JP2005229738A - Electric motor drive - Google Patents

Abstract

An object of the present invention is to constantly build an optimal current control system independent of load conditions and realize stable driving of an electric motor.
An electric motor drive device 3 includes a current detection unit 9 that detects a current flowing in a stator winding of an electric motor 4, and a current command value I * from a speed error between a target speed ω * and a rotational speed ω1 of the electric motor 4. A speed control unit 11 for generating a rotation output, a rotation output detection unit 18 for detecting a value related to the rotation output of the electric motor 4, and a current control gain correction unit for correcting a preset current control gain based on the detected rotation output value 16 and a current control unit 12 that creates a voltage command value V * from a current error between the current command value I * and the detected current value using the corrected current control gain, and this current control gain correction unit 16 makes it possible to always construct an optimum current control system regardless of the load condition and to realize stable driving of the electric motor.
[Selection] Figure 1

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 technologies, 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 shows a system configuration of the electric motor drive device of Patent Document 1. The motor drive device 3 includes an inverter 5 including freewheeling diodes 6a to 6f paired with a plurality of switching elements 5a to 5f, a speed control unit 11, a current control unit 12, a PWM signal generation unit 13, and an induced voltage estimation unit. 14 and a rotor position speed estimation unit 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 AC / DC converter 5, thereby driving the motor 4 that is a brushless DC motor.

  In the motor driving device 3, 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 means 15) in order to realize the target speed given from the outside. 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

  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 means 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, the conventional configuration does not include means for correcting a preset PI control gain in accordance with a value related to the rotational output of the motor (such as the current and rotational speed of the motor), and the PI control gain is approximately equal to the inductance of the motor. In particular, in an electric motor composed of a concentrated winding stator, since the inductance value of the motor changes depending on the load, the apparent PI control gain responsiveness changes when the inductance value of the motor changes, In addition to not being able to obtain a satisfactory control specification with a preset PI control gain, there is a problem that the number of design man-hours for optimal adjustment of the PI control gain increases.

  The present invention solves the above-mentioned conventional problems, and an object thereof is to provide an electric motor drive device for always constructing an optimal current control system independent of load conditions and realizing stable electric motor drive. And

  In order to solve the above-described conventional problems, a plurality of pairs of switching elements including an upper arm switching element arranged on the high voltage side and a lower arm switching element arranged on the low voltage side are provided, 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 And a current control gain for correcting the current control gain in the current control means based on the value related to the rotational output of the motor and the motor. And a correction means, said current control gain correction means is that in proportion to the value relating to the rotation output of the motor to correct the current control gain so that the current control gain is reduced.

  By this current control gain correction means, a preset current control gain can be corrected according to a value relating to the rotation output of the electric motor.

  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 a PWM signal for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value Generating means, and voltage command correction means for correcting the voltage command value based on a value related to the rotation output of the electric motor. Decree correcting means is for correcting the voltage command value such that the voltage command value in proportion to the value relating to the rotation output of the electric motor is reduced.

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 value related to the rotation output of the electric motor, thereby setting the preset current control gain. In addition to obtaining the same effect as that obtained by performing correction according to the value related to the rotation output of the electric motor, it is possible to reduce the amount of calculation and the memory in the calculation means such as a microcomputer.

  The electric motor drive device of the present invention corrects a preset current control gain according to a value related to the rotational output of the electric motor, so that an optimum current control system can always be constructed without depending on the load state, and a stable electric motor Can be realized.

  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. Detected by 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, and a current command value and current detection means for the motor Current control means for creating a voltage command value from a current error with respect to the detected current value, PWM signal generation means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value, and an electric motor Current control gain correction means for correcting the current control gain in the current control means based on the value related to the rotational output of the current control means The current control gain correction means corrects the current control gain so that the current control gain becomes smaller in proportion to the value related to the rotation output of the electric motor, so that the preset current control gain becomes a value related to the rotation output of the electric motor. By correcting accordingly, an optimal current control system can always be constructed without depending on the load status, 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. Detected by 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, and a current command value and current detection means for the motor Current control means for creating a voltage command value from a current error with respect to the detected current value, PWM signal generation means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value, and an electric motor Voltage command correcting means for correcting a voltage command value based on a value related to the rotation output of the motor, the voltage command correcting means comprising: By correcting the voltage command value so that the voltage command value becomes smaller in proportion to the value related to the rotation output, the same effect as when the preset current control gain is corrected according to the value related to the rotation output of the motor can be obtained. As a result, the optimum current control system can always be constructed without depending on the load status, and stable driving of the motor can be realized. Further, compared with the first invention, the calculation amount and memory in the calculation means such as a microcomputer And the cost of the calculation means can be reduced.

  In the third aspect of the invention, in particular, in the motor drive device of the first or second aspect of the invention, the current control gain (or voltage command value) has a preset lower limit value, so that the current control gain (or voltage command value) Value) can be prevented, and unstable operation of the motor, such as hunting and turbulence, can be avoided.

  In the fourth aspect of the invention, in particular, the electric motor drive device according to any one of the first to third aspects of the present invention has a current control gain (or voltage command) only when a value related to the rotational output of the electric motor is larger than a preset reference value. The current control gain (or voltage command value) is not corrected when the value is less than the reference value, and when the effect of the current control gain correction is large (below the preset power reference value) Only when the current control gain (or voltage command value) is corrected, the amount of computation and memory in the computing means such as a microcomputer can be reduced, and the cost of the computing means can be reduced.

  In the fifth aspect of the invention, in particular, the motor driving device of the fourth aspect of the invention performs switching of correction so that the value becomes continuous when switching with or without correction of the current control gain (or voltage command value). 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 motor such as hunting and turbulence can be prevented.

  In the sixth aspect of the invention, in particular, the electric motor drive device according to any one of the first to fifth aspects of the invention corrects the current control gain (or voltage command value) in synchronization with the control cycle of the inverter, and at least the inverter It is possible to correct the current control gain (or voltage command value) for each of the control cycles, and the load status can be reflected in the current control system in real time.

  According to the seventh aspect of the invention, in particular, the electric motor drive device of the sixth aspect of the invention is provided every n cycles (n ≧ 2) of the inverter control cycle only when the value related to the rotational output of the electric motor is equal to or less than a preset reference value. This is to correct the current control gain (or voltage command value), and when the effect of correcting the current control gain (or voltage command value) is small (within the preset value of the fluctuation range), By correcting the current control gain (or voltage command value) every n control cycles (n ≧ 2), 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. .

  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 a first embodiment of the present invention. In FIG. 1, the electric motor drive device 3 includes an inverter 5 including free-wheeling diodes 6 a to 6 f paired with a plurality of switching elements 5 a to 5 f, a voltage detection unit 10, 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 are provided.

  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 AC / DC converter 5, thereby driving the motor 4 that is a brushless DC motor.

  In the motor driving device 3, 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 means 15) in order to realize the target speed given from the outside. 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 corrects a preset current control gain (PI control gain) of the current control unit 12 based on the value related to the rotation output of the electric motor 4 detected by the rotation output detection unit 18.

  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 means 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.

  First, the necessity of correcting the current control gain will be described.

  FIG. 5 is a diagram showing an example of a block diagram of the current control unit 12 described later. The response of the motor current depends on the response of the PI compensation unit on the control side and the resistance R and inductance L on the motor side. Determined by circuit response.

  However, as shown in FIG. 6, the inductance of the motor is saturated by the current flowing through the motor and the inductance value decreases. In particular, in an electric motor composed of a concentrated winding stator, the saturation appears remarkably when the magnetic flux concentrates.

  Therefore, in the block diagram of the current control unit 12 in FIG. 5, the responsiveness of the current flowing to the motor apparently changes due to the change in the inductance value of the motor. For example, when the load is large, the control is too effective and the hunting is performed. Therefore, it is necessary to correct the current control gain according to the load condition.

  Here, as shown in FIG. 6, since the inductance characteristic of the motor is approximately expressed by a linear function, the correction of the current control gain is also changed in a linear function according to the load condition.

  Although the inductance characteristic of the motor is approximated by a linear function, it is not particularly limited to a linear function. For example, the current control gain may be corrected according to the actual inductance characteristic. Needless to say.

  In order to know the load condition, the rotation output detection unit 18 uses a current command value I * obtained from the speed control unit 11 described later or a phase current detection value obtained from the current detectors 7a and 7b and the current detection unit 9. Any current value (iu, iv, iw), any speed value of target speed ω * or estimated speed ω1 (estimated by rotor magnetic pole position speed estimating means 15 described later), or current command An equivalent motor output obtained by the product of either the current value of the value I * or the phase current detection value (iu, iv, iw) and the speed value of the target speed ω * or the estimated speed ω1 is output.

As for the phase current command value I *, the target speed ω *, and the estimated speed ω1, one value is determined for the driving situation and the load situation, so the output value of the rotation output detection unit 18 is one. Since the phase current detection values (iu, iv, iw) are for three phases, they can be set to one value by calculating the effective value I1 for one phase, for example. The equivalent motor output can be derived from the product of the current value (I * or effective value I1) and the speed value (ω * or ω1).

  However, since the inductance of the motor changes depending on the current flowing through the motor as described above, either the current command value I * or the effective value I1 should be used originally. For example, the load depends on the rotation speed of the motor. May increase in proportion, the speed value of either the target speed ω * or the estimated speed ω1 may be used. Further, by using the equivalent motor output obtained by the product of the current value and the speed value, it is possible to know the situation of the load more.

  Below, the case where the output of the rotation output detection part 18 is the electric current command value I * is demonstrated concretely.

  First, the speed control unit 11 performs PI control represented by Expression (1) so that the speed error Δω (= ω * −ω1 / np) between the target speed ω * given from the outside and the estimated speed ω1 becomes zero. To calculate the current command value I *.

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 current control gain correction unit 16, the current control gain set in advance based on the current command value I * which is the output value of the rotation output detection unit 18 is expressed by the equations (2) and (3). Correct by calculation.

KPKn '= Kg · KPKn (2)
KIKn '= Kg · KIKn (3)
(KPKn ′: current control proportional gain correction value, KPKn: current control proportional gain setting value,
KIKn ′: current control integral gain correction value, KIKn: current control proportional gain setting value,
n = 1, 2, 3 (for three phases), Kg: correction coefficient)
Here, FIG. 3 is a diagram showing an operation explanatory diagram in the first embodiment of the correction coefficient Kg according to the present invention, and has a preset lower limit value Kmin (value relating to rotation output (here, current If the command value I *) is larger than P1, the correction coefficient is Kmin).

  Specifically, the correction coefficient Kg can be derived by the equation (4) using the initial value K0 and the lower limit value Kmin of the correction coefficient.

Kg = α1 · (I * −P1) + Kmin (I * <P1)
= Kmin (I * ≧ P1)
However, α1 = − (K0−Kmin) / P1 (4)
In the case where there is no lower limit value Kmin, if the correction coefficient Kg is extremely small, the responsiveness is excessively lowered and the convergence is deteriorated.

As described above, by setting the lower limit value Kmin as the correction coefficient Kg, excessive correction of the current control gain can be prevented, and unstable operation of the electric motor such as hunting and turbulence can be avoided.

FIG. 4 is a diagram for explaining the operation of the correction coefficient Kg according to the present invention in the second embodiment.
Here, the current control gain is corrected only when the value related to the rotation output (here, the current command value I *) is larger than the preset reference value P2, and when the value is less than the reference value P2, the current control gain is corrected. The initial value K0 is maintained without performing any operation.

  In FIG. 4, the correction is switched so that the value becomes continuous when the current control gain is corrected or not.

  Specifically, the correction coefficient Kg can be derived from Equation (5) using the initial value K0 and the lower limit value Kmin of the correction coefficient.

Kg = K0 (I * ≦ P2)
= Α2 · (I * −P2) + Kmin (P2 <I * ≦ P1)
= Kmin (I * ≧ P1)
However, α2 = − (K0−Kmin) / (P1−P2) (5)
That is, the correction coefficient Kg is changed in accordance with the inductance characteristics of the motor shown in FIG. Here, the reference value P2 is set to substantially coincide with the saturation start point of the inductance of the motor shown in FIG.

  As described above, by correcting the current control gain only when the effect of correcting the current control gain is large (when the current control gain is equal to or less than a preset reference value), it is possible to reduce the calculation amount and memory in the calculation means such as a microcomputer. The cost of the means can be reduced.

  Furthermore, by performing correction switching so that the value is continuous when switching with and without correction of the current control gain, control stability and reliability associated with switching with and without correction of the current control gain can be improved, Unstable operation of the motor, such as hunting and turbulence, can be prevented.

  Further, a specific method relating to the correction timing of the current control gain according to the present invention will be described below.

  The electric motor drive device of the present invention corrects the current control gain in synchronization with the control cycle of the inverter, corrects the current control gain for each cycle of the inverter control cycle, and outputs the result in real time to the inverter output ( PWM signal) can be reflected, so that the load condition can be reflected in the drive performance of the electric motor without time delay.

  In addition, the electric motor drive device of the present invention is configured such that the current control gain (or voltage command) is increased every n cycles (n ≧ 2) of the inverter control cycle only when the value related to the rotational output of the electric motor is equal to or less than a preset reference value P2. Value).

  Here, referring to the inductance characteristics of the motor shown in FIG. 5, since the change in inductance is small, the effect of correcting the current control gain is small in this case.

  Therefore, when the effect of the correction of the current control gain is small (when the reference value P2 or less is set in advance), the microcomputer corrects the current control gain every n cycles (n ≧ 2) of the inverter control cycle. The amount of calculation and memory in the calculation means such as can be reduced, and the cost of the calculation means can be reduced.

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

id * = − I * · sin (βT) (6)
iq * = I * · cos (βT) (7)
Further, 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 means 15). The current value of the estimated position) is obtained by performing two-phase to three-phase conversion by the calculation of equations (8) to (10).

  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)} (8)
iv * = {√ (2/3)} · {id * · cos (θ1−120 °)
−iq * · sin (θ1−120 °)} (9)
iw * = {√ (2/3)} · {id * · cos (θ1 + 120 °)
−iq * · sin (θ1 + 120 °)} (10)
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 voltage command value is obtained by the PI control represented by the equations (11) to (13). (Vu *, vv *, vw *) is calculated.

vu * = KPK1 ′ · (iu * −iu) + KIK1 ′ · Σ (iu * −iu)
(11)
vv * = KPK2 ′ · (iv * −iv) + KIK2 ′ · Σ (iv * −iv)
(12)
vw * = KPK3 ′ · (iw * −iw) + KIK3 ′ · Σ (iw * −iw)
(13)
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 command value (id, iq) is obtained by the calculations of Expressions (14) and (15).

id = {√ (2)} · {iu · sin (θ1 + 60 °) + iv · sin (θ1)}
(14)
iq = {√ (2)} · {iu · cos (θ1 + 60 °) + iv · cos (θ1)}
(15)
Further, the dq-axis voltage command values (vd *, vq *) are obtained by the calculations of equations (16) and (17).

vd * = KPD ′ · (id * −id) + KID ′ · Σ (id * −id)
(16)
vq * = KPQ ′ · (iq * −iq) + KIQ ′ · Σ (iq * −iq)
(17)
(KPD ′: d-axis current proportional gain correction value, KID ′: d-axis current integral gain correction value,
(KPQ ': q-axis current proportional gain correction value, KIQ': q-axis current integral gain correction value)
Therefore, the phase voltage command values (vu *, vv *, vw *) are calculated by Equations (18) to (20) 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)} (18)
vv * = {√ (2/3)} · {vd * · cos (θ1−120 °)
−vq * · sin (θ1−120 °)} (19)
vw * = {√ (2/3)} · {vd * · cos (θ1 + 120 °)
-Vq * · sin (θ1 + 120 °)} (20)
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 this embodiment will be described.

  The induced voltage values (eu, ev, ew) induced in the windings of the respective phases use the phase current detection values (iu, iv, iw) and the phase voltage command values (vu *, vv *, vw *). Is obtained by the calculation of the equations (21) to (23).

eu = vu * -R.iu-L.d (iu) / dt (21)
ev = vv * −R · iv−L · d (iv) / dt (22)
ew = vw * −R · iw−L · d (iw) / dt (23)
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.

  Further, when the formulas (21) to (23) are expanded, the following formula is obtained.

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 (24)
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 (25)
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 (26)
Where R is the resistance per winding phase, la is the leakage inductance per winding phase, La is the average effective inductance per winding phase, and Las is the effective inductance amplitude per winding phase. It is. 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 (24) to (26) are simplified, Expressions (27) to (29) shown below are obtained. Here, assuming that the phase current detection values (iu, iv, iw) are sine waves, the phase current detection values (iu, iv, iw) are created from the current command amplitude 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) (27)
ev = vv *
+ R ・ I * ・ sin (θ1 + βT−120 °)
+1.5 ・ (la + La) ・ cos (θ1 + βT−120 °)
-1.5 · Las · cos (θ1-βT-120 °) (28)
ew = vw *
+ R ・ I * ・ sin (θ1 + βT + 120 °)
+1.5 ・ (la + La) ・ cos (θ1 + βT + 120 °)
-1.5 · Las · cos (θ1-βT + 120 °) (29)
In the present embodiment, the induced voltage estimation unit 14 obtains an induced voltage estimated value (eu, ev, ew) from Expressions (27) to (29).

  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) (30)
evm = em · sin (θ1 + βT−120 °) (31)
ewm = em · sin (θ1 + βT + 120 °) (32)
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 reference value esm (s = u, v, w (s represents a phase)) thus obtained and the induced voltage estimated value es is obtained.

ε = es-esm (s = u, v, w) (33)
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. By correcting the current control gain according to the rotation output of the electric motor 4 by the current control gain correction unit 16, it is possible to always construct an optimal current control system regardless of the load condition, and to realize stable driving of the electric motor.

(Embodiment 2)
FIG. 2 is a system configuration diagram of an electric motor drive device according to the second embodiment 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 motor drive device 3 includes an inverter 5 composed of free-wheeling diodes 6 a to 6 f paired with a plurality of switching elements 5 a to 5 f, a voltage detection unit 10, a speed control unit 11, a 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 provided.

  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 correction value Vh * based on the value related to the rotation output of the electric motor 4 obtained by the rotation output detection unit 18. 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 performs switching based on the drive signal for the inverter 5 to output the voltage command correction value Vh *. Element 5
The signals a to 5f are converted into drive signals for electrically driving, and the switching elements 5a to 5f are operated by the drive signals.

  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 (11) to (13), 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 (18) to (20).

  Next, the voltage command correction unit 17 obtains the phase voltage command values (vu *, vv *, vw *) obtained from the current control unit 12 and the correction coefficient Kg represented by the equation (5) as in the following equation. The phase voltage command correction values (vuh *, vvh *, vwh *) are obtained by multiplication.

  Note that the correction coefficient Kg in this case is the same as that described in the first embodiment, and here, in the above description, the voltage command value may be substituted for the current control gain.

vuh * = Kg · vu * (34)
vvh * = Kg · vv * (35)
vwh * = Kg · vw * (36)
The phase voltage command correction values (vuh *, vvh *, vwh *) in the electric motor drive device according to the present embodiment and the phase voltage command values (vu *, vv *, vw *) in the electric motor drive device according to the first embodiment. It is clear from the contents and formulas described above that the number of computations associated with the correction is halved compared to the motor driving device in the first embodiment. (Since three phases are combined, six current control gains are set in the first embodiment, so six calculations are required for correction. In this embodiment, the voltage command value is corrected. The operation involved is only 3 times).

  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.

Further, in the induced voltage estimation unit 14, the phase voltage command value (vu) in the equations (27) to (29)
Induced voltage estimated values (eu, ev, ew) are obtained using phase voltage command correction values (vuh *, vvh *, vwh *) instead of *, vv *, vw *).

  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 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. By correcting the voltage command value calculated by the current control unit 12 using the current control gain according to the value related to the rotational output of the electric motor 4, the preset current control gain corresponds to the value related to the rotational output of the electric motor 4. As a result, the optimum current control system can always be constructed without depending on the load condition, stable driving of the electric motor 4 can be realized, and further, compared with the first embodiment. Therefore, 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 block diagram which shows the system configuration | structure of the electric motor drive device in the 1st Embodiment of this invention. The block diagram which shows the system configuration | structure of the electric motor drive device in the 2nd Embodiment of this invention. Explanatory drawing of operation | movement in 1st Embodiment of the correction coefficient concerning this invention Explanatory drawing of operation | movement in 2nd Embodiment of the correction coefficient concerning this invention The block diagram which shows an example of the current control part concerning this invention The characteristic view which shows an example of the inductance characteristic of the electric motor concerning this invention Block diagram showing the system configuration of a conventional motor drive device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectification 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 18 Rotation output detection 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 detection means for detecting a current flowing in a stator winding of the motor, a current command value for the motor and a current detected by the current detection means Current control means for creating the voltage command value from a current error with a detected value; PWM signal generation means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value; A current control gain for correcting a current control gain in the current control means based on a value related to the rotational output of the motor. And a correction means, said current control gain correction means, electric motor drive device, wherein the current control gain in proportion to the value relating to the rotation output of the motor to correct the current control gain to be small. 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 detection means for detecting a current flowing in a stator winding of the motor, a current command value for the motor and a current detected by the current detection means Current control means for creating the voltage command value from a current error with a detected value; PWM signal generation means for generating a PWM signal for controlling the operation of each switching element of the inverter based on the voltage command value; Voltage command correction means for correcting the voltage command value based on a value related to the rotation output of the electric motor, and the voltage command Positive means, electric motor drive device, characterized in that the voltage command value in proportion to the value relating to the rotation output of the motor to correct the voltage command value so as to decrease. The electric motor drive device according to claim 1, wherein the current control gain (or the voltage command value) has a preset lower limit value. The current control gain (or the voltage command value) is corrected only when a value related to the rotation output of the motor is larger than a preset reference value, and when the value is less than the reference value, the current control gain (or The electric motor drive device according to claim 1, wherein the voltage command value is not corrected. 5. The electric motor drive device according to claim 4, wherein the correction is switched so that the value becomes continuous when the current control gain (or the voltage command value) is switched with or without correction. 6. The electric motor drive device according to claim 1, 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 the voltage command value) is corrected every n cycles (n ≧ 2) of the control cycle of the inverter only when a value related to the rotational output of the motor is equal to or less than a preset reference value. The electric motor drive device according to claim 6, wherein The electric motor drive device according to any one of claims 1 to 7, further comprising a speed control unit that creates the current command value from a speed error between a target speed of the motor given from outside and a rotational speed of the motor. The electric motor drive device according to any one of claims 1 to 8, wherein the value related to the rotational output of the electric motor is a current value of either the current command value or the detected current value. 10. The electric motor drive device according to claim 1, wherein the value related to the rotational output of the electric motor is a speed value of either the target speed or the rotational speed. The value related to the rotational output of the electric motor is an equivalent electric motor output obtained by the product of the current value of either the current command value or the detected current value and the speed value of either the target speed or the rotational speed. The electric motor drive device of any one of Claims 1-10.

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