a discharge resistor 70, and a discharge switch element 71 as parts for safety measures. After the motor is driven, the power converter 200 is electrically disconnected from the battery 901 with the contactor 902 turned off by a command from the host controller. However, in the voltage smoothing capacitor 500 in the power conversion device 200, the voltage when connected to the battery 902 remains.

  Since the power converter 200 may be touched by the operator for maintenance after the motor is stopped, the electric charge remaining in the voltage smoothing capacitor 500 is usually stopped after the motor 900 is stopped. Means are provided for rapid discharge. Conventionally, as this means, after the motor 900 is stopped, the discharge switch element 71 is turned on, and the voltage of the voltage smoothing capacitor 500 is lowered by the discharge resistor 70.

  However, when the discharge switch element 71 has an open failure due to some cause, it is difficult to discharge the voltage smoothing capacitor 500.

  Therefore, in the patent document (Japanese Patent Application Laid-Open No. 2009-232620), means for discharging the voltage smoothing capacitor by turning on the upper and lower power semiconductor elements in the inverter device for a short time and consuming the charge of the capacitor by the power semiconductor element is provided. is suggesting.

  However, in the method described in the patent document, the energization is performed for a very short time. However, since the ON operation and the OFF operation are repeated with a higher current than in the normal operation, the surge voltage generated when the current is turned off is the normal switching operation. It becomes the same level as time. Therefore, the upper limit of the short-circuit current needs to be controlled with an extremely short pulse so as not to exceed the rated current of the power semiconductor element.

  However, when the main circuit inductance is low, the effect of preventing the current flow is reduced, and the current increases instantaneously. Therefore, it is difficult to prevent the current from exceeding the rated current even for extremely short pulses. is there.

  In addition, due to variations in the drive circuit, the rated current may be exceeded, and the power semiconductor element may break down due to the surge voltage when turned off.

  Specifically, since a current of 5 kA / us flows, it increases by 1 kA with a variation of 200 ns, so that control is very difficult.

    As another proposal described in JP-A-2009-232620, two systems of gate power supply voltages having different voltages are prepared, and the voltage applied to the gate at the time of short circuit discharge is set to a lower voltage than usual, thereby reducing the saturation current. Thus, a method for limiting the short-circuit current at the rated current level has been proposed. However, in this method, it is necessary to prepare two gate power supply voltages, which complicates the apparatus and reduces the reliability.

JP 2009-232620 A

  An object of the present invention is to provide a highly reliable short-circuit discharge means.

  A power conversion device according to the present invention includes a power conversion circuit having a plurality of power semiconductor elements constituting an upper arm circuit and a lower arm circuit that are bridge-connected, and voltage smoothing that smoothes a voltage applied to the power conversion circuit. A capacitor, a driver circuit that drives the power semiconductor element, and a current flowing through the power semiconductor element is detected to be greater than or equal to a predetermined value, and is determined to be in an overcurrent state. By transmitting over-current protection means that cuts off at a speed and a simultaneous ON signal of the plurality of power semiconductor elements to the driver circuit for a predetermined period or more determined by the overcurrent detection means, the upper arm circuit and Short-circuit discharge that discharges the charge of the voltage smoothing capacitor by short-circuiting a plurality of power semiconductor elements constituting the lower arm circuit A step of discharging the voltage smoothing capacitor to a predetermined voltage or less by repeating the operation of discharging by the short-circuit discharge means again after a predetermined time has elapsed after the short-circuit discharge means has been operated. Let

  According to the present invention, a highly reliable capacitor charge discharging means can be provided.

It is a block diagram of the system for motor drive. It is a circuit block diagram concerning this embodiment. It is a timing chart figure concerning this embodiment. The flowchart regarding the short circuit discharge method of Example 1 is shown. FIG. 5 shows a timing chart when a short-circuit discharge can be normally performed in the process shown in FIG. A state in which the capacitor voltage Vhvdc is reduced due to the short-circuit discharge is shown, and a state in which the capacitor voltage Vhvdc is decreasing as the simultaneous ON operation is repeated is shown. It is a follow chart figure which shows the flow of the soft process in the short circuit discharge process in Example 2. FIG. It is a timing chart about the case where a short circuit discharge process can be normally performed using the discharge process using the flowchart of FIG. FIG. 8 is a timing chart for a case where the discharge process is stopped in the diagnosis process because the power semiconductor element has failed during the discharge process using the discharge process using the flowchart of FIG. 7. FIG. 9 is a block configuration diagram illustrating a configuration of a third embodiment. It is a timing chart figure explaining the invention concerning Example 4. FIG.

Next, a power converter according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 2 shows a circuit block diagram according to the first embodiment of the present invention.

  In FIG. 2, the motor control controller 100a sends an upper arm drive signal IN_P and a lower arm drive signal IN_N to at least the upper arm driver circuit 30p and the lower arm driver circuit 30n, and the upper arm driver circuit 30p and the lower arm driver circuit 30n By driving the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n, ON / OFF of the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n is controlled.

  When the motor control controller 100a receives the overcurrent detection signals ALM_P and ALM_N from the upper arm driver circuit 30p and the lower arm driver circuit 30n, the motor control controller 100a receives the upper arm drive signal IN_P and the lower arm drive signal IN_N. By stopping, driving of the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n is stopped.

  The upper arm driver circuit 30p detects a drive unit that drives the upper arm power semiconductor element 40p and an overcurrent flowing through the upper arm power semiconductor element 40p, and appropriately shuts off the upper arm power semiconductor element 40p. And an overcurrent protection unit that transmits an overcurrent detection signal ALM_P notifying the motor control controller 100a that an overcurrent has occurred.

  Similarly, the lower arm driver circuit 30n has the same function as the upper arm driver circuit 30p.

  The upper arm power semiconductor element 40p has two main terminals through which a main current flows, a control terminal for controlling on / off of the main current by an applied voltage, and a sense current terminal through which a current proportional to the current flowing through the main current flows.

  Each of the overcurrent protection units of the upper arm driver circuit 30p and the lower arm driver circuit 30n can detect an overcurrent state by detecting a voltage drop generated in the resistor Rs by the current flowing through the sense terminal.

  The lower arm power semiconductor element 40n has the same structure and function as the upper arm power semiconductor element 40p.

  The voltage smoothing capacitor 500 has a function of absorbing voltage ripple generated when switching control of the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n.

  In the present embodiment, in the short-circuit discharge operation, the motor control controller 100a simultaneously transmits a drive signal to the upper arm driver circuit 30p and the lower arm driver circuit 30n, and the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n are turned on. By simultaneously turning them on, a short-circuit current instantaneously reaching several thousand A is applied between the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n, thereby discharging the voltage smoothing capacitor 500. The voltage is lowered.

  Here, the details of the operation at the time of short-circuit discharge will be described using the timing chart of FIG. In FIG. 3, the horizontal axis represents time, and the vertical axis represents each part voltage current waveform.

  IN_P is an upper arm drive signal, IN_N is a lower arm drive signal, Vge_P is an upper arm gate-emitter voltage, Voc_P is an upper arm current sense voltage, ALM_P is an overcurrent detection signal, Vhvdc is a capacitor voltage, Vce_P is an upper arm collector to An emitter voltage, Ic, is a collector current passing through the upper arm to the lower arm.

  The motor control controller 100a that has determined that the short-circuit discharge is necessary turns on the upper arm drive signal IN_P and the lower arm drive signal IN_N simultaneously at the timing a.

  The drive units of the upper arm driver circuit 30p and the lower arm driver circuit 30n that have received the ON signal increase the gate voltage of the power semiconductor element, and in the upper arm, the gate to emitter voltage Vge_P of the upper arm power semiconductor element 40p increases. The upper arm power semiconductor element 40p is turned on.

  Similarly, in the lower arm, the gate-emitter voltage Vge_N of the lower arm power semiconductor element 40n rises, and the lower arm power semiconductor element 40n is turned on (not shown).

  When the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n are turned on, the P-side electrode and the N-side electrode of the voltage smoothing capacitor 500 are short-circuited by the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n. It becomes a state.

  The saturation level of the short-circuit current depends on the gate-emitter voltage that is the control terminal of the power semiconductor element, and is usually as large as 3 kA to 5 kA when the power semiconductor element has a rated current of about 600 A. The state where the short-circuit current has reached the saturation level is the state at timing b.

  When a collector current Ic passing through the upper arm to the lower arm flows through the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n, as shown in FIG. 2, the sense current Is is proportional to the level of Ic. Flows. The sense current Is flows through the sense resistor Rs to become a voltage value, passes through a filter, becomes the upper arm current sense voltage Voc_P, and is monitored by the overcurrent protection unit of the upper arm driver circuit 30p.

  When the collector current Ic passing through the upper arm to the lower arm increases and the upper arm current sense voltage Voc_P exceeds a predetermined determination level at timing c, the overcurrent protection unit of the upper arm driver circuit 30p is in an overcurrent state. Recognize that.

  At timing d, the power semiconductor element operates to turn off the gate-emitter voltage and, after a predetermined delay time, the upper arm overcurrent detection signal ALM_P changes from H → L to cause the controller to overcurrent. Informs that has occurred.

  When switching the power semiconductor element, a surge voltage of dV = LxdIc / dt is generated according to the main circuit inductance L and the collector current cutoff speed. Here, when the collector current Ic passing through the upper arm to the lower arm is in a large current state, if an attempt is made to cut off at a normal off speed at a high speed, dIc / dt increases and the surge voltage dV becomes excessive. At this time, since the capacitor voltage Vhvdc + dV is applied to the upper arm collector-emitter voltage Vce_P, if this voltage exceeds the withstand voltage of the power upper arm power semiconductor element 40p, the upper arm power semiconductor element 40p will withstand the breakdown voltage. There is a risk of causing.

Therefore, as shown in FIG. 2, the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n are cut off at a low speed by the higher resistance Rg2 than usual, whereby the surge voltage becomes lower than the withstand voltage of the power semiconductor element. So that it is set.
In FIG. 3, since the power semiconductor element is in a normal state and both the upper and lower arms are simultaneously turned on, the upper arm collector to emitter voltage Vce_P share the lower arm collector to emitter voltage Vce_N and the capacitor voltage Vhvdc + dV. The arm collector-emitter voltage Vce_P is in the vicinity of the capacitor voltage Vhvdc, but when the lower arm is short-circuited, all Vhvdc + dV is applied to the upper arm power semiconductor element 40p.

  This soft shut-off state continues until timing e. In this embodiment, the time is set to about 3 us in the period from a to d until the soft shut-off starts from the occurrence of a short circuit due to simultaneous ON, and about 10 us in the period from a to e until the soft shut-off ends. Adjustment is made according to the filter constant of the terminal to which the arm current sense voltage Voc_P is applied and the short-circuit tolerance of the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n.

  After that, at timing f, the motor control controller 100a confirms that the overcurrent detection signal is generated by the overcurrent detection signal ALM_P and that the capacitor voltage Vhvdc has dropped by a predetermined value or more by the signal of the capacitor voltage Vhdvc, Both the top and bottom of the cancellation are off signals.

  This overcurrent detection signal ALM_P is set so as to be at L level for a certain time in the timer circuit. In this embodiment, the temperature of the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n rises due to a short circuit. And it is set more than the time to return to the original temperature again.

  After that, at timing g, the overcurrent detection signal ALM_P that has been set to the predetermined timer time becomes the H state, and the overcurrent protection unit of the upper arm driver circuit 30p is no longer in the overcurrent state to the motor control controller 100a. Communicate that.

  In this embodiment, the predetermined timer time is set to about 8 ms, but this value is a temperature rise for a moment due to the loss due to short-circuit discharge in the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n, and then the temperature Is set to a value that is about the thermal time constant that decreases.

  By repeating the above operation a plurality of times, the capacitor charge is discharged and the voltage is lowered.

  FIG. 4 shows a flowchart regarding the short-circuit discharge method of the first embodiment.

  In process 1, an upper and lower arm simultaneous on signal is transmitted.

  Thereafter, in process 2, it is confirmed that the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N, which are alarm signals for overcurrent detection, are generated in the upper and lower arms.

  Thereafter, in process 3, it is confirmed that the alarm signal is released after 10 ms. If not canceled, it is determined that some abnormality has occurred, and the discharge process is terminated.

  If released, the process proceeds to the next process, and in process 4, it is confirmed whether the capacitor voltage Vhvdc is 60 V or less. If not, the upper and lower arms are simultaneously turned on again.

  FIG. 5 shows a timing chart when the short-circuit discharge can be normally performed in the process shown in FIG. The numbers shown at the top of FIG. 5 correspond to the process numbers shown in FIG. FIG. 6 shows how the capacitor voltage Vhvdc decreases due to short circuit discharge, and shows how the capacitor voltage Vhvdc decreases as the simultaneous ON operation is repeated.

  According to the discharge process for short-circuiting the power semiconductor element described above, the soft-shut-off operation is performed while the power semiconductor element is short-circuited by the simultaneous on-operation for a time that the overcurrent detection unit of the driver circuit 30 can detect the overcurrent Thus, a highly reliable capacitor charge discharging means can be provided with a simple configuration.

  Next, the form of Example 2 which concerns on this invention is demonstrated using FIG. FIG. 7 is a follow chart showing the flow of the soft process in the short-circuit discharge process in the second embodiment.

  First, in process 1, the motor control controller 100a sends a simultaneous on signal to the upper and lower arms to the driver circuit 30, and the driver circuit 30 turns on the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n by simultaneously turning on the upper and lower arms. Short circuit.

  Next, in the determination process 2, the motor control controller 100a detects an overcurrent detection signal ALM_P or an overcurrent detection signal ALM_N that is an overcurrent detection alarm signal from the overcurrent protection unit of the upper arm driver circuit 30p or the lower arm driver circuit 30n. If it does not occur, it is determined that there is an abnormality in the circuit, and the process is terminated. If the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N are generated, the process proceeds to the next process.

  Next, in the determination process 3, it is a process for confirming whether or not the overcurrent alarm is canceled after about 10 ms. If not released, it is determined that there is an abnormality in the circuit and the power semiconductor element, and the discharge process is stopped. If canceled, the process proceeds to the next process.

  In the next process 4, only the upper arm is turned on. Since the lower arm is not turned on, if both the upper and lower arms are normal, the short-circuit operation is not performed, so that no overcurrent occurs and neither the overcurrent detection signal ALM_P nor the overcurrent detection signal ALM_N occurs. However, if the lower arm is damaged by the previous short-circuit discharge and a short-circuit failure occurs, only the upper arm is turned on, a short-circuit occurs and an overcurrent flows. When an overcurrent flows, the overcurrent protection unit detects the overcurrent and transmits an overcurrent alarm signal to the controller.

  Next, in the determination process 5, the presence / absence of the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N is confirmed. If no overcurrent alarm is generated, both the upper and lower arms are normal, and the process proceeds to the next process 6. If an overcurrent alarm occurs, it is determined that the lower arm has failed, and the discharge process is stopped.

  Process 6 is a process for turning on only the lower arm. Since the upper arm is not turned on, if both the upper and lower arms are normal, the short circuit operation will not occur, so no overcurrent will occur and no overcurrent detection alarm will occur. However, if the upper arm is damaged by the previous short-circuit discharge and a short-circuit failure has occurred, only the upper arm is turned on, a short circuit occurs and an overcurrent flows. When an overcurrent flows, the overcurrent protection units of the upper arm driver circuit 30p and the lower arm driver circuit 30n detect the overcurrent and transmit an overcurrent alarm signal to the controller.

  The determination process 7 is confirmation of the presence / absence of the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N. If no overcurrent alarm is generated, both the upper and lower arms are normal, and the process proceeds to the next determination process. If an overcurrent alarm occurs, it is determined that the lower arm has failed, and the discharge process is stopped.

  Finally, in the determination process 8, it is determined whether or not the discharge is completed. If the voltage Vhdvc of the capacitor is 60 V or less, the discharge process is terminated, and if it is, the process returns to process 1 and the discharge process is continued.

  Next, a case where the short-circuit discharge process can be normally performed using the discharge process using the flowchart of FIG. 7 will be described using the timing chart of FIG.

  First, at timing 1, the upper arm drive signal IN_P and the lower arm drive signal IN_N are simultaneously turned on. Then, a short circuit current flows from the capacitor by short-circuiting the upper arm and the lower arm. Then, the overcurrent protection units of the upper arm driver circuit 30p and the lower arm driver circuit 30n detect the overcurrent, and transmit the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N to the motor control controller 100a. The voltage of the voltage smoothing capacitor 500 is decreased during the period in which the short-circuit current flows due to the short-circuit current flowing from the voltage smoothing capacitor 500.

  Next, at timing 2, the motor control controller 100a confirms that the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N are generated, and that the voltage of the voltage smoothing capacitor 500 has decreased to a predetermined value or less, and short-circuit discharge occurs. After confirming that the process has been operated normally, the process proceeds to the next operation.

  Next, at timing 3, it is confirmed that the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N from the upper and lower arms are released.

  At timing 4, only the upper arm is turned on.

At timing 5, it is confirmed whether or not the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N are generated. Since the overcurrent detection signal ALM_P and the overcurrent detection signal ALM_N are not generated, the process proceeds to the next process.
At timing 6, only the lower arm is turned on, and it is confirmed that no overcurrent alarm signal is generated at timing 7, and since there is no occurrence, the level of Vhvdc is confirmed at timing 8 and is 60 V or more. Continue the discharge process.

  Next, with reference to the timing chart of FIG. 9, a case will be described in which the discharge process is stopped in the diagnosis process because the power semiconductor element has failed during the discharge process using the discharge process using the flowchart of FIG.

  The operation up to timing 3 is the same as that in the timing chart of FIG.

  At timing 4, when only the upper arm is turned on, at timing 5, when it is confirmed whether or not an overcurrent alarm is generated, an overcurrent alarm is generated from the upper and lower arms. For this reason, it is determined that some abnormality has occurred in the lower arm, such as a short-circuit failure in the lower arm, and the short-circuit discharge process is stopped.

  As described above, according to the discharge process of the second embodiment described with reference to FIGS. 7, 8, and 9, the failure of the power semiconductor element can be detected after the short circuit discharge. It is possible to prevent the power semiconductor element from failing and further causing the paired arm to fail due to an additional short-circuit operation, thereby causing a complete vertical short-circuit fault. By this diagnosis processing, it is possible to provide a highly reliable capacitor charge discharging means with a simple configuration.

  Next, the form of Example 3 of this invention is demonstrated using FIG. FIG. 10 is a block diagram illustrating the configuration of the third embodiment. The difference between the third embodiment and the second embodiment is that a simultaneous on prevention circuit for preventing simultaneous turn-on between the water temperature sensor 20, the motor control controller 100a, and the upper arm driver circuit 30p and the lower arm driver circuit 30n. 25 is mounted.

  Cooling water flows through the power conversion device 200 to cool the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n, and the water temperature sensor 20 directly or indirectly adjusts the temperature of the cooling water to the thermistor. The temperature information WTEMP is sent to the motor control controller 100a.

  Since a loss occurs in the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n at the time of short-circuit discharge processing when a short-circuit current is supplied and interrupted, the upper arm power semiconductor element 40p and The temperature of the lower arm power semiconductor element 40n increases. Therefore, when the water temperature is high, the temperature of the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n rises, and the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n may be damaged due to thermal destruction. .

  Therefore, in Example 3, based on the water temperature information WTEMP from the water temperature sensor 20, if the water temperature information WTEMP is equal to or greater than a predetermined value, the upper and lower arms simultaneous on processing 1 in the flowchart in FIG. The processing to widen the interval between is performed. In FIG. 7, the interval from the normal process 1 to the next process 1 is about 50 ms, but by separating the interval from 100 ms to 200 ms, the temperature of the power semiconductor element is prevented from rising beyond an allowable value. can do. Further, when it is determined that the water temperature further rises to an abnormal level, it is determined that the discharge process is not performed.

  In the third embodiment, the information of the water temperature sensor 20 is used to determine whether to perform the short-circuit discharge process, but the water temperature information from the host controller and the flow rate information for confirming whether the cooling water is flowing are used. Also good.

  The simultaneous on prevention circuit 25 is connected to the upper arm driver circuit 30p and the lower arm driver circuit 30p when the upper arm drive signal IN_P ′ and the lower arm drive signal IN_N ′ output from the motor control controller 100a are both turned on at the same timing. The upper arm drive signal IN_P and the lower arm drive signal IN_N which are output signals to the arm driver circuit 30n are turned off.

  As a result, the output from the motor control controller 100a is simultaneously turned on due to some abnormality, and the upper arm power semiconductor element 40p and the lower arm power semiconductor element 40n are prevented from being short-circuited. However, if there is the simultaneous on prevention circuit 25, short circuit discharge processing cannot be performed. Therefore, in the third embodiment, only when the short-circuit discharge process is performed, the simultaneous ON prevention invalidation signal DSOP is sent from the motor control controller 100a to the simultaneous ON prevention circuit 25, and the simultaneous on prevention function is invalidated. Yes.

  As described above, with the function of the third embodiment described with reference to FIG. 9, it is possible to reduce the possibility that the power semiconductor element breaks down by performing the short-circuit discharge treatment only when the cooling water having an appropriate water temperature is flowing. More reliable capacitor charge discharging means can be provided. Further, by releasing the simultaneous ON prevention circuit only during the short-circuit discharge process, the capacitor charge discharge means with higher reliability can be provided by performing the short-circuit discharge process.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, the short-circuit discharge process is performed only when an abnormality occurs in the vehicle or the power conversion device.

  As an operation at the time of a typical abnormality of an electric vehicle, a contactor open during a regenerative operation of the power conversion device is raised. During normal regenerative operation, regenerative energy from the motor is returned to the battery. However, if the contactor is opened during the motor regeneration operation of the power converter, the regenerative energy from the motor loses its place and the capacitor inside the power converter is charged.

  As a result, the voltage of the capacitor rises rapidly. To solve this problem, the capacitor voltage is monitored, and when the voltage exceeds a predetermined level, the regenerative operation is first stopped. Furthermore, at this time, assuming that the induced voltage of the motor exceeds the breakdown voltage of the power semiconductor module inside the power conversion device and the components such as the capacitor, the upper or lower arm of the power semiconductor module is turned on. Thus, the control for preventing the application of the induced voltage to the inverter is performed by short-circuiting the motor terminal, and the three-phase short control is performed.

  In the fourth embodiment, processing for performing a short-circuit discharge operation is performed only at such an abnormality. FIG. 11 shows the operation of the short-circuit discharge process in Example 4 of the present invention. The short-circuit discharge process is performed by detecting the overvoltage and turning on the upper arm once in a state where the three lower arms are continuously turned on.

  Further, in the fourth embodiment, the same process is performed when the controller 100a detects a vehicle abnormality in the form of a crash signal by detecting that the vehicle has collided with an acceleration sensor or the like. It also has a function to perform the operation.

  Further, the fourth embodiment also has means for counting the number of short-circuit discharge treatments and storing it in the storage device. Depending on the power semiconductor element, the number of short circuits may be limited. When performing a short-circuit operation more than the guaranteed number of short-circuits, the power semiconductor element may be damaged in the worst case. Therefore, by counting the number of short-circuit discharges and using this count later in failure analysis or the like, it can be analyzed whether the failure of the power semiconductor element is due to short-circuit discharge or another factor.

  As described above, by performing short-circuit discharge processing only when a truly abnormal state is detected, it is possible to perform short-circuit discharge processing even for power semiconductor elements with low short-circuit tolerance, and with a simple configuration, reliable A high-capacity capacitor charge discharging means can be provided.

DESCRIPTION OF SYMBOLS 20 ... Water temperature sensor, 25 ... Simultaneous ON prevention circuit, 30 ... Driver circuit, 30p ... Upper arm driver circuit, 30n ... Lower arm driver circuit, 31p ... Upper arm overcurrent detection circuit, 31n ... Lower arm overcurrent detection circuit, 40p ... upper arm power semiconductor element, 40n ... lower arm power semiconductor element, 50 ... current sensor, 60 ... voltage sensor, 70 ... discharge resistor, 71 ... discharge switch element, 100a ... motor controller, 100b ... gate driver circuit, DESCRIPTION OF SYMBOLS 200 ... Power converter, 300 ... Power semiconductor module, 500 ... Voltage smoothing capacitor, 900 ... Motor, 901 ... Battery, 902 ... Contactor, ALM_N ... Overcurrent detection signal, ALM_P ... Overcurrent detection signal, DSOP ... Simultaneous ON prevention Invalidation signal, Ic: Collect through upper arm to lower arm Current, IN_N: Lower arm drive signal, IN_P: Upper arm drive signal, Is: Sense current, Rs: Sense resistor, Vce_N: Lower arm collector to emitter voltage, Vce_P: Upper arm collector to emitter voltage, Vge_P: Upper arm gate to Emitter voltage, Vhvdc ... capacitor voltage, Voc_P ... upper arm current sense voltage, WTEMP ... water temperature information

Claims (5)

A power conversion circuit having a plurality of power semiconductor elements constituting a bridge-connected upper arm circuit and lower arm circuit;
A voltage smoothing capacitor for smoothing a voltage applied to the power conversion circuit;
A driver circuit for driving the power semiconductor element;
An overcurrent protection means for detecting that the current flowing through the power semiconductor element is equal to or greater than a predetermined value and determining that it is in an overcurrent state, and shutting off the power semiconductor element at a speed slower than normal;
A plurality of power semiconductors constituting the upper arm circuit and the lower arm circuit by transmitting a simultaneous ON signal of the plurality of power semiconductor elements to the driver circuit for a predetermined period or more determined by the overcurrent detection means. Short-circuit discharge means for discharging the electric charge of the voltage smoothing capacitor by short-circuiting the element,
A power conversion device that discharges the voltage smoothing capacitor to a predetermined voltage or less by repeatedly performing an operation of discharging by the short-circuit discharge unit again after a predetermined time has elapsed after the short-circuit discharge unit has been operated. The power conversion device according to claim 1,
During the operation of the repetitive short-circuit discharge means, the power semiconductor element constituting the upper arm circuit is turned on for a predetermined period, and the failure of the power semiconductor element constituting the lower arm circuit due to the occurrence of overcurrent is detected. Lower arm failure diagnosis means to check,
After turning on the power semiconductor element that constitutes the upper arm circuit, after a predetermined period, the power semiconductor element that constitutes the lower arm circuit is turned on for a predetermined period. Upper arm failure diagnosis means for checking a failure of the power semiconductor element constituting the circuit;
A power conversion device that stops the repetitive processing when one of the upper arm failure diagnostic unit and the lower arm failure diagnostic unit determines that the power semiconductor element is defective. The power conversion device according to claim 1,
A controller that outputs a drive signal to the driver circuit;
Simultaneous on prevention means for turning off the output when the drive signals transmitted from the controller to the driver circuit are simultaneously turned on between the driver circuit and the controller;
A simultaneous on-prevention invalidating means for invalidating the simultaneous on-preventing means by a signal from the controller. The power conversion device according to claim 1,
The power semiconductor element is cooled by a water cooling method in which cooling water is flowed to cool it,
The controller receives cooling water presence / absence information that can confirm whether or not the cooling water is flowing at a predetermined flow rate at a predetermined water temperature, and changes the short-circuit discharge repetition interval according to the state of the cooling water . The power conversion device according to claim 1,
The short-circuit discharge means is a power conversion device that is executed when an overvoltage is applied to the voltage smoothing capacitor and includes a short-circuit discharge number storage unit that stores the number of short-circuit discharges.

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