JP3508982B2 - AC 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 control of an inverter for driving an AC electric motor, and particularly to smooth start.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. First, FIG. 3 will be described. The first control device 40 outputs a voltage command Vc to the power converter 1, and the power converter 1 applies a voltage according to the command Vc to the AC motor 2. The acceleration / deceleration limiter 3 inputs the angular frequency command ωc,
The angular frequency ωm is set so that the acceleration / deceleration is limited and the acceleration / deceleration is followed.
Is output. For example, even if ωc changes stepwise, the output ωm changes obliquely with a limited inclination.
The voltage magnitude command generator 4 receives the angular frequency ωm and outputs a voltage magnitude command Vm proportional to it, for example. The integrator 5 integrates the angular frequency ωm and outputs the voltage phase θv. The size of the vector converter is the voltage magnitude command V
A voltage command Vc whose phase is the voltage phase θv at m is obtained and output. With the above configuration, the AC motor 2 rotates at a rotation speed corresponding to the angular frequency command ωc.

Next, FIG. 4 will be described. The second control device 41 outputs the voltage command Vc to the power converter 1, and the power converter 1 applies a voltage according to the command Vc to the AC motor 2.
The current detector 14 detects the input current vector i of the electric motor 2, and the voltage detection means 15 detects or estimates the input voltage vector v. The magnetic flux calculator 13 calculates and outputs the magnetic flux vector φ of the rotor of the electric motor 2 by an integral calculation from the outputs of the current detector 14 and the voltage detector 15. Torque calculator 12
Calculates the output torque T of the electric motor 2 from φ of the output of the magnetic flux calculator 13 and i of the output of the current detector 14, and outputs it.
The torque magnetic flux controller 11 obtains a voltage command Vc such that the output φ of the magnetic flux calculator 13 and the torque T output from the torque calculator 12 follow the magnetic flux command φc and the torque command Tc of those command values. Output. With the above configuration, the AC motor 2 comes to output the torque according to the torque command Tc in the magnetic flux state having the magnitude of the magnetic flux command φc.

Finally, FIG. 5 will be described. The third control device 42 outputs a voltage command Vc to the power converter 1, and the power converter 1 applies a voltage according to the command Vc to the AC motor 2. The current command converter 21 outputs a current command vector ic corresponding to the torque command Tc and the magnetic flux command φc. The frequency command converter 26 inputs the torque command Tc, the magnetic flux command φc, and the rotational angular frequency ωr of the motor 2 which is the output of the speed detector 27, and outputs the rotational angular frequency command ωc of the rotor magnetic flux. The integrator 25 determines the rotation angular frequency command ωc of the rotor magnetic flux.
Is integrated over time to find the phase θ of the rotor magnetic flux. The frequency command converter 26 and the integrator 25 serve as the phase calculating means 28 for obtaining the phase of the magnetic flux. The rotational coordinate transformation 24 performs rotational coordinate transformation on the output i of the current detector 14 at the opposite phase of the phase θ of the rotor magnetic flux to obtain a current vector ix on the coordinate synchronized with the magnetic flux.
Is output. The current controller 22 uses the current command vector ic
To obtain and output a voltage command vector Vx such that ix follows. The rotational coordinate conversion 23 performs rotational coordinate conversion of Vx with the phase θ of the rotor magnetic flux and outputs a voltage command vector Vc on stationary coordinates. With the above configuration, the AC motor 2 comes to output the torque according to the torque command Tc in the magnetic flux state having the magnitude of the magnetic flux command φc.

[0005]

In the prior art shown in FIG. 3, the acceleration / deceleration limiter 3 and the integrator 5 are provided, and these require their respective initial values ω0 and θ0. However, since it is difficult to obtain those initial values, ω
0 = θ0 = 0. Therefore, at the time of starting the first control device, the angular frequency ωm must be 0, which is the initial value ω0.
It will rise from the value of. If the electric motor 2 is an induction motor, the angular frequency ωm rises from 0 even when the electric motor 2 is started in a rotating state. Therefore, if the electric motor 2 is an induction motor, it is dangerous to accelerate from deceleration to ωm again. If the electric motor 2 is a synchronous electric motor, it will not be in a synchronous state and will be in a step-out state. Further, the initial value of the voltage phase θv does not always have a voltage phase that matches the phase of the magnetic flux, which may cause an overcurrent.

In the prior art shown in FIG. 4, the magnetic flux calculator 1
3, which requires the initial value φ0 of the magnitude of the magnetic flux and the phase θ0 of the magnetic flux because the magnetic flux is obtained by the integral calculation as described above. However, since it is difficult to obtain the initial value, φ0 = 0 is set. However, when the electric motor 2 is a synchronous electric motor, the magnetic flux of the rotor always exists, and even when the electric motor 2 is an induction motor, residual magnetic flux may exist. Therefore, since the initial value of the magnetic flux calculation is incorrect, an incorrect magnetic flux calculation is performed, and the torque is calculated accordingly, so that the output torque according to the torque command cannot be obtained.

In the prior art shown in FIG. 5, the integrator 25 in the phase calculating means 28 is provided and an initial value θ0 is required. However, since it is difficult to obtain the initial value,
θ0 = 0. However, since the phase of the magnetic flux of the rotor rarely starts from 0, the magnetic flux phase θ of the output of the phase calculation means 28 includes an error. Therefore, the output torque according to the torque command cannot be obtained. The present invention has been made in view of the above-mentioned points, and an object thereof is to provide initial values in various control devices and enable the control device to be started without problems.

[0008]

In order to solve the above-mentioned problems, according to the present invention, in claim 1, the input current of the electric motor is zero or therefor during a minute time after the electric power is supplied to the AC electric motor. A minute current control means for controlling the power converter so as to have a close value, a voltage detection means for detecting or estimating the voltage vector of the input of the electric motor in the minute period, and a voltage vector of the output of the voltage detection means. A first magnetic flux estimating means for estimating and calculating the magnitude and phase of the magnetic flux of the rotor of the electric motor and the rotational angular frequency;
The output of the first magnetic flux estimating means is an initial value of a numerical value for calculating or outputting the state variable of the AC electric motor in the AC electric motor control device.

According to a second aspect of the present invention, there is provided a minute current control means for controlling the power converter so that an input current of the motor becomes zero or a value close to that during a minute time after the power is supplied to the AC motor. , A voltage integration means for time-integrating the voltage vector of the output of the voltage detection means in the minute period, and the magnitude and phase of the magnetic flux of the rotor of the electric motor and the rotation angular frequency from the voltage integration vector of the output of the voltage integration means. And a second magnetic flux estimating means for estimating and calculating, and an output of the second magnetic flux estimating means is an initial value of a numerical value for calculating or outputting a state variable of the alternating current motor in the alternating current motor control device.

In the third aspect of the invention, there is provided a minute current control means for controlling the power converter so that the input current of the electric motor becomes zero or a minute magnitude of direct current close to zero.

According to a fourth aspect of the present invention, the output of the first magnetic flux estimating means or the second magnetic flux estimating means is an initial value of the frequency and phase of the voltage applied to the electric motor immediately after the minute time.

According to a fifth aspect of the present invention, magnetic flux calculating means for calculating magnetic flux of the rotor of the electric motor is provided, and the output of the first magnetic flux estimating means or the second magnetic flux estimating means is used as an initial value of the magnetic flux calculating means. The feature is that it is used immediately after the time.

According to a sixth aspect of the present invention, there is provided a phase calculation means for generating a frequency command of the magnetic flux based on the torque command and the magnetic flux command of the electric motor and integrating the frequency command to obtain the phase of the magnetic flux of the rotor. The phase of the magnetic flux output from the first magnetic flux estimating means or the second magnetic flux estimating means is used immediately after the minute time as an initial value of the phase calculating means.

According to a seventh aspect of the present invention, the voltage vector of the output of the voltage detecting means at any two points within the minute period is V1, V2, and the phase difference between V1 and V2 is from the V1 detecting point to the V2 detecting point. The rotational angular frequency of the magnetic flux on the secondary side is obtained by dividing by the elapsed time of
Or the average value of V1 and V2 is divided by the rotation angular frequency to obtain the magnitude of the magnetic flux of the rotor, and in the direction opposite to the rotation angular frequency by 90 degrees from the phase of V2. There is provided a first magnetic flux estimating means for making the rotated phase the phase of the magnetic flux of the rotor at the time of V2.

In claim 8, the voltage integration vector of the output of the voltage integrating means at any three points within the minute period is F1, F2, F3, and the center F0 of the circle passing through F1, F2, F3 is obtained. , F1-F0 and F3-F0 are divided by the time from the F1 detection time to the F3 detection time to obtain the rotational angular frequency of the magnetic flux of the rotor, and F3-
Let the phase of F0 be the phase of the magnetic flux of the rotor at the time of detecting F3,
A second magnetic flux estimating means for setting the magnitude of F3-F0 to the magnitude of the magnetic flux of the rotor at the time of detecting F3 is provided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention are shown in FIGS. 1 and 2 and will be described with reference to these drawings. In FIG. 1, the start-related signal generator 55 has a power converter start signal S0 that is 1 when the start is ON and 0 when the start is OFF, a minute time signal S1 that is 1 only for a minute time after the start is ON, and a minute signal after the start is ON. After the lapse of time, the controller start signal S2 which becomes 1 is output.

The power converter 1 uses the power converter start signal S.
The command Vc is issued to the AC motor 2 when 0 is 1.
Apply the street voltage. When the minute time signal S1 is 0, the switch 54 outputs the voltage command Vc of the output of the first controller 40, the second controller 41, or the third controller 42.
1 is selected and output to the power converter 1 as Vc0. On the other hand, when the minute time signal S1 is 1, the minute current control means 5
The output voltage command Vc2 of 1 is selected and output to the power converter 1 as Vc0.

The minute current control means 51 includes a current detector 14
Voltage command Vc2 such that the input current vector i of the electric motor 2 of the output of 0 is a DC with a small magnitude of zero or close thereto.
Is output.

The first magnetic flux estimating means 53 inputs the voltage vector v of the output of the voltage detecting means 15 at any two time points when the minute time signal S1 is 1, and outputs them as V
1, V2 and the phase difference between V1 and V2 is divided by the elapsed time from the V1 detection time to the V2 detection time to obtain the rotational angular frequency ω0 of the magnetic flux of the rotor, and the magnitude of V1 or V2 or V1 The magnitude φ0 of the magnetic flux of the rotor is obtained by dividing the average value of the magnitudes of V2 by the rotation angular frequency, and the phase θ0 rotated by 90 degrees in the direction opposite to the rotation angular frequency from the phase of V2 is obtained. Ω0, φ0,
Outputs θ0.

When the controller start signal S2 becomes 1, the first control device 40 outputs ω0 of the output of the first magnetic flux estimating means.
Is the initial value of the acceleration / deceleration limiter 3 in FIG. 3, and the value obtained by advancing the phase of 90 ° from the output of the first magnetic flux estimating means is the initial value of the integrator 5 in FIG.

The second control device 41 outputs the output φ of the first magnetic flux estimating means when the controller start signal S2 becomes 1.
0 and θ0 are initial values of the magnetic flux calculator 13 in FIG.

When the controller start signal S2 becomes 1, the third controller 42 outputs θ0 of the output of the first magnetic flux estimating means.
Is the initial value of the integrator 25 in FIG.

In FIG. 2, description of the same parts as in FIG. 1 will be omitted. The voltage integration means 56 inputs the voltage vector v of the output of the voltage detection means 15, integrates it over time, and outputs it as a voltage integration vector F.

The second magnetic flux estimating means 57 inputs the voltage integration vector F of the output of the voltage integrating means 56 at any three points when the minute time signal S1 is 1, and inputs them to F1, F2 and F3. Then, the center F0 of the circle passing through F1, F2, and F3 is obtained, and the phase difference between F1-F0 and F3-F0 is divided by the time from the F1 detection time to the F3 detection time to determine the rotation angle of the magnetic flux of the rotor. Find the frequency ω0, F3
-The phase of F0 is the phase θ0 of the magnetic flux of the rotor at the time of detecting F3.
Then, the magnitude of F3−F0 is output as the magnitude φ0 of the magnetic flux of the rotor at the time of detecting F3.

When the controller start signal S2 becomes 1, the first controller 40 outputs ω0 of the output of the second magnetic flux estimating means.
Is the initial value of the acceleration / deceleration limiter 3 in FIG. 3, and the value obtained by advancing the phase of θ0 of the output of the second magnetic flux estimating means by 90 degrees is the initial value of the integrator 5 in FIG.

When the controller start signal S2 becomes 1, the second control unit 41 outputs the output φ of the second magnetic flux estimating means.
0 and θ0 are initial values of the magnetic flux calculator 13 in FIG.

The third control device 42 outputs θ0 of the output of the second magnetic flux estimating means when the controller starting signal S2 becomes 1.
Is the initial value of the integrator 25 in FIG.

The reason why the magnitude and phase of the magnetic flux and the rotational angular frequency can be obtained by the first magnetic flux estimating means 53 and the second magnetic flux estimating means 57 will be described below. The AC motor is generally represented by v = R1 · i + L · P (i) + P (φx) (1). Here, R1 is the primary winding resistance, L is the leakage inductance, v is the input voltage vector, i is the input current vector, φx is the secondary magnetic flux vector, and P () is the time derivative. The input current vector i in the minute current control means 53 is
Since the direct current is zero or a very small value close to zero, the first and second terms on the right side of the equation (1) can be ignored. If the secondary magnetic flux vector rotates at an angular frequency of ω0, then φx = φ0 · EXP (j · ω0 · t) can be expressed. Where φ0 is the magnitude of the secondary magnetic flux vector, EX
P () represents an exponential function, t represents time, and j represents an imaginary unit. Then, equation (1) can be rewritten as v = j · ω0 · φ0 · EXP (j · ω0 · t) (2) if φ0 is constant. From equation (2), it can be seen that the input voltage vector v has a 90 ° phase advance from the secondary magnetic flux vector, its magnitude is ω0 · φ0, and its rotational angular frequency is ω0. Therefore, the first magnetic flux estimating means 5
By the method of 3, it is possible to obtain φ0, ω0, θ0.

For the same reason as above, ignoring the first term and the second term of the equation (1) and integrating both sides, integration (v) = φ0 · EXP (j · ω0 · t) + F0 (3) Become. The integration (v) is to integrate the input voltage vector v with time, and is the same as the voltage integration vector F of the output of the voltage integration means 56. F0 is the initial value of integration. From the equation (3), the voltage integration vector F has a center F0.
It can be seen that the vector has a magnitude of φ0 and rotates at an angular frequency of ω0. Therefore, the 3 of the second magnetic flux estimating means 57
It is understood that the two voltage integration vectors F1, F2, F3 pass through a circle centered on F0, and φ0, ω0, θ0 can be obtained by the method of the second magnetic flux estimating means 57.

[0030]

According to the present invention, the initial value of the numerical value in the AC motor control device can be set to an appropriate value, so that there are various problems such as sudden deceleration immediately after the control device is started, overcurrent and deterioration of control accuracy. The transient phenomenon can be suppressed.

[Brief description of drawings]

FIG. 1 is one embodiment of the present invention.

FIG. 2 is another embodiment of the present invention.

FIG. 3 is an example of a conventional technique.

FIG. 4 is a second prior art example.

FIG. 5 is a third prior art example.

[Explanation of symbols]

1 power converter 2 AC motor 3 Acceleration / deceleration limiter 4 Voltage magnitude command generator 5 integrator 6 Vector converter 11 Torque flux controller 12 Torque calculator 13 Magnetic flux calculator 14 Current detector 15 Voltage detection means 21 Current command converter 22 Current controller 23 Rotational coordinate converter 24 rotary coordinate converter 25 integrator 26 Frequency command calculator 27 Speed detector 28 Phase calculation means 40 First control device 42 Second control device 43 Third control device 51 Micro current control means 53 First magnetic flux estimating means 54 switch 55 Start-related signal generator 56 voltage integrating means 57 Second magnetic flux estimating means

Claims (4)

(57) [Claims] 1. An AC motor control device for controlling an electric power converter for supplying electric power to an AC motor such as an induction motor or a synchronous motor, wherein a minute time after starting to supply electric power to the AC motor is A minute current control means for controlling the power converter so that the input current becomes zero,
Voltage detection means for detecting or estimating the input voltage vector of the AC motor in the minute period, and the calculation of the magnitude and phase of the magnetic flux of the rotor of the motor and the rotation angular frequency from the voltage vector of the output of the voltage detection means. First to do
An AC motor control device comprising a magnetic flux estimating means. 2. An AC motor control device for controlling a power converter that supplies power to an AC motor such as an induction motor or a synchronous motor, wherein a minute time after starting to supply power to the AC motor is A minute current control means for controlling the power converter so that the input current becomes zero,
The voltage integrating means for time-integrating the voltage vector of the output of the voltage detecting means in the minute period, and the magnitude and phase of the magnetic flux of the rotor of the AC motor and the rotational angular frequency from the voltage integrating vector of the output of the voltage integrating means. And a second magnetic flux estimating means for estimating and calculating. 3. The voltage vector of the output of the voltage detecting means at any two points in the minute period is V1, V2, and the phase difference between V1 and V2 is the elapsed time from the V1 detecting point to the V2 detecting point. The rotational angular frequency of the secondary side magnetic flux is obtained by dividing by, and the magnitude of V1 or V2, or the average value of the magnitudes of V1 and V2 is divided by the rotational angular frequency to determine the magnitude of the magnetic flux of the rotor. First, the phase is obtained by rotating the magnetic flux of the rotor at the time of V2 by determining the phase and rotating the phase by 90 degrees in the direction opposite to the rotational angular frequency from the phase of V2.
The AC motor control device according to claim 1, further comprising a magnetic flux estimating means. 4. The voltage integration vectors of the outputs of the voltage integration means at arbitrary three points in the minute period are F1, F.
2, F3, the center F0 of the circle passing through F1, F2, and F3 is obtained, and the phase difference between F1-F0 and F3-F0 is divided by the time from the F1 detection time to the F3 detection time to determine the magnetic flux of the rotor. The rotation angular frequency of is calculated, and the phase of F3-F0 is F
The phase of the magnetic flux of the rotor at the time of 3 detection, and the magnitude of F3-F0 is the magnitude of the magnetic flux of the rotor at the time of F3 detection.
The AC motor control device according to claim 2, further comprising a magnetic flux estimating means.