JPH10225196A - Controller for induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sustain an operation by normally performing high performance vector speed control using a speed sensor and making a switch to sensorless vector control upon failure of the speed sensor. SOLUTION: Speed control is performed by normally outputting a detection speed ωr(s) from a speed sensor 3 as a speed feedback ωr and the detection speed ωr(s) added with a slip frequency ωs as a primary frequency ω0 through a switching means 18. A switch command CH is delivered from a failure detection means 17 upon failure of the speed sensor 3 and speed control is performed by outputting a primary frequency ω0(SL), calculated by a speed estimating means 16 as a primary frequency ω0 and an estimated speed determined by subtracting the slip frequency ωs from the primary frequency ω0(SL) as a speed feedback ωr thus sustaining the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the speed of an induction motor by performing vector control using a speed sensor, and more particularly, to controlling an induction motor capable of continuing operation even if the speed sensor fails. Related to the device.

[0002]

2. Description of the Related Art An inverter device is generally used as a speed control device for an induction motor. V / f control, SF control, vector control, sensorless vector control, etc. are used for the control of the inverter device depending on the application. Especially, vector control has good control accuracy, control response is high speed, and torque is directly controlled. It is widely used as a high-performance control method because of its capability.

FIG. 5 shows an example of the configuration of vector control using a speed sensor. An induction motor 1 is driven by an inverter device 2 and its driving speed ωr is controlled by a speed sensor 3.
And is used as a feedback signal. The detected speed ωr is compared with the speed reference ωr ^*, and the error is amplified by the speed control circuit 4 and output as the torque reference T ^* . The torque reference T ^* is divided by the secondary magnetic flux reference Φ2 ^* by the divider 5 and converted into a torque current reference i2q ^* , and further multiplied by the induction motor constant (L2 / M) to be converted into a primary current torque current reference i1q ^* . Is done. The secondary magnetic flux reference Φ2 ^* is converted by the excitation current calculation circuit 6 into the primary current exciting current reference i1d ^* . Torque current reference i1q ^*
And the exciting current reference i1d ^* are vector-added by the primary current vector calculation circuit 7 and output as a primary current reference vector i1 ^* . The value obtained by multiplying the torque current reference i2q ^* by the constant (R2) of the induction motor is calculated by the divider 8 as the secondary magnetic flux reference Φ.
The result is divided by 2 ^* and output as the slip frequency ωs, added to the detected speed ωr by the adder 9, and output as the primary frequency ω0. The primary frequency .omega.0 is integrated by the integrator 10 and converted to a primary current phase .theta.0. The primary current reference calculation circuit 11 calculates a primary current reference vector i1 ^* and a primary current phase θ0.
To generate and output three-phase current references iu ^* , iv ^* , and iw ^* . Current control circuit 12U, 12V, 12W
Compares the current references iu ^* , iv ^* , iw ^* with the three-phase detected currents iu, iv, iw detected by the current detector 13, respectively, controls the inverter device 2, and calculates the primary current of the induction motor 1. Control. As described above, the vector control is performed using the speed sensor, and the speed control of the high-performance induction motor is performed.

In sensorless vector control without using a speed sensor, a method is generally used in which current and voltage of an induction motor are detected and speed is estimated by calculation. FIG. 6 shows a configuration example of this type of sensorless vector control, in which a voltage detector 14, a secondary voltage operation circuit 1
5. A primary frequency estimating circuit 16 is newly added.

The voltage detector 14 detects the primary voltages Vu, Vv, Vw of the induction motor 1, the current detector 13 detects the primary currents iu, iv, iw of the induction motor 1, and the secondary voltage calculation circuit 15 And the primary current phase θ0
, The primary frequency ω0 and the d-axis component V2 of the secondary voltage
Calculate the d and q axis components V2q.

FIG. 7A shows an example of the internal configuration of the secondary voltage calculation circuit 15. The primary voltage Vu, Vv, Vw and the primary current iu, iv, iw are coordinate-transformed based on the primary current phase θ0. The signals are converted into d-axis components V1d and i1d and q-axis components V1q and i1q by the units 15a and 15b, respectively, and the d-axis component V2d and the q-axis component V2q of the secondary voltage are calculated by equations (1) and (2).

[0007]

V2d = V1d-R1.i1d + L.omega.0.i1q (1) V2q = V1q-R1.i1q-L.omega.0.i1d (2) (where R1 is the primary resistance of the induction motor and L is the inductance) The frequency estimating circuit 16 is configured, for example, as shown in FIG. 7 (b), and calculates the equation (3) based on the d-axis component V2d and the q-axis component V2q of the secondary voltage and the secondary magnetic flux reference Φ2 ^* .
The primary frequency ω0 is calculated by estimation.

[0008]

Ω0 = (V2d / Φ2 ^* ) · Kq−Kd · V2d (3) (where Kq and Kd are constants) In such sensorless vector control, vector control is performed without using a speed sensor. .

[0009]

In the above-described vector control using the speed sensor, there is a problem that the operation becomes impossible if the speed sensor fails, and the sensorless vector control enables a highly reliable operation. There is a problem that the accuracy and response of the speed control are inferior to the vector control using the speed sensor, and the speed sensor has to be used in applications that require high-precision speed control and high-speed control response. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to normally perform speed control by high-performance vector control using a speed sensor.
It is an object of the present invention to provide a control device for an induction motor that can switch to sensorless vector control and continue operation when a speed sensor fails.

[0011]

In order to achieve the above object, a control device for an induction motor according to the present invention comprises an inverter for driving the induction motor, a torque current reference and an excitation current reference based on a torque command and a magnetic flux reference. Vector control means for generating and controlling the inverter, a speed sensor for detecting the speed of the induction motor, speed estimation means for calculating an estimated speed of the induction motor from detected values of voltage and current of the induction motor, Failure detection means for outputting a switching command when the abnormality of the speed sensor is determined, and switching means for switching from the detected speed to the estimated speed based on the switching command, and usually performs speed control based on the detected speed. When the speed sensor fails, the speed control is continued based on the estimated speed. (Claim 1) An inverter for driving an induction motor, vector control means for generating a torque current reference and an excitation current reference based on a torque command and a magnetic flux reference, and the vector control means based on the torque current reference and the excitation current reference. Voltage calculation means for calculating the d-axis voltage component contributing to the excitation of the induction motor and the q-axis voltage component contributing to the torque and controlling the inverter; a speed sensor for detecting the speed of the induction motor; Speed estimation means for calculating an estimated speed of the induction motor from a current detection value and the d-axis voltage component and the q-axis voltage component; failure detection means for outputting a switching command when an abnormality of the speed sensor is determined; Switching means for switching from the detected speed to the estimated speed based on a switching command, and usually performs speed control based on the detected speed. When the speed sensor fails, the speed control is continued based on the estimated speed. (Claim 2) Further, the failure detection means detects when the speed detected by the speed sensor changes beyond a predetermined rate of change ( It is determined that the speed sensor has failed (when an abrupt change that is not normally possible), and the switching command is output from that point. (Claim 3) Further, the speed estimating means may be configured to operate in a normal driving state.
Compensating means for comparing the estimated speed of the induction motor with the speed detected by the speed sensor to correct the estimated speed, to obtain a more accurate estimated speed, and to continue speed control using the estimated speed as speed feedback. Improve control accuracy. (Claim 4) Further, the correction means obtains a speed deviation between the estimated speed and the speed detected by the speed sensor and a rate of change of the speed deviation, and based on the primary resistance of the induction motor based on the speed deviation. And correcting the second control constant set based on the primary leakage inductance of the induction motor based on the rate of change of the speed deviation. (Claim 5) Further, the speed estimating means includes torque components V1q and i1q of primary current and primary voltage of the induction motor and excitation components V1d and i.
When the torque component V2q and the excitation component V2d of the secondary voltage are obtained from 1d using the first control constant and the second control constant corrected by the correction means, the torque component V2 of the secondary voltage is obtained.
The primary frequency ω0 (SL) is calculated from 2q, the excitation component V2d and the secondary magnetic flux reference Φ2 ^*, and the slip frequency ωs is subtracted from the primary frequency ω0 (SL) to output the estimated speed ωr (SL).
(Claim 6) Further, the primary frequency ω always calculated by the speed estimating means.
Speed control is performed using 0 (SL) and the estimated speed ωr (SL),
The switching means is omitted. (Claim 7)

[0012]

FIG. 1 is a block diagram of an embodiment corresponding to claims 1 and 3 of the present invention. In the figure, 17 is a speed sensor 2
A failure detection circuit 18 for monitoring the speed detection signal ωr (s) and outputting a switching command CH when it is determined that the speed sensor 2 is abnormal. The fault detecting circuit 18 detects the speed feedback signal ωr and the primary frequency ω0 based on the switching command CH. This is a switching circuit for switching, which is newly added in the present invention. Others are the same as those of the related art (FIGS. 5 and 6), and the description is omitted.

In the present embodiment, a signal detected by the speed sensor 3 is normally used as a speed feedback signal to drive the vehicle under high-precision speed control. If the speed sensor 3 fails, an output from the primary frequency estimating circuit 16 is output. The speed feedback signal ωr is estimated and calculated based on the primary frequency ω0 (SL), and the speed control can be continuously performed by switching to the sensorless vector control.

FIG. 2 shows a specific example of the failure detection circuit 17 and the switching circuit 18. The failure detection circuit 17 detects the detection speed ω of the induction motor 1 detected via the speed sensor 3.
a differentiating circuit 17a for outputting a signal dωr (s) / dt proportional to the rate of change of r (s), a setting unit 17b for setting a detection level DL that is impossible in normal operation, and a signal dωr (s) / d
When t exceeds the detection level DL, a comparator 17c is determined to be abnormal. The comparator 17c outputs a switching command CH when the comparator 17c determines abnormal.

The switching circuit 18 comprises an adder 18a, a subtractor 18
b, changeover switches 18c and 18d, and in normal operation, the changeover switch 18c operates at the detection speed ω of the speed sensor 3.
r (s) is output as speed feedback ωr, and the changeover switch 18d outputs the output of the adder 18a as the primary frequency ω0. When the speed sensor 3 fails and the switching command CH is output from the failure detection circuit 17, the changeover switch 18c outputs the output of the subtractor 18b as speed feedback ωr, and the changeover switch 18d outputs the changeover signal CH from the primary frequency estimation circuit 16. The output primary frequency ω0 (SL) is output as the primary frequency ω0.

In the above configuration, when the speed sensor 3 is normal, the switching command CH is not output from the failure detection circuit 17 and the detection speed ωr (s) of the speed sensor 3 output from the adder 18a and the slip frequency ωs The sum is given as the primary frequency ω0, and the speed control with high accuracy is performed using the detected speed ωr (s) of the speed sensor 3 as the speed feedback ωr.

If the speed sensor 3 fails, the failure detection circuit 17
, The primary frequency ω0 (SL) output from the primary frequency estimating circuit 16 is given as the primary frequency ω0, and the primary frequency ω0 ( Estimated speed ωr (SL) obtained by subtracting slip frequency ωs from SL) is output as speed feedback ωr, and is switched to sensorless vector control. Therefore, when the speed sensor fails, the operation can be continued by the sensorless vector control. (Claims 1 and 3) FIG. 3 is a configuration diagram of an embodiment corresponding to claims 2 and 3 of the present invention.

In FIG. 1, reference numerals 19a and 19b denote two-axis (d-axis and q-axis in a rotating coordinate system) signals and three-axis (U, in a stationary coordinate system).
A coordinate conversion circuit for performing signal conversion between (V, W phases) signals;
20q is a q-axis current control circuit, 20d is a d-axis current control circuit, and 16A is a primary frequency estimation circuit.

In this embodiment, the three-phase primary currents iu, iv, and iw detected by the current detector 13 are converted by a coordinate conversion circuit 19a.
Is converted into a two-phase torque current i1q and an exciting current i1d, and the q-axis current control circuit 20q compares i1q ^* and i1q to output a q-axis voltage reference V1q ^* , and the d-axis current control circuit 20d
Compares i1d ^* with i1d and outputs d-axis voltage reference V1d ^* . The coordinate conversion circuit 19b controls the inverter 3 based on V1q ^* and V1d ^* , and controls the q-axis current and the d-axis current. The primary frequency estimating circuit 16A calculates the torque current i1q
Based on the excitation current i1d, the q-axis voltage reference V1q ^*, and the d-axis voltage reference V1d ^* , the primary frequency ω0
(SL) is calculated. Other components are the same as those in FIG.

In the above configuration, when the speed sensor 3 is normal, the switching command CH is not output from the failure detection circuit 17, and the detected speed ωr of the speed sensor 3 is set as the primary frequency ω0.
(s) and the sum of the slip frequency ωs and the speed sensor 3
Ωr (s) is used as speed feedback ωr to perform high-accuracy speed control.

The speed sensor 3 becomes abnormal and the failure detection circuit 1
7, the switching command CH is output, the primary frequency ω0 (SL) output from the primary frequency estimating circuit 16A is given as the primary frequency ω0, and the primary frequency ω0 (SL) output from the primary frequency estimating circuit 16A is Slip frequency ωs
Is output as speed feedback ωr, and is switched to sensorless vector control.

Therefore, in the present embodiment, the operation can be continued even when the speed sensor fails without using the voltage detector 14. According to the present invention, when calculating the estimated speed of the induction motor, a function of correcting the estimated speed based on the speed detected by the speed sensor 3 is added to improve the calculation accuracy of the estimated speed, and the sensorless operation is performed. Accuracy of speed control in vector control can be improved.

FIG. 4 shows a main configuration for correcting the d-axis component V2d and the q-axis component V2q of the secondary voltage to improve the calculation accuracy of the primary frequency ω0 (SL) and to improve the calculation accuracy of the estimated speed. This is specifically shown, and can be added to the configuration of FIG.

In FIG. 4, reference numeral 21 denotes a control constant correction circuit which compares the detected speed ωr (S) of the speed sensor 3 with the estimated speed ωr (SL) and outputs control constants R1 (c) and L (c). is there. Further, multipliers 15m to 15q are added to the secondary voltage calculation circuit 15 to correct the d-axis component V2d and the q-axis component V2q of the secondary voltage based on the control constants R1 (c) and L (c). Is added.

The control constant correction circuit 21 detects the detection speed ωr
(S) and the estimated speed ωr (SL) are compared by a subtractor 21a to determine a speed deviation Δωr, and the adder 21f adds the control to the control constant (primary resistance R1 of the induction motor) set by the setter 21c to control. The constant R1 (c) is obtained. Further, the differentiator 21b
, The change dΔωr / dt of the speed deviation Δωr is obtained, and the control constant L (c) is obtained by adding to the control constant (primary leakage inductance L1 of the induction motor) set by the adder 21g by the adder 21g.

The secondary voltage calculation circuit 15 includes a coordinate conversion unit 15
a, 15b, the primary voltages Vu, Vv, Vw and the primary current iu,
iv and iw are d-axis components V1d and i1d, and q-axis component V1q, respectively.
And i1q, the d-axis component V2d of the secondary voltage and the q-axis component V
At the time of conversion to 2q, the calculations of the equations (4) and (5) are performed using the control constants R1 (c) and L (c).

[0027]

V2d = V1d−R1 (c) · i1d + L (c) · ω0 · i1q (4) V2q = V1q−R1 (c) · i1q−L (c) · ω0 · i1d (5) Similarly, the calculation of equation (3) is performed to calculate a more accurate primary frequency ω0 (SL).

According to this embodiment, a control constant for obtaining an accurate estimated speed ωr (SL) can be obtained when speed control is performed using the detected speed ωr (S) of the speed sensor 3 as a feedback signal. However, it is possible to improve the accuracy of the speed control in the case of operating with sensorless vector control due to failure.

Although FIG. 4 shows an example in which the configuration is added to the configuration of FIG. 1, it goes without saying that the coordinate conversion unit 15a of the secondary voltage calculation circuit 15 can be omitted and added to the configuration of FIG. In addition, when the configuration of FIG. 4 is added, the error between the calculated estimated speed ωr (SL) and the detected speed ωr (S) of the speed sensor 3 becomes so small as to be almost negligible. Even during normal operation, the estimated speed ωr (SL) is always used as the speed feedback ωr and the calculated primary frequency ω0 (SL) is used as the primary frequency ω0, and when the speed sensor fails, the control constant before the failure is retained. Thus, the operation can be continued by the sensorless vector control. According to this embodiment, it is not necessary to switch between the speed feedback ωr and the primary frequency ω0 when the speed sensor fails, and a simple configuration can be achieved. (Claim 7)

[0030]

As described above, according to the present invention,
It is possible to provide an induction motor control device which normally achieves excellent control performance by vector control using a speed sensor or sensorless vector control and can continue operation by sensorless vector control even when a speed sensor fails.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment according to claims 1 and 3 of the present invention.

FIG. 2 is a detailed view of a main part of the embodiment.

FIG. 3 is a configuration diagram of an embodiment according to claims 2 and 3 of the present invention.

FIG. 4 is a configuration diagram of a main part of an embodiment according to claims 4, 5, and 6 of the present invention.

FIG. 5 is a configuration diagram of a conventional device using a speed sensor.

FIG. 6 is a configuration diagram of a conventional device of sensorless vector control.

7A and 7B are diagrams showing a main part of a conventional device, wherein FIG. 7A is a configuration diagram of a secondary voltage calculation circuit 15, and FIG. 7B is a configuration diagram of a primary frequency estimation circuit 16;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Induction motor, 2 ... Inverter apparatus, 3 ... Speed sensor, 4 ... Speed control circuit, 5 ... Divider, 6 ... Excitation current calculation circuit, 7 ... Primary current vector calculation circuit, 8 ...
Divider, 9: Adder, 10: Integrator, 11: Primary current reference arithmetic circuit, 12U, 12
V, 12W: current control circuit 13: current detector,
14: voltage detector, 15: secondary voltage calculation circuit,
15m to 15q Multiplier 16 Primary frequency estimating circuit 16A Primary frequency estimating circuit 17
Failure detection circuit, 18 ... Switching circuit, 19
A, 19B: coordinate conversion circuit, 20d: d-axis current control circuit, 20q: q-axis current control circuit, 21: control constant correction circuit.

Claims (7)

[Claims] 1. An inverter for driving an induction motor, vector control means for generating a torque current reference and an excitation current reference based on a torque command and a magnetic flux reference to control the inverter, and a speed for detecting a speed of the induction motor. A sensor, speed estimation means for calculating an estimated speed of the induction motor from detected values of voltage and current of the induction motor, failure detection means for outputting a switching command when the speed sensor is determined to be abnormal, and the switching command Switching means for switching from the detected speed to the estimated speed based on the detected speed, and usually performs speed control based on the detected speed, and when the speed sensor fails, continues the speed control based on the estimated speed. A control device for an induction motor, characterized in that: 2. An inverter for driving an induction motor, vector control means for generating a torque current reference and an excitation current reference based on a torque command and a magnetic flux reference, and the induction motor based on the torque current reference and an excitation current reference. Voltage calculating means for calculating the d-axis voltage component contributing to the excitation and the q-axis voltage component contributing to the torque and controlling the inverter, a speed sensor for detecting the speed of the induction motor, and a current detection for the induction motor. A speed estimating means for calculating an estimated speed of the induction motor from a value and the d-axis voltage component and the q-axis voltage component; a failure detecting means for outputting a switching command when an abnormality of the speed sensor is determined; Switching means for switching from the detected speed to the estimated speed based on the detected speed. Normally, speed control is performed based on the detected speed. Control device when the capacitors has failed induction motor, characterized in that to continue the velocity control on the basis of the estimated speed. 3. The control device for an induction motor according to claim 1, wherein said failure detecting means detects a failure of said speed sensor when a detection speed of said speed sensor changes beyond a predetermined rate of change. A control device for an induction motor, wherein it is determined that the switching has been performed, and the switching command is output from that time. 4. The control device for an induction motor according to claim 1, wherein said speed estimating means compares an estimated speed of said induction motor with a detected speed of said speed sensor in a normal operation state. A control unit for correcting the estimated speed, and improving control accuracy when speed control is continued using the estimated speed as speed feedback. 5. The control device for an induction motor according to claim 4, wherein said correction means obtains a speed deviation between said estimated speed and a speed detected by said speed sensor and a rate of change of said speed deviation. The first control constant set based on the primary resistance of the induction motor is corrected based on the first control constant, and the second control constant set based on the primary leakage inductance of the induction motor based on the rate of change of the speed deviation is calculated. A control device for an induction motor, wherein the control device performs correction. 6. A control device for an induction motor according to claim 5, wherein said speed estimating means includes a torque of a secondary voltage based on torque components V1q and i1q of a primary current and a primary voltage of the induction motor and excitation components V1d and i1d. When the component V2q and the excitation component V2d are obtained, they are obtained using the first control constant and the second control constant corrected by the correction means, and the torque component V2q and the excitation component V2d of the secondary voltage and the secondary magnetic flux reference Φ2 ^* A primary frequency ω0 (SL) is calculated from the following, and the slip frequency ωs is subtracted from the primary frequency ω0 (SL) to output an estimated speed ωr (SL). 7. The control device for an induction motor according to claim 6, wherein the speed control is always performed using the primary frequency ω0 (SL) and the estimated speed ωr (SL) calculated by the speed estimating means. A control device for an induction motor, characterized by omitting means.