JP2010028927A - Control method and controller of electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method and a controller of an electric motor which estimate a more accurate offset value. <P>SOLUTION: Outputs vd and vq from a current controller 2 are converted from a voltage command on the dq coordinate system to a voltage command on the three-phase AC coordinate system by a dq/three-phase converter 3 and a voltage is applied to an electric motor 7. A current flowing through the electric motor 7 is detected by a current detector 6, and the position of the electric motor 7 is detected by a position detector 8 and converted into a speed by a position/speed converter 9. Furthermore, the current flowing through the electric motor 7 is converted from the three-phase AC coordinate system to the dq coordinate system by a three-phase/dq converter 11, a current on the dq coordinate is estimated based on the speed information output from the position/speed converter 9 and the outputs vd and vq from the current controller 2, and the offset value of the current detector 6 is estimated from the difference between the estimated current (idsim, iqsim) and the current output from the three-phase/dq converter 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor control method and control apparatus for controlling a drive current of a motor, and more particularly to a method and apparatus for correcting an offset of a current sensor.

Conventionally, there has been known a control device that detects a drive current value of a motor with a current detector and feeds back the drive current value to drive control. In this type of device, when the detection value of the current detector is offset, the motor drive current is offset to the positive side or the negative side, thereby generating an eddy current due to magnetic flux fluctuation in the rotor, There may be problems such as a decrease in torque due to demagnetization of the permanent magnet due to heat generation and an increase in vibration / noise due to torque pulsation.
As a technique for correcting such an offset of the drive current, there is a motor control device disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-289992 (see Patent Document 1).
JP 2001-298990 A

  However, in the technique of Patent Literature 1, in a motor control device including a drive signal generation unit that generates a drive signal for a motor and a current supply unit that supplies a drive current corresponding to the drive signal to the motor. A current detection unit that detects a current value of a drive current of the motor, an offset amount calculation unit that calculates an offset amount of the drive current based on a current value detected when the motor is driven, and based on the calculated offset amount And a drive signal correction unit that corrects the drive signal, and corrects the drive current based on the detected current of the motor. Therefore, there is a problem that the calculated value of the offset amount is inaccurate.

  It is an object of the present invention to provide a motor control method and control apparatus that can solve the above-described problems and can estimate a more accurate offset value.

In order to solve the above-mentioned problems, the present invention converts the output vd and vq from the current controller (2) for controlling the excitation current id and the torque current iq of the motor (7) into dq / 3-phase conversion. The voltage command on the dq coordinate is converted into a three-phase alternating current coordinate system by the device (3), the PWM control of the PWM inverter (5) is performed based on the voltage instruction from the dq / 3-phase converter (3), and the motor In the motor control method of applying a power supply voltage to (7), detecting a current flowing through the motor (7), and feeding back the drive current value to the drive control, the three-phase current flowing through the motor (7) Two-phase current is detected by the current detector (6), the position of the rotor of the motor (7) is detected by the position detector (8), and the motor (7) obtained from the position detector (8) is detected. ) Position information of the rotor The iu + Δu1 and iv + Δv1 to which the offset values Δu1 and Δv1 obtained by the current detector (6) are converted to the speed and added from the current detector (6) are added to the A / D converter. Iuoff (= iu + Δu1 + Δu2), ivoff (= iv + Δv1) obtained by converting the values obtained by adding the offset components Δu2, Δv2 by the A / D converter to iu + Δiu1 and iv + Δiv1, respectively, according to (10) + Δv2) is converted from the three-phase alternating current coordinate system to the dq coordinate system by the three-phase / dq converter (11), the velocity information output from the position / velocity converter (9), and the current control The current on the dq coordinate is estimated based on the outputs vd and vq of the generator (2), and from the difference between the estimated currents idsim and iqsim and the current output from the three-phase / dq converter (11), The purpose is to estimate the offset value of the current detector (6).
The present invention also includes a speed controller (1) for controlling the speed of the motor (7), and a current controller (for controlling the excitation current id and the torque current iq of the motor (7)). 2), a dq / 3-phase converter (3) for converting the output vd, vq from the current controller (2) from a voltage command on the dq coordinate to a three-phase AC coordinate system, and the dq / 3 Position for detecting the position of the inverter (5) for applying PWM control based on the voltage instruction from the phase converter (3) and applying the power supply voltage to the motor (7) and the rotor of the motor (7) A three-phase current flowing through the motor (7) in a motor control device that detects a current flowing through the motor (7) and feeds back the drive current value to the drive control. Said current detection for detecting the current of two phases (6), a position / speed converter (9) for converting the position information of the rotor of the motor 7 obtained from the position detector (8) into a speed, and the current detector (6) Iuoff (= iu + Δu1 + Δu2) and ivoff obtained by adding iu + Δu1 and iv + Δv1 obtained by adding offset values Δu1 and Δv1 by the current detector and offset values Δu2 and Δv2 of the A / D converter (10), respectively. The A / D converter (10) for discretizing (= iv + Δv1 + Δv2), and the three-phase / dq converter (11) for converting the discretized iuoff and ivoff from the three-phase AC coordinate system to the dq coordinate system ), Velocity information output from the position / velocity converter (9), and a current simulator (12) for estimating the current on the dq coordinate based on the outputs vd and vq of the current controller (2) , The estimated currents idsim and iqsim from the current simulator (12) and the three-phase / q converter from the difference between the current output from (11) is to comprise current offset estimator for estimating the offset value (13) of said current detector (6).

  According to the motor control method and control apparatus of the present invention, a robust current control system that does not cause torque pulsation or the like can be obtained by removing the offset of the current detector.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram of a motor control apparatus showing an embodiment of the present invention. The inside of the dotted line in FIG. 1 constitutes the central processing unit CPU.
First, the circuit configuration of FIG. 1 will be described. Reference numeral 1 denotes a speed controller for controlling the speed of a multi-phase, for example, three-phase AC motor (hereinafter abbreviated as a motor) 7. Reference numeral 2 denotes a current controller for inputting the signal (iqref) from the speed controller 1 to control the excitation current id and the torque current iq. The output of the current controller 2 is a voltage on the dq coordinate axis. The commands are vd and vq. Reference numeral 3 denotes a dq / 3-phase converter for converting the output from the current controller 2 and the voltage commands vd and vq from the voltage command on the dq coordinate to the three-phase AC coordinate system. Reference numeral 4 denotes an AC power source for driving the motor 7. Reference numeral 5 denotes an inverter for performing PWM control so that the voltage output from the AC power supply 4 becomes a voltage instruction obtained from the dq / 3-phase converter 3 and supplying a drive current to the motor 7. 6 is a current detector connected between the inverter 5 and the motor 7, and this current detector 6 is for detecting U-phase and V-phase currents among the three-phase currents flowing through the motor 7. . The output from the current detector 6 is multiplied by an offset (Δu1, Δv1) by the current detector 6. The motor 7 is controlled by a drive current supplied from the inverter 5 to each phase (U phase, V phase, W phase) of the motor 7.

Reference numeral 8 denotes a position detector such as an encoder that is built in or is provided with the motor 7 and detects the position of the rotor of the motor 7. A position / speed converter 9 is connected to the position detector 8 and converts the position information of the rotor of the motor 7 obtained from the position detector 8 into a speed. Reference numeral 10 is connected to the current detector 6, and an A / D converter (analog / digital conversion) for taking into the CPU the current on the offset (Δu1, Δv1) obtained from the current detector 6 by the current detector 6 The offset value of the A / D converter 10 itself is multiplied by the output of the current detector when it is taken into the CPU. A three-phase / dq converter 11 converts the outputs iuoff (= iu + Δu1 + Δu2) and ivoff (= iv + Δv1 + Δv2) of the A / D converter from the three-phase AC coordinate system to the dq coordinate system. The current controller 2 is connected to the output side of the three-phase / dq converter 11.
12 is connected to the position / speed converter 9 and the output side of the current controller 2, and dq based on the motor speed ω obtained by the position / speed converter 9 and the outputs vd and vq of the current controller 2. It is a current simulator that estimates current on coordinates, and its output is expressed by idsim and iqsim.

Reference numeral 13 denotes an output (iuoff, ivoff) of the A / D converter 10 which is an output of the three-phase / dq converter 11 by connecting the output side of the three-phase / dq converter 11 and the output side of the current simulator 12. Based on the current (idoff, iqoff) converted on the dq coordinate axis and the estimated current (idsim, iqsim) on the dq coordinate axis that is the output of the current simulator 12, the offset current (iddet, iqdet) on the dq axis is calculated. A current offset estimator for estimation. Reference numeral 14 denotes a dq / 3-phase converter that converts an offset current value (iddet, iqdet) on the dq axis, which is an output of the current offset estimator 13, into an offset value for each of the U and V phases.
In the embodiment, the dotted line is used for the CPU, but the same configuration can be assembled and implemented without using the CPU.

Next, the operation of the motor control apparatus will be described.
As shown in Equation 1, the current obtained from the current detector 6 is offset by the current detector 6 (Δu1, Δv1). When the current obtained from the current detector 6 is input to the CPU, it is always A / A D converter 10 (analog / digital converter) is used. The sum of the offset (Δu 2, Δv 2) that is applied when the current is discretized by the A / D converter 10 and the offset value (Δu 1, Δv 1) by the current detector 6 is given by Equation 1.

  The output of the A / D converter 10 is Equation 2 (iuoff, ivoff), and iu and iv are currents for the U phase and V phase that are actually flowing through the motor 7, respectively. Δu and Δv are offsets by the current detector 6 and the A / D converter 10.

  When the current including the offset is used as described above, the current on the dq coordinate used in the current controller 2 is calculated by the three-phase / dq converter 11 as shown in idoff and iqoff. And a value including the offsets Δu and Δv by the A / D converter 10, and the sensor current waveform of FIG. In Equation 3, id and iq are sensor currents on the dq coordinate axis that do not include offsets by the current detector 6 and the A / D converter 10 (see FIG. 2). θe is the electrical angle of the motor.

  Next, the current simulator 12 calculates the winding resistance, which is an electric parameter of the motor, from the motor speed ω obtained by the position / speed converter 9 and the voltage command values vd and vq on the dq coordinate as the output of the current controller 2. The idsim and iqsim, which are currents on the dq coordinate, are estimated using the winding inductance, and are represented by the block diagram of FIG. When there is no offset by the current detector 6 and the A / D converter 10, idsim and iqsim are estimated by the differential equations shown in Equations 4, 5, and 6. In Equations 4 to 6, Rn is the nominal value of the winding resistance of the motor 7, Ln is the nominal value of the winding inductance of the motor 7, ωre is the rotational electrical angular velocity of the motor 7, ΔVq is the output error correction value of the inverter, φfn Is the nominal value of the number of flux linkages of the motor, and Tc is the sampling time. Here, ΔVq is for correcting the voltage applied to the motor 7 by the PWM inverter 5 of FIG.

  As described above, the current simulator 12 uses the voltage commands vd and vq output from the current controller 2. The voltage commands vd, vq are actually converted into three-phase voltage commands vu, vv, vw by the dq / 3-phase converter 3 and input to the PWM inverter 5. However, the PWM inverter 5 generates an output voltage error with respect to the three-phase voltage command value due to a dead time, a forward drop, or the like due to a switching element such as an IGBT or a MOSFET. Even if this actually applied voltage is converted into a voltage value on the dq coordinate, an error occurs from the voltage command values vd and vq output from the current controller 2. This is corrected by ΔVq in FIG. In Equation 7, Vfd represents the IGBT forward drop voltage, Td represents the dead time, and ton and toff represent the turn-on and turn-off times of the switching element, respectively.

  When the current detector 6 has an offset, idoff and iqoff, which are currents including the offset, are fed back to the current controller 2, so that the outputs vd and vq of the current controller 2 are also output including the offset. In the steady state, Equations 8 and 9 are obtained.

  Since Equation 8 is also input to the current simulator 12, vdoff and vqoff of Equation 8 are input to vd and vq of Equations 4 and 5, and the output of the current simulator 12 is Equations 10 and 11, respectively. It is represented by

  Next, the current offset estimator 13 uses the value obtained by converting the output of the current detector 6 to the dq axis (idoff, iqoff) and the output of the current simulator 12 (idsim, iqsim) to calculate the current due to the offset on the dq axis using Equation 12. The error (iddet, iqdet) is estimated, and FIG. 5 shows the difference between the d-axis sensor current and the estimated current, and FIG. 6 shows the difference between the q-axis sensor current and the estimated current, respectively.

  Based on the output of the offset estimator 13, the offset current (iudet, ivdet) of each phase of U and V is expressed by Equation 13 in the dq / 3-phase converter 14 as shown in FIG. Can be estimated.

(Other embodiment 1)
Another embodiment of the offset estimation of the current detector 6 in the case where a parameter error is included in the nominal values Rn and Ln of the electrical parameters will be described.
Even in this case, FIG. 1 is used. However, the implementation procedure is different. FIG. 8 showing the sensor current and the estimated current is the detection current id, iq when there is an error in the electrical parameter (Ra = αRn, La = βLn), and the output of the current simulator 12 (idsim ′, iqsim ′). In the steady state, there is a direct current offset. If there is a parameter error, the effect of the parameter error appears in the DC component of the current simulator 12.

In this state, if the nominal value Rn of the resistance of the current simulator 12 is adjusted so that the direct current component of idsim, as shown in FIG.

  If Expression 14 is established, the output of the current simulator 12 becomes Expression 15 and Expression 16.

(Other embodiment 2)
The nominal values (catalog values) Rn0 and Ln0 used in the current simulator 12 have errors of α times and β times, respectively, with respect to the actual winding resistance Ra and winding inductance La. Ra = αRn0 and La = βLn0.

This will be explained with reference to the flowchart shown in FIG.
In step 1, a constant load is applied, and a step-like command is given as a speed command (S1).
In step 2, the current simulator output is compared with the id and idsim ′ of the current detector output (S2). The waveform at this time is shown in FIG.
Next, in step 3, Rn of the current simulator 12 is adjusted to Rn1 so that the direct current component of the current simulator output idsim ′ becomes 0 in the same manner as the id (id = 0) of the current detector output. Ra = βRn1 (S3) The waveform at this time is shown in FIG.
In step 4, β is calculated from the q-axis current output iqsim ′ of the current simulator 12 using Rn 1 and the q-axis current iq obtained from the current detector 6. La is calculated from La = βLn0 using β = iqsim ′ / iq and the obtained β (S4).
Next, in step 5, Rn of the current simulator 12 is returned to Rn0, the obtained La = βLn0 is used to configure the current simulator 12, and the current simulator output and the id and idsim ′ of the current detector output are again set. Compare (S5). The waveform at this time is shown in FIG.
In step 6, Ln of the current simulator 12 is adjusted to Ln1 so that the direct current component of the current simulator output idsim 'becomes 0 in the same manner as id = 0 of the current detector output (S6). Ln = αLn1. The waveform at this time is shown in FIG.
Finally, in step 7, α is calculated from the q-axis current output iqsim ′ of the current simulator 12 using Ln1 and the q-axis current iq obtained from the current detector 6. Ra is identified from α = iqsim ′ / iq, Ra = αRn (S7).

The present invention is a method and apparatus for estimating an offset value of a current sensor from a difference between an estimated current estimated based only on motor speed information ω and a voltage command on dq coordinates and a sensor current.
In addition, the DC component of the estimated current becomes an error due to fluctuations in the electrical parameters, and the offset of the current sensor becomes a ripple component. A method and apparatus for estimating an offset value by both D converters 10.
According to the above embodiment, a robust current control system that does not cause torque pulsation or the like can be obtained by removing the offset of the current detector 6.

  Needless to say, the present invention is not limited to the above-described embodiment, and can be implemented with appropriate modifications within a scope not changing the gist of the present invention.

It is a block diagram which shows embodiment of this invention. It is a figure which shows the output current of a three phase / dq converter by the simulation result of the offset estimation by this invention. It is a block diagram of a current simulator. It is a figure which shows an estimated electric current by the simulation result of the offset estimation by this invention. It is a simulation result of offset estimation by this invention, and is a figure which shows the difference of the detected current of d-axis, and an estimated current. It is a simulation result of offset estimation by this invention, and is a figure which shows the difference of the detected current of q-axis, and an estimated current. It is a figure which shows an estimated offset in the simulation result of the offset estimation by this invention. The detected current and the estimated current at the time of parameter error. It is a figure which shows the state which adjusted the direct current component of idsim so that it might approach id from FIG. It is a flowchart which shows other embodiment of this invention. It is a wave form diagram which compares the current simulator output by other embodiment of this invention, and id and idsim 'of a current detector output. It is the wave form diagram which adjusted Ln of the current simulator by other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Speed controller 2 Current controller 3 dq / 3 phase converter 4 AC power supply 5 Inverter 6 Current detector 7 Electric motor (motor)
8 Position detector 9 Position / speed converter 10 A / D converter 11 3 phase / dq converter 12 Current simulator 13 Offset estimator 14 dq / 3 phase converter

Claims (6)

A voltage command on the dq coordinate is output by the dq / 3-phase converter (3) from the output vd, vq from the current controller (2) for controlling the excitation current id of the motor (7) and the torque current iq. To a three-phase alternating current coordinate system, PWM control of the PWM inverter (5) is performed based on a voltage instruction from the dq / 3-phase converter (3), a power supply voltage is applied to the motor (7), and In the motor control method of detecting the current flowing through the motor (7) and feeding back the drive current value to the drive control,
Two-phase current out of the three-phase currents flowing through the motor (7) is detected by a current detector (6), and the position of the rotor of the motor (7) is detected by a position detector (8). The position information of the rotor of the motor (7) obtained from the detector (8) is converted into speed by the position / speed converter (9), and the current iuoff on which the offset obtained from the current detector (6) is mounted. , Ivoff is converted from the three-phase alternating current coordinate system to the dq coordinate system by the three-phase / dq converter (11), the velocity information output from the position / velocity converter (9), and the current controller ( The current on the dq coordinate is estimated based on the outputs vd and vq of 2), and from the difference between the estimated current (idsim, iqsim) and the current output from the three-phase / dq converter (11), The offset of the current detector (6) Control method of the motor and estimates the value.   When the DC component of the estimated current becomes an error due to fluctuations in electrical parameters, and the offset of the current detector (6) becomes a ripple component, the resistance and inductance parameters of the motor (7) change. The motor control method according to claim 1, wherein the offset value is estimated based on both output signals of the current detector (6) and the A / D converter (10). The voltage applied to the motor (7) by the PWM inverter (5) is corrected using an output error correction value ΔVq of the inverter expressed by the following equation (Equation 7). A method for controlling the motor according to 1.

A speed controller (1) for controlling the speed of the motor (7);
A current controller (2) for controlling an excitation current id and a torque current iq of the motor (7);
A dq / 3-phase converter (3) for converting the output vd, vq from the current controller (2) from a voltage command on the dq coordinate to a three-phase AC coordinate system;
An inverter (5) for performing PWM control based on a voltage instruction from the dq / 3-phase converter (3) and applying a power supply voltage to the motor (7);
A position detector (8) for detecting the position of the rotor of the motor (7);
A motor control device that detects a current flowing through the motor (7) and feeds back the drive current value to the drive control.
The current detector (6) for detecting the current of two phases of the three-phase current flowing through the motor (7);
A position / speed converter (9) for converting the position information of the rotor of the motor (7) obtained from the position detector (8) into a speed;
A three-phase / dq converter (11) for converting a current (iuoff, ivoff) with an offset obtained from the current detector (6) from a three-phase AC coordinate system to a dq coordinate system;
A current simulator (12) for estimating the current on the dq coordinate based on the velocity information output from the position / velocity converter (9) and the outputs vd and vq of the current controller (2);
The offset value of the current detector (6) is estimated from the difference between the estimated current (idsim, iqsim) from the current simulator (12) and the current output from the three-phase / dq converter (11). A motor control device comprising a current offset estimator (13).   Using the fact that the DC component of the estimated current (idsim, iqsim) of the current simulator (12) becomes an error due to fluctuations in electrical parameters, and the offset of the current detector (6) becomes a ripple component, The offset value is estimated by the current offset estimator (13) based on both output signals of the current detector (6) and the A / D converter (10) even when the resistance and inductance parameters vary. The motor control device according to claim 4. 6. The voltage applied to the motor (7) by the PWM inverter (5) is corrected using the output error correction value ΔVq of the inverter expressed by the following equation (Equation 7). The motor control apparatus described.

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