JP2015080290A - Motor control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction in drivability of a vehicle by suppressing influences of current sensor abnormality.SOLUTION: A motor control system 8 includes a control device 40 that controls a motor 30 via an inverter 20. The control device 40 generates first voltage commands Vd* and Vq* through feedforward control from a torque command Tq* and a motor rotation speed θ of the motor 30, converts the torque command Tq* of the motor 30 into current commands Id* and Iq* and generates a second voltage command through feedback control from a current deviation that is a differential between real currents Id and Iq detected by a current sensor 31 and the current commands Id* and Iq*. The first voltage commands Vd* and Vq* and the second voltage command are added and defined as voltage command values Vd# and Vq# of the motor. When abnormality of the current sensor 31 is detected, a gain to be used for the feedback control of the motor 30 is reduced further than that in normal time.

Description

  The present invention relates to a motor control system that controls a motor via an inverter.

  Conventionally, an electric vehicle such as a hybrid vehicle or an electric vehicle that travels by the power of a motor is known. In a motor control system mounted on such an electric vehicle, the drive of the motor is normally controlled using an inverter.

  In the motor drive system, the operation of a drive circuit such as an inverter is controlled according to a required torque instructed by a user operation of an accelerator or a brake, and the motor is driven. At this time, the current supplied from the inverter to the motor is fed back to the drive circuit, and feedback control may be performed so as to match the current command value calculated from the required torque. The current actually supplied to the motor is detected by a current sensor provided in a power line connecting the inverter and the motor.

  As a related document, Patent Document 1 discloses that a sum of a feed-forward motor voltage generation value and a feedback feedback motor voltage generation value is controlled as a motor voltage command value in an induction motor buckle control device. It is described to do. In this vector control device as well, it is stated that the motor current used for feedback control is detected by three current sensors corresponding to the number of motor phases.

JP 2001-169599 A

  If a failure occurs in the current sensor or the like, the motor drive voltage cannot be correctly generated by feedback. As a result, the feedback voltage is larger or smaller than the actual voltage until a current sensor abnormality is detected and the vehicle shifts to the fail-safe mode, causing vehicle acceleration / deceleration to change the vehicle output. However, there is a problem that drivability deteriorates. Here, the fail-safe mode is a safety measure for securing the power necessary to safely evacuate the vehicle to the road shoulder, repair shop, etc. when it is determined that there is an abnormality in the current sensor or the like. .

  An object of the present invention is to provide a motor control system capable of reducing a fluctuation in motor output at the time of failure of a current sensor in current feedback control and suppressing a decrease in drivability of a vehicle.

  A motor control system according to the present invention includes a motor, an inverter connected to the motor, a current sensor that detects a current flowing between the inverter and the motor, and a control device that controls the inverter to drive the motor. The motor control system comprises a control device, wherein the control device generates a first voltage command by feedforward control from the torque command of the motor and a motor rotation speed, converts the torque command of the motor into a current command, and uses the current sensor. A second voltage command is generated by feedback control from a current deviation that is a difference between the detected actual current and the current command, and the first voltage command and the second voltage command are added to obtain the voltage command value of the motor. When the abnormality of the current sensor is detected, the gain used in the feedback control of the motor is made smaller than normal. It is intended.

  According to the motor control system of the present invention, when the abnormality of the current sensor is detected, the gain used for the feedback control of the motor is made smaller than that in the normal state, so that the influence of the abnormality detection value output from the current sensor is reduced. be able to. Thereby, the voltage command value of the motor is less likely to change suddenly due to the influence of the current sensor abnormality, so that there is no significant influence on the behavior of the vehicle (for example, sudden acceleration or sudden deceleration). Therefore, even if an abnormality occurs in the feedback control system, a decrease in drivability can be suppressed.

It is a figure which shows roughly the structure of the motor control system which is one embodiment of this invention. It is a block diagram which shows the PI control part in the control apparatus of FIG. It is a graph which shows the time when abnormality of a current sensor is detected in the control apparatus of FIG. 1, and the relationship between dq-axis current. It is a graph which shows the control change process by the control apparatus of FIG. 1 by the relationship between time and torque.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to the application, purpose, specification, and the like. In addition, when a plurality of embodiments and modifications are included in the following, it is assumed from the beginning that these characteristic portions are used in appropriate combinations.

  In the following description, the motor control system is used as an example of a vehicle on which a motor is mounted. However, the motor control system may be other than the vehicle as long as it uses a motor control system that executes vector control.

  The vehicle will be described as using one motor / generator having a motor function and a generator function as a motor. However, this is an example, and two or more motors / generators may be used. Good. Alternatively, one motor having only a motor function and one motor having only a generator function may be used. In addition to the motor, the vehicle may be a hybrid vehicle equipped with an engine. In this case, the vehicle may be a hybrid vehicle provided with a charging port on the vehicle body.

  Hereinafter, a configuration including a battery that is a voltage source, a voltage converter, an inverter, and a smoothing capacitor will be described as a power supply circuit connected to the motor. However, this is an example and may include other elements. Good. For example, a system main relay, a low voltage DC / DC converter, etc. can be included. In addition to the battery, a fuel cell may be included as a voltage source. Further, the voltage converter may be omitted and the voltage of the voltage source may be supplied to the inverter as it is.

  FIG. 1 is a diagram showing an overall configuration of a motor control system 8 for a motor mounted on a vehicle. The motor control system 8 includes a motor 30, a power supply circuit 10 connected to the motor 30, and a control device 40 that controls the operation of these components as a whole. The control device 40 is an assembly of circuits having several control functions. Here, the control device 40 is shown mainly with respect to a portion that performs vector control. Parts 62 and 64 to be changed are shown.

  The motor 30 is a motor generator (MG) mounted on the vehicle and functions as a motor when electric power is supplied from a battery 12 as a voltage source included in the power supply circuit 10, and is driven by an engine not shown. It is a three-phase synchronous motor that functions as a generator when driving or braking a vehicle.

  The rotational position sensor 32 provided in the motor 30 has a function of detecting the rotational position of the rotor as the rotational angle θ. For example, a resolver can be used as the rotational position sensor 32. The detected rotation angle θ data is transmitted to the control device 40 through an appropriate signal line. In the control device 40, the rotation angle θ is used for vector control, and is converted into the rotation speed ω of the motor 30 from the time derivative of the rotation angle θ and used for voltage command calculation of the motor 30 and the like.

  The power supply circuit 10 is a circuit connected to the motor 30 and supplies electric power to the motor 30 when the motor 30 functions as a drive motor, or receives regenerative power when the motor 30 functions as a generator and receives the battery 12. Has the function of charging. The power supply circuit 10 includes a battery 12 as a secondary battery, a smoothing capacitor 14 on the battery 12 side, a voltage converter 16, a smoothing capacitor 18 on the inverter 20 side, and an inverter 20.

  The battery 12 is a voltage source that supplies driving power for the motor 30. For example, a lithium ion assembled battery or a nickel hydride assembled battery having a voltage between terminals of about 200V can be used. Instead of the battery 12, a power storage device such as a capacitor may be used as a voltage source.

  The voltage converter 16 is a circuit having a function of boosting the voltage on the battery 12 side to, for example, about 650 V using the energy storage action of the reactor, and is also called a boost converter. The voltage converter 16 has a bi-directional function, and when supplying power from the inverter 20 side as charging power to the battery 12 side, it also has an action of stepping down the high voltage on the inverter 20 side to a voltage suitable for the battery 12. .

  The smoothing capacitor 14 on the battery 12 side and the smoothing capacitor 18 on the inverter 20 side have a function of suppressing and smoothing fluctuations in voltage and current between the positive electrode bus and the negative electrode bus on the respective sides. The voltage VH between the positive electrode bus and the negative electrode bus on the inverter 20 side is called a system voltage.

  The inverter 20 is configured to include a plurality of switching elements that operate under the control of the control device 40, and is a circuit that performs power conversion between AC power and DC power. The inverter 20 converts the DC power from the battery 12 side into AC three-phase driving power when the vehicle is powered, and supplies it as driving power to the motor 30, and conversely when the vehicle is braking, the motor 30 AC / DC conversion function for converting AC three-phase regenerative power from the DC to DC power and supplying the battery 12 as a charging current.

  A current flowing through each of the three wirings connecting the inverter 20 and the motor 30 is detected using an appropriate current sensor 31 as a current flowing in each phase of the motor 30 and transmitted to the control device 40. Since each phase coil of the motor 30 is commonly connected at the neutral point, each phase current flowing through the motor 30 is (U phase current value Iu + V phase current value Iv + W phase current value Iw) = 0. Therefore, even if each of the three phase currents is not detected, two phase currents are detected, and the remaining phase currents can be obtained by calculation using the above relationship. In the example of FIG. 1, since it is shown that the U-phase current Iu and the V-phase current Iv are detected, the remaining W-phase current Iw is obtained by calculation. The detected phase currents are transmitted to the control device 40 through appropriate signal lines. In the vector control, the control device 40 first converts the d-axis current value Id and the q-axis current value Iq, and compares them with the d-axis current command value Id * and the q-axis current command value Iq * to be used for current feedback control. It is done.

  The control device 40 has a function of controlling the operation of the motor 30 mounted on the vehicle as a whole through control of the power supply circuit 10 and the like. In particular, here, the operation of the motor 30 is controlled by vector control, and the control method is switched while an abnormality is detected in the current sensor 31 and the mode shifts to the fail-safe mode. First, a part related to vector control will be described, and then a part related to switching of control methods will be described.

  The operation control of the motor 30 is switched between the rectangular wave mode, the overmodulation mode, and the sine wave PWM mode depending on the operation conditions of the motor 30. Here, a configuration for performing sine wave PWM control will be mainly described.

  The part related to vector control is a part that performs current feedback control in sinusoidal PWM control. That is, in the sine wave PWM control mode, each phase current value of the motor 30 is converted into the d-axis current value Id and the q-axis current value Iq in the three-phase two-phase coordinate conversion unit 42, while the torque command value Tq *. To calculate a d-axis current command value Id * and a q-axis current command value Iq *. Then, current feedback is performed in which the d-axis current value Id is fed back to the d-axis current command value Id *, and the q-axis current value Iq is fed back to the q-axis current command value Iq *.

  The three-phase two-phase coordinate conversion unit 42 obtains two current values and a rotation angle θ among the respective phase currents of the motor 30, and calculates the d-axis current value Id and the q-axis current value Iq based on each phase current value. Has a function to calculate. In the example of FIG. 1, coordinate conversion is performed based on the U-phase current value Iu, the V-phase current value Iv, and the rotation angle θ of the motor 30.

  The torque command value Tq * is calculated based on a user request torque obtained from an accelerator opening degree not shown. The current command generation unit 44 has a function of calculating the torque command value Tq * as a set of the d-axis current command value Id * and the q-axis current command value Iq * using, for example, a table or map created in advance.

Further, the control device 40 includes a Vdq map 60 created in advance. Vdq map 60
Is stored in a storage device (not shown). The Vdq map 60 has a function of generating a set of a d-axis voltage command Vd * and a q-axis voltage command Vq * as a first voltage command according to the input torque command value Tq *. The generated d-axis voltage command Vd * and q-axis voltage command Vq * are input to a PI control unit 50 described later. In the present embodiment, the d-axis voltage command Vd * and the q-axis voltage command Vq * have been described as being generated from a map. However, the present invention is not limited to this, and is in a form other than a map (for example, a table). It may be stored, or may be calculated based on the torque command value Tq * and the motor rotation speed ω (or the motor rotation speed).

  FIG. 2 is a block diagram showing the PI control unit 50 of the control device 40 in FIG. As shown in FIG. 2, the PI control unit 50 includes subtractors 46 and 48, a PI calculation unit 51, and adders 47 and 49.

  The subtractor 46 has a function of subtracting the d-axis current value Id from the d-axis current command value Id * input to the PI control unit 50 and calculating a d-axis current deviation ΔId that is a difference between them. The subtractor 48 has a function of subtracting the q-axis current value Iq from the q-axis current command value Iq * input to the PI control unit 50 to calculate the q-axis current deviation ΔIq. Here, the d-axis current value Id and the q-axis current value Iq correspond to the motor actual current input from the three-phase / two-phase coordinate conversion unit 42 to the PI control unit 50.

The PI calculation unit 51 performs proportional-integral control on the d-axis current deviation ΔId and the q-axis current deviation ΔIq under a predetermined gain, and sets the corresponding d-axis voltage deviation ΔVd and q-axis voltage deviation ΔVq to the second value. It has a function to generate as a voltage command. Specifically, the PI calculation unit 51 calculates the d-axis voltage deviation ΔVd and the q-axis voltage deviation ΔVq by the following formulas (1) and (2).
ΔVd = Kpd (Id * −Id) + Kid (Id * −Id) dt (1)
ΔVq = Kpq (Iq * −Iq) + Kiq (Iq * −Iq) dt (2)
In equations (1) and (2), Kpd and Kpq are proportional gains for dq axis current control, and Kid and Kiq are integral gains for dq axis current control.

  The adder 47 has a function of generating the d-axis voltage command value Vd # by adding the d-axis voltage deviation ΔVd calculated by the PI calculation unit 51 to the d-axis voltage command Vd *. The adder 49 has a function of adding the q-axis voltage deviation ΔVq calculated by the PI calculation unit 51 to the q-axis voltage command Vq * to generate a q-axis voltage command value Vq #. The d-axis voltage command Vd # and the q-axis voltage command value Vq # generated by the PI control unit 50 are input to the two-phase / three-phase coordinate conversion unit 56.

  The two-phase / three-phase coordinate conversion unit 56 has a reverse conversion relationship with the three-phase / two-phase coordinate conversion unit 42 described above, and has a function of converting a dq voltage value into each phase voltage value. That is, it has a function of converting the d-axis voltage command value Vd # and the q-axis voltage command value Vq # into the phase voltage command values Vu, Vv, Vw based on the rotation angle θ of the motor 30. In these conversions, the system voltage VH supplied from the voltage converter 16 to the inverter 20 is also reflected.

  The PWM generation unit 54 has a function of generating a control signal for each switching element constituting the inverter 20 by comparing each phase voltage command value Vu, Vv, Vw with a carrier that is a predetermined carrier wave. The inverter 20 is a circuit that performs power conversion between AC power and DC power as described above. Since the inverter 20 includes six switching elements in the example of FIG. 1, six control signals are output from the PWM generator 54 to the inverter. 20 is supplied. As a result, a PWM signal of each phase corresponding to each phase voltage command value is supplied to the motor 30.

  In this manner, in the sine wave PWM control mode, control is performed in which the actual current values Id and Iq of the motor 30 are fed back with respect to the current command values Id * and Iq * corresponding to the torque command value Tq *.

  Since the portion related to the vector control has been described above, the change of the control method when an abnormality is detected in the current sensor 31 in the control device 40 will be described with reference to FIGS. FIG. 3 is a graph showing the relationship between time and dq-axis current when an abnormality of the current sensor 31 is detected in the control device 40 of FIG. FIG. 4 is a graph showing the control change process by the control device 40 of FIG. 1 in relation to time and torque.

  As shown in FIG. 1, the control device 40 includes a current sensor abnormality detection unit 62 and a dPI control change processing unit 64. The current sensor abnormality detection unit 62 has a function of detecting an abnormality of the current sensor 31 that measures each phase current flowing through the motor 30. Specifically, the current sensor abnormality detection unit 62 determines whether the absolute values of the d-axis current value Id and the q-axis current value Iq acquired from the three-phase / two-phase coordinate conversion unit 42 are greater than a predetermined current threshold value Ithr. To monitor.

  Then, as shown in FIG. 3, when at least one of the absolute values of the d-axis current value Id and the q-axis current value Iq becomes larger than the current threshold value Ithr at time t1, the current sensor 31 is suspected of being abnormal. Is continued for a predetermined time or more, a temporary abnormality flag is set at the timing of time t2. Here, the time interval between the times t1 and t2 can be set to, for example, one control cycle, specifically, ten to several tens of msec.

  The current sensor abnormality detection unit 62 then continues when a state in which the absolute values of the d-axis current value Id and the q-axis current value Iq are larger than a predetermined current threshold value Ithr continues for a predetermined time threshold value tthr (for example, 200 to 300 msec). The determination of the current sensor abnormality is finalized at the timing of time t3, and the mode is shifted to the fail safe mode. Here, the fail-safe mode is a safety measure for securing the power necessary to safely evacuate the vehicle to the road shoulder or repair shop when it is determined that there is an abnormality in the feedback system such as the current sensor. That is. Specifically, in the case of a multi-motor type electric vehicle, the motor voltage command value Vd *, Vq * or the motor current command value is switched in one motor type electric vehicle to switch to running by another motor without abnormality of the current sensor. Limiting Id * and Iq * to permit only sine wave PWM control at a low vehicle speed, or switching to engine running in a hybrid vehicle.

  The current sensor abnormality detection unit 62 determines that the sensor temporary abnormality flag indicates that the absolute value of each of the d-axis current value Id and the q-axis current value Iq is not greater than the predetermined current threshold value Ithr beyond the time threshold value tthr. It is determined that no abnormality has occurred in the current sensor 31. By doing so, it is possible to avoid a current sensor abnormality being immediately detected when the current value increases instantaneously due to a disturbance such as noise.

  When the sensor abnormality confirmation signal is input from the current sensor abnormality detection unit 62, the PI control change processing unit 64 changes the processing of the PI calculation unit 51 in the PI control unit. Specifically, the proportional gains Kpd and Kpq and the integral gains Kid and Ki used for the calculation of PI control (the above formulas (1) and (2)) are set smaller than normal. More specifically, the proportional gains Kpd and Kpq and the integral gains Kid and Ki are all set to zero.

  Thereby, both the d-axis voltage deviation ΔVd and the q-axis voltage deviation ΔVq calculated by the PI calculation unit 51 become zero. Therefore, dq-axis voltage command values Vd # and Vq # output from PI control unit 50 via adders 47 and 49 are derived from Vdq map 60 based on torque command value Tq * and motor rotation speed ω. The d-axis voltage command Vd * and the q-axis voltage command Vq * become the d-axis voltage command value Vd # and the q-axis voltage command value Vq # as they are.

  That is, in this case, feed-forward control based on the torque command value Tq * and the motor rotation speed ω is executed instead of the current feedback control using the value detected by the current sensor 31. As described above, when the abnormality of the current sensor 31 is detected, the gain used for feedback control of the motor 30 is made smaller than that in the normal state, so that the influence of the abnormality detection value output from the current sensor 31 can be reduced. As a result, the voltage command value of the motor 30 is unlikely to change suddenly due to the influence of the abnormality of the current sensor, so that there is no significant influence on the behavior of the vehicle (for example, sudden acceleration or sudden deceleration). Therefore, even if an abnormality occurs in the feedback control system, a decrease in drivability can be suppressed.

  Referring to FIG. 4, the conventional torque fluctuation state is indicated by a one-dot chain line, and the torque fluctuation state by the feedforward control in the present embodiment is indicated by a solid line 71. In the conventional configuration, the current feedback control was performed during the period from the temporary abnormality of the current sensor (time t2) to the transition to the fail-safe mode. Therefore, the torque suddenly increases (or decreases) due to the abnormality of the current sensor 31. As a result, a sudden acceleration feeling (or a sudden deceleration feeling) due to torque fluctuation may be given to the user of the vehicle. On the other hand, according to the present embodiment, as indicated by a solid line 71 in FIG. 7, the torque fluctuation at the time of detecting a temporary abnormality of the current sensor can be reduced, and as a result, a decrease in drivability can be suppressed. is there.

  In addition, this invention is not limited to embodiment mentioned above and its modification, A various improvement and improvement are possible in the matter described in a claim, and its equivalent range.

  For example, in the above description, the proportional gains Kpd and Kpq and the integral gains Kid and Kiq are all set to zero when a temporary abnormality of the current sensor 31 is detected. However, the present invention is not limited to this. For example, only the proportional gains Kpd and Kpq may be set to zero, or the values of the proportional gains Kpd and Kpq and the integral gains Kid and Ki may be made smaller than normal.

  When only the proportional gains Kpd and Kpq are zeroed, the values of the integral terms including the integral gains Kid and Ki are output as ΔVd and ΔVq, and the torque Tq is the previously calculated value as indicated by the solid line 72 in FIG. It will be maintained at Tq_pre. Also, when the values of the proportional gains Kpd, Kpq and the integral gains Kid, Ki are smaller than normal values, as shown by the solid line 73 in FIG. By suppressing the increase rate, it is possible to suppress a sense of incongruity such as rapid acceleration given to the user. Also by these, the same operation effect as embodiment mentioned above can be produced.

  8 motor control system, 10 power supply circuit, 12 battery, 14, 18 smoothing capacitor, 16 voltage converter, 20 inverter, 30 motor, 31 current sensor, 32 rotational position sensor, 40 control device, 42 3-phase 2-phase coordinate conversion unit , 44 Current command generation unit, 46, 48 subtractor, 47, 49 adder, 50 PI control unit, 51 PI calculation unit, 56 2-phase 3-phase coordinate conversion unit, 54 PWM generation unit, 60 Vdq map, 62 Current sensor Abnormality detection unit, 64 control change processing unit, 71, 72, 73 Solid line.

Claims (1)

A motor control system comprising: a motor; an inverter connected to the motor; a current sensor that detects a current flowing between the inverter and the motor; and a control device that controls the inverter to drive the motor,
The control device generates a first voltage command by feedforward control from the torque command of the motor and the motor rotation speed, converts the torque command of the motor into a current command, and the actual current detected by the current sensor and the current A second voltage command is generated by feedback control from a current deviation that is a difference from the command, and the first voltage command and the second voltage command are added to obtain a voltage command value of the motor, and an abnormality of the current sensor is detected. If this is done, the gain used in the feedback control of the motor is made smaller than normal,
Motor control system.

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