JPH08223998A - Observer for induction motor control circuit and input voltage correction method therefor - Google Patents

Abstract

PURPOSE: To obtain an observer for an induction motor control circuit in which the interlinking flux on the rotor side and the speed can be estimated accurately while eliminating the voltage sensor without requiring any error correction for the voltage command value calculated from the current being fed to an induction motor. CONSTITUTION: The observer comprises a correction controller 9 for replacing the voltage command vector generated from a voltage command generating circuit in a current control step with a combined voltage command vector from phase q and phase d current controllers 2, 3 in the current control step added with a correction amount comprising the sum of an estimated interlinking flux on the rotor side in the current control step, the inner product of errors of the actual stator current vector in the current control step and an estimated stator current vector, and the integrated value of the inner product up to the current control step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an observer for an induction motor control circuit and its input voltage correction method.

[0002]

2. Description of the Related Art A conventional observer for an induction motor control circuit will be described with reference to the flowchart shown in FIG. When digital control is used, first, k · T _s seconds (k
Is an integer representing the order of control steps, and T _s is a cycle of control steps) and at least two phases of stator-side current (for example, U-phase current) supplied from the inverter to the induction motor.

[0003]

[Outside 1] V phase current

[0004]

[Outside 2] And stator side voltage (eg U phase voltage

[0005]

[Outside 3] V phase voltage

[0006]

[Outside 4] Is detected, and the current and voltage are coordinate-converted into the α-β axis coordinate system normally used for vector control by three-phase / two-phase conversion, and the α-phase current at k · T _s second is measured.

[0007]

[Outside 5] β-phase current

[0008]

[Outside 6] α-phase voltage

[0009]

[Outside 7] β-phase voltage

[0010]

[Outside 8] To calculate. After that, the theory of electronics D vol. III
． No. 11, p. Expressions (1) and (2) shown in 954 to 960 (1991) are sequentially expanded to expressions (3) and (4) (expressions (1) to (4),
The estimated value of the control step (k + 1) is calculated from the estimated value of the control step k using an observer for the induction motor control circuit which operates according to the last description of the conventional technique). That is, the α-phase current estimated value at k · T _s seconds estimated in the control loop of control step k

[0011]

[Outside 9] (The upper symbol represents the estimated value) and α-phase current

[0012]

[Outside 10] Estimation error with

[0013]

[Equation 1] β-phase current estimated value

[0014]

[Outside 11] And β-phase current

[0015]

[Outside 12] Estimation error with

[0016]

[Equation 2] Estimated value of field flux on the α-phase rotor side

[0017]

[Outside 13] , Β-phase rotor side estimated field flux

[0018]

[Outside 14] , Α phase voltage

[0019]

[Outside 15] , Β-phase voltage

[0020]

[Outside 16] And speed

[0021]

[Outside 17] Or speed estimate

[0022]

[Outside 18] Using, the estimated value at (k + 1) · T _s seconds

[0023]

[Outside 19] To calculate.

The equations cited in the above description of the prior art are shown below.

[0025]

(Equation 3)

[0026]

[Equation 4] R _s = stator resistance, R _r = rotor resistance, L _M = rotor stator mutual inductance, L _s = stator self-inductance, L _r = rotor self-inductance,

[0027]

[Outside 20] = Speed,

[0028]

[Outside 21] = Speed estimation value, g ₁ , g ₂ , g ₃ , g ₄ = observer feedback gain,

[0029]

[Outside 22] = Stator α-phase current,

[0030]

[Outside 23] = Stator β-phase current,

[0031]

[Outside 24] = Stator α-phase voltage,

[0032]

[Outside 25] = Stator β-phase voltage,

[0033]

[Outside 26] = Stator α phase current estimated value,

[0034]

[Outside 27] = Stator β-phase current estimated value,

[0035]

[Outside 28] = Estimated rotor α-phase field magnetic flux,

[0036]

[Outside 29] = Estimated value of rotor β-phase field magnetic flux,

[0037]

(Equation 5)

[0038]

(Equation 6)

[0039]

(Equation 7)

[0040]

However, in the above-mentioned conventional induction motor control circuit, it is strongly desired to eliminate the voltage sensor to reduce the cost. One way to achieve this is as follows: α phase voltage command value

[0041]

[Outside 30] β-phase voltage command value

[0042]

[Outside 31] To

[0043]

[Outside 32] Could be used instead of. In this case, there may be an error between the voltage command value and the actual value.

[0044]

[Outside 33] And speed estimate

[0045]

[Outside 34] There was a problem that an error occurred.

In view of the above problems, the present invention is directed to a voltage command value.

[0047]

[Outside 35] It is an object of the present invention to provide an observer for an induction motor control circuit and an input voltage correction method therefor capable of accurately estimating the rotor side interlinkage magnetic flux and speed by performing error correction on the.

[0048]

In order to solve the above-mentioned problems, an input voltage correction method for an observer for an induction motor control circuit according to the present invention uses a stator-side current of an induction motor as an observed value and a stator-side voltage command value as an observation value. In the observer for the induction motor control circuit configured as an input, the inner product value of the estimated rotor side interlinkage magnetic flux value and the stator current estimation error obtained by subtracting the estimated stator current from the stator side current, and the inner product value Is added to the stator side voltage command value as a correction term as a correction term to be newly used as an input to reduce the error in the estimated value.

Further, the observer for the induction motor control circuit of the present invention generates a voltage command vector from the input speed command and current command, and the stator current estimation vector in the next control step one cycle after the current control step. A vector control circuit that outputs each phase voltage command from the voltage command generation circuit to generate, the voltage command vector from the voltage command generation circuit, and the rotor side interlinkage magnetic flux estimation vector in the next control step, and the vector control circuit outputs In order to supply the stator current estimation vector and the rotor side interlinkage flux estimation vector in the next control step to the induction motor control circuit including the inverter that drives the induction motor based on each phase voltage command, the current control step Stator current estimation vector and rotor side flux linkage estimation vector and An induction motor that estimates a stator current estimation vector and a rotor side interlinkage flux estimation vector for the next control step from the voltage command vector from the voltage command generation circuit and the error between the actual stator current vector and the stator current estimation vector. An observer for a control circuit, the inner product value of the rotor side interlinkage flux estimation vector of the current control step, the error between the actual stator current vector and the stator current estimation vector of the current control step, and the inner product value The voltage from the voltage command generation circuit for the current control step is calculated by adding the correction amount, which is the sum of the integral value up to the current control step, to the voltage command vector from the voltage command generation circuit for the current control step. It has a vector correction circuit for replacing the command vector.

For example, according to the present invention, the rotor side interlinkage magnetic flux estimation value vector in the α-β axis coordinate system

[0051]

(Equation 8) And stator side current estimation error

[0052]

[Equation 9] A voltage correction amount V _{c (k)} obtained by multiplying the inner product of

[0053]

[Equation 10] Is the voltage command vector absolute value

[0054]

[Equation 11] To correct the absolute value of the voltage command vector, then d
-Α-phase and β-phase voltages converted from the q-axis coordinate system to the α and β-axis coordinate systems

[0055]

[Outside 36] To be used as an observer input value.

[0056]

[Function] The above inner product value

[0057]

(Equation 12) Is the absolute value of the command voltage as shown in the simulation results of Figs.

[0058]

(Equation 13) Is the absolute value of the actual voltage

[0059]

[Equation 14] When compared to

[0060]

(Equation 15) If

[0061]

[Equation 16] This corresponds to the case (see FIG. 3). Also,

[0062]

[Equation 17] If

[0063]

(Equation 18) (See FIG. 4). Therefore, the voltage correction amount V _c

[0064]

[Formula 19] Consists of

[0065]

[Outside 37] Corrected by adding to

[0066]

(Equation 20) Is converted to the α-β axis coordinate system as the voltage command absolute value,
β-phase voltage command

[0067]

[Outside 38] Is an observer input, the integral term of V _{c (k)}
By the action of

[0068]

[Equation 21] Ie

[0069]

[Equation 22] The voltage command value is corrected until Therefore, finally, the error between the voltage command value input to the observer and the actual voltage becomes zero. Other estimates as a result of zero error

[0070]

[Outside 39] And speed estimate

[0071]

[Outside 40] The error of can be reduced.

[0072]

Embodiments of the present invention will now be described with reference to the drawings. 1 is a block diagram showing a control system of an induction motor to which an embodiment of an input voltage correction method of the present invention is applied, and FIG. 2 is a flow chart showing a digital control operation of the control system of FIG. The phase converter 7 has k · T _s
At least two phases of stator-side current (for example, U-phase stator current) supplied from the inverter circuit 5 to the induction motor 10 at a time point of seconds (k is an integer representing the order of control steps, T _s is a cycle of control steps).

[0073]

[Outside 41] And V-phase stator current

[0074]

[Outside 42] Is detected (step S1) and converted into an α-β axis coordinate system,

[0075]

[Outside 43] When

[0076]

[Outside 44] Is derived (step S2). Estimated stator current value calculated in the control loop of control step (k)

[0077]

[Outside 45] (The upper symbol represents the estimated value), rotor side interlinkage magnetic flux

[0078]

[Outside 46] When

[0079]

[Outside 47] Is used to calculate the voltage correction amount V _{c (k)} by the equation (5).

[0080]

(Equation 23)

[0081]

[Equation 24]

[0082]

(Equation 25) Output of q-phase current controller

[0083]

[Outside 48] (* Represents a command value) and the output of the d-phase current controller

[0084]

[Outside 49] Is input (step S3), voltage command absolute value

[0085]

[Outside 50] Is calculated by the equation (6) (step S4).

[0086]

(Equation 26) This is corrected using V _{c (k)} , and the corrected voltage command absolute value

[0087]

[Outside 51] Is derived according to equation (7) (step S5).

[0088]

[Equation 27] The voltage command value whose absolute value has been changed is α from the dq axis coordinate system.
− Observer input voltage command by converting to β axis coordinate system

[0089]

[Outside 52] When

[0090]

[Outside 53] Is obtained (step S6). this

[0091]

[Outside 54]Equation (8) (shown at the end of the description of the embodiment
(K + 1) T _sEach estimated value in seconds

[0092]

[Outside 55] , And equation (9) (shown at the end of the description of the example)

[0093]

[Outside 56] Is derived (step S8).

Regarding the change in the speed of the induction motor, the case of the conventional example is shown in FIG. 5A, and the case of the present example is shown in FIG.
Each is shown in (b). Speed estimation value according to the present embodiment

[0095]

[Outside 57] Is more accurate than the conventional example

[0096]

[Outside 58] You can see that

FIG. 6 also shows the same contents as in FIG. 5, and FIG. 6 (a) shows the simulation result of the response waveform when the error correction of the voltage command input is not performed, and FIG. 6 (b). Shows the simulation result of the response waveform when the error correction of the voltage command input is performed.

The formulas quoted in the above description of the embodiments are shown below.

[0099]

[Equation 28]

[0100]

[Equation 29]

[0101]

As described above, according to the present invention, the voltage command and the actual voltage are corrected by using the inner product value of the estimated rotor side interlinkage magnetic flux and the estimated stator current error without using the stator side voltage as a parameter. , The current estimated value is obtained by correcting the error of the voltage command input which is the observer input term.

[0102]

[Outside 59] Estimated rotor flux linkage

[0103]

[Outside 60] And the speed estimate

[0104]

[Outside 61] The error from the true value of can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an observer for an induction motor control circuit according to the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG.

FIG. 3 is a time chart showing a change in inner product value between the rotor side interlinkage magnetic flux estimation vector and the error between the actual stator current vector and the stator current estimation vector in the embodiment of FIG.

FIG. 4 is a time chart showing a change in inner product value between a rotor side interlinkage magnetic flux estimation vector and an error between an actual stator current vector and a stator current estimation vector in the embodiment of FIG.

FIG. 5A is a time chart showing a change in speed of an induction motor tested by a conventional example. (B) is a time chart showing a change in speed of the induction motor tested by the embodiment of FIG. 1.

FIG. 6A is a time chart showing a change in speed of an induction motor simulated by a conventional example.
(B) is a time chart showing a change in speed of the induction motor simulated by the embodiment of FIG. 1.

FIG. 7 is a flowchart showing an operation of an observer of a conventional example.

[Explanation of symbols]

 1 Speed Controller 2 q Phase Current Controller 3 d Phase Current Controller 4 Vector Control Circuit 5 Inverter Circuit 6, 7 Phase Converter 8 Magnetic Flux Estimator 9 Correction Controller 10 Induction Motor

Claims (2)

[Claims] 1. An observer for an induction motor control circuit, which is configured by using a stator side current of an induction motor as an observation value and a stator side voltage command value as an input, and estimating an estimated rotor side interlinkage magnetic flux and a stator side. An inner product value of the stator current estimation error obtained by subtracting the stator current estimated from the current, and a correction amount consisting of an integrated value of the inner product value added as a correction term to the stator side voltage command value is used as a new input, A method for correcting an input voltage of an observer for an induction motor control circuit, characterized by reducing an error in an estimated value. 2. A voltage command generation circuit for generating a voltage command vector from an inputted speed command and current command, and a stator current estimation vector in the next control step one cycle after the current control step, and a voltage command generation circuit. And a vector control circuit for outputting each phase voltage command from the rotor side interlinkage flux estimation vector in the next control step, and an inverter for driving the induction motor based on each phase voltage command output from the vector control circuit In order to supply the stator current estimation vector and rotor side interlinkage flux estimation vector in the next control step to the induction motor control circuit consisting of, the stator current estimation vector and rotor side interlinkage flux estimation vector in the current control step And the voltage command vector from the voltage command generation circuit, and the actual In the observer for the induction motor control circuit, which estimates the stator current estimation vector and the rotor side interlinkage flux estimation vector in the next control step from the error between the stator current vector and the stator current estimation vector at the time of the current control step From the sum of the rotor side interlinkage flux estimation vector of, the inner product value of the error between the actual stator current vector and the stator current estimation vector of the current control step, and the integral value of the inner product value up to the current control step And a vector correction circuit for replacing the voltage command vector from the voltage command generation circuit of the current control step by adding the correction amount to the voltage command vector from the voltage command generation circuit of the current control step. An observer for the induction motor control circuit.