JP2010119268A - Apparatus and method for detecting fault of inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a fault in an inverter, which supplies an AC motor with a drive current according to the voltage phase of the voltage of rectangular waves, based on the voltage phase of the voltage of the rectangular waves calculated by a rectangular wave controller. <P>SOLUTION: A fault detecting unit determines whether the voltage phase ϕv of the voltage of the rectangular waves calculated by a rectangular wave voltage control unit and the phase ϕlimit of a limiter coincide with each other or not (S300). When the voltage phase ϕv and the limiter phase ϕlimit are coincident (YES in S300), a fault counter is incremented (S310). If the fault counter exceeds a predetermined fault determination time (YES in S320), the detecting unit determines an abnormal state where an open failure occurs in the inverter (S330). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for detecting an abnormality in an inverter, and more particularly to a technique for detecting an abnormality in an inverter that supplies a drive current corresponding to a rectangular wave voltage to an AC motor.

  Conventionally, many methods for detecting an abnormality in a control system of an AC power supply or an AC motor have been developed.

  For example, in Japanese Patent Laid-Open No. 2003-235154 (Patent Document 1), in a converter device that converts a three-phase AC power source into a DC voltage, an arbitrary two-phase AC power source voltage phase difference of the three-phase AC power source is calculated, An apparatus is disclosed that, when this phase difference is more than a predetermined value from 120 °, determines that a three-phase AC power supply is missing.

  Japanese Patent Application Laid-Open No. 2004-153957 (Patent Document 2) generates an inverter connected in parallel to a system via an inductive impedance, and generates a voltage control signal according to the difference between the output current of the inverter and a reference current. In a power converter having a voltage control circuit that controls the output voltage of the inverter according to the voltage control signal, the three-phase voltage of the system is converted to the dq axis, and the change in the d axis voltage obtained by this conversion A power conversion device that determines a system abnormality by comparing a rate with a planned value is disclosed.

By the way, conventionally, there is known a technique for switching an AC motor control method between a pulse width modulation (PWM) control method and a rectangular wave voltage control method in accordance with an operation region of the AC motor. For example, a control device disclosed in Japanese Patent Application Laid-Open No. 2008-154398 (Patent Document 3) includes an AC motor operating region, a region A in which PWM control is performed in accordance with motor torque and motor rotation speed, PWM control, The rectangular wave voltage control is selected when the operation region of the AC motor is the region B.
JP 2003-235154 A JP 2004-153957 A JP 2008-154398 A

  By the way, if one phase of each phase arm of the inverter has an open failure (failure that is always off) during rectangular wave voltage control, the half-wave of the motor current of the failed phase will not flow, and on average the offset Current flows to the AC motor. In a drive control system that does not have a hardware circuit that detects such an open failure, an offset current continues to flow to the AC motor, an eddy current is generated in the rotor of the AC motor, and the rotor becomes overheated. A secondary failure may occur that reduces the output of the.

  However, techniques for detecting an open failure of an inverter that occurs during rectangular wave voltage control without using a dedicated hardware circuit are disclosed in Japanese Patent Application Laid-Open Nos. 2003-235154, 2004-153957, and 2008-154398. It is not disclosed in any of the publications.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to detect an abnormality of an inverter that supplies a drive current corresponding to a voltage phase of a rectangular wave voltage to an AC motor using a rectangular wave control device. It is an object of the present invention to provide a control device and a control method capable of detecting based on a calculated voltage phase of a rectangular wave voltage.

  A control device according to a first aspect of the invention is an inverter abnormality detection device that supplies a drive current corresponding to a voltage phase of a rectangular wave voltage calculated by a rectangular wave control device to an AC motor. The rectangular wave control device increases the voltage phase of the rectangular wave voltage within a range equal to or less than a predetermined upper limit phase when the output torque of the AC motor is smaller than the torque command value. The abnormality detection device determines whether or not the state in which the voltage phase and the upper limit phase match continues for a predetermined time, and detects that the inverter is abnormal when it is determined that the matching state has continued for a predetermined time. .

  In the control device according to the second invention, the torque command value is limited to a predetermined upper limit torque value or less. The output torque of the AC motor has a characteristic that it increases as the voltage phase increases in the small phase region where the voltage phase is smaller than the predetermined phase, and becomes maximum torque when the voltage phase is the predetermined phase. The upper limit phase is set to a predetermined phase at which the output torque of the AC motor becomes the maximum torque. The upper limit torque value is set to a value smaller than the maximum torque.

  In the control device according to the third aspect of the invention, the inverter includes a plurality of arms respectively corresponding to each phase of the AC motor, and each of the plurality of arms includes two switching elements connected in series. The abnormality detection device detects an open failure in which one switching element included in any one of the plurality of arms is always in an OFF state when the matching state continues for a predetermined time.

  In the control device according to the fourth aspect of the invention, the rectangular wave control device continues to increase the voltage phase in a range equal to or less than the upper limit phase when the output torque of the AC motor is smaller than the torque command value. The output torque of the AC motor has a characteristic that it continuously becomes lower than the torque command value when an open failure occurs.

  In the control device according to the fifth aspect of the invention, the abnormality detection device detects that the inverter is normal when the voltage phase and the upper limit phase do not match.

  The control device according to a sixth aspect of the invention is an abnormality detection method performed by an abnormality detection device for an inverter that supplies a drive current corresponding to the voltage phase of the rectangular wave voltage calculated by the rectangular wave control device to the AC motor. The rectangular wave control device increases the voltage phase of the rectangular wave voltage within a range equal to or less than a predetermined upper limit phase when the output torque of the AC motor is smaller than the torque command value. The abnormality detection method includes a step of determining whether or not the state in which the voltage phase and the upper limit phase coincide with each other for a predetermined period of time, and if it is determined that the state of coincidence has continued for a predetermined period of time, the inverter is abnormal. Detecting.

  According to the present invention, it is possible to detect an inverter abnormality that occurs during rectangular wave voltage control based on the voltage phase of the rectangular wave voltage calculated by the rectangular wave control device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

FIG. 1 is an overall configuration diagram of a motor drive system according to an embodiment of the present invention.
Referring to FIG. 1, motor drive system 100 includes a DC voltage generation unit 10 #, a smoothing capacitor C0, an inverter 14, and an AC motor M1.

  AC motor M1 is, for example, a drive motor that generates torque for driving drive wheels of a hybrid vehicle or an electric vehicle. Alternatively, AC motor M1 may be configured to have a function of a generator driven by an engine, or may be configured to have both functions of an electric motor and a generator. Furthermore, AC motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle so that the engine can be started, for example.

  DC voltage generation unit 10 # includes a DC power supply B configured to be chargeable, system relays SR1 and SR2, a smoothing capacitor C1, and a step-up / down converter 12.

  DC power supply B includes a secondary battery such as nickel metal hydride or lithium ion. Or you may comprise the direct-current power supply B with electrical storage apparatuses, such as an electric double layer capacitor. The DC voltage Vb output from the DC power source B is detected by the voltage sensor 10. Voltage sensor 10 outputs detected DC voltage Vb to control device 30.

  System relay SR1 is connected between the positive terminal of DC power supply B and positive electrode line 6, and system relay SR1 is connected between the negative terminal of DC power supply B and negative electrode line 5. System relays SR1 and SR2 are turned on / off by signal SE from control device 30. More specifically, system relays SR1 and SR2 are turned on by H (logic high) level signal SE from control device 30, and are turned off by L (logic low) level signal SE from control device 30. Smoothing capacitor C <b> 1 is connected between positive electrode line 6 and negative electrode line 5.

  Buck-boost converter 12 includes a reactor L1, power semiconductor switching elements Q1, Q2, and diodes D1, D2.

  Power semiconductor switching elements Q 1 and Q 2 are connected in series between positive electrode line 7 and negative electrode line 5. On / off of power semiconductor switching elements Q 1 and Q 2 is controlled by switching control signals S 1 and S 2 from control device 30.

  In the embodiment of the present invention, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor is used as a power semiconductor switching element (hereinafter simply referred to as “switching element”). Etc. can be used. Anti-parallel diodes D1 and D2 are arranged for switching elements Q1 and Q2, respectively.

  Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and positive electrode line 6. Further, the smoothing capacitor C 0 is connected between the positive electrode line 7 and the negative electrode line 5.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17 provided in parallel between positive electrode line 7 and negative electrode line 5. Each phase arm includes a switching element connected in series between positive electrode line 7 and negative electrode line 5. For example, U-phase arm 15 includes switching elements Q3 and Q4. V-phase arm 16 includes switching elements Q5 and Q6. W-phase arm 17 includes switching elements Q7 and Q8. Further, antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are turned on / off by switching control signals S3 to S8 from control device 30.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M1. Typically, AC motor M1 is a three-phase permanent magnet motor, and is configured by commonly connecting one end of three coils of U, V, and W phases to a neutral point. Furthermore, the other end of each phase coil is connected to the midpoint of the switching elements of each phase arm 15-17.

  In the step-up operation, the step-up / down converter 12 boosts a DC voltage VH obtained by boosting the DC voltage Vb supplied from the DC power supply B (this DC voltage corresponding to the input voltage to the inverter 14 is hereinafter also referred to as “system voltage”). Supply to the inverter 14. More specifically, in response to switching control signals S1 and S2 from control device 30, an ON period of switching element Q1 and an ON period of Q2 are alternately provided, and the step-up ratio is equal to the ratio of these ON periods. It will be a response.

  Further, during the step-down operation, the step-up / down converter 12 steps down the DC voltage VH (system voltage) supplied from the inverter 14 via the smoothing capacitor C0 and charges the DC power supply B. More specifically, in response to switching control signals S1 and S2 from control device 30, a period in which only switching element Q1 is turned on and a period in which both switching elements Q1 and Q2 are turned off are alternately provided, The step-down ratio is in accordance with the duty ratio during the ON period. Instead of the period in which both switching elements Q1, Q2 are turned off, a period in which only switching element Q2 is turned on may be provided in accordance with the on period of antiparallel diode D2. In this case, in principle, switching elements Q1, Q2 are repeatedly turned on and off in a complementary manner.

  Smoothing capacitor C0 smoothes the DC voltage from step-up / down converter 12, and supplies the smoothed DC voltage to inverter 14. The voltage sensor 13 detects the voltage across the smoothing capacitor C 0, that is, the system voltage, and outputs the detected value VH to the control device 30.

  Inverter 14 performs switching operation of switching elements Q3 to Q8 in response to switching control signals S3 to S8 from control device 30. The inverter 14 is supplied with a DC voltage VH from the smoothing capacitor C0.

  When the torque command value of AC motor M1 is positive (Trqcom> 0), inverter 14 converts the DC voltage into an AC voltage and outputs a positive torque by the switching operation of switching elements Q3 to Q8. The motor M1 is driven.

  Further, when the torque command value of AC motor M1 is zero (Trqcom = 0), inverter 14 converts the DC voltage into the AC voltage and the torque becomes zero by the switching operation of switching elements Q3 to Q8. The AC motor M1 is driven.

  By such control, AC motor M1 is driven to generate zero or positive torque designated by torque command value Trqcom.

  Further, during regenerative braking of a hybrid vehicle or electric vehicle equipped with motor drive system 100, torque command value Trqcom of AC motor M1 is set to be negative (Trqcom <0). In this case, the inverter 14 converts the AC voltage generated by the AC motor M1 into the DC voltage VH by the switching operation of the switching elements Q3 to Q8, and converts the converted DC voltage VH (system voltage) to the smoothing capacitor C0. To the step-up / down converter 12.

  Note that regenerative braking here refers to braking with regenerative power generation when the driver driving a hybrid vehicle or electric vehicle performs foot braking, or turning off the accelerator pedal while driving, although the foot brake is not operated. This includes decelerating the vehicle (or stopping acceleration) while generating regenerative power.

  Current sensor 24 detects a motor current flowing through AC motor M <b> 1 and outputs the detected motor current to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 24 has a motor current for two phases (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect.

  The rotation angle sensor (resolver 25) detects the rotor rotation angle θ of AC motor M1, and sends the detected rotation angle θ to control device 30. The control device 30 calculates the rotational speed (rotational speed) of the AC motor M1 based on the rotational angle θ.

  The control device 30 includes a torque command value Trqcom input from an electronic control unit (not shown) provided outside, a battery voltage Vb detected by the voltage sensor 10, and a system voltage detected by the voltage sensor 13. Based on VH, motor currents iv and iw from current sensor 24, and rotation angle θ from resolver 25, AC motor M1 outputs a voltage in accordance with torque command value Trqcom. Control the behavior.

  Switching control signals S1 to S8 for controlling buck-boost converter 12 and inverter 14 as described above are generated and output to buck-boost converter 12 and inverter 14.

  During the step-up operation of the step-up / down converter 12, the control device 30 feedback-controls the output voltage VH of the smoothing capacitor C0, and generates the switching control signals S1 and S2 so that the output voltage VH becomes a voltage command value.

  Further, when receiving a signal RGE indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control device 30 performs switching control so as to convert the AC voltage generated by the AC motor M1 into a DC voltage. Signals S3 to S8 are generated and output to inverter 14. Thereby, the inverter 14 converts the AC voltage generated by the AC motor M <b> 1 into a DC voltage and supplies it to the step-up / down converter 12.

  Further, when receiving a signal RGE indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control device 30 switches the switching control signals S1, S2 so as to step down the DC voltage supplied from the inverter 14. Is output to the step-up / down converter 12. As a result, the AC voltage generated by AC motor M1 is converted into a DC voltage, stepped down, and supplied to DC power supply B.

  Furthermore, control device 30 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

  Next, power conversion in the inverter 14 controlled by the control device 30 will be described in detail.

  FIG. 2 is a diagram for explaining a control method used in the motor drive system 100. As shown in FIG. 2, the motor drive system 100 switches between three control modes for voltage conversion in the inverter 14. Specifically, the three control modes are control modes of sine wave PWM control, overmodulation PWM control, and rectangular wave voltage control.

  The sine wave PWM control is used as a general PWM control method, and the switching element in each phase arm is turned on / off by comparing the voltage between a sine wave voltage command value and a carrier wave (typically a triangular wave). Control according to. As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. The ratio is controlled. As is well known, in sine wave PWM control, the fundamental wave component amplitude can only be increased to about 0.61 times the inverter input voltage.

  On the other hand, in the rectangular wave voltage control, an AC motor is applied to one pulse of a rectangular wave with a ratio of the high level period to the low level period of 1: 1 corresponding to the case where the PWM duty is maintained at the maximum value within the above-mentioned fixed period. To do. As a result, the modulation rate is increased to about 0.78.

  The overmodulation PWM control performs PWM control similar to the sine wave PWM control after distorting the carrier wave to reduce the amplitude. As a result, the modulation factor can be increased to a range of about 0.61 to 0.78 by distorting the fundamental wave component. In the present embodiment, both the sine wave PWM control, which is a normal PWM control method, and the overmodulation PWM control are classified into PWM control methods.

  In AC motor M1, when the number of rotations and output torque increase, the induced voltage increases and the required voltage increases. The boosted voltage by the converter 12, that is, the system voltage VH needs to be set higher than this motor required voltage (induced voltage). On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by the converter 12, that is, the system voltage.

  Therefore, in a region where the required motor voltage (induced voltage) is lower than the maximum system voltage value (VH maximum voltage), a PWM control method using sine wave PWM control or overmodulation PWM control is applied, and motor current according to vector control is applied. The output torque is controlled to the torque command value Trqcom by the control.

  On the other hand, when the required motor voltage (induced voltage) reaches the maximum value of the system voltage (VH maximum voltage), the rectangular wave voltage control method is applied while maintaining the system voltage VH. Since the amplitude of the fundamental wave component is fixed during the rectangular wave voltage control, the torque control is executed by the voltage phase control of the rectangular wave pulse based on the deviation between the estimated torque value obtained by the calculation and the torque command value.

  FIG. 3 is a flowchart for explaining a control method selection method. As shown in the flowchart of FIG. 3, upon receiving a torque command value Trqcom of AC motor M <b> 1 (step S <b> 100) calculated by a host ECU (not shown) based on a required vehicle output according to the accelerator opening, etc., control device 30. Calculates the required motor voltage (induced voltage) from the torque command value Trqcom of AC motor M1 and the number of revolutions based on a preset map or the like (step S110), and further calculates the maximum required motor voltage and system voltage. According to the relationship with (VH maximum voltage), it is determined which of the rectangular wave voltage control method and the PWM control method (sine wave PWM control method / overmodulation PWM control method) is to be used to control the motor (step S120). . Whether to use the sine wave PWM control method or the overmodulation PWM control method when applying the PWM control method is determined according to the modulation rate range of the voltage command value according to the vector control. According to the control flow, an appropriate control method is selected from the plurality of control methods shown in FIG. 2 according to the operating condition of AC motor M1.

  FIG. 4 is a diagram showing the relationship between the control method and the output torque of AC motor M1. As shown in FIG. 4, when the rotational speed of AC motor M1 is included in low rotational speed range A1, PWM control is applied. When PWM control is applied, the control range of output torque (torque command value Trqcom) of AC motor M1 is limited by upper limit torque line L1 shown in FIG.

  On the other hand, when the rotation speed of AC motor M1 is included in high rotation speed range A2, rectangular wave voltage control is applied. When the rectangular wave voltage control is applied, the control range of the output torque (torque command value Trqcom) of AC motor M1 is expanded to upper limit torque line L2 shown in FIG. Thereby, the output improvement of AC motor M1 is implement | achieved.

  FIG. 5 is a control block diagram of PWM control executed by the control device 30. As shown in FIG. 5, PWM control unit 200 includes a current command generation unit 210, coordinate conversion units 220 and 250, a PI calculation unit 240, a PWM signal generation unit 260, and a control mode determination unit 270. .

  Current command generation unit 210 generates a d-axis current command value Idcom and a q-axis current command value Iqcom corresponding to torque command value Trqcom according to a table or the like created in advance.

  The coordinate conversion unit 220 converts the V-phase current iv and the W-phase current iv detected by the current sensor 24 by coordinate conversion (3 phase → 2 phase) using the rotation angle θ of the AC motor M1 detected by the resolver 25. Based on this, the d-axis current Id and the q-axis current Iq are calculated.

  A deviation ΔId (ΔId = Idcom−Id) with respect to the command value of the d-axis current and a deviation ΔIq (ΔIq = Iqcom−Iq) with respect to the command value of the q-axis current are input to the PI calculation unit 240. PI calculating section 240 performs PI calculation with a predetermined gain on d-axis current deviation ΔId and q-axis current deviation ΔIq to obtain a control deviation, and d-axis voltage command value Vd # and q-axis voltage command value corresponding to the control deviation. Vq # is generated.

  The coordinate conversion unit 250 converts the d-axis voltage command value Vd # and the q-axis voltage command value Vq # into the U-phase, V-phase, W-phase by coordinate conversion (2 phase → 3 phase) using the rotation angle θ of the AC motor M1. Each phase voltage command value Vu, Vv, Vw of the phase is converted. The system voltage VH is also reflected in the conversion from the d-axis and q-axis voltage command values Vd # and Vq # to the phase voltage command values Vu, Vv and Vw.

  When the PWM control method (sine wave PWM control method / overmodulation PWM control method) is selected according to the flowchart shown in FIG. 3, the control mode determination unit 270 performs the sine wave PWM control method according to the following modulation factor calculation. One of the overmodulation PWM control methods is selected.

  Control mode determination unit 270 uses line d voltage command value Vd # and q axis voltage command value Vq # generated by PI operation unit 240 to calculate line voltage amplitude Vamp according to the following equations (1) and (2). calculate.

Vamp = | Vd # | .cosφ + | Vq # | .sinφ (1)
tan φ = Vq # / Vd # (2)
Further, the control mode determination unit 270 calculates the modulation factor Kmd, which is the ratio of the line voltage amplitude Vamp by the above calculation to the system voltage VH, that is, according to the following equation (3).

Kmd = Vamp / VH # (3)
Control mode determination unit 270 selects one of sine wave PWM control and overmodulation PWM control according to modulation factor Kmd obtained by the above calculation. As described above, the selection of the control method by the control mode determination unit 270 is reflected in the carrier wave switching in the PWM signal generation unit 260. That is, in the overmodulation PWM control method, the carrier wave used in the PWM modulation in the PWM signal generation unit 260 is switched from the general one in the sine wave PWM control method.

  Alternatively, when the modulation rate Kmd obtained by Expression (3) exceeds the range that can be realized by the PWM control method, the control mode determination unit 270 outputs the output that prompts the change to the rectangular wave voltage control method. You may send out with respect to ECU (not shown).

  The PWM signal generation unit 260 generates the switching control signals S3 to S8 shown in FIG. 1 based on the comparison between the voltage command values Vu, Vv, Vw in each phase and a predetermined carrier wave. The inverter 14 is switching-controlled according to the switching control signals S3 to S8 generated by the PWM control unit 200, whereby an AC voltage for outputting torque according to the torque command value Trqcom input to the current command generation unit 210. Is applied.

  As described above, a closed loop for controlling the motor current to the current command value (Idcom, Iqcom) corresponding to the torque command value Trqcom is configured, whereby the output torque of the AC motor M1 is controlled according to the torque command value Trqcom.

  FIG. 6 is a control block diagram of rectangular wave voltage control executed by the control device 30. Referring to FIG. 6, rectangular wave voltage control unit 400 includes a coordinate conversion unit 220, a torque estimation unit 420, a PI calculation unit 430, a phase limiter 432, and a rectangular wave generation unit 440 that are the same as those in the PWM control method. And a signal generator 450.

  The coordinate conversion unit 220 performs coordinate conversion of each phase current obtained from the V-phase current iv and the W-phase current iw by the current sensor 24 into a d-axis current It and a q-axis current Iq, as in the PWM control method.

  Torque estimation unit 420 estimates output torque of AC motor M1 using d-axis current Id and q-axis Iq obtained by coordinate conversion unit 220. The torque estimation unit 420 is configured by, for example, a torque calculation map that outputs a torque estimation value Trq with the d-axis current Id and the q-axis current Iq as arguments.

  Deviation ΔTrq (ΔTrq = Trqcom−Trq) of estimated torque value Trq with respect to torque command value Trqcom is input to PI calculation unit 430. PI calculation unit 430 performs PI calculation with a predetermined gain on torque deviation ΔTrq to obtain a control deviation, and sets phase φ of the rectangular wave voltage according to the obtained control deviation.

  FIG. 7 is a flowchart illustrating a method of setting the phase φ of the rectangular wave voltage when positive torque is generated (Trqcom> 0). As shown in FIG. 7, the PI calculation unit 430 determines whether or not the deviation ΔTrq (ΔTrq = Trqcom−Trq) is positive (whether or not the torque is insufficient) (S200), and the deviation ΔTrq is positive. If so, the voltage phase φ of the rectangular wave voltage is advanced (S210). Otherwise, the voltage phase φ of the rectangular wave voltage is delayed (S220). Thus, in the rectangular wave voltage control, the estimated torque value Trq is made to follow the torque command value Trqcom by manipulating the voltage phase φ of the rectangular wave voltage.

  Returning to FIG. 6, the phase limiter 432 outputs a voltage phase φv obtained by applying a predetermined limit to the phase φ output from the PI calculation unit 430 to the rectangular wave generation unit 440.

  FIG. 8 is a diagram illustrating an output torque characteristic of AC motor M1 with respect to voltage phase φ of the rectangular wave voltage. As shown in FIG. 8, the output torque is the maximum torque when the voltage phase φ is a predetermined phase φm. In a region where the voltage phase φ is smaller than φm (small phase region), the output torque increases as the voltage phase φ increases (advance angle). On the other hand, in the region where the voltage phase φ is larger than φm (large phase region), the output torque decreases as the voltage phase φ increases, contrary to the small phase region.

  The phase limiter 432 sets the limiter phase φlimit in the vicinity of the phase φm in order to control the voltage phase φ in the above-described small phase region, and the voltage phase φv output from the phase limiter 432 to the rectangular wave generator 440 is: The limiter phase is limited to φlimit or less.

  Returning to FIG. 6, the rectangular wave generation unit 440 generates the phase voltage command values (rectangular wave pulses) Vu, Vv, and Vw according to the voltage phase φv. The signal generator 450 generates switching control signals S3 to S8 according to the phase voltage command values Vu, Vv, and Vw. When inverter 14 performs a switching operation according to switching control signals S3 to S8, a rectangular wave pulse according to voltage phase φv is applied as each phase voltage of the motor.

  As described above, in the rectangular wave voltage control, torque feedback control is performed in which the estimated torque value Trq follows the torque command value Trqcom by controlling the voltage phase φv of the rectangular wave voltage within a range equal to or less than the limiter phase φlimit. However, the upper limit torque line L2 during the rectangular wave voltage control shown in FIG. 4 is set to a value smaller than the maximum torque of the AC motor M1 shown in FIG. That is, torque command value Trqcom is limited to a value smaller than the maximum torque.

  Therefore, when the system is normal, as shown in FIG. 8, the voltage phase φ is controlled within a range that is smaller than the limiter phase φlimit by a predetermined value or less, and even if the limiter phase φlimit is temporarily reached, The phase φlimit is not maintained for a long time.

  However, if one of the phase arms 15 to 17 of the inverter 14 has an open failure during the rectangular wave voltage control (a failure in which one of the switching elements Q3 to Q8 is always off), the motor of the failed phase A half wave of current stops flowing, and on average, an offset current flows to AC motor M1. Due to the influence of the offset current, an eddy current is generated in the rotor of the AC motor M1, and the rotor generates heat. Therefore, a secondary failure occurs in which the magnetic force of the rotor decreases and the output of the AC motor M1 decreases.

  In this embodiment, as shown in FIG. 6, in order to prevent a secondary failure of the AC motor M1 due to an open failure of the inverter 14, an abnormality detection for detecting an open failure of the inverter 14 is performed. It is characterized in that the portion 460 is provided.

  Abnormality detection unit 460 detects an open failure of inverter 14 by monitoring the relationship between voltage phase φv and limiter phase φlimit.

  FIG. 9 is a flowchart for explaining an abnormality detection method by the abnormality detection unit 460. As shown in FIG. 9, the abnormality detection unit 460 determines whether or not the voltage phase φv matches the limiter phase φlimit (S300). If voltage phase φv and limiter phase φlimit match (YES in S300), abnormality detection unit 460 adds an abnormality counter (S310), and if the abnormality counter is equal to or longer than a predetermined abnormality determination time (S320). YES), it is determined that there is an abnormal state in which an open failure has occurred (S330). If the abnormality counter has not reached the abnormality confirmation time (NO in S320), the process returns to S300 again.

  On the other hand, when voltage phase φv and limiter phase φlimit do not match (NO in S300), abnormality detection unit 460 determines that the open state is normal (S340). At this time, the abnormality counter is reset.

  FIG. 10 is a timing chart of the U-phase current iu, the estimated torque value Trq, and the voltage phase φv when the U-phase upper arm (switching element Q3) of the inverter 14 has an open failure during the rectangular wave voltage control.

  In a normal state up to time t1 when the upper arm of the U phase is open-failed, the U phase current iu flows normally, so that the estimated torque value Trq substantially matches the torque command value Trqcom, and the voltage phase φv is the limiter phase. It is controlled by a value smaller than φlimit by a predetermined amount.

  If the U-phase upper arm fails at time t1, the upper half of the U-phase current iu does not flow as shown in FIG. 10, and an offset current flows to the AC motor M1 on average. Due to this influence, if the torque shortage state (deviation ΔTrq> 0) in which estimated torque value Trq is lower than torque command value Trqcom continues (YES in S200). In order to make the estimated torque value Trq follow the torque command value Trqcom, the process of advancing the voltage phase φ of the rectangular wave voltage is continued (S210).

  Due to this, when voltage phase φv reaches limiter phase φlimit at time t2 (YES at S300), an abnormality counter addition process is performed (S310), and when the abnormality counter reaches the abnormality confirmation time at time t3. (YES in S320), it is determined that there is an abnormal state in which an open failure has occurred (S330).

  As described above, in the present embodiment, the inverter open failure is detected by monitoring the relationship between the voltage phase φv of the rectangular wave voltage and the limiter phase φlimit. Therefore, it is possible to detect an open failure of the inverter without separately providing a hardware circuit for detecting the open failure. Therefore, it is possible to prevent a secondary failure of the motor due to an open failure of the inverter.

  In the present embodiment, the open failure is detected based on the time when the voltage phase φv after the limit by the phase limiter 432 matches the limiter phase φlimit. For example, the voltage phase before the limit by the phase limiter 432 is detected. An open failure may be detected based on the time when φ exceeds the limiter phase φlimit.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a whole block diagram of a motor drive system. It is a figure explaining the control system used with a motor drive system. It is a flowchart explaining the selection method of a control system. It is a figure which shows the relationship between a control system and the output torque of an AC motor. It is a control block diagram of PWM control executed by the control device. It is a control block diagram of rectangular wave voltage control executed by the control device. It is a flowchart explaining the setting method of the phase of a rectangular wave voltage. It is a figure which shows the output torque characteristic of the AC motor with respect to the phase of a rectangular wave voltage. It is a flowchart explaining an abnormality detection method. It is a timing chart of a U-phase current, a torque estimated value, and a voltage phase when a U-phase upper arm of the inverter fails during rectangular wave voltage control.

Explanation of symbols

5 Negative electrode wire, 6 Positive electrode wire, 7 Positive electrode wire, 10 # DC voltage generator, 10 Voltage sensor, 13 Voltage sensor, 12 Converter, 14 Inverter, 15 U phase arm, 16 V phase arm, 17 W phase arm, 24 Current Sensor, 25 resolver, 30 control device, 100 motor drive system, 200 PWM control unit, 210 current command generation unit, 220, 250 coordinate conversion unit, 240, 430 PI calculation unit, 260 PWM signal generation unit, 270
Control mode determination unit, 400 rectangular wave voltage control unit, 420 torque estimation unit, 432 phase limiter, 440 rectangular wave generation unit, 450 signal generation unit, 460 abnormality detection unit, B DC power supply, C0, C1 smoothing capacitor, D1-D8 Diode, L1 reactor, M1 AC motor, Q1-Q8 switching element, SR1, SR2 System relay.

Claims (6)

An inverter abnormality detection device that supplies a drive current corresponding to a voltage phase of a rectangular wave voltage calculated by a rectangular wave control device to an AC motor,
The rectangular wave control device increases the voltage phase of the rectangular wave voltage within a range below a predetermined upper limit phase when the output torque of the AC motor is smaller than a torque command value,
The abnormality detection device determines whether or not the state in which the voltage phase matches the upper limit phase has continued for a predetermined time, and determines that the inverter is abnormal when determining that the matching state has continued for a predetermined time. An inverter abnormality detection device that detects the presence of an inverter. The torque command value is limited to a predetermined upper limit torque value or less,
The output torque of the AC motor increases as the voltage phase increases in a small phase region where the voltage phase is smaller than a predetermined phase, and becomes a maximum torque when the voltage phase is the predetermined phase. Have
The upper limit phase is set to the predetermined phase where the output torque of the AC motor becomes the maximum torque,
The inverter abnormality detection device according to claim 1, wherein the upper limit torque value is set to a value smaller than the maximum torque. The inverter includes a plurality of arms each corresponding to each phase of the AC motor, and each of the plurality of arms includes two switching elements connected in series,
The abnormality detection device detects an open failure in which one switching element included in any one of the plurality of arms is always in an off state when the matching state continues for a predetermined time. The abnormality detection device for an inverter according to claim 1 or 2. The rectangular wave control device, when the output torque of the AC motor is smaller than the torque command value, continues to increase the voltage phase in the range below the upper limit phase,
The inverter abnormality detection device according to any one of claims 1 to 3, wherein the output torque of the AC motor has a characteristic of continuously lowering than the torque command value when the open failure occurs.   The inverter abnormality detection device according to claim 1, wherein the abnormality detection device detects that the inverter is normal when the voltage phase and the upper limit phase do not match. An abnormality detection method performed by an abnormality detection device of an inverter that supplies a drive current corresponding to a voltage phase of a rectangular wave voltage calculated by a rectangular wave control device to the AC motor, wherein the rectangular wave control device When the output torque is smaller than the torque command value, the voltage phase of the rectangular wave voltage is increased within a range below a predetermined upper limit phase,
The abnormality detection method is:
Determining whether the voltage phase and the upper limit phase match for a predetermined time;
And detecting an abnormality of the inverter when it is determined that the matching state has continued for a predetermined time.

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