JP2010178449A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a torque fluctuation of a motor with an open fault. <P>SOLUTION: A neutral point voltage operation unit 28 corrects voltage command values Vu*, Vv* and Vw* of respective phases, which are input to a PWM operation unit 30 so long as a motor 10 is in the middle of regeneration driving when an open fault decision part 27 determines an open fault. When switching elements of arms Up, Vp and Wp on an upper side have open faults, for example, the neutral point voltage is offset in a reducing direction from the reference voltage. Thus, the voltage command values of the respective phases are corrected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric motor control device.

  2. Description of the Related Art Conventionally, an electric motor control device that controls a multiphase AC motor such as a three-phase AC motor via an inverter is known. The inverter includes a plurality of series circuits of an upper switching element connected to the positive side of the power source and a lower switching element connected to the negative side of the power source corresponding to each phase of the multiphase AC motor, An interconnection point of a pair of switching elements in each series circuit is connected to each phase winding of the motor.

  For example, Patent Document 1 discloses a control device for a three-phase AC motor that can continue vector control and generate torque in an electric motor when it is determined that an open failure in which an inverter switching element continues to be turned off. Yes. For example, when the open failure phase is a U-phase upper switching element, the voltage vector is fixed at a timing when the three-phase voltage command value changes from negative to positive. Thereafter, the voltage vector is inverted by 180 degrees on condition that the q-axis current becomes zero. This is intended to generate some positive torque.

JP 2005-94873 A

  However, according to the technique disclosed in Patent Document 1, since the voltage phase is inverted by 180 degrees, the d-axis and q-axis currents may be disturbed in a transient state, which may cause torque fluctuations.

  This invention is made | formed in view of this situation, The objective is to suppress the torque fluctuation of the electric motor accompanying an open failure.

  In order to solve such a problem, the present invention is based on the neutral point voltage on the condition that the electric motor is being regeneratively driven when the switching element on the positive electrode side of the power supply is open in any phase. Each voltage command value of each phase is corrected by offsetting in the direction of decreasing from the voltage. Alternatively, if the switching element on the negative side of the power supply in any phase has an open failure, the neutral point voltage is offset in the direction of increasing from the reference voltage on the condition that the motor is being regeneratively driven. Each of the voltage command values for each phase is corrected.

  According to the present invention, a scene of turning on an open-failed switching element is suppressed. Therefore, the return corresponding to the switching element in which the open failure has occurred can be transferred to the return corresponding to the other switching element, and a predetermined line voltage can be applied to the electric motor. As a result, it is possible to suppress the influence of the switching element that has failed open, and to suppress the torque fluctuation of the electric motor.

Configuration diagram schematically showing the motor 10 and its control system Explanatory drawing which shows the structure of the controller 20 typically Illustration of neutral point voltage and reference voltage Explanatory drawing showing the transition of U-phase voltage command value Vu * and carrier Explanatory drawing which shows transition of the line voltage of each phase of the electric motor 10

  FIG. 1 is a configuration diagram schematically showing an electric motor 10 and its control system according to an embodiment of the present invention. In the present embodiment, a control system for controlling the electric motor 10 applied as a drive motor for an electric vehicle will be described. The electric vehicle includes an electric motor control system including an electric motor 10, a controller 20, and an inverter 40, and a power supply 50.

  The electric motor 10 includes, for example, a plurality of phase windings star-connected around a neutral point (in this embodiment, three phase windings including a U-phase winding, a V-phase winding, and a W-phase winding) Is a three-phase AC motor. The electric motor 10 is driven by an interaction between a magnetic field generated by supplying three-phase AC power converted in the inverter 40 to each phase winding and a magnetic field generated by a permanent magnet of the rotor.

  The controller 20 is an electric motor control device that controls the electric motor 10 via the inverter 40, and specifically controls the output torque of the electric motor 10 by controlling a switching element that constitutes the inverter 40. As the controller 20, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. Details of the function of the controller 20 will be described later.

  The inverter 40 is subjected to PWM control according to the drive signal output from the controller 20, thereby converting the DC power supplied from the power supply 50 into multiphase AC power (in this embodiment, U-phase AC power, V-phase AC power). 3 phase AC power composed of electric power and W phase AC power), and the 3 phase AC power is supplied to each phase winding of the motor 10.

  The inverter 40 is mainly composed of three switching circuits corresponding to the respective phases of the electric motor 10. Inverter 40 includes a U-phase switching circuit, a V-phase switching circuit, and a W-phase switching circuit between a positive bus connected to the positive electrode of power supply 50 and a negative bus connected to the negative electrode of power supply 50. Switching circuit. A smoothing capacitor C is connected between the positive electrode bus and the negative electrode bus on the power supply 50 side of the switching circuit for each phase.

  The U-phase switching circuit mainly includes a pair of arms (switches) Up and Un connected in series with each other, and the V-phase switching circuit has a pair of arms (switches) Vp connected in series with each other. , Vn. The W-phase switching circuit mainly includes a pair of arms (switches) Wp and Wn connected in series. Each of the arms Up to Wn is mainly composed of a switching element such as an NPN type transistor, and a free-wheeling diode is connected in parallel between the collector and the emitter of each transistor.

  The interconnection points of the U-phase pair of arms Up and Un, the V-phase pair of arms Vp and Vn, and the W-phase pair of arms Wp and Wn are respectively It functions as an output point for each phase current. A corresponding phase winding of the electric motor 10 is connected to each output point.

  In this specification, in each switching circuit, the arms Up, Vp, Wp connected to the positive bus side, that is, the positive side of the power supply 50 are referred to as upper arms Up, Vp, Wp. In each switching circuit, the arms Un, Vn, Wn connected to the negative bus side, that is, the negative side of the power supply 50 are referred to as lower arms Un, Vn, Wn. The three-phase alternating current generated by inverter 40 is referred to as U-phase alternating current Iu, V-phase alternating current Iv, and W-phase alternating current Iw, respectively. Each AC current Iu, Iv, Iw is positive in the direction in which the current flows to the motor 10 side.

  The power source 50 is a direct current power source that outputs direct current power, and is a battery such as a nickel metal hydride battery or a lithium ion battery that stores or discharges electric power.

  Hereinafter, details of the controller 20 which is one of the features of the present embodiment will be described. This controller 20 is configured so that the three-phase arms Up to Wn (specifically, switching elements) of the inverter 40 so that the actual torque of the motor 10 becomes a torque command value that is a command value of the torque generated in the motor 10. To control each. Specifically, the controller 20 calculates a three-phase voltage command value based on the torque command value, and the voltage applied to each phase of the electric motor 10 matches the calculated three-phase voltage command value. Thus, the drive signal for driving the arms Up to Wn of the respective phases of the inverter 40 is generated. Then, the controller 20 controls the arms Up to Wn constituting the inverter 40 by the generated drive signal.

  Various information is input to the controller 20 in order to control the inverter 40. The resolver 11 detects the position of the rotor of the electric motor 10, and the detection result (rotor information Im) is read by the controller 20. The current sensor 12 is provided corresponding to each phase, and detects an AC current of each phase of the motor 10, that is, a U-phase AC current Iu, a V-phase AC current Iv, and a W-phase AC current Iw, respectively. The detected currents Iu, Iv, Iw are read by the controller 20. The voltage sensor 41 detects the DC voltage of the capacitor C in the inverter 40, that is, the DC voltage Vdc of the power supply 50, and the detected DC voltage Vdc is read by the controller 20. Further, the torque command value T * calculated in the host device is input to the controller 20.

  FIG. 2 is an explanatory diagram schematically showing the configuration of the controller 20. As shown in the figure, the controller 20 includes an Id / Iq command value calculation unit 21, a Vd / Vq command value calculation unit 22, a current feedback control unit (current F / B control unit) 23, and a rotation speed / phase. Detection unit 24, 3-phase / 2-phase conversion unit 25, 2-phase / 3-phase conversion unit 26, open failure determination unit 27, neutral point voltage operation unit 28, dead time correction unit 29, PWM calculation Part 30. In the present embodiment, the Id / Iq command value calculation unit 21, the Vd / Vq command value calculation unit 22, the current feedback control unit 23, the rotation speed / phase detection unit 24, the three-phase / two-phase conversion unit 25, and the two-phase / 3. The phase conversion unit 26 has a function as a calculation unit that calculates voltage command values Vu *, Vv *, and Vw * to be applied to each phase of the electric motor 10 based on the torque command value T *.

  Based on the torque command value T *, the rotational speed Nm of the motor 10, and the DC voltage Vdc of the power source 50, the Id / Iq command value calculation unit 21 outputs a torque that matches the torque command value T *. To calculate a d-axis current command value Id * and a q-axis current command value Iq *. The calculated d-axis and q-axis current command values Id * and Iq * are output to the current feedback control unit 23. The Id / Iq command value calculation unit 21 corresponds to each parameter of the torque command value T *, the rotational speed Nm of the electric motor 10 and the DC voltage Vdc of the power supply 50, and the d-axis and q-axis current command values Id * and Iq *. A map describing the relationship is held, and the d-axis and q-axis current command values Id * and Iq * are calculated by referring to the map. A map describing this correspondence is acquired in advance through experiments and simulations.

  Here, the dq-axis coordinate system is an orthogonal coordinate system including a d-axis and a q-axis that rotate at an electrical rotation speed that is an integral multiple of the mechanical rotation speed of the electric motor 10. In the case of the electric motor 10 that is a three-phase synchronous motor, the dq axis coordinate system rotates in synchronization with the motor rotation. With the dq axis coordinate system, the current supplied to the stator winding of the electric motor 10 is divided into a field component current (d axis current) and a torque component current (q axis current) and is displayed as a vector. The rotation speed Nm of the electric motor 10 is calculated by the rotation speed / phase detection unit 24 based on the detection signal Im output from the resolver 11, and the calculation result is input to the Id / Iq command value calculation unit 21. ing.

  Based on the torque command value T *, the rotational speed Nm of the electric motor 10, and the DC voltage Vdc of the power source 50, the Vd / Vq command value calculation unit 22 calculates a predetermined d-axis voltage command value Vd ″ *, q The shaft voltage command value Vq ″ * is calculated. The Vd / Vq command value calculation unit 22 includes parameters for the torque command value T *, the rotational speed Nm of the motor 10 and the DC voltage Vdc of the power supply 50, and the d-axis and q-axis voltage command values Vd ″ *, Vq ″. A map describing a correspondence relationship with * is held, and d-axis and q-axis voltage command values Vd ″ * and Vq ″ * are calculated by referring to the map. The map describing the correspondence is acquired in advance through experiments and simulations. The Vd / Vq command value calculation unit 22 does not perform feedback control unlike the current feedback control unit 23 described later, and is uniquely determined according to the torque command value T *, the rotational speed Nm of the motor 10 and the DC voltage Vdc of the power source 50. The fixed d-axis and q-axis voltage command values Vd ″ * and Vq ″ * are determined respectively.

  The three-phase / two-phase converter 25 performs coordinate conversion of the detected three-phase alternating currents Iu, Iv, Iw into a d-axis current Id and a q-axis current Iq based on the phase (electrical angle) θ. The phase θ required for the calculation of the three-phase / two-phase conversion unit 25 represents the position of the rotor as an electrical phase. In the rotation speed / phase detection unit 24 based on the detection result Im of the resolver 11. Desired. The d-axis and q-axis currents Id and Iq calculated in the three-phase / two-phase conversion unit 25 are output to the current feedback control unit 23.

  The current feedback control unit 23 includes the d-axis and q-axis currents Id and Iq from the three-phase / two-phase conversion unit 25, and the d-axis and q-axis current command values Id * and Iq from the Id / Iq command value calculation unit 21. Based on *, d-axis and q-axis voltage command values Vd ′ * and Vq ′ * are calculated. The current feedback control unit 23 applies a control law such as PI control or PID control so that the deviation between the d-axis and q-axis currents Id and Iq and the d-axis and q-axis current command values Id * and Iq * becomes small. Using these, the d-axis and q-axis voltage command values Vd ′ * and Vq ′ * are calculated. The d-axis and q-axis voltage command values Vd ′ * and Vq ′ * output from the current feedback control unit 23 are the d-axis and q-axis voltage command values Vd ″ * output from the Vd / Vq command value calculation unit 22. , Vq ″ * and the added d-axis and q-axis voltage command values Vd * and Vq * are input to the two-phase / three-phase converter 26.

  The two-phase / three-phase converter 26 performs coordinate conversion of the d-axis and q-axis voltage command values Vd * and Vq * into the voltage command values Vu *, Vv *, and Vw * of each phase based on the phase θ. . The voltage command values Vu *, Vv *, and Vw * of each phase calculated from the Id / Iq command value calculation unit 21 through the two-phase / three-phase conversion unit 26 are basically input to the PWM calculation unit 30 described later. In order to generate the drive signal Sid of the inverter 40, it is compared with the carrier. However, in the present embodiment, from the viewpoint of torque fluctuation suppression and dead time correction at the time of open failure, via the neutral point voltage operation unit 28 and the dead time correction unit 29, after being corrected as necessary, Input to the PWM calculation unit 30.

  The open failure determination unit 27 has a function as failure determination means for detecting an open failure in which the arms Up to Wn (specifically, switching elements) of the inverter 40 are kept off. Specifically, the open failure determination unit 27 obtains the current rotation direction related to the rotor of the electric motor 10 from the amount of phase change calculated based on the phase θ. The open failure determination unit 27 stores the phase θ at the failure diagnosis start timing, and the rotor for each of the U, V, W phase upper arms Up, Vp, Wp and the lower arms Un, Vn, Wn. Integrate the three-phase alternating currents Iu, Iv, and Iw at the phase until one rotation in the same direction (∫i · dθ). When the rotor makes one rotation, each of the calculated integration values is processed and compared with a preset threshold Th (threshold is a value greater than 0). In this comparison result, when the integral value of the upper arm or the lower arm of a certain phase is equal to or less than the threshold value and the state continues for a predetermined number of revolutions, the arm that falls below the threshold value is determined as an open failure arm.

  When an open failure is determined for the upper arm, the open failure determination unit 27 outputs information Sdi including a command for offsetting the neutral point voltage in a direction to decrease from the reference voltage to the neutral point voltage operation unit 28. If the lower arm is determined to have an open failure, the open failure determination unit 27 outputs information Sdi including an instruction to offset the neutral point voltage in a direction to increase from the reference voltage to the neutral point voltage operation unit. In addition to this, the open failure determination method may include a function for detecting an open failure in each of the arms Up to Wn, and the open failure determination unit 27 may monitor this.

  When the open failure determination unit 27 detects an open failure, the neutral point voltage operation unit 28 receives the voltage command value of each phase input to the PWM calculation unit 30 on the condition that the electric motor 10 is being regeneratively driven. It functions as a correction means for correcting Vu *, Vv *, and Vw *. Here, FIG. 3 is an explanatory diagram of the neutral point voltage and the reference voltage. The Id / Iq command value calculation unit 21 to the two-phase / three-phase conversion unit 26 described above uses values (sinusoidal waves) Lu, Lv, and Lw that periodically change with the neutral point voltage as the center voltage of the amplitude. Voltage command values Vu *, Vv *, and Vw * are calculated. This neutral point voltage is normally set so as to correspond to a reference voltage (generally 0 V) which is the center of amplitude of the carrier Lc used in the PWM calculation unit 30 described later (see FIG. 2A). Here, the carrier Lc is a carrier that fluctuates with a value (Vdc / 2) that is half the DC voltage Vdc of the power supply 50 around the reference voltage, and for example, a triangular wave or the like can be used.

  Based on the information Sdi from the open failure determination unit 27, the neutral point voltage operation unit 28 determines the neutral point voltage from the reference voltage when the upper arm Up, Vp, Wp has an open failure in any phase. Offset in the decreasing direction. That is, as the neutral point voltage is offset in the decreasing direction, the voltage command values Vu *, Vv *, and Vw * for each phase are also offset in the same direction in the decreasing direction. As a result, the voltage command values Vu *, Vv *, and Vw * for each phase are corrected. FIG. 5B shows a state where the neutral point voltage is offset from the reference voltage in the decreasing direction. On the other hand, based on the information Sdi from the open failure determination unit 27, the neutral point voltage operation unit 28 sets the neutral point voltage when the lower arm Un, Vn, Wn has an open failure in any phase. Offset in the direction of increasing from the reference voltage. That is, with the offset in the increasing direction of the neutral point voltage, the voltage command values Vu *, Vv *, and Vw * of each phase are also offset to the same extent in the increasing direction. As a result, the voltage command values Vu *, Vv *, and Vw * for each phase are corrected.

  Here, the offset amount of the neutral point voltage from the reference voltage can be set to an arbitrary value up to the maximum offset amount described below. For example, when the upper arm Up, Vp, Wp has an open failure, that is, when the neutral point voltage is offset in the decreasing direction, the maximum offset amount is the amount of each phase output from the 2-phase / 3-phase conversion unit 26. The minimum voltage command value (absolute value) of the voltage command values Vu *, Vv *, Vw * and the minimum potential (absolute value) that can be taken as the carrier Lc, that is, half the value of the DC power supply Vdc of the power supply 50 (Vdc / 2) (see (c) in the same figure). On the other hand, when the lower arm Un, Vn, Wn has an open failure, that is, when the neutral point voltage is offset in the increasing direction, the maximum offset amount is output from the 2-phase / 3-phase converter 26. The maximum voltage command value of the voltage command values Vu *, Vv *, and Vw * of each phase to be performed and the maximum potential that can be taken as a carrier, that is, half the value of the DC power supply Vdc of the power supply 50 (Vdc / 2) And the difference.

  In this embodiment, the neutral point voltage operation unit 28 offsets the neutral point voltage by the maximum offset amount. That is, the neutral point voltage operation unit 28 calculates the maximum offset amount of the neutral point voltage, and corrects the voltage command values Vu *, Vv *, Vw * of each phase based on the maximum offset amount (offset). ), The voltage command values Vuo *, Vvo *, and Vwo * for each phase are newly calculated. The calculated voltage command values Vuo *, Vvo *, Vwo * of each phase are output to the dead time correction unit 29.

  In addition, the neutral point voltage operation unit 28, when the determination of the open failure is not made in any of the arms Up to Wn, or when the electric motor 10 is in the power running drive even if the open failure is determined, Without performing the neutral point voltage offset operation as described above, the voltage command values Vu *, Vv *, and Vw * of each phase output from the two-phase / three-phase converter 26 are used as the voltage command values Vuo of each phase. *, Vvo *, Vwo * are output as they are.

  The dead time correction unit 29 corrects the voltage command values Vuo *, Vvo *, and Vwo * of each phase output from the neutral point voltage operation unit 28, and new voltage command values Vuoa * and Vvoa * of each phase. , Vwoa * is calculated. By this correction, the upper arm Up, Vp, Wp and the lower arm Un, Vn, Wn are prevented from being simultaneously turned on and short-circuited in each phase. , Vp, Wp and the lower arms Un, Vn, Wn are provided with a time during which the lower arms Un, Vn, Wn are simultaneously turned off (so-called dead time). The calculated voltage command values Vuoa *, Vvoa *, Vwoa * of each phase are output to the PWM calculation unit 30. Note that due to the existence of dead time, an error may occur between the voltage command value output from the controller 20 and the actually output voltage, and the output voltage may be distorted. Therefore, the dead time correction unit 29 may compensate the error voltage by adding a constant compensation voltage to the voltage command value (for details of the technique, refer to Japanese Patent Application Laid-Open No. 2008-2008). 141937) and the like.

  The PWM calculation unit 30 drives the inverter 40 based on a comparison between the voltage level of the carrier that periodically varies around the reference voltage and the voltage command values Vuoa *, Vvoa *, Vwoa * of each phase. It functions as a driving means for generating Sid. Specifically, the PWM calculation unit 30 compares the voltage command values Vuoa *, Vvoa *, Vwoa * and the carrier for each phase, and compares the carrier with the voltage command values Vuoa *, Vvoa *, Vwoa *. When the voltage level is smaller, a drive signal Sid for turning on the corresponding arm Up to Wn is generated. On the other hand, when the voltage command values Vuoa *, Vvoa *, Vwoa * are smaller than the voltage level of the carrier Generates a drive signal Sid for turning off the corresponding arms Up to Wn. Then, the PWM calculation unit 30 outputs the drive signal Sid to the inverter 40. The inverter 40 generates a PWM wave voltage corresponding to the drive signal Sid and applies it to the electric motor 10, thereby driving the electric motor 10.

  As described above, according to the present embodiment, the neutral point voltage operation unit 28, when the open failure determination unit 27 determines that an open failure has occurred, is based on the condition that the electric motor 10 is being regeneratively driven. The voltage command values Vu *, Vv *, and Vw * of each phase that are input to are corrected. In this case, when the switching elements of the upper arms Up, Vp, and Wp have an open failure, the neutral point voltage operation unit 28 offsets the neutral point voltage in the direction of decreasing from the reference voltage, thereby Correct each of the voltage command values. On the other hand, when the lower arm Un, Vn, Wn has an open failure, the neutral point voltage operating unit 28 offsets the neutral point voltage from the reference voltage in the direction of increasing the voltage command value for each phase. Each of Vu *, Vv *, and Vw * is corrected.

  FIG. 4 is an explanatory diagram showing the transition of the U-phase voltage command value Vu * and the carrier. In a section in which the alternating current Iu is positive, it is usually necessary to apply a positive voltage by flowing a current from the upper arm Up in response to an ON command for the upper arm Up. By the way, when the upper arm Up has an open failure, it becomes a reflux from the lower arm Un and a negative voltage is applied. As a result, the sine wave current may be disturbed.

  However, in this embodiment, when the upper arms Up, Vp, and Wp have an open failure, the neutral point voltage is offset in the direction of decreasing from the reference voltage. As the neutral point voltage is offset, the voltage command values Vu *, Vv *, and Vw * are also relatively offset in the decreasing direction. Therefore, in a scene where the alternating currents Iu, Iv, and Iw are positive, there is a scene where the carrier is smaller than the voltage command values Vu *, Vv *, and Vw *, that is, a scene that turns on the upper arms Up, Vp, and Wp. It is suppressed. As a result, the reflux that is originally performed in the upper arms Up, Vp, and Wp can be transferred to the lower arms Un, Vn, and Wn. As a result, as shown by the solid line waveform in the one-dot chain line region in FIG. 5, the line voltage as expected can be applied to the motor 10, the influence of the open-switching element is suppressed, and the torque fluctuation of the motor 10 can be reduced. Can be suppressed. Here, FIG. 5 is an explanatory diagram showing the transition of the line voltage of each phase of the electric motor 10, (a) is an explanatory diagram regarding a technique for not offsetting the neutral point voltage, and (b) is an intermediate diagram. It is explanatory drawing regarding the method of offsetting a sex point voltage.

  Further, when the lower arm Un, Vn, Wn has an open failure, the neutral point voltage is offset in the direction of increasing from the reference voltage. As the neutral point voltage is offset, the voltage command values Vu *, Vv *, Vw * are also relatively offset in the increasing direction. Therefore, in a scene where the alternating currents Iu, Iv, Iw are negative, a scene where the carrier is larger than the voltage command values Vu *, Vv *, Vw *, that is, a scene where the lower arms Un, Vn, Wn are turned on. Is suppressed. Thus, the reflux that is originally performed in the lower arms Un, Vn, Wn can be transferred to the upper arms Up, Vp, Wp. Thereby, the expected line voltage can be given to the electric motor 10, and the torque fluctuation of an electric motor can be suppressed.

  However, the pattern that can be replaced by the upper arm and the lower arm by the above-described method is only when the current flowing back in the upper arm is replaced with the lower arm in a scene where the AC current of each phase is positive. The current flowing from the DC power supply cannot be substituted. This means that the voltage phase and the current phase are reversed, and is effective only in the case of regenerative driving in which the motor rotation direction and the torque direction are opposite.

  Further, according to the present embodiment, when the neutral point voltage operation unit 28 offsets the neutral point voltage in the direction of decreasing from the reference voltage, the voltage command values Vu *, Vv *, and Vw * of each phase The neutral point voltage is offset in the decreasing direction in accordance with the difference between the absolute value of the minimum voltage command value and the half value of the power supply voltage Vdc and (Vdc / 2). On the other hand, when the neutral point voltage operation unit 28 offsets the neutral point voltage in the direction of increasing from the reference voltage, the neutral voltage control unit 28 determines the maximum voltage command value of the voltage command values Vu *, Vv *, and Vw * of each phase. The neutral point voltage is offset in the increasing direction in accordance with the difference from the half value (Vdc / 2) of the power supply voltage Vdc.

  According to such a configuration, the scene in which the line voltage of each phase in the electric motor 10 is maintained and the switching element in which an open failure has occurred is most suppressed. For this reason, the torque of the motor can be maintained, and the influence of the open failure element can be further reduced, so that torque fluctuation can be further suppressed.

DESCRIPTION OF SYMBOLS 10 ... Electric motor 11 ... Resolver 12 ... Current sensor 20 ... Controller 21 ... Id * Iq command value calculating part 22 ... Vd * Vq command value calculating part 23 ... Current feedback control part 24 ... Speed / phase detection part 25 ... 3 phase / Two-phase conversion unit 26 ... 2-phase / 3-phase conversion unit 27 ... Open failure determination unit 28 ... Neutral point voltage operation unit 29 ... Dead time correction unit 30 ... PWM calculation unit 40 ... Inverter 41 ... Voltage sensor 50 ... Power supply

Claims (2)

Corresponding to each phase of the multiphase AC motor, a plurality of series circuits of an upper switching element connected to the positive side of the power source and a lower switching element connected to the negative side of the power source are provided. In each of the motor control devices for controlling the multiphase AC motor via an inverter connected to a corresponding phase winding of the multiphase AC motor, the interconnection point of the pair of switching elements in each
Based on the torque command value required for the multi-phase AC motor, the command value of the voltage to be applied to each phase of the multi-phase AC motor, which varies periodically with the neutral point voltage as the center voltage of the amplitude Calculating means for calculating each voltage command value;
Failure determination means for determining an open failure in which the switching element of the inverter continues to be turned off;
Drive means for generating a drive signal for driving the inverter based on a comparison between the voltage level of the carrier that periodically varies around the reference voltage and the voltage command value of each phase;
A correction means for correcting the voltage command value of each phase input to the drive means on the condition that the electric motor is being regeneratively driven when an open failure is determined by the failure determination means;
The correction means includes
When the upper switching element in any phase has an open failure, the neutral point voltage is offset in a direction to decrease from the reference voltage, thereby correcting each of the voltage command values of each phase,
When the lower switching element in any phase has an open failure, each of the voltage command values of each phase is corrected by offsetting the neutral point voltage in the direction of increasing from the reference voltage. An electric motor control device. The correction means includes
When the neutral point voltage is offset in the direction of decreasing from the reference voltage, depending on the difference between the absolute value of the minimum voltage command value of the voltage command values of each phase and the half value of the power supply voltage , Offset the neutral point voltage in the decreasing direction,
In the case where the neutral point voltage is offset in the direction of increasing from the reference voltage, the neutral point voltage is determined according to the difference between the maximum voltage command value of the voltage command values of each phase and the half value of the power supply voltage. The motor control device according to claim 1, wherein the sex point voltage is offset in an increasing direction.

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