JP5376218B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device that drives an AC motor by converting a DC power source into AC.

  As a control method for a permanent magnet AC motor, for example, a three-phase synchronous motor, a control method called vector oriented control (FOC) is known. In the vector control, a motor current flowing through the stator coils of the three phases of the AC motor is represented by a vector of a d axis that is a direction of a magnetic field generated by a permanent magnet disposed on the rotor and a q axis that is orthogonal to the d axis. Performs feedback control by converting coordinates to components. In order to control an AC motor with high accuracy and high speed using vector control, it is necessary to detect the position of the rotor of the motor with high accuracy. Although there is a method for detecting the position of the rotor using the rotor position detection sensor, the rotor position detection sensor has a relatively large volume, which may increase the size of the apparatus or may be restricted in arrangement. On the other hand, a technique is known in which a rotor position is electrically detected by detecting a counter electromotive force induced in a stator coil when a rotor having a permanent magnet rotates. However, no back electromotive force is generated while the rotor is stopped, and the back electromotive force is small at the beginning of the movement of the rotor. Therefore, there is a problem that the position of the rotor cannot be detected when the motor is started. In view of this problem, Japanese Patent Laid-Open No. 2001-339999 (Patent Document) discloses a method for estimating the position of a rotor by applying a high-frequency current different from the rotational speed of the rotor to the motor and detecting a difference in magnetic resistance of the rotor. 1).

JP 2001-339999 A (7th to 10th, 43th to 68th paragraphs, etc.)

  The frequency of the high-frequency current superimposed in Patent Document 1 is a fixed value of 500 Hz, for example. Since the counter electromotive force starts to be generated when the rotor starts to rotate, the estimation accuracy may be lowered. Therefore, there is a need for a technique for estimating the rotor position satisfactorily regardless of the rotational speed of the rotor.

  The present invention was devised in view of the above problems, and a motor control device that detects the rotational position of a rotor and performs vector control of the motor without using a position detection sensor regardless of the rotational speed of the rotor of the motor. The purpose is to provide.

The characteristic configuration of the motor control device according to the present invention for achieving the above object is as follows:
The target current in the d-axis, which is the direction of the magnetic field generated by the permanent magnet arranged in the rotor of the AC motor, and the q-axis orthogonal to the d-axis, and the two-phase current of the d-axis and q-axis are converted and fed back. Based on the detection result of the three-phase current flowing in the stator coil of the AC motor, the drive current on the d-axis and the q-axis is calculated, and the drive voltage on the d-axis and the q-axis is calculated based on the drive current. A current control unit to calculate,
A frequency setting unit that sets a frequency of a high-frequency voltage to be superimposed on the drive voltage based on a rotational speed of the rotor and a target torque required for the AC motor ;
A high-frequency voltage superimposing unit that superimposes the high-frequency voltage having the set frequency on the drive voltage;
A frequency band to be blocked according to the frequency of the high-frequency voltage is set, a band stop filter that filters the two-phase current and feeds back to the current control unit,
A frequency band that is passed according to the frequency of the high-frequency voltage is set, and a band-pass filter that filters the two-phase current;
A rotational state computing unit that computes the rotational speed of the rotor and the rotational position of the rotor based on the two-phase current after passing through the band-pass filter;
It is in the point provided with.

  According to this characteristic configuration, the frequency of the high-frequency voltage superimposed on the drive voltage is set based on the rotational speed of the rotor and the target torque. Therefore, the high-frequency current superimposed on the drive current supplied from the DC power supply to the AC motor via the inverter circuit controlled based on the drive voltage after the high-frequency voltage is superimposed is also the rotor speed and the target torque. Depending on the situation. Unlike conventional motor control devices, the frequency of the superimposed high-frequency current is not a fixed value, so that the estimation accuracy of the rotor position may decrease due to the back electromotive force after the rotor starts rotating. It is suppressed. The current flowing in the stator coil of the motor includes a high-frequency current. The three-phase current including the high-frequency current is converted into a two-phase current and then fed back to the current control unit via the band stop filter. Is done. The band stop filter has a frequency band that is blocked according to the frequency band of the high-frequency current, so the high-frequency components that are intentionally superimposed to detect the rotor position are removed before being fed back to the current controller. Is done. Therefore, the current control unit can perform current control without being affected by the high frequency component. As described above, according to this characteristic configuration, it is possible to provide a motor control device that detects the rotational position of the rotor and performs vector control of the motor without using a position detection sensor regardless of the rotational speed of the rotor of the motor. .

  In addition, it is preferable that the frequency setting unit of the motor control device according to the present invention is configured to have a frequency table having the rotation speed of the rotor and the target torque as arguments.

  According to this, since the frequency is set by the frequency table using the rotation speed of the rotor and the target torque as arguments, the system configuration can be simplified.

A block diagram schematically showing a configuration example of a motor control system for driving an AC motor Block diagram schematically showing a configuration example of a motor control device Explanatory drawing showing an example of the frequency table

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of a motor control system that drives an AC motor. A motor control system that drives a motor 12 that is an AC motor includes an inverter circuit 5 that is interposed between the motor 12 and a DC power supply 20 and converts the output of the DC power supply 20 into a three-phase AC. . The inverter circuit 5 includes a plurality of switching elements. It is preferable to apply an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET) to the switching element. Here, the case where IGBT is used as a switching element is illustrated.

  The inverter circuit 5 is configured by a three-phase bridge circuit. Two IGBTs are connected in series between the input plus side 21 and the input minus side 22 of the inverter circuit 5, and this series circuit is connected in parallel in three lines. That is, a bridge circuit in which a set of series circuits corresponds to each of the stator coils u-phase, v-phase, and w-phase of the motor 12 is configured. In FIG. 1, IGBTs Q5, Q1, and Q3 are upper-stage switching elements corresponding to the u-phase, v-phase, and w-phase, respectively. The IGBTs Q6, Q2, and Q4 are lower-stage switching elements corresponding to the u-phase, the v-phase, and the w-phase, respectively. Note that flywheel diodes (regenerative diodes) are connected in parallel to the IGBTs Q1 to Q6, respectively. The flywheel diodes are connected in parallel such that the cathode terminal is connected to the collector terminal of the IGBT and the anode terminal is connected to the emitter terminal of the IGBT.

  The collectors of the IGBTs Q1, Q3, Q5 on the upper side of each phase are connected to the input plus side 21 of the inverter circuit 5, and the emitters are connected to the collectors of the IGBTs Q2, Q4, Q6 on the lower side of each phase. Further, the emitters of the IGBTs Q2, Q4, Q6 on the lower side of each phase are connected to the input minus side 22 (ground) of the inverter circuit 5. The intermediate points (IGBT connection points) of the series circuit by the IGBTs (Q5, Q6), (Q3, Q4), (Q1, Q2) of each phase to be paired are the u-phase, v-phase, and w-phase of the motor 12, respectively. The stator coils 12u, 12v, and 12w are connected to the stator coils 12u, 12v, and 12w, respectively.

  The gates of the IGBTs Q1 to Q6 are connected to an ECU 50 as a control unit via a driver circuit 51, and are individually controlled for switching. The ECU 50 is configured with a logic circuit such as a microcomputer as a core. The ECU 50 corresponds to the motor control device of the present invention. The drive signal input to the gate of the IGBT or MOSFET that switches the high voltage requires a voltage higher than the voltage of a general logic circuit, and therefore is input to the inverter circuit 5 via the driver circuit 51.

  The ECU 50 supplies the motor 12 with a three-phase AC drive current by performing PWM control on the IGBTs Q <b> 1 to Q <b> 6 based on the target torque and the rotational speed for the motor 12. Thereby, the motor 12 powers according to the rotation speed and the target torque. The motor 12 functions as a generator, and the regeneration when the inverter circuit 5 receives power from the motor 12 side is the same as during powering. ECU50 converts IGBTQQ1-Q6 into direct current | flow by carrying out PWM control based on the target torque with respect to the motor 12, and rotation speed. It is also possible to simply rectify using flywheel diodes connected in parallel to the IGBTs Q1 to Q6.

  Further, the ECU 50 performs feedback control based on the rotation speed and the motor current. As shown in FIG. 1, a current sensor that functions as a current detection unit 13 is provided to measure the drive current supplied to the u-phase, v-phase, and w-phase stator coils 12 u, 12 v, and 12 w of the motor 2. It has been. The detected value by the current sensor is received by the ECU 50 and used for feedback control. In this example, a configuration is shown in which the currents of all three phases are measured, but since the three phases are in an equilibrium state and the sum of instantaneous current values is zero, only the currents of the two phases are measured and the ECU 50 The remaining one-phase current may be obtained by calculation.

  The motor 12 may be provided with a rotation detection sensor such as a resolver, but in the present embodiment, a sensor for mechanically detecting the rotation angle of the rotor is not provided. As will be described later, in the present embodiment, the rotor position is electrically detected by detecting the counter electromotive force induced in the stator coils 12u, 12v, 12w as the rotor having the permanent magnet rotates. The method is used. Since the technique for electrically detecting the rotor position is known as described in Patent Document 1 and the like, detailed description thereof is omitted. Using the electrically obtained rotor position (rotation angle) and the electrical angle θ based on the rotor position, the rotational speed (angular velocity ω) of the motor 1 and the control timing of each of the IGBTs Q1 to Q6 of the inverter circuit 5 are calculated. .

  FIG. 2 is a block diagram schematically showing the configuration of the ECU 50 as the motor control device. In FIG. 2, the components other than the ECU 50 in the motor control system are simply simplified as appropriate. As described above, the ECU 50 is a functional unit that controls the motor 12 by vector control, and includes a logic circuit such as a microcomputer as a core. Therefore, each function part of ECU50 does not need to be comprised independently, respectively, and it is sufficient if each function is implement | achieved by cooperation with a program and common hardware.

  As shown in FIG. 2, the ECU 50 includes an inverter circuit control unit 10 including a target current setting unit 1, a current control unit 2, a two-phase / three-phase conversion unit 3, and a PWM control unit 4 in order to perform vector control. And a three-phase / two-phase converter 6. The ECU 50 includes a rotation state calculation unit 11 for calculating a rotation state such as the rotor position and the number of rotations. Further, the ECU 50 is a functional unit for superimposing a high frequency component on a drive voltage determined in vector control in order to electrically detect the rotation state, and includes a frequency setting unit 7, a high frequency voltage setting unit 15, and a high frequency voltage. A superimposing unit 16 is provided. Further, the ECU 50 includes a band pass filter 8 and a band stop filter 9 in which a frequency band is set according to the frequency component of the superimposed high frequency voltage.

  In the vector control, a motor current flowing through the stator coils of the three phases of the AC motor is represented by a vector of a d axis that is a direction of a magnetic field generated by a permanent magnet disposed on the rotor and a q axis that is orthogonal to the d axis. Performs feedback control by converting coordinates to components. The target current setting unit 1 is a functional unit that sets a target current for the d-axis and the q-axis for driving the motor 12 based on the rotation speed of the motor 12 and the target torque. The target current setting unit 1 receives a target torque required for the motor 12 from a control unit different from the ECU 50, for example, an ECU that controls the entire vehicle, and changes the rotational state such as the target torque and the rotational speed of the motor 12 to the target current. Based on this, the target current value is calculated. The rotation state of the motor 12 is calculated by the rotation number calculation unit 19 of the rotation state calculation unit 11.

  The current control unit 2 calculates a drive current on the d-axis and the q-axis by current control using proportional control (P control), proportional-integral control (PI control), and the like, and based on the drive current, the d-axis And a functional unit that calculates a driving voltage on the q-axis. The current control unit 2 calculates a drive current on the d-axis and the q-axis based on the target current on the d-axis and the q-axis set by the target current setting unit 1 and the fed back two-phase current. As for the two-phase current fed back, the detection result of the three-phase current flowing through the stator coils 12u, 12v, 12w by the current detection unit 13 is converted into the d-phase and q-axis two-phase currents in the three-phase / two-phase conversion unit 6. It has been done. More specifically, as will be described later, the fed back two-phase current is converted into a two-phase current by the three-phase / two-phase conversion unit 6 and then fed back via the band stop filter 9. When the driving current is calculated, the current control unit 2 calculates the d-axis voltage and the q-axis voltage, which are two-phase driving voltages, by substituting the determined driving current value into the voltage equation.

  The inverter circuit control unit 10 is a functional unit configured to include the 2-phase / 3-phase conversion unit 3 and the PWM control unit 4. The two-phase / three-phase converter 3 is a three-phase drive voltage that is a drive voltage for actually passing a drive current through the three-phase stator coils 12v to 12w using the two-phase drive voltage determined by the current control unit 2. It is a functional part that converts to The PWM control unit 4 is a function of generating a drive signal that drives and controls the inverter circuit 5 that is interposed between the DC power supply 20 and the motor 12 and converts DC to three-phase AC based on the three-phase drive voltage. Part. That is, the PWM control unit 4 generates a gate drive signal for switching the IGBTs Q <b> 1 to Q <b> 6 of the inverter circuit 5 in order to generate the three-phase drive voltage determined by the two-phase / three-phase conversion unit 3. The inverter circuit 5 is switching-controlled by the PWM control unit 4, converts the output of the DC power supply 20 into AC, and drives the motor 12.

  In this manner, the current flowing through the three-phase stator coils 12v to 12w of the motor 12 is detected, and this is fed back to perform vector control of the motor 12. However, in the present embodiment, a method of electrically detecting the rotor position by detecting the counter electromotive force induced in the stator coils 12u, 12v, 12w is used. Therefore, in addition to the functional units for vector control, the ECU 50 is added with a functional unit for electrically detecting the rotor position, and cooperates with the functional units for vector control.

  For example, a high frequency voltage superimposing unit 16 is provided between the inverter circuit control unit 10 and the current control unit 2, and the high frequency voltage is superimposed on the driving voltage determined by the current control unit 2. The inverter circuit control unit 10 receives the drive voltage on which the high-frequency voltage is superimposed. Therefore, the 2-phase / 3-phase converter 3 converts the drive voltage on the d-axis and the q-axis on which the high-frequency voltage is superimposed into a 3-phase drive voltage. Since PWM control is performed based on the three-phase drive voltage, the high-frequency current is also superimposed on the current flowing through the stator coils 12v to 12w. Since the current detected by the current detector 13 includes a high frequency component, the high frequency component is included even after the three-phase / two-phase converter 6 converts the current into a two-phase current.

  The high frequency component is superimposed to electrically detect the rotor position. Therefore, the high frequency component is very important information in calculating the rotor position and the rotation speed of the rotor in the rotation state calculation unit 11. Therefore, the two-phase current converted by the three-phase / two-phase conversion unit 6 is sent to the rotation state calculation unit 11 via the band-pass filter 8 in which a frequency band to be passed according to the frequency of the high-frequency voltage is set. Communicated. The band pass filter 8 is a variable filter in which a frequency band is set according to the frequency of the high frequency voltage.

  On the other hand, when a feedback current in vector control is fed back to the current control unit 2, the high frequency component is a noise component. Therefore, the two-phase current is fed back to the current control unit 2 via the band stop filter 9 in which a frequency band to be blocked according to the frequency of the high frequency voltage is set. The band stop filter 9 is a variable filter whose frequency band is set according to the frequency of the high frequency voltage. Since the frequency band to be blocked is set according to the frequency band of the high-frequency component included in the two-phase current, the high-frequency component intentionally superimposed for detecting the rotor position is not fed back to the current control unit 2. Removed. As a result, the current control unit 2 can perform current control without being affected by high frequency components.

  The frequency bands of the band pass filter 8 and the band stop filter 9 are set according to the frequency of the high frequency voltage, and the frequency of the high frequency voltage is set by the frequency setting unit 7. The frequency setting unit 7 sets the frequency of the high-frequency voltage to be superimposed on the drive voltage based on the rotational speed of the rotor and the target torque. The frequency setting unit 7 may set the frequency by performing sequential calculation, but as shown in FIG. 3, the frequency setting unit 7 is configured to have a frequency table with the rotor speed and the target torque as arguments, It is preferable to set the frequency by referring to a table. That is, the frequency setting unit 7 can be configured with a simpler configuration, and the frequency can be set stably without being affected by small changes in the rotational speed of the rotor and the target torque.

  The high frequency voltage setting unit 15 is a functional unit that sets a high frequency voltage having a set frequency. The high frequency voltage superimposing unit 16 is a functional unit that superimposes the high frequency voltage having the frequency set by the frequency setting unit 7 on the drive voltage calculated by the current control unit 2. That is, the high frequency voltage superimposing unit 16 superimposes the high frequency voltage according to the target torque and the rotational speed of the rotor. Unlike conventional motor control devices, the frequency of the superimposed high frequency is not a fixed value, so the possibility that the accuracy of estimation of the rotor position will be reduced due to the back electromotive force after the rotor starts rotating is suppressed. Is done.

  As described above, the motor control device of the present invention includes a functional unit that estimates the rotor position in cooperation with each functional unit that performs vector control. Therefore, it is possible to estimate the rotor position with high accuracy while suppressing the scale of the motor control device. In addition, a configuration is adopted in which a noise component due to a high frequency component is suppressed in a feedback current for vector control while cooperating with each functional unit that performs vector control. Further, since the frequency of the high frequency component is set according to the target torque and the rotational speed of the rotor, the rotational position of the rotor can be estimated well without using a position detection sensor regardless of the rotational speed of the rotor. .

  As described above, according to the present invention, it is possible to provide a motor control apparatus that detects the rotational position of the rotor and performs vector control of the motor without using a position detection sensor regardless of the rotational speed of the rotor.

1: target current setting unit 2: current control unit 5: inverter circuit 7: frequency setting unit 8: band pass filter 9: band stop filter 10: inverter circuit control unit 11: rotation state calculation unit 12: motor (AC motor)
12u, 12v, 12w: Stator coil 16: High frequency voltage superposition part

Claims (2)

The target current in the d-axis, which is the direction of the magnetic field generated by the permanent magnet arranged in the rotor of the AC motor, and the q-axis orthogonal to the d-axis, and the two-phase current of the d-axis and q-axis are converted and fed back. Based on the detection result of the three-phase current flowing in the stator coil of the AC motor, the drive current on the d-axis and the q-axis is calculated, and the drive voltage on the d-axis and the q-axis is calculated based on the drive current. A current control unit to calculate,
A frequency setting unit that sets a frequency of a high-frequency voltage to be superimposed on the drive voltage based on a rotational speed of the rotor and a target torque required for the AC motor ;
A high-frequency voltage superimposing unit that superimposes the high-frequency voltage having the set frequency on the drive voltage;
A frequency band to be blocked according to the frequency of the high-frequency voltage is set, a band stop filter that filters the two-phase current and feeds back to the current control unit,
A frequency band that is passed according to the frequency of the high-frequency voltage is set, and a band-pass filter that filters the two-phase current;
A rotational state computing unit that computes the rotational speed of the rotor and the rotational position of the rotor based on the two-phase current after passing through the band-pass filter;
A motor control device comprising:   2. The motor control device according to claim 1, wherein the frequency setting unit includes a frequency table in which the rotation speed of the rotor and the target torque are arguments.

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