JP2005151744A - Motor drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute an always most suited current control system that does not depend on power circumstances, and to achieve the stable drive of a motor. <P>SOLUTION: This motor drive unit 3 comprises: a current detection part 9 that detects a current flowing to a stator winding of the motor 4; a speed control part 11 that creates a current command value I* from a speed error between a target speed ω* and the rotational speed ω1 of the motor 4; a detection part 10 that detects a DC voltage of an inverter 5; a current control gain correction part 16 that corrects a current control gain set in advance on the basis of the detected DC voltage value; and a current control part 12 that creates a voltage command value v* from a current error between the current command value I* and the detected current value by using the corrected current control gain. By the current control gain correction part 16, the always most suited current control system can be constituted not depending on the power circumstances, and the stable drive of the motor can be achieved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electric motor drive device that drives an electric motor such as a brushless DC motor at an arbitrary rotation speed.

  In recent years, in an apparatus for driving an electric motor such as a compressor in an air conditioner, there is an increasing need to reduce power consumption from the viewpoint of protecting the global environment. Among them, as one of the power saving techniques, an inverter that drives a highly efficient electric motor such as a brushless DC motor at an arbitrary frequency is widely used. Furthermore, as a driving technique, a sine wave driving technique that is more efficient and can reduce noise is attracting attention as compared with the rectangular wave driving that is driven by a rectangular wave current.

  When driving an electric motor such as a compressor in an air conditioner, it is difficult to mount a sensor that detects the position of the rotor of the electric motor. A sinusoidal drive technology has been devised. As a method for estimating the position of the rotor, there is a method in which an induced voltage generated in a stator winding of an electric motor is estimated (see, for example, Patent Document 1).

  FIG. 7 is a system configuration diagram of a conventional electric motor driving device described in Patent Document 1. In FIG. As shown in FIG. 7, the electric motor drive device 3 includes an inverter 5 including freewheeling diodes 6 a to 6 f paired with a plurality of switching elements 5 a to 5 f, a speed control unit 11, a current control unit 12, and a PWM signal generation. Part 13, induced voltage estimation part 14, and rotor position speed estimation part 15.

  The input voltage from the AC power source 1 is rectified to DC by the rectifier circuit 2, and the DC voltage is converted into a three-phase AC voltage by the inverter 5, thereby driving the electric motor 4 which is a brushless DC motor.

  In the motor drive device 3, in order to realize a target speed given from the outside, the speed control unit 11 sets the target speed ω * and the current speed ω1 (the current value of the estimated speed estimated by the rotor magnetic pole position speed estimating unit 15). The current command value I * is calculated by proportional-integral control (hereinafter referred to as PI control) so that the speed error Δω with respect to is zero.

  The current control unit 12 includes a stator winding phase current command value created based on the current command value I * calculated by the speed control unit 11, and currents obtained from the current detectors 7 a and 7 b and the current detection unit 9. The voltage command value V * is calculated by PI control so that the current error from the detected value becomes zero.

  The induced voltage estimation unit 14 is detected by the current detection value of the motor 4 detected by the current detectors 7a and 7b and the current detection unit 9, the voltage command value V *, the voltage dividing resistors 8a and 8b, and the DC voltage detection unit 10. Based on the information on the DC voltage of the inverter 5 thus generated, the induced voltage generated in each phase of the stator winding of the electric motor 4 is estimated.

The rotor position speed estimation unit 15 estimates the magnetic pole position and speed of the rotor in the electric motor 4 using the induced voltage estimated by the induced voltage estimation unit 14. Based on the information on the estimated rotor magnetic pole position, the current control unit 12 generates a signal for driving the switching elements 5a to 5f in order for the inverter 5 to output the voltage command value V *. The drive signal is converted into a drive signal for electrically driving the switching elements 5a to 5f by the PWM signal generator 13. The switching elements 5a to 5f are operated by the drive signal.

With the above configuration, position sensorless sine wave drive is performed.
Japanese Patent No. 3419725

  However, since the conventional configuration does not include means for correcting a preset PI control gain according to the power supply voltage (AC power supply voltage or DC voltage such as a battery), the power supply circumstances (voltage value and stability of the power supply) For example, when the power supply voltage is increased, the PI control gain is apparently increased and the current of the motor 4 is hunted. Conversely, when the power supply voltage is decreased, the apparent PI control gain is decreased and the motor is decreased. 4 may fluctuate, and not only a satisfactory control specification cannot be obtained with a preset PI control gain, but the design man-hours for optimal adjustment of the PI control gain increase. It was.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and aims to provide an electric motor drive device that always builds an optimal current control system without depending on power supply circumstances and realizes stable electric motor drive. To do.

In order to solve the above-described conventional problems, the electric motor drive device of the present invention has a plurality of switching element pairs each composed of an upper arm switching element arranged on the high voltage side and a lower arm switching element arranged on the low voltage side, An inverter that converts a DC voltage into an AC voltage having a desired frequency and voltage by the operation of the switching element, and supplies the AC voltage as a drive voltage to a multi-phase motor;
Current detection means for detecting current flowing in the stator winding of the motor, current control means for creating a voltage command value from a current error between the current command value for the motor and the current detection value detected by the current detection means, and voltage Based on the output value of the PWM signal generating means for generating the PWM signal for controlling the operation of each switching element of the inverter based on the command value, the DC voltage detecting means for detecting the DC voltage of the inverter, and the DC voltage detecting means Current control gain correction means for correcting the current control gain in the current control means, and the current control gain correction means is a ratio between a preset reference value of the DC voltage of the inverter and the output value of the DC voltage detection means. The current control gain is corrected by multiplying the current control gain by the current control gain.

  By this current control gain correction means, a preset current control gain is corrected according to the DC voltage of the inverter.

  The electric motor drive device of the present invention has a plurality of switching element pairs each composed of an upper arm switching element arranged on the high voltage side and a lower arm switching element arranged on the low voltage side, and a DC voltage is generated by the operation of each switching element. An inverter that converts to an AC voltage of a desired frequency and voltage and supplies it as a driving voltage to a multi-phase motor, current detection means for detecting current flowing in the stator winding of the motor, current command value and current for the motor Current control means for creating a voltage command value from a current error from the detected current value detected by the detection means, and PWM signal generation for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value Means, DC voltage detecting means for detecting the DC voltage of the inverter, and a voltage command based on the output value of the DC voltage detecting means. Voltage command correcting means for correcting the voltage, and the voltage command correcting means multiplies a voltage command value by a ratio between a preset reference value of the DC voltage of the inverter and the output value of the DC voltage detecting means. This corrects the voltage command value.

The voltage command correction means corrects the voltage command value calculated by the current control means using the preset current control gain according to the DC voltage of the inverter, so that the preset current control gain is In addition to obtaining the same effect as when correcting according to the DC voltage, it is possible to reduce the amount of calculation and memory in the calculation means such as a microcomputer.

  The electric motor drive device of the present invention corrects a preset current control gain in accordance with the DC voltage of the inverter, so that an optimum current control system can be always constructed without depending on the power supply situation, and stable electric motor driving can be achieved. realizable.

  The first invention has a plurality of switching element pairs each composed of an upper arm switching element arranged on the high voltage side and a lower arm switching element arranged on the low voltage side, and a DC voltage is converted to a desired frequency by the operation of each switching element. An inverter that converts the voltage into an AC voltage and supplies it as a drive voltage to a multi-phase motor, current detection means for detecting the current flowing in the stator winding of the motor, the rotational speed of the motor, and a target given from the outside A speed control means for creating a current command value for the motor from a speed error with respect to the speed, a current control means for creating a voltage command value from a current error between the current command value and the current detection value detected by the current detection means, and a voltage PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the command value, and the DC voltage of the inverter DC voltage detecting means for detecting, and current control gain correcting means for correcting the current control gain in the current control means based on the output value of the DC voltage detecting means, the current control gain correcting means being set in advance By correcting the current control gain by multiplying the ratio of the reference value of the DC voltage of the inverter and the output value of the DC voltage detection means by the current control gain, the preset current control gain is changed to the DC voltage of the inverter. By making corrections according to the above, an optimal current control system can always be constructed without depending on the power supply situation, and a stable motor drive can be realized.

  The second invention has a plurality of switching element pairs each composed of an upper arm switching element arranged on the high voltage side and a lower arm switching element arranged on the low voltage side, and the DC voltage is converted to a desired frequency by the operation of each switching element. An inverter that converts the voltage into an AC voltage and supplies it as a drive voltage to a multi-phase motor, current detection means for detecting the current flowing in the stator winding of the motor, the rotational speed of the motor, and a target given from the outside A speed control means for creating a current command value for the motor from a speed error with respect to the speed, a current control means for creating a voltage command value from a current error between the current command value and the current detection value detected by the current detection means, and a voltage PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the command value, and the DC voltage of the inverter DC voltage detecting means for detecting, and voltage command correcting means for correcting a voltage command value based on an output value of the DC voltage detecting means, the voltage command correcting means being a reference for a DC voltage of a preset inverter The voltage calculated by the current control means using a preset current control gain by correcting the voltage command value by multiplying the ratio of the value and the output value of the DC voltage detection means by the voltage command value By correcting the command value according to the inverter DC voltage, the same effect as when the preset current control gain is corrected according to the inverter DC voltage can be obtained. A current control system can be constructed, and not only can a stable motor drive be realized, but also the amount of computation and memory in the computing means such as a microcomputer can be reduced compared to the first invention, It can be realized cost reduction calculation means.

  The third aspect of the invention is particularly the motor drive device of the first or second aspect of the invention, wherein the ratio is calculated by dividing the reference value of the direct current voltage by the output value of the direct current voltage detection means, and the output of the direct current voltage detection means When the value is less than zero, the current control gain is set even when the DC voltage of the inverter fluctuates significantly and the lower limit value of the DC voltage becomes less than zero by setting the maximum value set in advance to the ratio. (Or the voltage command value) can be corrected, and an optimum current control system can always be constructed in any power supply situation.

  The fourth aspect of the invention is particularly the electric motor drive device according to any one of the first to third aspects of the invention, wherein the ratio has at least a preset upper limit value or lower limit value, whereby a current control gain (or voltage command value). Can be prevented, and unstable operation of the motor, such as hunting and turbulence, can be avoided.

  The fifth aspect of the invention is particularly the electric motor drive device according to any one of the first to fourth aspects of the present invention, and only when the output value of the direct current voltage detecting means is outside the preset direct current voltage range (or (Voltage command value) is corrected, and if the current control gain (or voltage command value) is not corrected within the range, the current control gain correction effect is large (outside the preset DC voltage range) In this case, by correcting the current control gain (or voltage command value) only, it is possible to reduce the amount of computation and memory in the computing means such as a microcomputer, and the cost of the computing means can be reduced.

  According to a sixth aspect of the invention, in particular, in the electric motor drive device of the fifth aspect of the present invention, a switching grace period is provided at the time of switching with or without correction of the current control gain (or voltage command value). The control stability and reliability associated with switching with or without correction of the command value) can be improved, and unstable operation of the motor such as hunting and turbulence can be prevented.

  In particular, the seventh aspect of the invention is the electric motor drive device according to any one of the first to sixth aspects, wherein the current control gain (or voltage command value) is corrected in synchronization with the control cycle of the inverter, so that at least the inverter The current control gain (or voltage command value) can be corrected every control cycle, and the power supply situation can be reflected in the current control system in real time.

  The eighth aspect of the invention is an electric motor driving apparatus according to the seventh aspect of the invention, in particular, only when the fluctuation range of the output value of the DC voltage detection means is within a preset fluctuation range, the n cycle of the inverter control cycle. When the effect of correcting the current control gain (or voltage command value) is small by correcting the current control gain (or voltage command value) every time (n ≧ 2) (within a preset value of the fluctuation range) In this case, by correcting the current control gain (or voltage command value) every n cycles (n ≧ 2) of the inverter control cycle, it is possible to reduce the amount of calculation and memory in the calculation means such as a microcomputer. Cost reduction.

  The ninth aspect of the invention is particularly the electric motor drive device of any one of the first to eighth aspects, wherein the DC voltage detecting means removes noise caused by switching of the inverter from the instantaneous value of the input DC voltage of the inverter. By performing the filtering process for the output, the control stability and reliability can be improved by preventing malfunction due to noise, and the control performance of the motor can be prevented from deteriorating.

  The tenth aspect of the invention is particularly the electric motor drive apparatus according to any one of the first to ninth aspects of the invention, wherein the DC voltage detection means is set to have a common potential with the current control gain correction means (or voltage command correction means). By inputting the instantaneous value of the DC voltage obtained from the non-insulated circuit, the detection time can be shortened compared to the case of detecting the DC voltage using an insulating circuit such as a photocoupler.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a system configuration diagram of an electric motor drive device according to Embodiment 1 of the present invention. In FIG. 1, an electric motor driving device 3 includes an inverter 5 including freewheeling diodes 6 a to 6 f that are paired with a plurality of switching elements 5 a to 5 f, a current detection unit 9, and a voltage detection unit 10.
And a speed control unit 11, a current control unit 12, a PWM signal generation unit 13, an induced voltage estimation unit 14, a rotor position speed estimation unit 15, and a current control gain correction unit 16.

  The input voltage from the AC power source 1 is rectified to DC by the rectifier circuit 2, and the DC voltage is converted into a three-phase AC voltage by the inverter 5, thereby driving the electric motor 4 which is a brushless DC motor.

  In the motor drive device 3, in order to realize a target speed given from the outside, the speed control unit 11 sets the target speed ω * and the current speed ω1 (the current value of the estimated speed estimated by the rotor magnetic pole position speed estimating unit 15). The current command value I * is calculated by PI control so that the speed error Δω with respect to is zero.

  The current control gain correction unit 16 is configured based on the DC voltage information of the inverter 5 detected by the voltage dividing resistors 8a and 8b and the DC voltage detection unit 10, and the current control gain (PI control) of the current control unit 12 set in advance. (Gain) is corrected.

  The current control unit 12 is obtained from the phase current command value of the stator winding created based on the current command value I * calculated by the speed control unit 11, and the current detectors 7a and 7b and the current detection unit 9. The voltage command value V * is calculated by PI control using the current control gain corrected by the current control gain correction unit 16 so that the current error from the detected current value becomes zero.

  The induced voltage estimation unit 14 includes the current detection value of the electric motor 4 detected by the current detectors 7a and 7b and the current detection unit 9, the voltage command value V *, the voltage dividing resistors 8a and 8b, and the DC voltage detection unit 10. Based on the detected DC voltage information of the inverter 5, the induced voltage generated in each phase of the stator winding of the electric motor 4 is estimated.

  The rotor position speed estimation unit 15 estimates the magnetic pole position and speed of the rotor in the electric motor 4 using the induced voltage estimated by the induced voltage estimation unit 14. Based on the information on the estimated rotor magnetic pole position, the current control unit 12 generates a signal for driving the switching elements 5a to 5f in order for the inverter 5 to output the voltage command value V *. The drive signal is converted into a drive signal for electrically driving the switching elements 5a to 5f by the PWM signal generator 13. The switching elements 5a to 5f are operated by the drive signal.

  In FIG. 1, two current detectors 7 a and 7 b that detect the phase current of the motor 4 are provided and used for estimating the rotor position speed. However, the DC current on the input side of the inverter 5 (the inverter 5 Needless to say, means such as detecting the phase current of the electric motor 4 from the bus current) may be used.

  In FIG. 1, the speed control is performed so that the speed of the motor 4 follows the target speed ω * given from the outside. However, the torque of the motor 4 may be controlled. It goes without saying that it is good.

  Hereinafter, a specific method will be described.

  First, in the speed control unit 11, a speed error Δω (= ω *) between a target speed ω * given from the outside and the current speed ω1 (the current value of the estimated speed estimated by the rotor magnetic pole position speed estimating unit 15). The current command value I * is calculated by the PI control represented by the equation (1) so that -ω1 / np) becomes zero.

I * = KPW · (ω * −ω1 / np) + KIW · Σ (ω * −ω1 / np)
= KPW · Δω + KIW · ΣΔω (1)
(KPW: Speed control proportional gain, KIW: Speed control integral gain)
However, since the target speed ω * is the mechanical angular speed and the estimated speed ω1 is the electrical angular speed, the number of pole pairs np (1/2 of the number of poles) of the electric motor 4 is divided in order to set ω1 to the mechanical angular speed.

  Next, in the DC voltage detection unit 10, an instantaneous value of the DC voltage of the inverter 5 obtained from a non-insulated circuit (voltage dividing resistors 8 a and 8 b) set to have a common potential with the motor driving device 3 is input. In order to remove noise caused by switching of the inverter 5 from the instantaneous value Vdcn of the DC voltage, a DC voltage detection value obtained by performing filtering using a first-order digital low-pass filter represented by Expression (2) Output as Vdcf.

Vdcf (t) = KF.Vdcn (t) + (1-KF) .Vdcf (t-1)
(2)
(KF: filter gain, t: time)
Here, the filter gain KF is expressed by Expression (3).

KF = (2 · π · f · T) / (1 + 2 · π · f · T) (3)
(F: cutoff frequency, T: sampling period)
It is not always necessary to perform the filtering process, and the filtering process does not have to be performed according to the usage environment of the electric motor driving device 3 and the operation status of the electric motor 4.

  Next, the current control gain correction unit 16 corrects the current control gain set in advance based on the DC voltage detection value Vdcf by calculation represented by the equations (4) and (5).

KPKn ′ = Kpn · KPKn (4)
KIKn ′ = Kpn · KIKn (5)
(KPKn ′: current control proportional gain correction value, KPKn: current control proportional gain setting value,
KIKn ′: current control integral gain correction value, KIKn: current control integral gain setting value,
n = 1, 2, 3 (for three phases), Kpn: correction coefficient)
Here, FIG. 3 is a diagram for explaining the operation of the first embodiment of the correction coefficient Kpn, using the preset DC voltage reference value VR of the inverter 5 and the DC voltage detection value Vdcf obtained from the DC voltage detector 10. A correction coefficient Kpn is obtained as in Expression (6).

Kpn = VR / (Vdcf + δ) (6)
(Δ: Minute term to prevent zero split)
It should be noted that, instead of the minute term δ in equation (6), when the DC voltage detection value Vdcf is less than or equal to zero, the zero value is prevented by setting the maximum value of the correction coefficient Kpn set in advance to the correction coefficient Kpn. be able to.

  Next, the current control unit 12 uses the current command value I * and the current command phase βT calculated by the speed control unit 11 to calculate the dq-axis current command value (id *, Iq *).

id * = − I * · sin (βT) (7)
iq * = I * · cos (βT) (8)
Also, the phase current command value (iu *, iv *, iw *) of the stator winding is determined by the dq axis current command value (id *, iq *) and the current position θ1 (by the rotor magnetic pole position speed estimation unit 15). It is obtained by performing two-phase to three-phase conversion by calculation of equations (9) to (11) using the estimated current position of the estimated position.

  However, the estimated position θ1 is an electrical angle.

  Since the two-phase to three-phase conversion is publicly known, the description thereof is omitted.

iu * = {√ (2/3)} · {id * · cos (θ1)
−iq * · sin (θ1)} (9)
iv * = {√ (2/3)} · {id * · cos (θ1−120 °)
−iq * · sin (θ1−120 °)} (10)
iw * = {√ (2/3)} · {id * · cos (θ1 + 120 °)
−iq * · sin (θ1 + 120 °)} (11)
Therefore, the current error between the phase current command value (iu *, iv *, iw *) and the phase current detection value (iu, iv, iw) obtained from the current detectors 7a, 7b and the current detection unit 9 becomes zero. Thus, using the current control gain correction values (KPKn ′, KIKn ′, n = 1, 2, 3 (for three phases)), the phase voltage command by the PI control represented by the equations (12) to (14) The value (vu *, vv *, vw *) is calculated.

vu * = KPK1 ′ · (iu * −iu) + KIK1 ′ · Σ (iu * −iu) ·· (12) vv * = KPK2 ′ · (iv * −iv) + KIK2 ′ · Σ (iv * −iv) · (13) vw * = KPK3 ′ (iw * −iw) + KIK3 ′ Σ (iw * −iw) (14)
The phase current detection values (iu, iv, iw) are subjected to three-phase to two-phase conversion to obtain dq-axis current detection values (id, iq), and dq-axis current command values (id *, iq *) and dq-axis After obtaining the dq axis voltage command value (vd *, vq *) by PI control so that the current error from the current detection value (id, iq) becomes zero, the dq axis voltage command value (vd *, vq *) The phase voltage command values (vu *, vv *, vw *) may be obtained by performing two-phase to three-phase conversion.

  However, in this case, the current control gain correction unit 16 needs to perform correction by multiplying the dq-axis current control gain set in advance by the correction coefficient Kpn.

  Since the three-phase to two-phase conversion is also known in the same manner as the two-phase to three-phase conversion, its description is omitted.

  Specifically, the dq-axis current detection value (id, iq) is obtained by the calculations of Expressions (15) and (16).

id = {√ (2)} · {iu · sin (θ1 + 60 °) + iv · sin (θ1)}
.... (15)
iq = {√ (2)} · {iu · cos (θ1 + 60 °) + iv · cos (θ1)}
(16)
Further, the dq-axis voltage command values (vd *, vq *) are obtained by the calculations of equations (17) and (18).

vd * = KPD ′ · (id * −id) + KID ′ · Σ (id * −id) (17)
vq * = KPQ ′ · (iq * −iq) + KIQ ′ · Σ (iq * −iq) (18)
(KPD ′: d-axis current control proportional gain correction value, KID ′: d-axis current control integral gain
Correction value, KPQ ′: q-axis current control proportional gain correction value, KIQ ′: q-axis current control
Integral gain correction value)
Therefore, the phase voltage command values (vu *, vv *, vw *) are calculated by the equations (19) to (21) by performing two-phase to three-phase conversion on the dq-axis voltage command values (vd *, vq *). Is required.

vu * = {√ (2/3)} · {vd * · cos (θ1)
-Vq * · sin (θ1)} (19)
vv * = {√ (2/3)} · {vd * · cos (θ1−120 °)
-Vq * · sin (θ1-120 °)} (20)
vw * = {√ (2/3)} · {vd * · cos (θ1 + 120 °)
-Vq * · sin (θ1 + 120 °)} (21)
Here, in order for the inverter 5 to output the phase voltage command values (vu *, vv *, vw *) obtained as described above, signals for driving the switching elements 5a to 5f are generated.

  Next, a method for estimating the induced voltage of the electric motor in the present embodiment will be described.

  The estimated voltage estimated values (eu, ev, ew) induced in the windings of each phase are the phase current detection values (iu, iv, iw) and the phase voltage command values (vu *, vv *, vw *). It is calculated | required by calculation of Formula (22)-Formula (23) using.

eu = vu * −R · iu−L · d (iu) / dt (22)
ev = vv * −R · iv−L · d (iv) / dt (23)
ew = vw * −R · iw−L · d (iw) / dt (24)
Here, R is the resistance per phase of the winding of the electric motor 4, and L is its inductance. D (iu) / dt, d (iv) / dt, and d (iw) / dt are time derivatives of iu, iv, and iw, respectively.

  Moreover, the following equation is obtained by expanding the equations (22) to (24).

eu = vu *
-R.iu
− (La + La) · d (iu) / dt
-Las · cos (2θ1) · d (iu) / dt
-Las · iu · d {cos (2θ1)} / dt
+ 0.5 · La · d (iv) / dt
−Las · cos (2θ1−120 °) · d (iv) / dt
-Las · iv · d {cos (2θ1-120 °)} / dt
+ 0.5 · La · d (iw) / dt
−Las · cos (2θ1 + 120 °) · d (iw) / dt
-Las · iw · d {cos (2θ1 + 120 °)} / dt (25)
ev = vv *
-R ・ iv
− (La + La) · d (iv) / dt
−Las · cos (2θ1 + 120 °) · d (iv) / dt
-Las · iv · d {cos (2θ1 + 120 °)} / dt
+ 0.5 · La · d (iw) / dt
−Las · cos (2θ1) · d (iw) / dt
-Las · iw · d {cos (2θ1)} / dt
+ 0.5 · La · d (iu) / dt
−Las · cos (2θ1−120 °) · d (iu) / dt
-Las · iu · d {cos (2θ1-120 °)} / dt (26)
ew = vw *
-R ・ iw
− (La + La) · d (iw) / dt
-Las · cos (2θ1-120 °) · d (iw) / dt
-Las · iw · d {cos (2θ1-120 °)} / dt
+ 0.5 · La · d (iu) / dt
−Las · cos (2θ1 + 120 °) · d (iu) / dt
-Las · iu · d {cos (2θ1 + 120 °)} / dt
+ 0.5 · La · d (iv) / dt
−Las · cos (2θ1) · d (iv) / dt
-Las · iv · d {cos (2θ1)} / dt (27)
Here, R is a resistance per phase of the winding, la is a leakage inductance per phase of the winding, La is an average value of effective inductance per phase of the winding, and Las is a variation of effective inductance per phase of the winding. Amplitude (for embedded magnet type, constant value for surface magnet type). D (iu) / dt, d (iv) / dt, and d (iw) / dt are obtained by first-order Euler approximation. Note that the u-phase current iu is obtained by changing the sign of the sum of the v-phase current iv and the w-phase current iw.

  Furthermore, when Expressions (25) to (27) are simplified, Expressions (28) to (30) shown below are obtained. Here, assuming that the phase current detection value (iu, iv, iw) is a sine wave, the phase current detection value (iu, iv, iw) is created from the current command value I * and the current command phase βT. Simplified.

eu = vu *
+ R ・ I * ・ sin (θ1 + βT)
+1.5 · (la + La) · cos (θ1 + βT)
-1.5 · Las · cos (θ1-βT) (28)
ev = vv *
+ R ・ I * ・ sin (θ1 + βT−120 °)
+1.5 ・ (la + La) ・ cos (θ1 + βT−120 °)
-1.5 · Las · cos (θ1-βT-120 °) (29)
ew = vw *
+ R ・ I * ・ sin (θ1 + βT + 120 °)
+1.5 ・ (la + La) ・ cos (θ1 + βT + 120 °)
-1.5 · Las · cos (θ1-βT + 120 °) (30)
In the present embodiment, the induced voltage estimation unit 14 obtains an induced voltage estimated value (eu, ev, ew) from Expressions (28) to (30).

  Next, the rotor position speed estimation unit 15 estimates the magnetic pole position and speed of the rotor in the electric motor 4 using the induced voltage estimated values (eu, ev, ew). The rotor position / speed estimation unit 15 corrects the estimated position θ1 recognized by the electric motor drive device 3 using the error of the induced voltage, thereby obtaining the estimated position θ1 by converging it to a true value. Also, an estimated speed ω1 is generated therefrom.

  First, an induced voltage reference value (eum, evm, ewm) of each phase is obtained by the following equation.

eum = em · sin (θ1 + βT) (31)
evm = em · sin (θ1 + βT−120 °) (32)
ewm = em · sin (θ1 + βT + 120 °) (33)
Here, the induced voltage amplitude value em is obtained by matching the amplitude values of eu, ev, and ew.

  A deviation ε between the induced voltage estimated value es thus obtained and the induced voltage reference value esm (s = u, v, w (s represents a phase)) is obtained.

ε = es−esm (s = u, v, w) (34)
Since the estimated position θ1 becomes a true value when the deviation ε becomes 0, the estimated position θ1 is obtained by performing PI calculation using the deviation ε so that the deviation ε is converged to 0. Further, the estimated speed ω1 is obtained by calculating the fluctuation value of the estimated position θ1.

  Finally, the PWM signal generation unit 13 converts the switching elements 5a to 5f into drive signals for electrically driving based on the drive signal obtained from the current control unit 12. The switching elements 5a to 5f are operated by the drive signal.

  As described above, the electric motor drive device 3 according to the present embodiment generates the estimated position θ1 using the deviation ε between the induced voltage estimated value and the induced voltage reference value, allows the sinusoidal phase current to flow, and is set in advance. The current control gain is corrected according to the DC voltage of the inverter 5 by the current control gain correction unit 16, so that an optimum current control system can always be constructed regardless of the power supply situation, and a stable motor drive can be realized. .

(Embodiment 2)
FIG. 2 shows a system configuration diagram of the electric motor drive device according to Embodiment 2 of the present invention. The same components as those of the motor drive device shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted because it is duplicated. Hereinafter, different portions will be described.

  In FIG. 2, the electric motor drive device 3 includes an inverter 5 composed of freewheeling diodes 6 a to 6 f paired with a plurality of switching elements 5 a to 5 f, a current detection unit 9, a voltage detection unit 10, a speed control unit 11, The current control unit 12, the PWM signal generation unit 13, the induced voltage estimation unit 14, the rotor position speed estimation unit 15, and the voltage command correction unit 17 are configured.

  Parts different from the motor drive device 3 shown in FIG. 1 are as follows.

  The current control unit 12 obtains the voltage command v * using a preset current control gain. Further, the voltage command correction unit 17 corrects the voltage command v * based on the DC voltage information obtained by the DC voltage detection unit 10 and outputs a voltage command correction value vh *. Further, the induced voltage estimation unit 14 estimates the induced voltage based on the voltage command correction value vh *, and the PWM signal generation unit 13 electrically drives the switching elements 5a to 5f based on the voltage command correction value vh *. The switching elements 5a to 5f operate according to the drive signal.

  In FIG. 2, two current detectors 7 a and 7 b that detect the phase current of the motor 4 are provided and used for estimating the rotor position speed. However, the DC current on the input side of the inverter 5 (the inverter 5 Needless to say, means such as detecting the phase current of the electric motor 4 from the bus current) may be used.

  In FIG. 2, the speed control is performed so that the speed of the motor 4 follows the target speed ω * given from the outside. However, the torque of the motor 4 may be controlled. It goes without saying that it is good.

  Hereinafter, a specific method will be described.

  First, in the current control unit 12, for example, instead of the current control gain correction values (KPKn ′, KIKn ′, n = 1, 2, 3 (for three phases)) in the equations (12) to (14), the current control gain is used. Phase voltage command values (vu *, vv *, vw *) are obtained using set values (KPKn, KIKn, n = 1, 2, 3 (for three phases)).

  Similarly to the motor driving device shown in FIG. 1, the phase voltage command values (vu *, vv *, vw *) may be obtained from the dq axis voltage command values (vd *, vq *).

  That is, in the equations (17) and (18), the dq axis voltage command value (vd *) is obtained by using the current control gain setting value instead of the current control gain correction value (KPD ′, KID ′, KPQ ′, KIQ ′). , Vq *) is obtained, and the phase voltage command values (vu *, vv *, vw *) are obtained by performing two-phase to three-phase conversion as shown in equations (19) to (21).

  Next, the voltage command correction unit 17 calculates the phase voltage command values (vu *, vv *, vw *) obtained from the current control unit 12 and the correction coefficient Kpn expressed by the equation (6) as in the following equation. The phase voltage command correction values (vuh *, vvh *, vwh *) are obtained by multiplication.

vuh * = Kpn · vu * (35)
vvh * = Kpn · vv * (36)
vwh * = Kpn · vw * (37)
It should be noted that the phase voltage command correction values (vuh *, vvh *, vwh *) in the electric motor drive device in the second embodiment and the phase voltage command values (vu *, vv *) in the electric motor drive device in the first embodiment. , Vw *) is the same value as the above-described contents and equations, but in the electric motor driving apparatus according to the second embodiment, the number of calculations accompanying the correction is the electric motor driving apparatus according to the first embodiment. (In the first embodiment, six current control gains are set for the three phases, and six calculations are required for correction. Then, only three calculations are required for correcting the voltage command value).

  Here, in order for the inverter 5 to output the phase voltage command correction values (vuh *, vvh *, vwh *) obtained as described above, signals for driving the switching elements 5a to 5f are generated.

  In the induced voltage estimation unit 14, the phase voltage command correction values (vuh *, vvh *, vwh *) are substituted for the phase voltage command values (vu *, vv *, vw *) in the equations (28) to (30). ) To obtain the estimated voltage (eu, ev, ew).

  Finally, the PWM signal generation unit 13 converts the switching elements 5a to 5f into drive signals for electrically driving based on the drive signal obtained from the voltage command correction unit 17. The switching elements 5a to 5f are operated by the drive signal.

  As described above, the electric motor drive device 3 according to the second embodiment generates the estimated position θ1 using the deviation ε between the induced voltage estimated value and the induced voltage reference value, flows the sinusoidal phase current, and By correcting the voltage command value calculated by the current control unit 12 using the set current control gain according to the DC voltage of the inverter, the preset current control gain is corrected according to the DC voltage of the inverter. The same effect as the case can be obtained, an optimal current control system can always be constructed without depending on the power supply situation, and stable driving of the electric motor can be realized. Further, the calculation means such as a microcomputer as compared with the first embodiment The amount of computation and memory in the memory can be reduced, and the cost of the computing means can be reduced.

  FIG. 4 shows a second embodiment of the correction coefficient. In FIG. 4, the correction coefficient Kpn has an upper limit value Kpn1 and a lower limit value Kpn2 that are set in advance, and is expressed as in equation (38).

Kpn = Kpn1 (Vdcf ≦ Vdcf1)
VR / Vdcf (Vdcf1 <Vdcf ≦ Vdcf2)
Kpn2 (Vdcf ≧ Vpn2)
.... (38)
Note that the correction coefficient Kpn does not necessarily need to include both the upper limit value Kpn1 and the lower limit value Kpn2 as shown in FIG. 4, and may include only one of them depending on the use environment of the motor driving device and the operating condition of the motor. .

  As described above, since the correction coefficient according to the present embodiment has at least a preset upper limit value or lower limit value, excessive correction of the current control gain (or voltage command value) can be prevented, and hunting or irregularity can be prevented. The unstable operation of the motor can be avoided.

  Next, a specific method regarding switching of correction of the current control gain (or voltage command value) will be described below.

  The electric motor drive device of the present invention corrects the current control gain (or voltage command value) only when the output value of the DC voltage detecting means is outside the preset DC voltage range, and when the output value is within the range, the current control gain is corrected. The gain (or voltage command value) is not corrected.

  Here, the correction coefficient Kpn in this case is shown in FIG. 5 (third embodiment of the correction coefficient). In FIG. 5, in a preset DC voltage range (Vdcf3 to Vdcf4), the correction coefficient Kpn is not changed as the correction coefficient Kpn0 at the DC voltage reference value VR, and is expressed as in Expression (39). Is done.

  Further, the DC voltage range (Vdcf3 to Vdcf4) is a region where the change of the correction coefficient is small, and in practice, an optimum value is set according to the use environment of the motor driving device and the operating condition of the motor.

Kpn = VR / Vdcf (Vdcf ≦ Vdcf3)
Kpn0 (Vdcf3 <Vdcf ≦ Vdcf4)
VR / Vdcf (Vdcf ≧ Vpn4)
.... (39)
Needless to say, as described in the second embodiment of the correction coefficient, the correction coefficient Kpn may include at least a preset upper limit value or lower limit value.

  As described above, the current control gain (or the voltage command value) is corrected only when the current control gain correction effect is large (outside the preset DC voltage range), so that the calculation in the calculation means such as a microcomputer is performed. The amount and memory can be reduced, and the cost of the calculation means can be reduced.

  In addition, the electric motor drive device of the present invention performs switching with and without correction of the current control gain (or voltage command value) as described above. For example, a preset DC voltage range (Vdcf3 to Vdcf4) is used. When the DC voltage detection value Vdcf fluctuates in the vicinity of either the upper limit value Vdcf4 or the lower limit value Vdcf3, the correction coefficient Kpn obtained from the equation (39) changes rapidly, so there is no correction. A switching grace period is provided at the time of switching.

  Here, FIG. 6 shows an operation explanatory diagram at the time of switching with or without correction of the current control gain correction means (or voltage command correction means) in the present invention. FIG. 6 is an enlarged view of the vicinity of the lower limit value Vdcf3 of the DC voltage range in the correction coefficient shown in FIG. 5. A switching grace period is provided when switching with or without correction so that the correction coefficient Kpn does not change abruptly. To.

  Further, by similarly providing a switching grace period also in the vicinity of the upper limit value Vdcf4 of the DC voltage range, the correction coefficient Kpn is prevented from changing abruptly.

  Furthermore, regarding the setting of the switching grace period, the change rate of the correction coefficient (slope of the correction coefficient with respect to the DC voltage in the switching grace period) is set in advance according to the use environment of the motor driving device and the operating state of the motor.

  In this way, the control stability and reliability associated with switching with and without correction of the current control gain (or voltage command value) can be improved, and unstable operation of the electric motor such as hunting and turbulence can be prevented.

  Specific examples relating to the correction timing of the current control gain (or voltage command value) of the motor drive device of the present invention will be described below.

  In this embodiment, the current control gain (or voltage command value) is corrected in synchronization with the control cycle of the inverter, and the current control gain (or voltage command value) is corrected every cycle of the inverter control cycle. Since the result can be reflected in the inverter output (PWM signal) in real time, the power supply situation can be reflected in the drive performance of the electric motor without time delay.

  In another embodiment, the current control gain is set every n cycles (n ≧ 2) of the inverter control cycle only when the fluctuation range of the output value of the DC voltage detection means is within the preset fluctuation width setting value. (Or voltage command value) is corrected.

  Here, for example, referring to the correction coefficient shown in FIG. 3, when the fluctuation range of the DC voltage detection value Vdcf is small, the change of the correction coefficient Kpn is small. In this case, the current control gain (or voltage command value) is corrected. The effect becomes smaller.

  Therefore, when the effect of correcting the current control gain (or voltage command value) is small (within a preset value of the fluctuation range), the current control is performed every n cycles (n ≧ 2) of the inverter control cycle. By correcting the gain (or voltage command value), it is possible to reduce the amount of calculation and memory in the calculation means such as a microcomputer, and the cost of the calculation means can be reduced.

  As described above, the electric motor drive device according to the present invention can always build an optimal current control system without depending on the power supply situation by correcting the preset current control gain according to the DC voltage of the inverter. Since a stable motor drive can be realized, a position sensor such as a servo drive is provided, not only when a position sensor such as an encoder cannot be used like a compressor drive motor in an air conditioner. The present invention can be applied even when it is possible.

The system block diagram of the electric motor drive device in the 1st Embodiment of this invention The system block diagram of the electric motor drive device in the 2nd Embodiment of this invention Operation explanatory diagram of the first embodiment of the correction coefficient in the present invention Operation explanatory diagram of the second embodiment of the correction coefficient in the present invention Operation explanatory diagram of the third embodiment of the correction coefficient in the present invention Enlarged view near Vdcf in FIG. System configuration diagram of a conventional motor drive device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Electric motor drive device 4 Electric motor 5 Inverter 5a-5f Switching element 6a-6f Free-wheeling diode 7a, 7b Current detector 8a, 8b Voltage dividing resistor 9 Current detection part 10 DC voltage detection part 11 Speed control part 12 Current control unit 13 PWM signal generation unit 14 Induced voltage estimation unit 15 Rotor position speed estimation unit 16 Current control gain correction unit 17 Voltage command correction unit

Claims (11)

It has multiple switching element pairs consisting of upper arm switching elements arranged on the high voltage side and lower arm switching elements arranged on the low voltage side, and the DC voltage is converted to the AC voltage of the desired frequency and voltage by the operation of each switching element. And an inverter for supplying a drive voltage to a multi-phase motor,
Current detecting means for detecting a current flowing in a stator winding of the motor;
Current control means for creating a voltage command value from a current error between a current command value for the motor and a current detection value detected by the current detection means;
PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value;
DC voltage detection means for detecting the DC voltage of the inverter;
Current control gain correction means for correcting a current control gain in the current control means based on the output value of the DC voltage detection means,
The current control gain correction means corrects the current control gain by multiplying the current control gain by a ratio between a preset reference value of the DC voltage of the inverter and the output value of the DC voltage detection means. An electric motor drive device. It has multiple switching element pairs consisting of upper arm switching elements arranged on the high voltage side and lower arm switching elements arranged on the low voltage side, and the DC voltage is converted to the AC voltage of the desired frequency and voltage by the operation of each switching element. And an inverter for supplying a drive voltage to a multi-phase motor,
Current detecting means for detecting a current flowing in a stator winding of the motor;
Current control means for creating a voltage command value from a current error between a current command value for the motor and a current detection value detected by the current detection means;
PWM signal generating means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value;
DC voltage detection means for detecting the DC voltage of the inverter;
Voltage command correction means for correcting the voltage command value based on the output value of the DC voltage detection means,
The voltage command correcting means corrects the voltage command value by multiplying the voltage command value by a ratio between a preset reference value of the DC voltage of the inverter and the output value of the DC voltage detecting means. An electric motor drive device. A ratio is calculated by dividing the reference value of the DC voltage by the output value of the DC voltage detection means, and when the output value of the DC voltage detection means is less than or equal to zero, a preset maximum value is set as the ratio The electric motor drive device according to claim 1, wherein the electric motor drive device is provided. The electric motor drive apparatus according to claim 1, wherein the ratio has at least an upper limit value or a lower limit value set in advance. The current control gain or voltage command value is corrected only when the output value of the DC voltage detection means is outside the preset DC voltage range, and the current control gain or voltage command value is not corrected when the output value is within the above range. The electric motor drive device according to any one of claims 1 to 4, wherein the electric motor drive device is provided. 6. The electric motor drive device according to claim 5, wherein a switching grace period is provided at the time of switching with or without correction of the current control gain or voltage command value. The electric motor drive device according to any one of claims 1 to 6, wherein the current control gain or the voltage command value is corrected in synchronization with a control cycle of the inverter. The current control gain or voltage command value is corrected every n cycles (n ≧ 2) of the inverter control cycle only when the fluctuation range of the output value of the DC voltage detection means is within the preset fluctuation range setting value. The electric motor drive device according to claim 7. 9. The electric motor drive apparatus according to claim 1, wherein the DC voltage detection means outputs the instantaneous value of the input DC voltage of the inverter after performing a predetermined filtering process. The electric motor drive device according to claim 9, wherein the predetermined filter process is a process for removing noise caused by switching of the inverter. The input to the DC voltage detecting means is an instantaneous value of a DC voltage obtained from a non-insulated circuit set to have a common potential with the current control gain correcting means or the voltage command correcting means. The electric motor drive device of any one of 1-10.

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