JP5365838B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device capable of performing stable current control when driving a three-phase motor.

  Conventionally, in the drive control of a three-phase motor, the motor current is coordinate-converted into a vector component of the d-axis that is the direction of the magnetic field generated by the permanent magnet of the rotor of the motor and the q-axis vector component orthogonal to the d-axis. Some motors perform rotation control (drive control) (for example, Non-Patent Document 1). In the drive control of a three-phase motor similar to Non-Patent Document 1, the coil current is controlled according to the output torque of the motor by performing vector control that performs coordinate control on the coil current of the three-phase motor and performing feedback control. .

Sugimoto Hidehiko, “Theory and Design of AC Servo Systems, From Basics to Software Servo”, General Electronic Publishing, p. 180-215

  Here, in general vector control, the three-phase motor is controlled based on a voltage equation determined by the inductance, resistance value, angular velocity, and the like of the coil included in the three-phase motor. However, since the inductance, resistance value, and angular velocity (parameters of the three-phase motor) of these coils vary depending on operating conditions, the current response of the coil current (that is, motor current) has nonlinearity. For this reason, when simple PID control is used for rotation control of a three-phase motor, there is a problem that current control of the motor current is not stable when, for example, the parameters of the three-phase motor fluctuate.

  In view of the above problems, an object of the present invention is to provide a motor control device capable of performing stable current control of a motor current even when parameters of a three-phase motor fluctuate.

In order to achieve the above object, the motor control device according to the present invention is characterized by a d-axis d-axis current, which is a direction of a magnetic field generated by a permanent magnet disposed in a rotor of a three-phase motor, and the d-axis. A three-phase / two-phase converter that calculates a q-axis current of the orthogonal q-axis, a target current set from the total torque required to rotate the three-phase motor, the d-axis current, and the q-axis current An integration control unit for calculating the d-axis voltage command value and the q-axis voltage command value, and the d-axis voltage command value and the q-axis voltage command value for each of the three phases. The three-phase motor is converted from the three-phase voltage command value and the motor current supplied to the three-phase motor for each of the three phases. And a state quantity estimation unit for estimating the change amount of the motor current .

  With such a characteristic configuration, the state quantity of the three-phase motor can be easily estimated from the three-phase voltage command value and the motor current flowing through the three-phase motor in response to application of the three-phase voltage command value. Therefore, it is possible to appropriately specify the state quantity of the three-phase motor that changes according to the operation of the three-phase motor. Therefore, even when the parameter changes according to the operation of the three-phase motor, it is possible to perform stable current control of the motor current, and it is possible to perform control with excellent current response.

Further, it is preferable that the motor current is controlled by PWM control based on the three-phase voltage command value and the estimated change amount of the motor current.

  With such a configuration, PWM control is performed based on the three-phase voltage command value and the estimated state quantity, so that it is possible to perform operation control according to the state of the three-phase motor. Therefore, since the current control of the three-phase motor can be performed according to the state of the three-phase motor, the three-phase motor can be operated efficiently.

  Further, it is preferable that the state quantity estimation unit has a gain determined by characteristics of the three-phase motor.

  With such a configuration, the estimation reliability can be improved in estimating the state quantity of the three-phase motor. Therefore, it is possible to efficiently operate the three-phase motor.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a motor control device 100 of the present invention. Here, the motor control device 100 according to the present invention obtains voltage command values for the d-axis, which is the direction of the magnetic field generated by the permanent magnets disposed in the rotor of the three-phase motor 10, and the q-axis voltage command value orthogonal to the d-axis. The three-phase voltage command value for each of the three phases is converted, and the three-phase motor 10 is controlled by control based on the three-phase voltage command value. In order to realize such a function, the motor control apparatus 100 has a target current setting unit 1, an integration control unit 2, a two-phase / three-phase conversion unit 3, a PWM control unit 4, a frequency conversion unit 5, a three-phase / A two-phase conversion unit 6, a rotation angle calculation unit 7, a state quantity estimation unit 8, a sensitivity adjustment unit 9, and a three-phase motor 10 are configured (details will be described later).

  FIG. 2 is a diagram showing a configuration of an ECU 50 (described later), a frequency conversion unit 5 and a three-phase motor 10 in which the PWM control unit 4 is configured with other functional units. Although not shown, the three-phase motor 10 includes a rotor including a permanent magnet and a stator that generates a magnetic field for applying a rotational force to the rotor. This stator includes three-phase stator coils 10u, 10v, and 10w of U phase, V phase, and W phase. One end of each stator coil is connected in common at an electrically neutral point and Y-connected. The other end of each stator coil is connected to the frequency converter 5. In the present embodiment, since the coil is provided in the stator, it is described as a stator coil. However, unless otherwise specified, the stator coil and the coil are used as being synonymous.

  The frequency converter 5 controls the three-phase motor 10 and converts a DC voltage into an AC voltage. The DC voltage is supplied from a power source 20 connected to the frequency conversion unit 5. As shown in FIG. 2, the frequency converter 5 includes high-side transistors Q1, Q3, and Q5 connected to the positive voltage side of the power source 20, and a low-side transistor Q2 connected to the negative voltage side of the power source 20. A total of six transistors Q1 to Q6 including Q4 and Q6 are formed. For example, when only the transistor Q1 and the transistor Q4 are simultaneously turned on, a current flows from the power supply 20 to the second power supply line 22 via the first power supply line 21, the transistor Q1, the stator coil 10v, the stator coil 10w, and the transistor Q4. On the other hand, when only the transistor Q3 and the transistor Q2 are simultaneously turned on, a current flows from the power supply 20 to the second power supply line 22 via the first power supply line 21, the transistor Q3, the stator coil 10w, the stator coil 10v, and the transistor Q2. Thus, the frequency conversion unit 5 converts the output of the power supply 20 into an AC voltage.

  The direction of the current flowing through the stator coil 10v and the stator coil 10w is different between when only the transistor Q1 and the transistor Q4 are turned on and when only the transistor Q3 and the transistor Q2 are turned on. Therefore, an electromagnetic force corresponding to the direction in which the current flows acts on each stator coil, and an attractive force and a repulsive force are generated between the electromagnetic force and a permanent magnet provided in the rotor. Therefore, the rotor can obtain a rotational force by sequentially turning on the upper and lower pair transistors formed by the high-side transistor and the low-side transistor selected from the transistors Q1 to Q6.

  The transistors Q1 to Q6 are provided with diodes D1 to D6 so that the cathode terminal is connected to the collector terminal and the anode terminal is connected to the emitter terminal. Here, energy is stored in each stator coil during energization, but these diodes D1 to D6 are applied to peripheral components by back electromotive force generated due to the energy when the energization of each stator coil is stopped. It is arranged to prevent adverse effects.

  A series of control for the transistors Q1 to Q6 is performed by the PWM controller 4. As will be described in detail later, the PWM control unit 4 includes a target current setting unit 1, an integration control unit 2, a 2-phase / 3-phase conversion unit 3, a 3-phase / 2-phase conversion unit 6, a state quantity estimation unit 8, and a sensitivity adjustment unit. 9 and ECU 50 (see FIG. 1). The PWM control unit 4 controls the switching element included in the frequency conversion unit 5 by PWM (Pulse Width Modulation) control. In this embodiment, the switching elements included in the frequency conversion unit 5 correspond to the transistors Q1 to Q6. Therefore, the PWM control unit 4 operates the transistors Q1 to Q6 included in the frequency conversion unit 5 by PWM control.

  The three-phase motor 10 is provided with a position sensor 10a that detects the rotation angle of the rotor. The position sensor 10a converts the rotation angle of the rotor into an electrical angle θ and outputs a signal corresponding to the electrical angle θ. The rotation angle calculation unit 7 detects the rotation angle of the three-phase motor 10 based on the output signal. The ECU 50 monitors the rotation angle calculated by the rotation angle calculation unit 7 and the current between the frequency conversion unit 5 and each stator coil. In view of the overall configuration of the three-phase motor control device 100, the monitor is performed via each functional unit as shown in FIG. It does not cause a problem.

  The ECU 50 is configured by a microcomputer that operates at a low voltage such as 2.5 V or 3.3 V, for example. Therefore, depending on the current flowing through the transistors Q1 to Q6 and the electrical characteristics of the transistors Q1 to Q6, there is a possibility that the drive capability for turning on the transistors Q1 to Q6 may be insufficient. Therefore, a driver 51 (not shown in FIG. 1) for increasing the drive capability of the PWM signal of ECU 50 is arranged between ECU 50 and frequency converter 5. The driver 51 may be composed of a driver IC or a push-pull circuit assembled with transistors. Of course, when the drive capability of the PWM signal output from the ECU 50 is high, it is naturally possible to configure without the driver 51.

  Returning to FIG. 1, the target current setting unit 1 sets the target current from the total torque required to rotate the three-phase motor 10. The target current set by the target current setting unit 1 is transmitted to the integration control unit 2, and the output from the three-phase / two-phase conversion unit 6 is also transmitted to the integration control unit 2 as a feedback signal. The output from the three-phase / two-phase converter 6 corresponds to a calculation result calculated based on the motor current supplied to the three-phase motor 10, which will be described in detail later.

  Here, the motor control apparatus 100 uses the motor currents iu, iv, and iw as the d axis that is the direction of the magnetic field generated by the permanent magnets disposed on the rotor of the three-phase motor 10 and the q that is orthogonal to the d axis. Coordinate conversion is performed on the vector components Id and Iq of the shaft to control the rotation of the three-phase motor 10. FIG. 3 is a diagram showing the principle of this coordinate transformation. The three-phase motor shown in FIG. 3 includes a rotor 10r having a two-pole permanent magnet m, and the rotation angle of the rotor 10r and the electrical angle θ coincide. FIG. 3A is a diagram showing the relationship between the motor current (three-phase alternating current) waveform and the electrical angle θ, and FIG. 3B shows the rotor 10r and the stator 10s at time t1 in FIG. It is a figure which shows the current vector before and after the positional relationship and coordinate transformation. FIG. 3B shows the electrical angle θ that is the magnetic pole position of the rotor 10r with reference to the U-phase magnetic pole position of the stator 10s.

  As shown in FIG. 3B, the direction of the magnetic field generated by the permanent magnet m is defined as the d axis, and the direction orthogonal to the d axis is defined as the q axis. As shown in FIG. 3A, torque is generated by flowing three-phase alternating currents iu, iv, iw through the stator coils 10u, 10v, 10w according to the magnetic pole position of the rotor 10r. The vector ia (Ia) indicating the sum of the armature currents at the electrical angle θ at time t1 in FIG. 3A is zero because the W-phase current (W-phase motor current) iw is zero from FIG. 3A. , The vector sum of the U-phase current (U-phase motor current) iu and the V-phase current (V-phase motor current) iv. When the current vector ia at the electrical angle θ is decomposed with respect to the d-axis and the q-axis, a d-axis current Id and a q-axis current Iq are obtained. Thus, the three-phase motor currents iu, iv, and iw are coordinate-converted into a d-axis d-axis current Id and a q-axis q-axis current Iq.

  Here, in particular, in the permanent magnet embedded type synchronous motor, the inductance viewed from the stator coils 10u, 10v, and 10w changes depending on the relationship with the rotor 10r, that is, the relationship with the magnetic pole position. In the d-axis direction, which is the direction of the magnetic pole, the magnetic path is obstructed because it has a magnetic resistance proportional to the inverse of the permeability of the permanent magnet. On the other hand, in the q-axis direction, since the magnetic material such as silicon steel having a high permeability is passed, the value of the magnetic resistance is significantly smaller than that of the permanent magnet, and the magnetic path is not easily disturbed. For this reason, the q-axis inductance Lq is larger than the d-axis inductance Ld. Since the d-axis and the q-axis change in relation to the magnetic pole position when viewed from the stator coils 10u, 10v, and 10w, the inductance viewed from the stator coils 10u, 10v, and 10w changes.

  Therefore, in addition to the magnet torque (main torque) by the permanent magnet, reluctance torque is also generated due to the difference between the q-axis inductance Lq and the d-axis inductance Ld. When reluctance torque is not actively used, such as a surface magnet type synchronous motor, it is efficient to perform control with Id = 0. However, when using reluctance torque in a permanent magnet embedded synchronous motor or the like, it is more efficient to perform control with Id ≠ 0. In the permanent magnet embedded type synchronous motor, the operating point at which the maximum efficiency is obtained varies depending on the current phase angle β between the d-axis current Id and the q-axis current Iq shown in FIG. 4 (see equation (1)).

  The total torque T of the three-phase motor 10 is Pn: pole pair number, ψa: armature linkage flux, ia: armature current, Ld: d-axis inductance, Lq: q-axis inductance, β: current phase angle. It is represented by the torque equation shown in equation (2).

  In the formula (2), the first term in the braces indicates the magnet torque, and the second term indicates the reluctance torque. Moreover, since it is clear from FIG. 4 that the following equations (3) to (5) are obtained, the torque equation of the equation (2) can also be expressed as the following equation (6).

  As described above, the armature current Ia includes the d-axis current Id and the q-axis current Iq. Therefore, the torque equations shown in the equations (2) and (6) represent the torque of the three-phase motor 10 using the flux linkage, the d-axis and q-axis inductances, and the d-axis and q-axis currents. It can be said that it is an expression. The d-axis current Id and the q-axis current Iq are calculated by the three-phase / two-phase converter 6 described above.

  Returning to FIG. 1, the integration control unit 2 causes the three-phase / two-phase conversion unit 6 to perform coordinate conversion based on the target current set by the target current setting unit 1 and the motor current flowing through the three-phase motor 10. The d-axis current command value Idr and the q-axis current command value Iqr are calculated from the d-axis current Id and the q-axis current Iq obtained by the above. For example, the torque equation shown in the above equation (2) can be transformed into the equation of the armature current Ia. The integration control unit 2 calculates the d-axis current command value Idr and the q-axis current command value Iqr by substituting the target torque and other parameters to solve the deformed torque equation and performing vector decomposition by the phase angle β. Is possible. Alternatively, it is naturally possible to calculate the d-axis current command value Idr and the q-axis current command value Iqr from the equation (6). Further, the integration control unit 2 calculates a d-axis voltage command value Vdr and a q-axis voltage command value Vqr from the d-axis current command value Idr and the q-axis current command value Iqr based on the voltage equation. That is, the integral control unit 2 determines the d-axis voltage command value Vdr based on the target current set from the total torque necessary for rotating the three-phase motor 10 and the d-axis current Id and the q-axis current Iq. And the q-axis voltage command value Vqr can be calculated.

  The voltage equations representing the d-axis voltage Vd and the q-axis voltage Vq are: ψa: armature linkage flux, ω: angular velocity, Id: d-axis current, Iq: q-axis current, Ld: d-axis inductance, Lq: The q-axis inductance, Ra: armature resistance, p: differential operator is expressed as the following equation (7).

  Equation (7) is a voltage for driving the three-phase motor 10 using the interlinkage magnetic flux, the impedance of the stator coil of the three-phase motor 10 including the d-axis and q-axis inductances, and the d-axis and q-axis currents. It is clear that the voltage equation represents The integral control unit 2 substitutes the d-axis current command value Idr and the q-axis current command value Iqr and other parameters into the voltage equation shown in the equation (7), thereby obtaining the d-axis voltage Vd and the q-axis voltage Vq. calculate. The calculated d-axis voltage Vd and q-axis voltage Vq are output as a d-axis voltage command value Vdr and a q-axis voltage command value Vqr.

  The two-phase / three-phase conversion unit 3 converts the d-axis voltage command value Vdr and the q-axis voltage command value Vqr into three-phase voltage command values vu, vv, and vw for each of the three phases. The d-axis voltage command value Vdr and the q-axis voltage command value Vqr are calculated by the integration control unit 2 described above. The two-phase / three-phase conversion unit 3 converts the d-axis voltage command value Vdr and the q-axis voltage command value Vqr to the opposite of the coordinate conversion described above, thereby performing the three-phase voltage command values vu, vv, vw. Convert to Since this reverse conversion is the reverse conversion of the coordinate conversion described above with reference to FIGS. 3 and 4, detailed description of the conversion method is omitted.

  The calculation result obtained by the two-phase / three-phase conversion unit 3 is input to the above-described PWM control unit 4 together with outputs from a state quantity estimation unit 8 and a sensitivity adjustment unit 9 described later. Therefore, the PWM control unit 4 performs PWM control based on these inputs.

  The motor control device 100 is based on the d-axis current Id and the q-axis current Iq obtained by the coordinate conversion of the three-phase / two-phase conversion unit 6 from the motor current flowing through the three-phase motor 10 as described above. The target current set by the target current setting unit 1 is feedback-controlled. The motor control device 100 further has a function of improving the controllability of the current control of the three-phase motor 10. In order to improve the controllability of this current control, the motor control device 100 includes a state quantity estimation unit 8 and a sensitivity adjustment unit 9.

  The state quantity estimating unit 8 estimates the state quantity of the three-phase motor 10 from the three-phase voltage command value and the motor current supplied to the three-phase motor 10 for each of the three phases. The 3-phase voltage command value is transmitted from the 2-phase / 3-phase converter 3. The motor current is a current supplied to the three-phase motor 10 and is transmitted from the three-phase motor 10. The motor current may be configured to transmit a current value detected by a current detector (not shown). The state quantity is an amount indicating the state of the three-phase motor 10. In the present embodiment, the amount of change in the motor current of the three-phase motor 10 corresponding to the application of the three-phase voltage command value calculated by the two-phase / 3-phase converter 3 to the three-phase motor 10 corresponds. The state quantity estimation unit 8 estimates such a state quantity and transmits the estimated state quantity to the PWM control unit 4.

  FIG. 5 is a block diagram showing a schematic configuration of the state quantity estimation unit 8 and the sensitivity adjustment unit 9. Here, for example, when the state quantity in the U phase is estimated, the calculation is performed using the U-phase three-phase voltage command value vu and the U-phase motor current iu. FIG. 5 illustrates that the U-phase three-phase voltage command value vu and the U-phase motor current iu are transmitted to the state quantity estimation unit 8. Similarly, the three-phase voltage command values and the motor currents of the respective phases can be transmitted to the state quantity estimation unit 8 for calculation. Alternatively, it is naturally possible to provide a state quantity estimation unit 8 and a sensitivity adjustment unit 9 for each phase. The state quantity estimation unit 8 estimates a state quantity for each phase. Since the calculation processing related to this estimation is the same for each phase, the U phase will be described here. Further, in FIG. 1, the PWM control unit 4 and the frequency conversion unit 5 are illustrated as being inserted in series between the two-phase / three-phase conversion unit 3 and the three-phase motor 10. These are omitted. Since these functional units are in the closed-loop control via the state quantity estimating unit 8, even if they are described without considering them, there is no influence on the operational effects. The estimation of the state quantity is based on so-called observer feedback control. Since this observer feedback control is a well-known technique, detailed description thereof is omitted.

  The state quantity estimation unit 8 includes free parameters A, B, and C, a state feedback gain K, an observer gain G, and an integrator 8a. Free parameters A, B, and C are gains determined by the characteristics of the three-phase motor 10. The characteristics of the three-phase motor 10 are parameters such as an inductance value and a resistance value of a coil of the three-phase motor 10 and are uniquely determined by the three-phase motor 10. These free parameters A, B, and C are set when the motor control device 100 is manufactured, and are not changed thereafter. The observer gain G is a gain for response adjustment when feedback control is performed on the calculation result calculated by the free parameters A, B, and C and the integrator 8a. The state feedback gain K is used when the calculation result calculated by the integrator 8a (that is, the calculation output of the state quantity estimation unit 8) is fed back to the PWM control unit 4 calculated by the two-phase / three-phase conversion unit 3. This is a gain for adjusting the response. By appropriately adjusting the state feedback gain K and the observer gain G, the response speed of each output can be changed to suppress overshoot and undershoot.

  The sensitivity adjustment unit 9 suppresses variations in characteristics of the three-phase motor 10 and adjusts the sensitivity of the state quantity estimation unit 8. As described above, the state quantity estimation unit 8 includes the free parameters A, B, and C determined by the characteristics of the three-phase motor 10. However, these free parameters are unambiguously determined and have variations. The sensitivity adjustment unit 9 controls the output sensitivity of the state quantity estimation unit 8 by suppressing the influence of such variations (variations in characteristics of the three-phase motor 10). Similar to the state feedback gain K and the observer gain G described above, this sensitivity adjustment unit 9 can change the response speed of the output of the state quantity estimation unit 8 to suppress overshoot and undershoot. As described above, the calculation result calculated by the state quantity estimation unit 8 and the sensitivity adjustment unit 9 is fed back the three-phase voltage command value output from the two-phase / three-phase conversion unit 3 as the state quantity of the three-phase motor 10. Used to control.

  The PWM control unit 4 controls the motor current by PWM control based on the three-phase voltage command value and the estimated state quantity. That is, the PWM control unit 4 performs PWM control based on the three-phase voltage command value transmitted by the two-phase / three-phase conversion unit 3 and the state quantities estimated by the state quantity estimation unit 8 and the sensitivity adjustment unit 9. I do.

  Thus, the motor control device 100 performs feedback control based on the target current set by the target current setting unit 1 and the d-axis current Id and the q-axis current Iq calculated by the three-phase / two-phase conversion unit 6. And performing observer feedback control based on the three-phase voltage command value transmitted by the two-phase / three-phase converter 3 and the state quantities estimated by the state quantity estimating unit 8 and the sensitivity adjusting unit 9 Thus, stable current control can be performed even when the motor current of the three-phase motor 10 fluctuates greatly.

[Other Embodiments]
In the said embodiment, the coil was demonstrated as being provided in the stator which the three-phase motor 10 has. However, the scope of application of the present invention is not limited to this. Of course, it is also possible to apply the present invention to the three-phase motor 10 in which the coil is provided in the rotor.

The figure which shows schematic structure of a motor control apparatus The figure which shows the structure of a PWM control part, a frequency conversion part, and a three-phase motor Diagram showing the principle of coordinate transformation Vector diagram explaining the phase angle of the armature current The figure which shows schematic structure of a state quantity estimation part and a sensitivity adjustment part.

Explanation of symbols

1: target current setting unit 2: integration control unit 3: 2-phase / 3-phase conversion unit 4: PWM control unit 5: frequency conversion unit 6: 3-phase / 2-phase conversion unit 7: rotation angle calculation unit 8: state quantity estimation Unit 9: Sensitivity adjustment unit 10: Three-phase motor

Claims (3)

A three-phase / two-phase converter that calculates the d-axis d-axis current, which is the direction of the magnetic field generated by the permanent magnet disposed in the rotor of the three-phase motor, and the q-axis q-axis current orthogonal to the d-axis; ,
Based on the target current set from the total torque required to rotate the three-phase motor, the d-axis current, and the q-axis current, the d-axis voltage command value and the q-axis voltage command value An integration control unit for calculating
A two-phase / three-phase converter that converts the voltage command value for the d-axis and the voltage command value for the q-axis into a three-phase voltage command value for each of the three phases;
For each of the three phases, a state quantity estimating unit that estimates the amount of change in the motor current of the three-phase motor from the three-phase voltage command value and the motor current energized in the three-phase motor;
A motor control device comprising: The motor control device according to claim 1, wherein the motor current is controlled by PWM control based on the three-phase voltage command value and the estimated amount of change in the motor current .   The motor control device according to claim 1, wherein the state quantity estimating unit has a gain determined by characteristics of the three-phase motor.

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