JP2021191074A - Inverter controller - Google Patents

Abstract

To shorten a time period for correctly detecting a three-phase short circuit.SOLUTION: An inverter controller that controls a three-phase inverter circuit comprises: a three-phase short circuit control part that performs a three-phase short circuit at failure of a switching element; and a smoothing current calculation part that calculates a smoothing current value by performing smoothing processing on a value of an output phase current of the inverter circuit for a predetermined time period during the three-phase short circuit. The three-phase short circuit control part switches the three-phase short circuit from one arm to the other arm. The smoothing current calculation part executes reset processing of resetting the smoothing current value calculated so far to zero at the switching of the three-phase short circuit, and resumes the smoothing processing after the reset processing.SELECTED DRAWING: Figure 3

Description

The present invention relates to an inverter control device.

The diagnostic method for identifying the failure location of the power semiconductor in the in-vehicle inverter is to turn on / off all the upper or lower power semiconductors alternately in a safe state after the failure detection for the safety response of the function. Action is required. With regard to the technology related to safe operation in such failure diagnosis, further development of safety and reliability is required, and the diagnostic method is being improved.

The following patent documents are known as background techniques of the present invention. Patent Document 1 discloses a technique for determining a failed phase without using dedicated hardware. Further, Patent Document 2 discloses a technique for determining an abnormality when the threshold value of the filter value is exceeded. Further, Patent Document 3 discloses a technique capable of switching an arm that short-circuits in three phases in consideration of heat generation of the upper and lower switching elements to disperse the heat generation portion.

Japanese Unexamined Patent Publication No. 2010-246328 Japanese Unexamined Patent Publication No. 2011-41366 International Publication 2016/136815

In the technique of Patent Document 1, although the failed phase can be determined, it cannot be detected whether the phase is caused by the upper or lower arm. In the technique of Patent Document 2, the upper and lower arms that have failed can be identified by the ± of the filter current, but in reality, the normal phase is also dragged and the value moves and it becomes difficult to discriminate, so that it is difficult to realize the invention. In the technique of Patent Document 3, the failure diagnosis is not limited to the operation only at the time of the IGBT failure, but also corresponds to the unnecessary voltage rise at the time of regeneration.

In view of this, the present invention identifies which of the upper and lower arms the failure occurred after determining the failure of the IGBT, and further shortens the correct three-phase short-circuit detection time by clearing the filter value to zero at the time of switching. Is an issue.

The inverter control device according to the present invention is an inverter control device that controls a three-phase inverter circuit having switching elements of an upper arm and a lower arm in each phase, and the upper arm or the lower arm when the switching element fails. A three-phase short-circuit control unit that performs a three-phase short circuit that sets one of the switching elements to a current state in all phases, and the inverter while one of the upper arm and the lower arm is in a three-phase short circuit. The three-phase short-circuit control unit includes a smoothing current calculation unit that calculates a smoothing current value by smoothing the output phase current value of the circuit for a predetermined time, and the three-phase short-circuit control unit is either the upper arm or the lower arm. The three-phase short circuit is switched from one arm to the other arm, and the smoothing current calculation unit executes a reset process to set the smoothing current value calculated so far to 0 when the three-phase short circuit is switched. The smoothing process is restarted after the reset process.

According to the present invention, it is possible to shorten the time for correct three-phase short circuit detection.

It is a circuit block diagram of the power conversion apparatus which concerns on 1st Embodiment of this invention. It is an internal block diagram of the inverter circuit of FIG. It is an operation flowchart of the inverter control device which concerns on 1st Embodiment. It is a current waveform at the time of an open failure of an inverter circuit. It is a current waveform after smoothing processing at the time of an open failure of an inverter circuit. It is a current waveform at the time of a three-phase short circuit. It is a current waveform after smoothing processing at the time of a three-phase short circuit. It is a current waveform of three-phase short circuit control which concerns on 2nd Embodiment. It is a circuit block diagram of the inverter control device which concerns on 3rd Embodiment. It is an operation flowchart of the inverter control device which concerns on 3rd Embodiment. It is a current waveform at the time of failure which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the present embodiment is an example for explaining the present invention, and is appropriately omitted and simplified for the sake of clarification of the description. Further, the present invention can be carried out in various other forms, and each component may be singular or plural, unless otherwise specified. Similarly, the positions, sizes, shapes, ranges, etc. of each component shown in the drawings may not represent the actual positions, sizes, shapes, ranges, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range and the like disclosed in the drawings.

(Configuration of Inverter Control Device and First Embodiment)
FIG. 1 is a circuit configuration diagram of a power conversion device 100 including an inverter control device according to the first embodiment of the present invention.

The basic configuration of the power conversion device 100 will be described. The power conversion device 100 includes a control unit 40, a driver circuit 50, an inverter circuit 60, and a current detection unit 70. The control unit 40 includes a duty calculation unit 41, a PWM signal generation unit 42, an abnormality detection unit 43, a filter unit 44, a threshold value determination unit 45, a zero clear command unit 46, and a failure detection unit 47.

The inverter circuit 60 is a three-phase inverter circuit having a smoothing capacitor and six switching elements of an upper arm and a lower arm inside. The inverter circuit 60 converts the DC power obtained from the DC power source 10, which is a high-voltage DC power battery, into AC power to drive the motor 20 during power running. Further, the inverter circuit 60 converts the AC power generated by the rotation of the motor 20 into DC power at the time of regeneration, and charges the DC power supply 10. The motor 20 is a three-phase motor having three windings inside.

The current detection unit 70 measures the alternating current that is output from each phase of the inverter circuit 60 and flows through each of the U-phase, V-phase, and W-phase of the motor 20 by using a current sensor or the like installed in each phase. , Detects the current value.

Next, a control unit 40, which is an inverter control device for controlling the inverter circuit 60, will be described. The control unit 40 communicates with an electronic control device (not shown) provided outside the power conversion device 100, and inputs the target torque of the motor 20 received from the electronic control device to the duty calculation unit 41. Further, the control unit 40 uses the information that the failure detection unit 47 has detected the failure or abnormality of the inverter to set the switching elements for three phases of either the upper or lower arm of the inverter circuit 60 to the conduction state and perform short-circuit control. It is a three-phase short-circuit control unit.

The duty calculation unit 41 obtains a target current value to be passed through the motor 20 by using a target torque or the like received from an external electronic control device. This target current value is expressed, for example, in the form of a d-axis target current value and a q-axis target current value. Then, the duty calculation unit 41 calculates the duty value of each of the U phase, V phase, and W phase based on the target current value and the AC current value detected by the current detection unit 70, and the calculation result is a PWM signal. Output to the generation unit 42.

The PWM signal generation unit 42 controls the PWM signal based on the information received from the duty calculation unit 41 and the information received from the failure detection unit 47. For example, when failure information is output from the failure detection unit 47, the PWM signal is controlled so as not to drive the motor 20.

Here, the state in which the motor 20 is not driven is, for example, a state in which all six switching elements in the inverter circuit 60 are turned off (freewheel state), or a state in which the upper arm circuit of the six switching elements is switched. A state in which three elements are turned on and three switching elements in the lower arm circuit are turned off (upper arm active short state), and three switching elements in the upper arm circuit are turned off and three switching elements in the lower arm circuit are turned off. Is on (lower arm active short state).

The driver circuit 50 receives the PWM signal output by the PWM signal generation unit 42, and outputs a drive signal for switching ON / OFF of the switching element to the inverter circuit 60. As a result, the control unit 40 can control the inverter circuit 60 via the driver circuit 50.

The abnormality detection unit 43 detects an open failure of the switching element in the inverter circuit 60 via the current detection unit 70, and outputs a state abnormality of the switching element to the failure detection unit 47.

The failure detection unit 47 receives information on an open failure, which is a state abnormality of the switching element, from the abnormality detection unit 43, and outputs the failure information to a higher-level control device (not shown) and a PWM signal generation unit 42. The failure detection unit 47 determines that the IGBT is an open failure when the value of the low-pass filtered three-phase current exceeds the set threshold value.

The filter unit 44 is a current calculation unit that smoothes the phase current obtained from the current detection unit 70 for a predetermined time. When the filter unit 44 receives a zero clear instruction from the zero clear command unit 46, which will be described later, during a three-phase short circuit, the filter unit 44 resets the value of the output phase current of the holding inverter circuit 60, and performs a phase current smoothing process again. do. The smoothing process of the acquired current value is performed by a digitally processed low-pass filter provided in the filter unit 44, which is a smoothing current calculation unit.

The threshold value determination unit 45 monitors the phase current value smoothed by the filter unit 44, determines that the switching element has an abnormal state when it exceeds a predetermined threshold value, and outputs the information on the abnormal state to the zero clear command unit 46 and the failure. Output to the detection unit 47. The threshold value determination unit 45 switches the arm of the three-phase short circuit, and even after the holding value of the filter unit 44 is cleared, the threshold value determination is performed in the same manner.

The zero clear command unit 46 receives the information determination of the abnormal state of the threshold value determination unit 45, and outputs a zero clear instruction, which is an instruction to reset the phase current value before switching held by the filter unit 44, to the filter unit 44. This utilizes the fact that the behavior is confirmed by switching ON / OFF of the upper and lower arms and that the sum of the three-phase currents becomes zero amperes. This makes it possible to shorten the specific time, clear zero at the timing of switching the short circuit of each upper and lower arm, and smoothly confirm the behavior of the short circuit on the opposite side arm.

Although the detection means of the abnormality detection unit 43 has been described by the current smoothing process, other detection means may be used. Further, although a sensor for three-phase current is used for the current detection unit 70, a current sensor may be used for two phases and a calculated value may be obtained for the other phase by calculation.

FIG. 2 is an internal configuration diagram of the inverter circuit 60.

The inverter circuit 60 has a series circuit with U-phase, V-phase, and W-phase upper and lower arms.

The U-phase upper and lower arm series circuit 61 includes a U-phase upper arm switching element Tuu and a U-phase upper arm diode Du, and a U-phase lower arm switching element Tul and a U-phase lower arm diode Dul.

The V-phase upper and lower arm series circuit 62 includes a V-phase upper arm switching element Tv and a V-phase upper arm diode Dvu, and a V-phase lower arm switching element Tvl and a V-phase lower arm diode Dvl.

The W-phase upper / lower arm series circuit 63 includes a W-phase upper arm switching element Twoo and a W-phase upper arm diode Dwoo, and a W-phase lower arm switching element Twl and a W-phase lower arm diode Dwl.

The upper arm circuit 64 includes a U-phase upper arm switching element Tuu and a U-phase upper arm diode Du, a V-phase upper arm switching element Tv and a V-phase upper arm diode Dvu, and a W-phase upper arm switching element Tu and a W-phase upper arm. It has a diode Dwoo. The upper arm is a switching element installed for each phase and transmitting the positive power of the DC power supply 10 to the motor 20.

The lower arm circuit 65 includes a U-phase lower arm switching element Tul and a U-phase lower arm diode Dul, a V-phase lower arm switching element Tvl and a V-phase lower arm diode Dvl, and a W-phase lower arm switching element Twl and a W-phase lower arm. It has a diode Dwl. The lower arm is a switching element installed for each phase and transmitting the negative power of the DC power supply 10 to the motor 20.

The switching element of the power semiconductor is, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). In the present invention, the IGBT will be described as a power semiconductor.

The smoothing capacitor 66 smoothes the current generated by ON / OFF of the switching element, and suppresses the ripple of the DC power supplied from the DC power supply 10 to the inverter circuit 60. As the smoothing capacitor 66, for example, an electrolytic capacitor or a film capacitor is used.

FIG. 3 is an operation flowchart of the control unit 40 according to the first embodiment.

In step S1, the abnormality detection unit 43 acquires the AC current sensor value via the current detection unit 70, monitors the smoothed value, and does not limit which arm is the upper or lower arm of the switching element, the IGBT. The abnormal state of the above is determined, and the abnormality information is output to the failure detection unit 47. As a result, the failure detection unit 47 determines the failure of the IGBT and outputs the information to the PWM signal generation unit 42. The method of this detection means is not particularly limited. If it is determined in step S1 that it is abnormal, the process proceeds to step S2, and if not, the process ends.

In step S2, the PWM signal generation unit 42 receives failure information from the failure detection unit 47, controls the PWM signal to the driver circuit 50, and shifts to a three-phase short-circuit state using either the upper arm or the lower arm. That is, the control unit 40 that controls the three-phase short circuit sets the switching element of either the upper arm or the lower arm to the conduction state in all phases when the switching element fails. In step S3, the filter unit 44 smoothes the acquired AC current sensor value in the three-phase short-circuit state.

In step S4, the AC current sensor value after smoothing is monitored using a predetermined processing time required for determining the failure of the arm. When the smoothing sensor value exceeds a predetermined threshold value within the time, it is recognized that there is a failure of the three-phase short circuit, and it is determined in step S5 that one of the switching elements of the arm has an open failure. If not, the monitoring of the smoothing sensor value is continued until the predetermined processing time elapses in step S6, and steps S3 and S4 are repeated until the processing time elapses. If the processing time elapses, the process proceeds to step S7. It should be noted that a predetermined threshold value is provided to detect the median value of each phase current moving up or down from the normal state when a three-phase short circuit is performed using the arm on the side where the open failure occurs. ing.

That is, in steps S4 to S6, the filter unit 44 that calculates the smoothed current determines the value of the output phase current of the inverter circuit 60 while either the upper arm or the lower arm is short-circuited in three phases. For the time of smoothing.

In step S7, the arm carried out from step S2 to step S6 is switched, and a three-phase short circuit is carried out with the other arm. This is because the failure detection unit 47 sends a command to the PWM signal generation unit 42 for a three-phase short circuit with the arm on the opposite side of the arm, which has been carried out so far, so that the upper and lower sides of the three-phase short circuit arm are switched.

In step S8, the filter unit 44 executes a reset process of setting the held sensor value to 0, and in step S9, a smoothing process of the AC current sensor value in the three-phase short-circuit state is performed again. That is, at the same time as switching the three-phase short circuit, the sensor value which is the internally calculated value of the filter unit 44 is cleared to zero, and the reset output phase current value is smoothed again. By this processing, the filter calculation is restarted from the median zero point instead of the filter calculation from the upper and lower limit positions of the provided threshold value, so that it is possible to shorten the time until the determination result is obtained. ..

In step S10, the AC current sensor value after smoothing is monitored using a predetermined processing time. When the smoothing current sensor value exceeds a predetermined threshold value within the time, it is recognized that there is a failure of the three-phase short circuit, and if any switching element of the arm switched in step S7 is open failure, step S11. Judge with. If not, the monitoring of the smoothing sensor value is continued until the predetermined processing time elapses in step S12, and steps S9 and S10 are repeated until the processing time elapses. If the processing time elapses, the process proceeds to step S13.

In step S13, a failure notification signal corresponding to the failure location identified from the behavior of the current due to the three-phase short circuit carried out from step S2 to step S12 is transmitted to the host controller. When step S13 is completed, the process ends.

With the above operation flow, three-phase short circuit is repeated on the upper and lower arms, and by observing the current value, it is possible to identify which of the upper and lower arms is faulty and finally move to a safe state. .. In other words, by performing a three-phase short circuit while switching the upper and lower arms, it is possible to identify the faulty part while monitoring the smoothed three-phase current value, and it is possible to shorten the transition to a safe state according to the faulty part. .. As a result, it is possible to prevent erroneous detection of failure during three-phase short-circuit operation and shorten the time for correct three-phase short-circuit detection.

The operation flowchart described with reference to FIG. 3 will be described in detail with reference to FIGS. 4 to 7. FIG. 4 is an example of a current waveform at the time of an open failure of the inverter circuit 60.

In FIG. 4, the horizontal axis represents time and the vertical axis represents the current value (ampere). The alternating current flowing in the U phase is iu (solid line), the alternating current flowing in the V phase is iv (long dotted line), and the W phase is shown. Let the flowing alternating current be iw (short dotted line). Further, it is assumed that FIG. 4 shows, for example, an alternating current detected by the current detection unit 70 when the lower arm of the U phase fails from the state where the PWM signal is generated.

Before the time t in FIG. 4, when each switching element of the inverter circuit 60 is normal, an AC waveform with a phase shift of 120 ° is drawn for each of the AC currents iu, iv, and iwa. However, after time t, if the U-phase lower arm switching element fails open, the current that should have flowed through the switching element is interrupted, so the lower half of the U-phase AC current iu is missing. ing. Further, it can be seen that due to the influence of the U-phase alternating current iu, the V-phase alternating current iv and the W-phase alternating current iw are out of phase and the current sensor value is disturbed.

FIG. 5 shows the result of smoothing the current waveform shown in FIG.

In FIG. 5, in the normal state before the time t, the smoothed current values iu_f, iv_f, and iw_f are approximately 0 [A]. However, after the time t affected by the open failure, it can be seen that the current value obtained by smoothing the current sensor value with a filter (current value iu_f in this figure) is separated from approximately 0 [A] by one. .. This is because the regenerative current does not flow when the IGBT to be turned on fails due to a three-phase short circuit, and the current value is biased (has a bias) in a three-phase short circuit using a failed arm. It becomes a waveform.

When an open failure of the inverter circuit 60 occurs, no current flows through the failed power semiconductor. Specifically, when the power semiconductor of the upper arm fails open, no positive current flows, and when the power semiconductor of the lower arm fails open, no negative current flows.

Since the smoothed current value iu_f does not fall within the range of the provided threshold value 401 and the threshold value 402, the abnormality detection unit 43 can determine that the IGBT is open failure.

FIG. 6 is an example of a current waveform at the time of a three-phase short circuit.

When the control unit 40 detects an abnormality due to an open failure of the IGBT by the abnormality detection unit 43, the control unit 40 starts three-phase short-circuit control of either the upper or lower arm. By this three-phase short-circuit control, the three-phase switching element of the inverter circuit 60 is turned on. As shown in FIG. 6, when the three-phase short circuit of the failed phase is performed between the time t1 and the time t2, the failed phase in the three-phase short-circuited state accompanies the operation of the failed phase. It can be seen that the median value of the current sensor value of is no longer 0, and the median value of the normal phase is also deviated from zero.

FIG. 7 is a result of smoothing the current waveform during the three-phase short circuit control shown in FIG. 6 by the filter unit 44. Note that FIG. 7A shows the result of smoothing processing by the conventionally used processing method, that is, the control unit 40 is not provided with the zero clear command unit 46, and the filter unit is used when switching the arm for three-phase short circuit. It is the current waveform after the smoothing process at the time of the three-phase short circuit control when the reset of 44 is not performed, and FIG. 7 (b) is the current waveform after the smoothing process of the three-phase short circuit control which concerns on 1st Embodiment. Is.

In FIG. 7, the AC current sensor values iu, iv, and iw are smoothed values are iu_f2, iv_f2, and iw_f2, respectively. As shown in FIG. 6, since the median value of the current value of each phase fluctuates up and down between the time t1 and t2, the value changes from about 0 by performing the smoothing process also in FIG. 7.

First, when the value exceeds the set threshold value 71A, it is determined that the arm has failed. After that, when the threshold value falls below the threshold value 72A set during the three-phase short-circuit control, it is determined that the vehicle is in a safe state.

In FIG. 7A, it takes a certain amount of time for the output of the low-pass filter to fall below the threshold value 72A that can be determined to be in the normal state even if a three-phase short circuit is performed with the arm that is operating normally.

In the present invention, as shown in FIG. 7B, the smoothed filter value is cleared to zero when the upper and lower arms are switched between three-phase short circuits. As a result, it is possible to shorten the time from performing the three-phase short circuit on the arm to determining the safety state using a predetermined time. The normal state determination time can be shortened. This is the function of clearing the filter holding value to zero in step S8 of the operation flow of FIG.

According to the first embodiment of the present invention described above, the following effects are exhibited.

(1) The inverter control device 40 is an inverter control device that controls a three-phase inverter circuit 60 having switching elements for the upper arm and the lower arm in each phase, and is a device for controlling the upper arm or the lower arm when the switching element fails. A three-phase short-circuit control unit 40 that performs a three-phase short circuit that sets one of the switching elements to a current state in all phases, and an inverter circuit 60 while one of the upper arm and the lower arm is in a three-phase short circuit. A smoothing current calculation unit 44 that calculates the smoothing current value by smoothing the output phase current value for a predetermined time is provided, and the three-phase short-circuit control unit is an arm of either an upper arm or a lower arm. The three-phase short circuit is switched from to the other arm, and the smoothing current calculation unit executes a reset process to set the smoothing current value calculated up to that point to 0 when the three-phase short circuit is switched, and smoothes after the reset process. It is characterized by restarting the processing. Since this is done, it is possible to shorten the time for detecting a correct three-phase short circuit.

(2) The inverter control device 40 determines that the switching element of either the upper arm or the lower arm during the three-phase short circuit has failed when the smoothing current value exceeds a predetermined threshold value. It is characterized by including a determination unit 45. Since this is done, it is possible to determine which of the upper arm and the lower arm is out of order.

(Second embodiment)
FIG. 8 is a current waveform of the three-phase short circuit control according to the second embodiment. The AC current sensor values iu, iv, and iwa in the case of three-phase short-circuit control are represented as iu_f, iv_f, and iw_f that have been smoothed.

In the second embodiment of FIG. 8, the filter unit 44 receives the upper / lower arm switching instruction of the three-phase short circuit, that is, the zero clear instruction of the value, and then performs the smoothing process while holding the calculated filter output value. Further, a certain failure detection and determination dead time zone is provided for the threshold value determination unit 45 for a predetermined time, and the value holding and smoothing processing is continued without updating the filter value. This is set as the dead time zone 73.

This makes it possible to deal with the case where the inrush current observed at the time of arm switching is erroneously input when the three-phase short-circuit switching of the upper and lower arms is performed. That is, the inrush current is filtered and does not appear after smoothing. This configuration prevents the inrush current generated at the moment when the IGBT, which is a power semiconductor, is turned on, from being reflected in the output of the filter calculation as an excessive current value.

According to the second embodiment of the present invention described above, the following effects are exhibited.

(3) The inverter control device is characterized in that the threshold value determination unit 45 is provided with a dead time zone 73 in which failure determination is not performed for a predetermined time after switching the three-phase short circuit. Since this is done, it is possible to prevent the inrush current from being reflected in the output of the filter calculation as an excessive current value.

(Third embodiment)
FIG. 9 is a circuit configuration diagram of the inverter control device according to the third embodiment.

The power conversion device 100 is obtained by removing the abnormality detection unit 43 from the first embodiment described with reference to FIG. Other configurations are the same as those of the first embodiment.

FIG. 10 is an operation flowchart of the inverter control device according to the third embodiment.

Compared with the operation flowchart of FIG. 3 which is the first embodiment, the operation flowchart of FIG. 10 has no abnormality detection unit 43, so that the filter unit 44 and the threshold value determination unit 45 determine the abnormality of the IGBT, that is, open failure. There is a difference in the part responsible for the determination, and the filter unit 44 and the threshold value determination unit 45 are used together for the open failure diagnosis and the determination of the three-phase short circuit abnormality. Steps S105 to S116 of FIG. 10 have the same configuration as steps S2 to S13 of FIG.

The operation flow of FIG. 10 will be described. In order to detect the failure of the IGBT, the smoothed value of the AC current sensor value acquired in step S101 is monitored. When the set first threshold value is exceeded in step S102, it is determined in step S103 that the IGBT is abnormal, that is, the IGBT is in an open failure state. Since the three-phase short-circuit control is performed in the subsequent step as in the first embodiment, it is not necessary to specify the open failed phase or the upper and lower arms in this step.

After the determination in step S103, the value held by the filter unit 44 is reset by the instruction from the zero clear command unit 46 in step S104. Then, in step S105, the state shifts to a three-phase short-circuit state using either the upper arm or the lower arm. Again, in step S106, the AC current sensor value in the three-phase short-circuit state is smoothed.

The sensor value after smoothing in step S107 is monitored using a predetermined processing time. When the second threshold value set within the time is exceeded, it is determined in step S108 that the arm is open-failed. Otherwise, monitoring is continued in step S109 until the predetermined processing time elapses, and steps S106 and S107 are repeated until the processing time elapses. If the processing time elapses, the process proceeds to step S110.

In step S110, the upper and lower arms are switched to perform a three-phase short circuit, the value held by the filter unit is reset in step S111, and the smoothing process is performed again.

The value after smoothing in step S112 is monitored in step S113 for a predetermined processing time. When the second threshold value set within the time is exceeded, it is determined in step S114 that the arm is open-failed. If not, monitoring is continued until a predetermined processing time elapses in step S115, and steps S112 and S113 are repeated until the processing time elapses. If the processing time elapses, the process proceeds to step S116.

In step S116, the failure location is specified from the execution of the three-phase short circuit and the behavior of the current at that time, and the failure notification signal corresponding to the failure location is transmitted to the host controller to end the process. As can be seen from the above operation flow, the threshold value determination unit 45 determines by providing a plurality of threshold values according to the internal state of the inverter.

FIG. 11 is a current waveform at the time of failure in the third embodiment. The AC current sensor values iu, iv, and iw smoothed when the three-phase short circuit control is performed are set to iu_f2, iv_f2, and iw_f2.

The first threshold value described in FIG. 10 is the threshold value 72C. By outputting a sensor value exceeding the range of this threshold value from time t1 to t2, it is determined that the IGBT is abnormal, that is, the IGBT is open.

Further, after the detection of the open failure of the IGBT is determined, the filter value is cleared to zero at time t2. By doing so, the subsequent three-phase short circuit can be performed correctly. This eliminates the need for the configuration of the abnormality detection unit 43 described in the first embodiment.

When a three-phase short circuit is performed from time t2 to t3 and the sensor value exceeds the threshold range with the second threshold value 71C, it can be determined that the arm is out of order. After time t3, the configuration described in the second embodiment can be used to adopt a configuration in which zero clear and a dead zone are provided at the time of three-phase short-circuit switching.

That is, the threshold value determination unit 45 determines the failure of the switching element based on the first threshold value, and based on the second threshold value, the arm of either the upper arm or the lower arm during the three-phase short circuit. It is possible to determine the failure of the switching element.

According to the third embodiment of the present invention described above, the following effects are exhibited.

(4) The threshold value determination unit 45 of the inverter control device determines the failure of the switching element based on the first threshold value, and either the upper arm or the lower arm during the three-phase short circuit is determined based on the second threshold value. It is characterized in that it determines the failure of the switching element of. Since this is done, the configuration of the abnormality detection unit 43 can be omitted, and the storage capacity of the program in the control unit 40 can be reduced.

It should be noted that the above description is merely an example, and when interpreting the invention, there is no limitation or limitation on the correspondence between the description items of the above-described embodiment and the description items of the claims. Further, it is possible to delete, replace with another configuration, or add another configuration without departing from the technical idea of the invention, and the embodiment thereof is also included in the scope of the present invention.

100 ... power converter, 10 ... DC power supply, 20 ... motor, 40 ... control unit,
401, 402 ... Threshold, 41 ... Duty calculation unit, 42 ... PWM signal generation unit,
43 ... Abnormality detection unit, 44 ... Filter unit, 45 ... Threshold determination unit, 46 ... Zero clear command unit,
47 ... Failure detection unit, 50 ... Driver circuit, 60 ... Inverter circuit,
61 ... U-phase upper and lower arm series circuit, 62 ... V-phase upper and lower arm series circuit,
63 ... W phase upper and lower arm series circuit, 64 ... upper arm circuit, 65 ... lower arm circuit,
66 ... Smoothing capacitor, 70 ... Current detector, 71, 71A to 71C ... Threshold,
72, 72A-72C ... Threshold, 73 ... Insensitive time zone

Claims (4)

An inverter control device that controls a three-phase inverter circuit having switching elements for the upper arm and lower arm in each phase.
A three-phase short-circuit control unit that performs a three-phase short circuit that sets the switching element of either the upper arm or the lower arm to a conduction state in all phases when the switching element fails.
A smoothing current calculation unit that calculates the smoothing current value by smoothing the output phase current value of the inverter circuit for a predetermined time while either the upper arm or the lower arm is short-circuited in three phases. And, with
The three-phase short-circuit control unit switches the three-phase short circuit from one arm of the upper arm or the lower arm to the other arm.
At the time of switching the three-phase short circuit, the smoothing current calculation unit executes a reset process for setting the smoothing current value calculated up to that point to 0, and restarts the smoothing process after the reset process. Inverter control device as a feature. The inverter control device according to claim 1.
It is characterized by including a threshold value determining unit for determining that either the switching element of the upper arm or the lower arm during the three-phase short circuit is out of order when the smoothing current value exceeds a predetermined threshold value. Inverter control device. The inverter control device according to claim 2.
The threshold value determination unit is an inverter control device, characterized in that a dead time zone during which the failure determination is not performed is provided for a predetermined time from the switching of the three-phase short circuit. The inverter control device according to claim 2.
The threshold value determination unit determines the failure of the switching element based on the first threshold value, and based on the second threshold value, the switching element of either the upper arm or the lower arm during the three-phase short circuit. An inverter control device characterized by determining a failure.

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