JP4403781B2 - SR motor control device - Google Patents

Description

  The present invention relates to a control device for an SR motor, and more particularly to a device for driving and controlling an SR motor by performing current feedback control.

  As a torque control method for the SR motor, a method is known in which the energization start timing and energization end timing of the motor coil are determined, and the peak value of the motor coil current is controlled by a hysteresis comparator (see Patent Document 1). In this conventional method, the feed-forward control is performed by mapping the energization start timing and the energization end timing in advance.

JP 2002-281784 A

  However, current control using feedforward control has a problem that current control accuracy is low.

An SR motor control apparatus and control method according to the present invention controls an inverter that applies a voltage to an SR motor by the following method. The current value flowing in each phase of the SR motor is detected, and the sign of the detected current value is manipulated. The phase current values engineered code is converted into a current value on the orthogonal coordinate system rotating in synchronization with the rotation of the SR motor, in the orthogonal coordinate system, based on the converted current value and the current command value Then, the motor control voltage is calculated. The calculated motor control voltage is converted into a three-phase AC voltage, its absolute value is calculated, and an inverter that applies a voltage to the SR motor is controlled based on the calculated absolute value.

  According to the SR motor control device and control method of the present invention, the current flowing through the SR motor can be feedback-controlled, so that the current control accuracy can be improved.

-First embodiment-
FIG. 1 is a bottom view showing a schematic overall configuration of an electric vehicle using an SR motor (Switched Reluctance Motor) 1 as a travel drive source. The electric vehicle includes front left and right wheels 20a and 20b and rear left and right wheels 20c and 20d. SR motors 1a and 1b for rotating the wheels 20a and 20b are attached to axles 21a and 21b that rotatably support the two front wheels 20a and 20b, respectively. The SR motors 1 a and 1 b are supplied with electric power from the DC power supply 4 via the inverter 2.

FIG. 2 is a diagram showing the configuration of the first embodiment of the SR motor control device according to the present invention. Hereinafter, a method for controlling the SR motors 1a and 1b for driving the vehicle mounted on the electric vehicle by the SR motor control device according to the first embodiment will be described. However, hereinafter, the SR motors 1a and 1b are collectively referred to as the SR motor 1. The motor control device in the first embodiment includes a unipolar drive inverter 2, a smoothing capacitor 3, a DC power supply 4, a rotational position sensor 5, a phase speed calculator 6, a current code converter 7, a current coordinate system. It includes a converter 8, a torque controller 9, a current controller 10, a voltage coordinate converter 11, a voltage command generator 12, a gate drive signal generator 13, and current sensors 100a to 100c.

  In the motor control apparatus according to the first embodiment, various controls are performed in an orthogonal coordinate system that rotates in synchronization with rotation of a rotor (not shown) of the SR motor 1, that is, a dq coordinate system having a d axis and a q axis. Perform the operation. The rotational position sensor 5 is an encoder, for example, and detects the rotor position θm of the SR motor 1.

  Based on the rotational position θm detected by the rotational position sensor 5, the phase velocity calculator 6 calculates the electrical phase θe used for the control calculation on the dq coordinate system, and time-differentiates θm to obtain SR. The mechanical angular velocity ωm of the motor 1 is calculated. FIG. 3 is a diagram showing the U-phase inductance of the SR motor 1 that changes according to the rotation of the rotor of the SR motor 1. In the motor control apparatus according to the first embodiment, two periods of the fundamental wave component of the inductance change are set as one period of the electrical phase θe in the dq coordinate system.

  Current sensors 100 a, 100 b, and 100 c detect U-phase current Iu, V-phase current Iv, and W-phase current Iw that flow through SR motor 1, and output them to current code converter 7. The current code converter 7 performs a process of converting the signs of the U-phase, V-phase, and W-phase current values according to the electrical phase θe calculated by the phase velocity calculator 6.

  For example, regarding the U-phase current Iu, the sign is not converted when 0 ≦ θe <π, and the sign is converted and output when π ≦ θe <2π. That is, if the output current value of the U phase output from the current code converter 7 is Ius, Ius = Iu when 0 ≦ θe <π, and Ius = −Iu when π ≦ θe <2π. It becomes. FIG. 4 is a diagram showing the relationship between the U-phase inductance corresponding to the phase θe, the U-phase current detection value Iu, and the output current value Ius output from the current sign converter 7. As shown in FIG. 4, the output current Iu can be handled as an alternating current by manipulating the sign of the current in accordance with the phase θe.

  The output current value Ivs after the sign conversion processing of the V-phase current Iv is set to Ivs = Iv when 2π / 3 ≦ θe <5π / 3, and when 5π / 3 ≦ θe <8π / 3. , Ivs = −Iv. The output current value Iws after the sign conversion process of the W-phase current Iw is set to Iws = Iw when −2π / 3 ≦ θe <π / 3, and when π / 3 ≦ θe <4π / 3. And Iws = −Iw. Thereby, the current of the U phase, the V phase, and the W phase can be handled as a three-phase alternating current.

  The current coordinate converter 8 converts the currents Ius, Ivs, Iws output from the current sign converter 7 into a d-axis current Id and a q-axis current Iq in the dq coordinate system based on the following equation (1).

The torque controller 9 calculates a d-axis current command value Id ^* and a q-axis current command value Iq ^{* of} the motor based on the torque command value Te ^* of the SR motor 1 and the motor rotation speed ωm. The torque controller 9 calculates the current command values Id ^* and Iq ^* by referring to a map prepared in advance using the torque command value Te ^* and the motor rotation speed ωm as coordinate axes.

FIG. 5 is a block diagram showing the configuration of the current controller 10. The current controller 10 includes subtracters 200a and 200b and PI controllers 201a and 201b. The subtractor 200a calculates the difference between the current command value Id ^* calculated by the torque controller 9 and the d-axis actual current id input from the current coordinate converter 8, and the calculation result is calculated by the PI controller 201a. Output to. The subtractor 200b calculates the difference between the current command value Iq ^* and the q-axis actual current Iq, and outputs the calculation result to the PI controller 201b.

The PI controller 201a calculates a d-axis voltage command value vd by performing a PI (proportional / integral) calculation on the calculation result (Id ^* −Id) by the subtractor 200a. The PI controller 201b calculates a q-axis voltage command value vq by performing PI (proportional / integral) calculation on the calculation result (Iq ^* −Iq) by the subtractor 200b. That is, the current controller 10 calculates the voltage command value by performing current feedback control based on the actual current flowing through the SR motor 1 and the current command value. The voltage command values vd and vq calculated by the current controller 10 are output to the voltage coordinate converter 11.

  The voltage coordinate converter 11 converts the voltage command values vd, vq on the dq coordinate system calculated by the current controller 10 into the U-phase control voltage vus, the V-phase control voltage vvs, W based on the following equation (2). The phase control voltage vws is converted into a three-phase voltage.

The three-phase voltages vus, vvs, vws converted by the voltage coordinate converter 11 are output to the voltage command generator 12. The voltage command generator 12 calculates the absolute values of the three-phase voltages vus, vvs, vws converted by the voltage coordinate converter 11, and the calculation results vu ^* = | vus |, vv ^* = | vvs |, vw ^*. = | Vws | is output to the gate drive signal generator 13.

The gate drive signal generator 13 generates a drive signal for controlling on / off of the switches S <b> 1 to S <b> 6 constituting the inverter 2. First, based on the voltage value Vc of the smoothing capacitor 3 and the voltages vu ^* , vv ^* , vw ^* input from the voltage command generator 12, the modulation factor mu ^* , mv of each phase is obtained by the following equation (3). ^{* And} mw ^* are calculated.
mu ^* = vu ^* / Vc
mv ^* = vv ^* / Vc
mw ^* = vw ^* / Vc (3)

FIG. 6 is a diagram for explaining a method of generating a U-phase gate drive signal. As shown in FIG. 6, when the calculated modulation factor mu ^* and the magnitude of the triangular wave that is the carrier signal are compared, and the modulation factor mu ^* is larger than the triangular wave, the U-phase switch of the inverter 2 to be described later A gate drive signal (ON signal) for turning on S1 and S2 is output. On the other hand, when the modulation factor mu ^* is smaller than the triangular wave, a gate drive signal (OFF signal) for turning off the U-phase switches S1 and S2 is output. Although the method for generating the U-phase gate drive signal has been described with reference to FIG. 6, the V-phase and W-phase gate drive signals are also generated by the same method.

  The unipolar drive inverter 2 is a general inverter used for driving and controlling the SR motor 1 and includes switches S1 to S6 and freewheel diodes D1 to D6. The switches S1 and S2 are turned on when the U-phase gate drive signal is an ON signal and turned off when the signal is an OFF signal. Similarly, the switches S3 and S4 and the switches S5 and S6 are turned on when the V-phase and W-phase gate drive signals are ON signals, and are turned off when they are OFF signals. Thereby, the voltage of the DC power supply 4 is converted into a desired voltage value and applied to the SR motor 1 to control the driving of the SR motor 1. The smoothing capacitor 3 connected in parallel with the DC power supply 4 plays a role of suppressing voltage fluctuation.

  According to the control device for the SR motor in the first embodiment, the current value flowing in each phase of the SR motor 1 is detected, and the sign of the detected current value is converted, whereby the SR motor 1 is rotated. Current feedback control can be performed by converting into a current value on an orthogonal coordinate system (dq coordinate system) that rotates synchronously. Moreover, the voltage command value calculated | required by electric current feedback control is converted into a three-phase alternating voltage command value, and the signal for controlling the inverter 2 can be produced | generated by calculating | requiring the absolute value. Thereby, the control accuracy of the current flowing through the SR motor 1 can be improved. For example, in the conventional feedforward control, there is a problem that it is easily affected by control disturbance due to fluctuations in the voltage of the DC power supply 4, but according to the SR motor control device in the first embodiment, feedback control is performed. By performing the above, the actual current can be made to follow the current command value.

  Further, when an SR motor is used as a vehicle drive motor as in the SR motor control device according to the first embodiment, the ride comfort of the vehicle can be improved by improving the motor control accuracy. it can.

  In the SR motor control apparatus according to the first embodiment, the rotation period of the dq coordinate system is twice the change period when the inductance of each phase changes according to the rotation of the SR motor 1, so the sign is The manipulated current can be treated as alternating current. That is, in the dq coordinate system, the fundamental wave component of the motor current can be handled as a direct current amount, so that the response of the actual current does not deteriorate even when the motor rotates at high speed. On the other hand, when direct feedback control is performed on the current detection value of each phase of the SR motor 1, for example, the followability of the actual current with respect to the current command value becomes a problem at the time of high rotation of the motor. is there.

Further, since the map for calculating the current command value can be created based on the torque command value Te ^* and the motor rotation speed ωm, the conventional apparatus for mapping the energization start timing and the energization end timing is In comparison, the map creation effort and the map storage capacity of the control device can be reduced.

-Second Embodiment-
FIG. 7 is a diagram illustrating a configuration of the SR motor control device according to the second embodiment. What is different from the SR motor control device in the first embodiment is a current code converter 7a. Therefore, in the following, the process performed by the current code converter 7a will be described in detail, and the description of the same components will be omitted.

  The current code converter 7a performs a process of converting the signs of the U-phase, V-phase, and W-phase current values based on the magnitude of the current value flowing in each phase of the SR motor 1. That is, the current values Iu, Iv, Iw detected by the current sensors 100a to 100c are compared with a predetermined current threshold value, and if the current values Iu, Iv, Iw are less than the predetermined current threshold value, the output When the current value is 0 and there is a section larger than the predetermined current threshold, the current value of the section is output with the sign inverted every other section. This process will be described with reference to FIG.

  FIG. 8 is a diagram illustrating the relationship between the U-phase current Iu detected by the current sensor 100a and the U-phase current Ius output from the current sign converter 7a. In the SR motor control device according to the second embodiment, hysteresis is provided for the current threshold value. That is, the first current threshold value Iu1 and the second current threshold value Iu2 are determined in advance for the U-phase current. The current threshold values Iu1 and Iu2 can be determined based on the resolution of the current sensors 100a to 100c, the magnitude of the ripple current, and the like.

  The current code converter 7a compares the U-phase current Iu detected by the current sensor 100a with the second current threshold Iu2, and if Iu ≦ Iu2 holds, the output current value Ius = 0. To do. When the current Iu becomes larger than the second current threshold value Iu2, the output current value Ius = Iu is set (section (i)). Thereafter, when the current Iu becomes equal to or less than the first current threshold value Iu1, the output current value Ius = 0 is set again.

  If the current Iu becomes equal to or lower than the first current threshold Iu1 and Ius = 0 is output and then the current Iu becomes larger than the second current threshold Iu2, the sign of the U-phase current Iu is inverted and output. To do. That is, the output current value Ius = −Iu (section (ii)). Thereafter, when the current Iu detected by the current sensor 100a becomes equal to or less than the first current threshold value Iu1, the output current value Ius = 0 is set again. Thereafter, when the current Iu becomes larger than the second current threshold value Iu2, the output current value Ius = Iu is set (section (iii)) as in the section (i). Thereafter, this process is repeated.

  According to the SR motor control device in the second embodiment, a current threshold value is determined for each phase of the SR motor, and each phase current value detected by the current sensors 100a to 100c is a predetermined current. When the current value is equal to or smaller than the threshold value, the current value is set to 0, and the sign of the current value in every other section is negative for a section where the current value is larger than a predetermined current threshold. Thereby, like the SR motor control device in the first embodiment, current feedback control with high control accuracy can be performed. Further, when the current value sign conversion process is performed, it is only necessary to detect the current value without requiring the electrical phase θe. For example, the rotational position sensor 5 is omitted, or the detection accuracy is low. A rotational position sensor 5 can be used.

  According to the SR motor control device in the second embodiment, since hysteresis is provided in the current threshold value to be compared with the detected current value, the sign of the output current value can be obtained even when the detected current value includes noise. It is possible to prevent chattering that frequently switches.

  The present invention is not limited to the embodiment described above. For example, the SR motor has been described as being used as a vehicle driving motor for an electric vehicle, but may be used for other purposes. Further, the present invention is not limited by the type of SR motor, for example, the number of poles of the rotor and the stator.

  In the second embodiment, the current threshold is provided with hysteresis, but it is also possible to set only one current threshold without providing hysteresis.

  The correspondence between the constituent elements of the claims and the constituent elements of the first and second embodiments is as follows. That is, the inverter 2 controls the inverter, the current sensors 100a to 100c control the current detection means, the current code converters 7 and 7a control the current code operation means, the current coordinate converter 8 controls the coordinate conversion means, and the current controller 10 controls the current conversion means. The voltage calculation means, the voltage coordinate converter 11 constitutes the voltage conversion means, the voltage command generator 12 constitutes the absolute value calculation means, and the gate drive signal generator 13 constitutes the inverter control means. In addition, as long as the characteristic function of this invention is not impaired, each component is not limited to the said structure.

Bottom view showing a schematic overall configuration of an electric vehicle using an SR motor as a travel drive source The figure which shows the structure of 1st Embodiment of the control apparatus of SR motor by this invention. The figure which shows the relationship between the phase of the rotor of SR motor, and U phase inductance The figure which shows the relationship between U-phase inductance, U-phase current Iu, and output current Iu_k Block diagram showing the configuration of the current controller The figure for demonstrating the method to produce | generate a U-phase gate drive signal The figure which shows the structure of the control apparatus of SR motor in 2nd Embodiment. The figure which shows the relationship between the U-phase electric current Iu and the U-phase electric current Iu_k output from the current code converter 7a in the control apparatus of SR motor in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... SR motor 2 ... Inverter 3 ... Smoothing capacitor 4 ... DC power supply 5 ... Rotation position sensor 6 ... Phase speed calculator 7, 7a ... Current code converter 8 ... Current coordinate converter 9 ... Torque controller 10 ... Current controller DESCRIPTION OF SYMBOLS 11 ... Voltage coordinate converter 12 ... Voltage command generator 13 ... Gate drive signal generator 100a-100c ... Current sensor

Claims (7)

Detect current flowing in each phase of SR motor,
Manipulating the sign of each detected phase current value,
Each phase current value manipulated by the sign is converted into a current value on an orthogonal coordinate system that rotates in synchronization with the rotation of the SR motor,
Wherein in the orthogonal coordinate system, on the basis of the current command value of the SR motor and the converted current values, and calculates the motor control voltage,
Converting the calculated motor control voltage into a three-phase AC voltage;
Calculating the absolute value of the converted three-phase AC voltage;
An SR motor control method, comprising: controlling an inverter that applies a voltage to the SR motor based on the calculated absolute value of the three-phase AC voltage. An inverter for applying a desired voltage for each phase in order to drive and control the SR motor;
Current detection means for detecting current flowing in each phase of the SR motor;
Current sign operation means for manipulating the sign of each phase current value detected by the current detection means;
Coordinate conversion means for converting each phase current value whose code is operated by the current sign operation means into a current value on an orthogonal coordinate system that rotates in synchronization with the rotation of the SR motor;
In the orthogonal coordinate system, and the current value converted by the coordinate conversion means, on the basis of the current command value of the SR motor, and the control voltage calculating means for calculating a motor control voltage,
Voltage conversion means for converting the motor control voltage calculated by the control voltage calculation means into a three-phase AC voltage;
Absolute value calculating means for calculating an absolute value of the three-phase AC voltage converted by the voltage converting means;
An SR motor control device comprising: inverter control means for controlling the inverter based on the absolute value of the three-phase AC voltage calculated by the absolute value calculation means. The SR motor control device according to claim 2,
Phase detector for detecting the rotational phase of the rotor of the SR motor;
The SR motor control device, wherein the current sign operation means manipulates the sign of each phase current value based on the rotational phase detected by the phase detection means. The SR motor control device according to claim 2 ,
A current threshold is determined for each phase of the SR motor;
The current sign operation means sets the output current to 0 when each phase current value detected by the current detection means is less than or equal to the current threshold, and each phase current value detected by the current detection means When the current threshold value is larger than the current threshold value, the sign of the current value of every other interval is made negative with respect to the current value interval larger than the current threshold value. The SR motor control device according to claim 4,
A control device for an SR motor, wherein a hysteresis is provided for the current threshold value. In the control apparatus of SR motor in any one of Claims 2-5,
The SR motor control device characterized in that a rotation cycle of the orthogonal coordinate system is twice a change cycle when the inductance of each phase changes according to the rotation of the SR motor.   A vehicle using an SR motor controlled by the SR motor control device according to claim 2 as a travel drive source.

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