JP3403922B2 - Induction motor control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor control device for controlling an induction motor by speed sensorless vector control.

[0002]

2. Description of the Related Art In the control of an electric vehicle, for example, there is a running state in which an inverter accelerates an induction motor to a certain speed, then the inverter is stopped and the inertia of the electric vehicle is used for traveling. When the inverter is restarted from this running state to shift to the operation such as power running or regeneration, the frequency of the induction motor in the running state is detected from the information of the installed speed sensor to control the inverter frequency.

FIG. 16 is a block diagram of a conventional control device for an induction motor by vector control. Vector controller 10
For 0, the torque command value Tm ^* and the secondary magnetic flux command value φ2d ^* are input, and the magnetic flux axis (hereinafter referred to as d axis) voltage command value Vd ^*.
And a torque axis (hereinafter referred to as q axis) voltage command value Vq ^* are calculated and output. Slip frequency calculator 101 inputs the torque command value Tm ^* and the secondary magnetic flux command value .phi.2d ^*, calculates and outputs the slip frequency reference .omega.s ^*. Coordinate converter 1
02 receives the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* , converts them into three-phase voltage command values Vu ^* , Vv ^* , Vw ^* , and outputs them. The inverter 103 converts direct current supplied from a power source (not shown) into alternating current and drives the induction motor 104 in accordance with the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* . The speed sensor 105 detects a rotation frequency (hereinafter, referred to as a motor frequency) ωr of the induction motor 104.
The adder 106 adds the slip frequency reference ωs ^* and the motor frequency ωr and outputs the inverter frequency ωinv. The integrator 106 integrates the inverter frequency ωinv and outputs it to the coordinate converter 102.

[0004]

In the control device for an induction motor by such vector control, when the inverter 103 is restarted from the running state, the speed sensor 1 is used.
Since 05 can detect the motor frequency ωr of the induction motor 104, the inverter frequency ωinv can be obtained,
It is possible to perform a stable and reliable restart.

However, if the speed sensorless vector control without the speed sensor 105 is adopted,
Since the speed sensor is not provided, information on the motor frequency of the induction motor cannot be obtained. When the inverter is restarted when the motor frequency cannot be specified,
There are problems that a large transient torque is generated or an overcurrent occurs and the inverter stops.

Therefore, the present invention has been made to solve the above-mentioned problems, and estimates the motor frequency of the induction motor that is required when the inverter is restarted from the running state, and it is stable and reliable. It is an object of the present invention to provide an induction motor control device for controlling an induction motor by vector control without speed sensor, which can be restarted.

[0007]

In order to achieve the above-mentioned object, the invention as set forth in claim 1 includes a plurality of inverters for converting direct current into alternating current, and a plurality of induction motors respectively driven by these inverters. , A plurality of frequency estimation means for respectively estimating the rotation frequency of these induction motors, the rotation frequency estimated by these frequency estimation means, and the output voltage command value is calculated based on the torque command value and the magnetic flux command value. At least one of the plurality of induction motors when restarting each of the plurality of inverters from a vector control unit that controls each of the plurality of inverters based on a command value and a running state that stops the plurality of inverters. Estimate the rotation frequency of one induction motor and restart all of the inverters using this rotation frequency. Made and a restart means that.

According to a second aspect of the present invention, in the invention according to the first aspect, the restarting means is in the deactivation state,
Giving the magnetic flux command value to at least one inverter,
An induction motor comprising: an operating unit that operates the at least one inverter, and at the time of restarting each of the plurality of inverters from the running state, at least one inverter driven by the operating unit drives the induction motor. The rotation frequency is estimated, and all of the plurality of inverters are restarted by using this rotation frequency.

According to a third aspect of the present invention, in the invention according to the first aspect, the restarting means is in the deactivation state,
A magnetic flux command value lower than the magnetic flux command value is given to at least one inverter, and an operating means for operating the at least one inverter is provided, and when restarting each of the plurality of inverters from the derailed state, It is characterized in that the rotation frequency of the induction motor driven by at least one inverter operated by the operating means is estimated, and all the plurality of inverters are restarted using this rotation frequency.

According to a fourth aspect of the invention, in the invention according to the second or third aspect, a capacitor connected to the input side of at least one inverter operated by the operating means, and this capacitor It comprises a converter for supplying a DC voltage, and a voltage control means for controlling the converter so that the DC voltage supplied by the converter is lowered to the above-mentioned accelerating state.

According to a fifth aspect of the present invention, in the invention according to the second or third aspect, the operating means compares the switching frequency of at least one inverter operated in the deceleration state during normal operation. It is characterized in that it is controlled to be lowered.

According to a sixth aspect of the present invention, a plurality of inverters for converting direct current into alternating current, a plurality of induction motors driven by these inverters, and a plurality of frequency estimations for estimating rotation frequencies of these induction motors, respectively. Means and the rotation frequency estimated by these frequency estimating means,
A vector control means for calculating an output voltage command value based on the torque command value and the magnetic flux command value, and controlling each of the plurality of inverters based on the output voltage command value, and a row state for stopping the plurality of inverters When restarting each of the plurality of inverters, the rotation frequency of at least one induction motor of the plurality of induction motors is detected, and the rotation frequency detected by the detection means is used to detect the rotation frequency of the plurality of induction motors. And a restarting means for restarting all the inverters.

According to a seventh aspect of the present invention, an inverter for converting direct current into alternating current, an induction motor driven by the inverter, first frequency estimating means for estimating a rotation frequency of the induction motor, and the first frequency estimating means. Vector control means for calculating the output voltage command value based on the rotation frequency estimated by the frequency estimation means 1, the torque command value, and the magnetic flux command value, and controlling the inverter based on the output voltage command value; and the inverter. When the inverter is restarted from the running state in which the motor is stopped, the second frequency estimating means for estimating the rotation frequency of the induction motor and the rotation frequency estimated by the second frequency estimating means are used. A restart means for restarting the inverter, and the restart means when restarting the inverter by the restart means or when the restart is completed. Switching from moving means to the vector control unit comprising and a switching means for controlling said inverter.

According to an eighth aspect of the invention, in the invention of the seventh aspect, the second frequency estimating means causes the inverter to output an arbitrary voltage, and the phase current supplied to the induction motor. Detecting means, a calculating means for calculating a current component matching the vector direction of the voltage output from the inverter from the phase current detected by the current detecting means, and a current component calculated by this calculating means. So as to be zero, and an inverter frequency control means for controlling the inverter frequency of the inverter, when the current component approaches zero, the inverter frequency controlled by the inverter frequency control means as the rotation frequency. It is characterized by estimating.

According to a ninth aspect of the present invention, in the seventh aspect of the invention, the second frequency estimating means causes the inverter to output an arbitrary voltage and supplies the phase current to the induction motor. Current detecting means for detecting the phase current, a calculating means for calculating the magnitude of the phase current detected by the current detecting means, and a magnitude of the phase current calculated by the calculating means is minimized. Inverter frequency control means for controlling the inverter frequency is provided, and when the magnitude of the phase current is minimized, the inverter frequency controlled by the inverter frequency control means is estimated as the rotation frequency. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a control device for an induction motor showing a first embodiment of the present invention. The drive A comprises a vector controller 1A, an inverter 2A, an induction motor 3A, a current detector 4A, and a motor frequency estimator 5A. The vector controller 1A is
The torque command value Tm ^* , the secondary magnetic flux command value φ2d ^*, and the motor frequency ωrh, which will be described later, are input, and the three-phase voltage command value V is input.
It outputs u ^* , Vv ^* , and Vw ^* . Inverter 2A has 3
According to the phase voltage command values Vu ^* , Vv ^* , Vw ^* , the direct current supplied from the power source (not shown) is converted into alternating current to drive the induction motor 3A. The current detector 4A is an induction motor 3A.
The currents Iu and Iw flowing through are detected. The motor frequency estimator 5A inputs the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* output by the vector controller 1A and the currents Iu, Iw detected by the current detector 4A, and the motor frequency estimator 5A receives the induction motor 3A. Estimate the motor frequency ωrh. This motor frequency estimator 5A
The motor frequency ωrh estimated by is input to the vector controller 1A. Drive B is also drive A
The configuration is almost the same as that of the vector controller 1B, the inverter 2B, the induction motor 3B, the current detector 4B, the motor frequency estimator 5B, and the selector 6B. The vector controller 1B inputs the torque command value Tm2 ^* , the secondary magnetic flux command value φ2d2 ^*, and a motor frequency described later, and outputs three-phase voltage command values Vu2 ^* , Vv2 ^* , Vw2 ^* . The inverter 2B has three-phase voltage command values Vu2 ^* , Vv2 ^* ,
According to Vw2 ^* , direct current supplied from a power source (not shown) is converted into alternating current to drive the induction motor 3B. The current detector 4B uses the currents Iu2 and Iw2 flowing through the induction motor 3B.
To detect. The motor frequency estimator 5B has three-phase voltage command values Vu2 ^* , Vv2 ^* , which are output from the vector controller 1B.
Vw2 ^* and the currents Iu2, I detected by the current detector 4B
w2 and the motor frequency ωrh of the induction motor 3B
Estimate 2. The switching device 6B is the motor frequency estimator 5
The motor frequency ωrh estimated by A and the motor frequency ωrh2 estimated by the motor frequency estimator 5B
Select either one of. One motor frequency selected by the switch 6B is the vector controller 1B.
Entered in.

Here, for example, when considering control of an electric vehicle, there is a coasting state in which the operation of the inverters 2A and 2B is completely stopped and the vehicle runs by inertia. In this state,
Only very small residual magnetic flux remains in the induction motors 3A and 3B.

FIG. 2 is an operation sequence diagram of the drives A and B when restarting from the dead state. That is, the restart means will be described below. When the drives A and B in the ascending state are restarted, first, only the motor frequency estimator 5A of the drive A estimates the motor frequency ωrh. When the motor frequency ωrh estimated by the motor frequency estimator 5A is stable, the motor magnetic fluxes φ2d and φ2d2 of the induction motors 3A and 3B are started up, that is, the so-called restart operation is started. At this time, the motor frequency selector 6B of the drive B selects the motor frequency ωrh estimated by the motor frequency estimator 5A of the drive A. For this reason, the inverters 2A and 2B of both the drives A and B are controlled based on the motor frequency ωrh so that the motor magnetic fluxes φ2d and φ2d2 of the induction motors 3A and 3B respectively rise.
Then, the motor magnetic flux φ2d, φ of the induction motors 3A, 3B
At the time when 2d2 rises, a flag F indicating a declination state
The RUN changes from "1" to "0", and the motor frequency selector 6B operates to select the motor frequency ωrh2 estimated by the motor frequency estimator 5B of the drive B. After restarting from the power running state and entering the power running / regenerative state, the control is performed using the motor frequency independently estimated.

By carrying out the above control, it is possible to minimize the occurrence of transient torque and overcurrent at the time of restarting from the drive. That is, the estimation of the motor frequency is based on the induced voltage generated by the magnetic flux. In restarting from the running state, the induced voltage necessary for estimating the motor frequency does not exist, so it is indispensable to give some voltage to generate the magnetic flux, that is, the induced voltage. In this case, since the motor frequency is unknown, it is difficult to control the magnetic flux and the torque in a non-interfering manner, and some transient torque or current is generated. When multiple inverters restart at the same time from a running state, other inverters can suppress the transient torque and current value of the entire system by raising the magnetic flux according to the estimated value. is there.

Further, the drives A and B may be restarted from the purging state based on the sequence shown in FIG. In this sequence, even in the running state, only the secondary magnetic flux command value φ2d ^* is continuously supplied to the vector controller 1A of the drive A and the operation of the inverter 2A is not stopped. On the other hand, in the running state, the vector controller 1 of drive B
The secondary magnetic flux command value φ2d2 ^* is not given to B, and the operation of the inverter 2B is stopped. The motor frequency selector 6B of the drive B selects the motor frequency ωrh estimated by the motor frequency estimator 5A of the drive A when the flag FRUN indicating the running state is “1”, and the motor magnetic flux φ2d2 of the induction motor 3B. The inverter 2B is controlled so that the voltage rises. Then, the motor magnetic flux φ2d of the induction motor 3B
When 2 rises, the flag FRU indicating the progress status
N changes from "1" to "0" and the motor frequency selector 6B
Operates to select the motor frequency ωrh2 estimated by the motor frequency estimator 5B of the drive B. After restarting from the power running state and entering the power running / regenerative state, the control is performed using the motor frequency independently estimated.

With the above-described control, in a system including a plurality of inverters, at least one inverter is operated even during the running so that the magnetic flux is continuously applied to the induction motor. It is possible to estimate a stable motor frequency even when restarting from. Also, the inverter that has stopped operating uses this motor frequency estimated value to start the magnetic flux of its own induction motor,
When the estimated value of the motor frequency of its own becomes stable, all the inverters can be stably restarted by using the estimated value of the motor frequency of its own.

Further, the drives A and B may be restarted from the purging state based on the sequence shown in FIG. In this sequence, even in the running state, only the secondary magnetic flux command value φ2d ^* is continuously supplied to the vector controller 1A of the drive A and the operation of the inverter 2A is not stopped. On the other hand, in the running state, the vector controller 1 of drive B
The secondary magnetic flux command value φ2d2 ^* is not given to B, and the operation of the inverter 2B is stopped. It should be noted that the secondary magnetic flux command value φ that continues to be given to the vector controller 1A of the drive A in this running state
2d ^* is set small with respect to the secondary magnetic flux command value given in the normal state of power running or regenerative state. Then, upon restarting, the magnetic flux of the inverter 2A is raised. The subsequent sequence is similar to the sequence shown in FIG.

By the control as described above, in addition to the effect of the sequence control shown in FIG. 3, the output current value of the inverter 2A in the decelerating state can be reduced and the loss can be reduced.

FIG. 5 is a block diagram of an induction motor controller according to a second embodiment of the present invention. According to the embodiment of the present invention, at least one inverter is operated in a decelerating state as in the control by the operation sequence diagrams shown in FIGS. 3 and 4. The inverter 2A, which continues to operate in at least this row state, is connected to the converter 8 and the capacitor 9. The AC power supplied from the single-phase or 3-phase AC power supply 7 is converted into DC power by the converter 8, and the inverter 2A
Is converted into AC power to drive the induction motor 3A. The voltage Vdc across the terminals of the capacitor 9 is detected by the voltage detector 10, the deviation from the voltage command value Vdc ^* is calculated in the comparator 11, and the difference is input to the voltage controller 12. Voltage controller 1
2 controls the output voltage of the converter 8 so that the inter-terminal voltage Vdc matches the voltage command value Vdc ^* .

FIG. 6 shows the flag FRUN and the voltage command value Vd.
It is a relationship diagram of c ^* . When the flag FRUN indicating the running state as shown in FIG. 6 changes from “0” to “1”, the voltage command value Vdc ^* is set smaller than that in the normal power running or regeneration. Then, the voltage command value Vdc ^* is added to the inter-terminal voltage Vdc.
The converter 8 is controlled so that Then, the inter-terminal voltage Vdc controlled to be lower than the normal time is converted into alternating current by the inverter 2A.

By controlling in this manner, the loss of the inverter 2A also depends on the magnitude of the inter-terminal voltage Vdc, so that the inverter 2A that continues to operate even in the deceleration state.
Can be reduced.

FIG. 7 is a block diagram of a control device for an induction motor showing a third embodiment of the present invention. According to the embodiment of the present invention, at least one inverter is operated in a decelerating state as in the control by the operation sequence diagrams shown in FIGS. 3 and 4. The switching frequency Fs of the inverter 2A that continues to operate in this at least deceleration state is controlled. The switch 13A selects one of the switching frequencies Fs1 and Fs2 and supplies it to the inverter 2A as the switching frequency Fs. This switching frequency Fs2
Is a frequency lower than the switching frequency Fs1. That is, since the switching unit 13A normally sets the flag FRUN to "0" in the power running or regenerative state,
The switching frequency Fs1 is selected and given to the inverter 2A as the switching frequency Fs. On the other hand, since the flag FRUN is "1" in the dead state, the switch 13
A selects the switching frequency Fs2 and supplies it to the inverter 2A as the switching frequency Fs.

By controlling in this way, the loss of the inverter 2A is proportional to the number of times of switching of the switching element forming the inverter 2A, and therefore depends on the switching frequency of the inverter, so that the inverter that continues to operate even in the deceleration state The loss can be reduced by lowering the switching frequency of 2 A as compared with the normal time.

FIG. 8 is a block diagram of an induction motor controller according to a fourth embodiment of the present invention. The embodiment of the present invention is characterized in that at least one induction motor 3A is provided with a speed sensor 14A. When restarting from the ascending state, the switches 15A and 15B select the motor frequency ωr detected by the speed sensor 14A.
When the magnetic flux rises and the flag FRUN indicating the deceleration state becomes “0”, the switchers 15A and 15B cause the motor frequencies ωr estimated by the motor frequency estimators 5A and 5B, respectively.
Select h and ωrh2. Therefore, the detection value of the speed sensor 14A is used only during the restart from the running state,
When the magnetic flux rises, the motor frequency estimator 5A,
By controlling so that the motor frequency estimated by 5B is used, it is possible to stably and reliably raise the magnetic flux and perform so-called restart. In this case, the information from only one speed sensor needs to be known at least only at the time of restart, and sufficient accuracy is not necessary.

FIG. 9 is a block diagram of an induction motor controller according to a fifth embodiment of the present invention. The vector controller 16 inputs the torque command value Tm ^* and the secondary magnetic flux command value φ2d ^*, and outputs the dq axis voltage command values Vd1 ^* and Vq1 ^* . The slip frequency calculator 17 inputs the torque command value Tm ^* and the secondary magnetic flux command value φ2d ^* , and determines the slip frequency reference ω.
Calculate and output s ^* . The coordinate converter 18 inputs the dq-axis voltage command values Vd ^* , Vq ^* output via the switchers 27, 28 described later, and receives the three-phase voltage command values Vu ^* , Vu ^.
Convert to v ^* , Vw ^* and output. The inverter 19 is 3
According to the phase voltage command values Vu ^* , Vv ^* , Vw ^* , the direct current supplied from the power source (not shown) is converted into alternating current to drive the induction motor 20. The current detector 21 is the induction motor 20.
The currents Iu and Iw flowing through are detected. Coordinate converter 22
Inputs the currents Iu and Iw, converts them into dq-axis currents Id and Iq, and outputs them. The motor frequency estimator 23 inputs the dq-axis voltage command values Vd ^* , Vq ^* and the dq-axis currents Id, Iq and estimates the motor frequency ωrh1 of the induction motor 20. Further, the motor frequency estimator 24 uses the dq-axis current I
d and Iq are input, the motor frequency ωr of the induction motor 20
It outputs h2, inverter frequency ωinv2, and dq axis voltage command values Vd2 ^* , Vq2 ^* . The adder 25 adds the slip frequency reference ωs ^* and the motor frequency ωrh output via the switch 29, which will be described later, to obtain the inverter frequency ω.
Output inv1. The integrator 26 integrates the inverter frequency ωinv output via the switch 30 described later, and outputs the integrated result to the coordinate converters 18 and 22.

The switching devices 27 to 30 each obtain one output from two inputs based on the switching signals S1 and S2 shown in FIG. The switching signal S1 shows the signal "a" in the state where the motor frequency is estimated for restarting from the running state, and shows the signal "b" in the restarting state and the normal powering / regenerative state. The switching signal S2 shows a signal "a" from the state of estimating the motor frequency to the restart state, and shows a signal "b" in the normal power running / regeneration state. In the running state, since the operation of the inverter 19 is completely stopped, the switching signal S
1 and S2 are not output. That is, the switch 27 is
The d-axis voltage command value Vd output by the motor frequency estimator 24
2 ^* and the d-axis voltage command value V output by the vector controller 16
When d1 ^* is input and the switching signal S2 indicates the signal “a”, the d-axis voltage command value Vd2 ^* is selected, and when the switching signal S2 indicates the signal “b”, the d-axis voltage command value Vd1 ^* is selected. The voltage command value Vd ^* is output to the coordinate converter 18. The switching device 28 is the motor frequency estimator 24.
Q-axis voltage command value Vq2 ^* and vector controller 1
When the q-axis voltage command value Vq1 ^* outputted by 6 is inputted and the switching signal S2 shows the signal "a", the q-axis voltage command value V
q2 ^* , when the switching signal S2 indicates the signal “b”, the q-axis voltage command value Vq1 ^* is selected, and the q-axis voltage command value Vq ^* is selected ^.
Is output to the coordinate converter 18. Switch 29
Is the motor frequency ω output by the motor frequency estimator 24
rh2 and the motor frequency ωrh1 output from the motor frequency estimator 23 are input, the motor frequency ωrh2 is selected when the switching signal S2 indicates the signal “a”, and the motor frequency ωrh1 is selected when the switching signal S2 indicates the signal “b”. , And output to the adder 25 as the motor frequency ωrh. The switching device 30 inputs the inverter frequency ωinv2 output by the motor frequency estimator 24 and the inverter frequency ωinv1 output by the adder 25, and outputs the switching signal S
1 indicates the signal “a”, the inverter frequency ωin
When the switching signal S1 indicates the signal “b”, v2 is selected as the inverter frequency ωinv1 and output to the integrator 26 as the inverter frequency ωinv.

First, in the normal power running / regenerative state, both the switching signals S1 and S2 show the signal "b" as described above.
Therefore, the vector controller 16 makes the torque command value Tm ^*
And the secondary magnetic flux command value φ2d ^* are input, the dq-axis voltage command values Vd1 ^* and Vq1 ^* calculated are the dq-axis voltage command value V
d ^* , Vq ^* , and the motor frequency estimator 23 d
q-axis voltage command values Vd ^* , Vq ^* (Vd1 ^* , Vq1 ^* ) and d
Motor frequency ω estimated by inputting q-axis currents Id and Iq
rh1 is obtained as the motor frequency ωrh. Then, the motor frequency ωrh (ωrh obtained by the adder 25
The inverter frequency ωinv1, which is the sum of 1) and the slip frequency ωs ^* , is obtained as the inverter frequency ωinv. The above operation is similar to the operation of so-called speed sensorless vector control.

In the power running state, the operation of the inverter 19 is stopped, but when starting from the power running state, the motor frequency must first be estimated. Therefore, when the motor frequency is estimated, the switching signals S1 and S2 both show the signal "a" as described above. Therefore, the dq-axis voltage command values Vd2 ^* , Vq2 ^* output by the motor frequency estimator 24 are the dq-axis voltage command values Vd ^* , Vq ^*.
And the inverter frequency ωinv2 similarly output by the motor frequency estimator 24 is
Obtained as inv. Thus, when the inverter frequency ωinv is obtained in the derailing state, the switching signal S
Only 1 changes from the signal "a" to the signal "b". When the switching signal S1 becomes the signal “b”, the vector controller 16 inputs the torque command value Tm ^* and the secondary magnetic flux command value φ2d ^* to calculate the dq-axis voltage command values Vd1 ^* and Vq1 ^{*, which} are the dq-axis voltages. The inverter frequency ωinv1 which is obtained as the command values Vd ^* and Vq ^{* and} is the sum of the motor frequency ωrh (ωrh2) obtained by the adder 25 and the slip frequency ωs ^*
Is obtained as the inverter frequency ωinv. Then, the switching signal S2 changes from the signal "a" to the signal "b" at the time of or during the restart, that is, at the time of rising or rising of the speed. This shifts to a normal speed sensorless vector control system.

In the speed sensorless vector control, it is necessary to estimate the motor frequency. To estimate this motor frequency, it is essential to have a certain amount of magnetic flux that can be grasped almost accurately. Since the estimator that estimates the motor frequency in the normal state does not operate stably because it is extremely small even if it does not exist, it may be difficult to estimate the motor frequency. When the magnetic flux is raised in a state where the estimated value of the motor frequency is not stable, an excessive transient torque is generated or the magnetic flux does not rise. Therefore, as in the present embodiment, the estimation of the motor frequency at the time of restarting from the run is performed by an estimator provided separately from the estimator for estimating the motor frequency at the normal time, so that stable and reliable You can reboot.

FIG. 11 shows a state in which the switching signals S1 and S2 are the signal "a", centering on the motor frequency estimator 24 in the fifth embodiment shown in FIG. 30 and the like are omitted.

The motor frequency estimator 24 determines the d-axis voltage command value Vd2 ^* as the dq-axis voltage command values Vd2 ^* and Vq2 ^{* .}
Is set to 0, and the q-axis voltage command value Vq2 ^{* is set} to an arbitrary value Vref.
Set to and output. This set and output value is
As the dq axis voltage command values Vd ^* and Vq ^* , the coordinate converter 18
Given to. In this case, the output voltage vector matches the q axis on the dq axis rotating coordinate system. A current component matching the output voltage vector, that is, the q-axis current Iq is input to the inverter frequency controller 24a. The inverter frequency controller 24a has, for example, a configuration in which the input is PI-controlled, and the current component that corresponds to the output voltage vector, that is, q
Inverter frequency ωi that makes the axial current component Iq zero
Output nv2. This value is the inverter frequency ωin
It is given to the integrator 38 as v. When the zero-current detector 24b detects that the q-axis current component Iq becomes zero or near zero, the inverter frequency ω at that time point
Inv2 is held by the latch device 24c, and this value is output as the motor frequency ωrh2.

Further, FIG. 12 shows a state in which the switching signals S1 and S2 are the signal "a" centering on the motor frequency estimator 24 in the fifth embodiment shown in FIG.
The switches 27 to 30 are omitted.

[0038] Motor Frequency estimator 24, dq-axis voltage command value Vd2 ^*, as Vq2 ^*, d-axis voltage command value Vd2 ^*
Is set to 0, and the q-axis voltage command value Vq2 ^{* is set} to an arbitrary value Vref.
Set to and output. This set and output value is
As the dq axis voltage command values Vd ^* and Vq ^* , the coordinate converter 18
Given to. The current vector length calculator 24d inputs the dq axis currents Id and Iq, calculates the magnitude I1 thereof, and outputs the magnitude I1. The minimization controller 24e outputs an inverter frequency ωinv2 that minimizes the magnitude I1. This value is given to the integrator 38 as the inverter frequency ωinv. Then, when the magnitude I1 becomes the minimum, the inverter frequency ωinv2 is held by the latch device 24f, and this value is output as the motor frequency ωrh2.

In FIG. 13, on the dq axis rotating coordinate system, a voltage on the q axis is given, the d axis voltage is set to zero, and the motor frequency is set to 1.
It is a graph showing each dq-axis current value in a steady state when it is 00 Hz. The horizontal axis is the inverter frequency. From FIG. 13, it can be seen that the sign of the q-axis current is reversed between positive and negative at 100 Hz where the inverter frequency matches the motor frequency. It can also be seen that the magnitude I1 has a minimum value at 100 Hz where the inverter frequency matches the motor frequency, and the magnitude I1 gradually increases as the distance from 100 Hz increases.

FIGS. 14 and 15 show dq axes in a steady state when a voltage on the q axes is given on the dq axis rotating coordinate system, the d axis voltage is zero, and the motor frequency is 50 Hz and 150 Hz. It is a graph showing each electric current value. In this case as well, the inverter frequency matches the motor frequency.
It can be seen that the sign of the q-axis current is reversed between positive and negative at a frequency of Hz or 150 Hz. Also, at the point where the inverter frequency matches the motor frequency, 50 Hz or 150 Hz,
Size I1 takes the minimum value, 50Hz or 150Hz
As you move away from, you can see that the number increases.

Utilizing the characteristics shown in FIGS. 13 to 15, when the q-axis current is positive, the inverter frequency is controlled to be lowered, and when the q-axis current is negative, the inverter is controlled. By controlling to increase the frequency, the inverter frequency and the motor frequency can be matched. Further, the minimum value of the magnitude I1 is searched for, and the frequency at the time of reaching the minimum value matches the motor frequency. Since such control does not depend on the motor parameter, it is possible to accurately estimate the motor frequency.

In the configuration of the motor frequency estimator shown in FIG. 11, the motor frequency is estimated by directly detecting the q-axis current and determining that the q-axis current has become zero or near zero.
In consideration of the speed of motor frequency estimation, this portion can obtain the same operation and effect even when the inverter frequency is latched with a certain time delay from the start of estimation and the inverter frequency is used as the motor frequency.

In the configuration of the motor frequency estimator shown in FIG. 12, the magnitude I1 is minimized to estimate the motor frequency. The magnitude of the current value on the dq axis rotating coordinate system is proportional to the magnitude of the current value on the stationary coordinate system, and the effective value of the phase current is also proportional. Therefore, even if the magnitude of the current value on the stationary coordinate system or the effective value of the phase current is minimized instead of minimizing the magnitude of the current value on the dq-axis rotating coordinate system, the same effect can be obtained. it can.

[0044]

As described above, according to the present invention,
When restarting from a running state, generation of unnecessary overcurrent and torque can be prevented, and stable and reliable restart can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a control device for an induction motor showing a first embodiment of the present invention.

FIG. 2 is an operation sequence diagram when restarting from a dead state.

FIG. 3 is an operation sequence diagram when restarting from a dead state.

FIG. 4 is an operation sequence diagram when restarting from a dead state.

FIG. 5 is a configuration diagram of a control device for an induction motor showing a second embodiment of the present invention.

FIG. 6 is a relationship diagram between a flag and a voltage command value.

FIG. 7 is a configuration diagram of a control device for an induction motor showing a third embodiment of the present invention.

FIG. 8 is a configuration diagram of a control device for an induction motor showing a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram of a control device for an induction motor showing a fifth embodiment of the present invention.

FIG. 10 is a diagram showing a switching signal.

11 is a detailed explanatory diagram of the motor frequency estimator shown in FIG. 9. FIG.

12 is a detailed explanatory diagram of the motor frequency estimator shown in FIG. 9. FIG.

FIG. 13 is a graph showing dq-axis current values.

FIG. 14 is a graph showing dq-axis current values.

FIG. 15 is a graph showing dq-axis current values.

FIG. 16 is a block diagram of a conventional induction motor control device.

[Explanation of symbols]

1A, 1B, 16 ... Vector controllers 2A, 2B, 19 ... Inverters 3A, 3B, 20 ... Induction motors 4A, 4B, 21 ... Current detectors 5A, 5B, 23, 24 ... Motor frequency estimators 6B, 13A, 15A , 15B, 27, 28, 29, 3
0 ... Switching device 8 ... Converter 9 ... Capacitor 10 ... Voltage detector 12 ... Voltage controller 17 ... Slip frequency calculator 18, 22 ... Coordinate converter 24a ... Inverter frequency controller 24b ... Zero current detectors 24c, 24f ... Latch 24d ... Current vector length calculator 24e ... Minimization controller

Claims (9)

(57) [Claims] 1. A plurality of inverters for converting a direct current into an alternating current, a plurality of induction motors respectively driven by these inverters, a plurality of frequency estimation means for estimating respective rotation frequencies of these induction motors, and these frequency estimation means. Vector control means for calculating the output voltage command value based on the estimated rotation frequency, the torque command value, and the magnetic flux command value, and controlling each of the plurality of inverters based on the output voltage command value; and the plurality of inverters. When restarting each of the plurality of inverters from the running state in which the plurality of induction motors are stopped, the rotation frequency of at least one induction motor of the plurality of induction motors is estimated, and the rotation frequency is used to estimate the rotation frequency Control device for an induction motor having restarting means for restarting all of the inverters. 2. The control device for the induction motor according to claim 1, wherein the restarting means gives the magnetic flux command value to at least one inverter in the deceleration state,
Operating means for operating a plurality of inverters, and at the time of restarting each of the plurality of inverters from the running state, the rotational frequency of the induction motor driven by at least one inverter operated by the operating means is set. A controller for an induction motor, which estimates and restarts all of the plurality of inverters using this rotation frequency. 3. The control device for the induction motor according to claim 1, wherein the restarting means applies a magnetic flux command value lower than the magnetic flux command value to at least one inverter in the deceleration state, Rotation frequency of an induction motor driven by at least one inverter operated by the operation means when the inverter is restarted from the running state, the operation means operating the inverter. Is estimated and all of the plurality of inverters are restarted using this rotation frequency. 4. The induction motor control device according to claim 2 or 3, wherein a capacitor connected to an input side of at least one inverter operated by the operation means, and a DC voltage applied to the capacitor. A control device for an induction motor, comprising: a converter to be supplied; and a voltage control means for controlling the converter so that the DC voltage supplied to the converter is lowered to the above-mentioned accelerating state. 5. The control device for an induction motor according to claim 2 or 3, wherein the operating means lowers a switching frequency of at least one inverter operated in the deceleration state as compared with a normal operation. A control device for an induction motor, which is controlled as described above. 6. A plurality of inverters for converting DC into AC, a plurality of induction motors driven by these inverters, a plurality of frequency estimation means for estimating rotation frequencies of these induction motors, and these frequency estimation means. Vector control means for calculating the output voltage command value based on the estimated rotation frequency, the torque command value, and the magnetic flux command value, and controlling each of the plurality of inverters based on the output voltage command value; and the plurality of inverters. When restarting each of the plurality of inverters from the running state in which the motor is stopped, the rotation frequency of at least one induction motor of the plurality of induction motors is detected, and the rotation frequency detected by the detection means is detected. Control means for restarting all of the plurality of inverters by using Apparatus. 7. An inverter for converting direct current to alternating current, an induction motor driven by this inverter, a first frequency estimating means for estimating a rotation frequency of the induction motor, and the first frequency estimating means for estimating the rotation frequency. The output frequency command value is calculated based on the rotation frequency, the torque command value, and the magnetic flux command value, and the vector control means for controlling the inverter based on the output voltage command value, and from the row state in which the inverter is stopped When restarting the inverter, second frequency estimating means for estimating the rotation frequency of the induction motor, and the rotation frequency estimated by the second frequency estimating means are used to restart the inverter. Restarting means, and when the restarting of the inverter by the restarting means is completed or when the restarting is completed, And a switching means for controlling the inverter by switching to a torque control means. 8. The induction motor control device according to claim 7, wherein the second frequency estimation means causes the inverter to output an arbitrary voltage and detects a phase current supplied to the induction motor. A current detecting means, a calculating means for calculating a current component matching the vector direction of the voltage output from the inverter from the phase current detected by the current detecting means, and the current component calculated by this calculating means becomes zero. So that the inverter frequency control means for controlling the inverter frequency of the inverter is provided, and when the current component approaches zero, the inverter frequency controlled by the inverter frequency control means is estimated as the rotation frequency. An induction motor control device characterized by: 9. The induction motor control device according to claim 7, wherein the second frequency estimating means causes the inverter to output an arbitrary voltage and detects a phase current supplied to the induction motor. Current detecting means, calculating means for calculating the magnitude of the phase current detected by the current detecting means, and the inverter frequency of the inverter so as to minimize the magnitude of the phase current calculated by the calculating means. And an inverter frequency control means for controlling, wherein the inverter frequency controlled by the inverter frequency control means is estimated as the rotation frequency when the magnitude of the phase current is minimized. Control device.