JP2015154579A - motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform discharging by a motor coil while preventing a motor from being rotated in an unallowable direction.SOLUTION: A motor control device includes: a motor connected with a rotation mechanism of which the rotating direction is limited; an inverter including a capacitor for smoothing DC power; and a magnetic pole position detection circuit for detecting a rotating state of the motor. The motor control device also includes a control section for controlling an exciting current component that excites the motor together with a permanent magnet and a torque current component that generates torque in the motor, in a motor current supplied from the inverter to the motor. The control section sets the exciting current component to a first predetermined value that is not zero, and sets the torque current component to a second predetermined value which is not zero, in such a manner that the motor is rotated only in a limited direction. Electric charge stored in the capacitor is discharged by a loss caused by Joule heat generated in a coil of the motor.

Description

  The present invention relates to a motor control device, and more particularly to a motor control device for a vehicle drive motor system.

  In a system in which an output from a DC power source is converted into an AC voltage by an inverter and an AC motor is driven, the inverter has an element that performs high-speed switching in order to control the voltage applied to the AC motor. A capacitor for smoothing the fluctuating DC voltage is disposed between the inverter and the DC power source.

During system operation, the contactor between the DC power supply and the inverter is closed, the DC power supply and the inverter are connected, and power is supplied from the DC power supply to the inverter. At this time, electric charge is accumulated in the capacitor, and the voltage of the capacitor becomes substantially the same as the voltage of the DC power supply. The voltage of the DC power supply is usually several hundred volts in a system that requires an output of about several tens of kW such as a hybrid vehicle or an electric vehicle.
The capacitor remains charged even after the DC power source and the inverter are disconnected when the system operation is stopped. When repairing the equipment after the system operation is stopped, it is desirable to discharge the capacitor voltage to a low voltage in a short time when the system operation is stopped in order to ensure the safety of the work.

    Conventionally, a method has been proposed in which Joule heat is generated in a motor winding by passing a current through an AC motor, and a capacitor is discharged due to the loss.

    In a system in which an AC motor is connected to a rotation mechanism with a restricted rotation direction, it is necessary to pass a current through the motor winding so that the AC motor rotates only in the restricted direction during discharge. For example, when an oil pump is connected to an AC motor, the direction of rotation of the oil pump is uniquely determined, and if reverse rotation is applied in the restricted direction, reverse flow of oil due to negative pressure, damage to the oil pump, etc. Will occur.

    Therefore, out of the motor current supplied to the AC motor, the d-axis current command for exciting the motor together with the permanent magnet is set to non-zero, and the q-axis current command for applying torque to the motor is set to zero, whereby the torque is supplied to the motor. A method of discharging without generating has been proposed. For example, there is JP-A-9-70196 as an example, in which the motor torque T is d-axis current Id, q-axis current Iq, d-axis inductance Ld, q-axis inductance Lq, armature linkage flux. This is because it is expressed as “T = p {φ + (Ld−Lq)} Id · Iq” using the constant φ and the number of pole pairs p.

Japanese Patent Laid-Open No. 9-70196

    However, even if the q-axis current command is set to zero, if there is an error in the detected value of the motor magnetic pole position used when converting the motor current into the d-axis current component and the q-axis current component, torque is applied to the motor. A shaft current may be generated, and the motor may rotate forward or negatively.

  A motor control device according to the present invention includes a motor coupled to a rotation mechanism whose rotation direction is limited, an inverter having a capacitor that smoothes DC power, and a magnetic pole position detection circuit that detects a rotation state of the motor. A motor control device that controls a motor comprising: an excitation current component that excites the motor together with a permanent magnet in a motor current supplied from the inverter to the motor; a torque current component that generates torque in the motor; A control unit configured to control the torque current component so that the excitation current component is set to a non-zero first predetermined value and the motor rotates only in a limited direction. A second predetermined value of zero is set, and the electric charge stored in the capacitor is discharged with a loss due to Joule heat generated in the winding of the motor.

  In another embodiment of the motor control device of the present invention, when the control unit detects acceleration of the motor that is equal to or greater than a threshold value after setting the first predetermined value and the second predetermined value to a minimum value. The second predetermined value is decreased, and the first predetermined value and the second predetermined value are increased when an acceleration less than a threshold value is detected.

  According to the present invention, it is possible to discharge the motor winding while suppressing the rotation of the motor in an unacceptable direction.

  Furthermore, the discharge time is shortened while minimizing the generated torque.

1 is a block diagram of a motor control device according to a first embodiment of the present invention. It is a conceptual diagram explaining the torque current and excitation current component in a rotating coordinate system. It is a flowchart explaining the flow from starting to a stop of the motor control apparatus in the 1st Embodiment of this invention. It is a conceptual diagram explaining the shift | offset | difference of a rotating coordinate system when there exists an error in magnetic pole position detection. It is a conceptual diagram explaining the current command when the torque current command considering the theoretical maximum error is set in the positive direction in advance. It is a conceptual diagram explaining the current command on the actual motor when the torque current command considering the theoretical maximum error is set in the positive direction in advance. It is a block diagram of the motor control apparatus in the 2nd Embodiment of this invention. It is the figure which showed the processing flow of the discharge processing apparatus in the 2nd Embodiment of this invention. It is a schematic diagram explaining the state of the excitation current command and the torque current command when increasing the current command while suppressing the torque generated in the motor. It is a schematic diagram explaining the state of the excitation current command and the torque current command when increasing the current command while suppressing the torque generated in the motor. It is a schematic diagram explaining the state of the excitation current command and the torque current command when increasing the current command while suppressing the torque generated in the motor. It is a schematic diagram explaining the state of the excitation current command and the torque current command when increasing the current command while suppressing the torque generated in the motor.

  FIG. 1 is a system diagram illustrating an overview of a motor control device including a DC power source, an AC motor, and a device for performing discharge processing of a capacitor according to the first embodiment of the present invention.

  The system includes a DC power supply 10, a contactor 20, an AC motor 30, a magnetic pole position detection circuit 40 for the AC motor 30, an inverter 50, a capacitor 60, a voltage detection circuit 70 for the capacitor 60, and a current detection circuit 80. The control device 90 and the rotating mechanism 100 connected to the AC motor 30 via a rotating shaft are provided.

  The DC power supply 10 is a DC power supply of several hundreds [V], and supplies power to the inverter 50 when the contactor 20 is in a closed state.

  Capacitor 60 smoothes the output of DC power supply 10 and has the same voltage as DC power supply 10 when contactor 20 is closed. The voltage applied to the capacitor 60 is detected by the voltage detection circuit 70 and transmitted to the control device 90. The electric power supplied from the DC power supply 10 to the inverter 50 is interrupted when the contactor 20 is opened.

    Inverter 50 incorporates a plurality of switching elements (for example, IGBT), and converts power from DC power supply 10 from DC to three-phase AC. The switching element built in the inverter 50 is arranged for each of the three phases on the positive electrode side and the negative electrode side of the DC power supply 10, and changes the pulse width of the voltage generated by the switching of these six elements in total, A pulse width modulation method applied to AC motor 30 is possible.

  AC motor 30 is composed of two parts: a stator having three-phase (U-phase, V-phase, and W-phase) windings, and a rotor that generates torque by magnetic flux that changes when current flows through the windings. The current flowing through AC motor 30 is detected by current detection circuit 80 and transmitted to control device 90.

  The AC motor 30 is connected to a rotation mechanism 100 limited to only normal rotation via a rotation shaft.

  The magnetic pole position detection circuit 40 detects a magnetic pole position that changes as the rotor of the AC motor 30 rotates, and the magnetic pole position is transmitted to the control device 90. The detected value of the magnetic pole position includes an error due to a factor represented by an error that occurs when the magnetic pole position is attached to the AC motor 30 and an error caused by the detection accuracy of the magnetic pole position detection circuit 40.

  The rotation mechanism 100 is a device that is limited to forward rotation only, and includes, for example, an oil pump that pumps oil using torque of a rotation shaft. The rotation direction of the oil pump is uniquely determined. If negative rotation is applied, there is a possibility that reverse flow of oil or damage to the oil pump may occur due to negative pressure.

  The control device 90 includes a rotation speed calculation circuit 91, a current map circuit 92, a PI control circuit 93, a dq / three-phase conversion circuit 94, a PWM signal generation circuit 95, a three-phase / dq conversion circuit 96, a discharge The processing circuit 97 is configured to receive an external torque command from the outside and control the motor current. As shown in FIG. 2, the motor current is converted into an excitation current and a torque current in a rotating coordinate system that rotates according to the magnetic pole position.

  The rotation speed calculation circuit 91 acquires the magnetic pole position θ from the magnetic pole position detection circuit 40, and generates the rotation speed ω of the motor from the amount of change in the magnetic pole position θ.

  The current map circuit 92 outputs a specified torque based on a torque command value received from the outside, and outputs a d-axis current command value Id * that is an excitation current command value and a q-axis current command that is a torque current command value. The value Iq * is generated according to the motor rotation speed ω generated by the rotation speed calculation circuit 91 and the voltage Vdc of the capacitor 60. When the capacitor discharging process is performed with the contactor 20 open, the current map circuit 92 outputs 0 for both the d-axis current command value Id * and the q-axis current command value Iq *.

  The three-phase / dq conversion circuit 96 uses the d-axis actual current value Id and the q-axis based on the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current detection circuit 80 according to the magnetic pole position θ. An actual current value Iq is generated.

  The PI control circuit 93 includes a d-axis current command value Id * and a q-axis current command value Iq * obtained from the current map circuit 92, and a d-axis discharge current command value Id ′ and q-axis obtained from the discharge processing circuit 97. The value obtained by adding the discharge current command value Iq ′, the d-axis actual current value Id obtained from the three-phase / dq conversion circuit 96, and the q-axis actual current value Iq are compared, and PI calculation is performed on the difference. The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are generated.

  The dq / three-phase conversion circuit 94 uses the d-axis voltage command value Vd * and the q-axis voltage command value Vq * to drive the three-phase voltage command values Vu * and Vv * for driving the motor according to the magnetic pole position θ. , Convert to Vw *.

  The PWM signal generation circuit 95 generates a PWM drive signal for on / off control of the switching element built in the inverter 50 based on the three-phase voltage command values Vu *, Vv *, Vw * and the capacitor voltage Vdc.

  The discharge processing circuit 97 outputs a d-axis discharge current command value Id ′ and a q-axis discharge current command Iq ′ necessary for discharging by the winding of the motor when the contactor 20 is in the open state to perform the capacitor discharging process. When the contactor 20 is closed and the AC motor 30 is controlled, the discharge processing circuit 97 outputs 0 for both the d-axis discharge current command value Id ′ and the q-axis discharge current command Iq ′.

  FIG. 3 is a flowchart for explaining the flow from start to stop of the motor control device.

When the system is started in Step 10, the contactor 20 is closed in Step 20, whereby the DC power supply 10 and the inverter 50 are connected, and a voltage is applied to the capacitor 60.
When the preparation for controlling the AC motor 30 is completed, the process proceeds to step 30, and the AC motor 30 can be controlled. The control device 90 determines the d-axis current command value Id * and the q-axis current command from the target external torque command. Calculation of the value Iq * and output control of the PWM signal are performed.
When a stop request to the system is confirmed in step 40, the contactor 20 is opened in step 50, and the DC power supply 10 and the inverter 50 are electrically disconnected.
Next, in order to discharge the electric charge remaining in the capacitor 60, a discharging process in step 60 is performed.
When the voltage of the capacitor 60 falls below a predetermined value due to the discharge process, the completion of the discharge process is confirmed in step 70, and the system is stopped in step 80.

Next, details of the discharge processing circuit 97 which is a characteristic part of the present embodiment will be described.
In order to prevent the motor from rotating negatively during the discharge process, the torque T expressed by Equation 1 must always be 0 or more. Therefore, the discharge current command is set so that the torque current Iq flowing to the motor is 0 or more. It is necessary to set a value.
[Equation 1]
T = Pn • (Φ + (Ld − Lq) • Id) • Iq
here,
Pn: the number of pole pairs of the motor,
Φ [Wb]: Motor flux,
Ld [H]: d-axis inductance,
Lq [H]: q-axis inductance,
Id, Iq: Excitation current and torque current on the actual motor On the other hand, the detection value of the magnetic pole position by the magnetic pole position detection circuit 40 includes errors due to a plurality of factors as described above. Assuming that the detection error is θe, the rotational coordinate system (broken line in FIG. 4) on the real motor is shifted by the error θe with respect to the rotational coordinate system (solid line in FIG. 4) viewed from the control device 90.

  Therefore, the motor can be prevented from rotating negatively by setting a discharge current command value that does not cause the torque current on the actual motor to be negative even when the maximum theoretical error value of the detected value of the magnetic pole position exists.

  5 and 6 show a state where the discharge current command value is set so that the torque current does not become negative as described above. Assuming that the maximum theoretical error of the detected value of the magnetic pole position is the theoretical maximum error θm in FIG. 5, the discharge processing circuit 97 has the torque current component Iq in consideration of the excitation current component Id necessary for the discharge and the theoretical maximum error θm. A current command I consisting of is set.

  The current command I becomes a current component I ′ as shown in FIG. 6 on the actual motor, and the rotation axis of the current component is deviated because of an error in detecting the magnetic pole position (broken line in FIG. 6).

  Here, since the deviation of the rotation axis is within the theoretical maximum error θm, the torque current component Iq ′ is always 0 or more, and negative rotation of the motor can be prevented.

  Further, since the discharge process is performed after a system stop request, it is necessary to suppress the torque transmitted from the AC motor 30 to the rotating mechanism 100 as much as possible during the discharge process.

  For example, when the rotation mechanism 100 is an oil pump, it is desired to suppress generation of unnecessary hydraulic pressure as much as possible after a system stop request.

  On the other hand, when the contactor 20 is changed from the closed state to the open state, a high voltage of several hundreds V remains in the capacitor. Therefore, it is desired that the time until the discharge process is completed is as short as possible.

  As described above, in this embodiment, the discharge current command is set as follows.

  The d-axis discharge current command value Id´ is set to a value that satisfies the desired discharge processing completion time, and the q-axis discharge current command value Iq´ has the maximum theoretical error of the detected value of the magnetic pole position described above. Even if the torque current on the actual motor does not become negative, set it to the minimum value.

  The specific value of the d-axis discharge current command value Id ′ is obtained from the relationship between the charge remaining in the capacitor and the loss due to Joule heat generated in the motor winding.

  In addition, although the present Example showed the example which used the rotation mechanism 100 restrict | limited only to positive rotation, it is applicable also when the rotation mechanism 100 is restrict | limited only to negative rotation.

  In that case, the q-axis discharge current command value Iq ′ is set to the minimum value at which the torque current is not positive.

  FIG. 7 is a system diagram illustrating an outline of a motor control device including a DC power source, an AC motor, and a device that performs discharge processing of a capacitor according to the second embodiment. In the present embodiment, discharge control circuit 97 receives rotation speed ω output from rotation speed calculation circuit 91 as input, and calculates acceleration from the amount of change in rotation speed ω.

  In addition, about the element which has the same function as Example 1, the description is abbreviate | omitted by providing the same code | symbol. Furthermore, the duplicate description is omitted about the same effect | action and effect obtained by having having the same structure as Embodiment 1. FIG.

  In FIG. 8, the d-axis discharge current command value Id ′ and the q-axis discharge current command value Iq ′ are set to a predetermined value 1 and a predetermined value 2, respectively, and the predetermined value 1 and the predetermined value 2 are changed according to the acceleration of the motor. FIG. 6 is a diagram illustrating a processing flow of a discharge processing circuit 97 that performs a discharge process while suppressing torque generated in the AC motor 30.

  In step 10, the calculation process of the discharge current command value in the discharge process is started. In step 20, the minimum value in consideration of the theoretical maximum error θm shown in the first embodiment is set to the predetermined value 1 and the predetermined value 2. The minimum value is the minimum control resolution.

  When the acceleration of the motor is less than the threshold value (step 30), the discharge current command value equivalent to step 20 is added to the predetermined value 1 and the predetermined value 2 in step 50.

  If step 50 is repeated and the acceleration of the motor becomes equal to or greater than the threshold, in step 40, the minimum resolution is subtracted from the predetermined value 2 of the set discharge current command value. Step 40 is repeated until the motor acceleration is below the threshold.

  By repeating the above steps 30, 40, and 50, the predetermined value 1 and the predetermined value 2 are increased without generating negative torque in the motor.

  At this time, if the predetermined value 1 reaches the value necessary for discharge in step 60, the discharge current command value is determined and held until the discharge is completed.

  9, 10, 11, and 12 are diagrams for explaining the outline of the predetermined value 1 and the predetermined value 2 that are increased and decreased by the processing flow of the discharge processing circuit 97 shown in FIG.

  FIG. 9 is a schematic diagram showing the predetermined value 1 and the predetermined value 2 in step 20 in FIG. After starting the calculation process of the discharge current command in the discharge process in Step 10, the discharge current command in which the torque discharge current corresponding to the theoretical maximum error θm is applied in the positive direction is set to the predetermined value 1 and the predetermined value 2 in the minimum unit of resolution. Set to. By inputting the discharge current command for each minimum unit, it is possible to detect a discharge current command in which acceleration equal to or greater than a threshold value occurs in AC motor 30.

When the acceleration of AC motor 30 is less than the threshold value, a discharge current command in which a torque discharge current command corresponding to the theoretical maximum error θm is applied in the positive direction is added to predetermined value 1 and predetermined value 2 for the minimum unit of resolution. (Fig. 10)
When the acceleration becomes equal to or greater than the threshold value in step 30, the predetermined value 1 is left as it is and the predetermined value 2 is subtracted as shown in FIG.

  By repeating the process of FIG. 11, the acceleration of the AC motor 30 is set to be less than the threshold value.

  Once the predetermined value 2 is subtracted (step 40), if the acceleration is less than the threshold value, the minimum resolution of the discharge current command value is added to the predetermined value 1 and the predetermined value 2 as shown in FIG.

  As a result, the torque generated by the AC motor 30 is suppressed as much as possible, and a current of a magnitude necessary for discharging can be passed through the motor winding in a state where the motor is not rotated negatively.

  The setting of the threshold value related to acceleration is determined in consideration of, for example, the magnitude of torque that is allowed to be transmitted to the rotation mechanism 100 after a system stop request.

  In addition, although the present Example showed the example which used the rotation mechanism 100 restrict | limited only to positive rotation, it is applicable also when the rotation mechanism 100 is restrict | limited only to negative rotation.

  In that case, the predetermined value 1 and the predetermined value 2 are increased in the negative direction without generating positive torque in the motor. In addition, adaptation is possible by reversing the motor acceleration, torque discharge current, predetermined value 1 and predetermined value 2 operations of the second embodiment in the positive and negative directions.

DESCRIPTION OF SYMBOLS 10 DC power supply 20 Contactor 30 AC motor 40 Magnetic pole position detection circuit 50 Inverter 60 Capacitor 70 Voltage detection circuit 80 Current detection circuit 90 Control apparatus 100 Rotation mechanism

Claims (2)

A motor control apparatus for controlling a motor, comprising: a motor connected to a rotation mechanism whose rotation direction is limited; an inverter having a capacitor for smoothing DC power; and a magnetic pole position detection circuit for detecting a rotation state of the motor. Because
A control unit that controls an excitation current component that excites the motor together with a permanent magnet in a motor current supplied from the inverter to the motor, and a torque current component that generates torque in the motor;
The controller sets the excitation current component to a non-zero first predetermined value, sets the torque current component to a non-zero second predetermined value so that the motor rotates only in a limited direction, A motor control device that discharges the electric charge stored in the capacitor by a loss due to Joule heat generated in the winding of the motor. The motor control device according to claim 1,
The control unit decreases the second predetermined value when detecting acceleration of the motor that is equal to or greater than a threshold value after detecting the first predetermined value and the second predetermined value to a minimum value, and detects acceleration that is less than the threshold value. A motor control device that increases the first predetermined value and the second predetermined value when the control is performed.