JP3123304B2 - Induction motor vector 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 the setting of an exciting current command value and a rated torque current in a vector control device for an induction motor.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional vector control device. Speed control unit 2 of the induction motor 1, to obtain a torque current command I _T by a proportional integral operation from the deviation of the speed detection value omega _r from the speed command omega * and the speed detection unit 3.

[0003] Torque current instruction I _T and exciting current command I ₀ for perpendicular thereto becomes a command value in d-q axis coordinate system rotating in synchronization with the primary angular frequency omega _1, both command and the induction motor 1 The slip frequency ω _S is obtained by the slip frequency calculator 4 from the secondary time constant (τ ₂ ).

The slip frequency ω _S is added to the detected speed value ω _r of the induction motor ₁ to be converted into a primary angular speed ω ₁ , and the angular speed ω ₁ is further integrated by an integration operation unit 5 to obtain a phase angle θ _O. .

[0005] The current control unit 6 performs the calculation by the proportional integral operation from the deviation between the torque current command I _T and the exciting current command torque current detection value of each relative I ₀ I _TFB and the exciting current detection value I _OFB, rotation The coordinate axis torque axis voltage _VT and excitation axis voltage V _O are obtained.

The torque current detection value _ITFB and the excitation current detection value I _OFB are calculated from the two-phase current detection values of the induction motor 1.

Voltage control signals V _O and V _T from current control unit 6
Are fixed-phase three-phase voltages V _U , V _V ,
It is converted to V _W and is used as an output voltage control signal of the PWM inverter 8.

Here, the exciting current command value I ₀ is set according to the rated torque current of the induction motor. Further, the torque current command value _IT is obtained by performing a ratio calculation on the calculation result of the speed control unit 2 with respect to the rated torque current.

[0009]

In THE INVENTION Problems to be Solved conventional vector control apparatus is given by the ratio of the excitation current command value I ₀ and the rated torque current value is given as the setting input data, typically an induction motor rated current (design value) .

However, if there is an error between the set and inputted excitation current value and rated torque current value and the rated current value and design value of the actual motor, an error occurs in the torque output in proportion to the error.

This problem has been addressed by adjusting both the exciting current and the rated torque current for each actual machine. For this purpose, the induction motor to be used is subjected to actual load operation and no-load test. It requires torque measurement and calculation of various constants, and requires much labor to calculate the set value.

[0012] This trouble also requires each measurement again when the same induction motor is to be derated.

Further, if there is an error in the measurement of the excitation inductance or the leakage inductance with the actual machine constant, the error needs to be changed again, but after this adjustment, the reference of the excitation current command and the torque current command is used. It is necessary to adjust the rated torque current data again, and the adjustment is time-consuming.

It is an object of the present invention to provide a vector control device which makes it possible to reliably and easily set an exciting current and a rated torque current.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of controlling the speed command of an induction motor and the deviation of a detected speed value.
From the difference, the torque current
Give the decree I _T, Oyo said torque current command and the exciting current command I ₀
In vector control system of induction <br/> guide motor for vector control of induction motor based on Bisuberi frequency, a primary inductance L ₁ of the induction motor, no-load terminal voltage V ₀ and one order at a base speed of the motor From frequency F _n,

(Equation 3) Setting of the excitation current command I _{0 according} to
And parts, the rated torque current value I ₂ for the speed control unit obtains the torque current command I _T, the rated output P _ower the primary inductance L ₁ and the exciting inductance M 'and the terminal voltage V ₀ which the induction motor Next formula

(Equation 4) And a rated torque current setting unit set according to the following.

[0016]

(Equation 3)

Set according to [0017], the rated output P _ower the primary inductance L ₁ and the exciting inductance M 'and the terminal voltage V ₀ which rated torque current value I ₂ is an induction motor for obtaining a torque current command I _T of the induction motor Next formula

[0018]

(Equation 4)

It is characterized in that it is set according to:

[0020]

(1) Calculation of excitation current In a vector-controlled induction motor, the voltage-current equation when the torque current is zero can be expressed by the following equations (1) and (2).

[0021]

V _1d = R ₁ · I _1d (1) V _1q = (Lσ + M ′) ω ₁ · I _1d (2) V _1d ; primary d-axis winding voltage R ₁ ; primary winding resistance V _1q ; Primary q-axis winding voltage Lσ; Equivalent leakage inductance I _1d ; Excitation current M ′; Equivalent excitation inductance ω ₁ ; Primary angular frequency By the way, dq rotating in synchronization with the primary angular frequency ω ₁
Axis coordinate induction motor voltage V _1d expressed in systems, expressed in voltages V ₁ of V _1q three-phase AC amounts below (3), the equation (4).

[0022]

(Equation 6)

When the exciting current I _1d expressed in the dq axis coordinate system is represented by the three-phase alternating current I ₀ , the following equation (5) is obtained.

[0024]

(Equation 7)

From the above equations (2), (4) and (5), the voltage V ₁ of the induction motor becomes the following equation (6).

[0026]

(Equation 8)

Here, _let us consider a case where the induction motor has no load at the base speed. The voltage at this time is V ₀ , and the primary frequency wave is approximated by the rated frequency Fn. Then, the excitation current I ₀ is obtained by the following equation (7) from the equation (6).

[0028]

(Equation 9)

V ₀ ; motor terminal voltage (V) when there is no load at the base speed L ₁ ; primary inductance (H) From the equation (5), the exciting current I _1d in the dq axis coordinate system is ) Or (9).

[0030]

(Equation 10)

Therefore, according to the present invention, the exciting current is determined from the constant L ₁ , the terminal voltage V ₀ and the primary angular frequency ω ₀ according to the equation (7) or the equations (8) and (9). I do.

(2) Calculation of Rated Torque Current The equations for calculating the output _Power and the torque T of the induction motor are given by the following equations (10) and (11), respectively.

[0033]

[Equation 11]

P _ole ; number of poles When the equation (11) is substituted into the equation (10) and arranged, the output of the induction motor is as shown in the equation (12).

[0035]

_Power = (2πf · M ′ · I _1d · I _1q ) (12) _Power : induction motor output (W) I _1d ; exciting current (A) f; primary frequency (H _Z ) I _1q ; torque current (A) Here, when the excitation current I _1d and the torque current I _1q represented in the dq axis coordinate system are represented by the three-phase AC quantity excitation current I ₀ and the torque current I ₂ , (13), Equation (14) is obtained.

[0036]

(Equation 13)

By substituting the equations (13) and (14) into the equation (12), the output of the induction motor can be expressed by the equation (15).

[0038]

_Power = 3 · (2πf · M ′) I ₀ · I ₂ = 3 · V _m · I ₂ (15) V _m in the equation (15) is the value of the induction motor shown in FIG. It corresponds to the voltage (phase voltage) induced in the exciting inductance M ′ of the TI type equivalent circuit.

[0039] Here, when the terminal voltage of the induction motor at no load at the base speed is V _0, since V ₀ is divided substantially divided by the equivalent excitation inductance M 'equivalent leakage inductance Lσ, V _m is (16 ) Can be expressed as

[0040]

(Equation 15)

Substituting equation (16) into equation (15),
When M '+ Lσ = L _1, the output of the induction motor becomes the following equation.

[0042]

(Equation 16)

Therefore, from the equation (17), the rated torque current I
₂ is obtained by the following equation (18).

[0044]

[Equation 17]

Further, the rated torque current I _1q in the dq axis coordinate system can be obtained by equation (19).

[0046]

(Equation 18)

Accordingly, the present invention reduces the rated torque current to (1
It is determined from the constant L ₁ , the terminal voltage V _0, and the equivalent excitation inductance M ′ according to the expression 8) or the expression (19), and this is set as a rated torque current set value for obtaining a torque current command.

[0048]

FIG. 2 is a block diagram showing a main part of an embodiment of the present invention. 3 is different from FIG. 3 in that the exciting current setting value I ₀ is obtained by the calculation of the above equation (8) or (9), and the rated torque current is obtained by the calculation of the above equation (19). The point is that a rated torque current setting unit 12 is provided.

The setting units 11 and 12 perform calculations and settings in the dq axis coordinate system.

Therefore, in the calculation of the exciting current command, the setting corresponding to the actual machine can be made from the no-load voltage value V ₀ of the induction motor, the primary frequency _Fn and the primary inductance L ₁ at no load at the base speed.

[0051] Further, the calculation of the rated torque current can from the rated output P _ower equivalent excitation inductance M 'and the no-load voltage V ₀ which the induction motor is set in accordance with the actual machine.

[0052]

As evident from the foregoing description, according to the present invention, the induction excitation current command I ₀ of the motor and the primary inductance L ₁ of the induction motor, the terminal voltage V ₀ and the primary frequency of the no-load at a base speed of the motor set from F _n, the torque current command I
Rated torque current value for obtaining a _T is due to so as to set the rated output P _ower the primary inductance L ₁ and the exciting inductance M 'and the terminal voltage V ₀ which the induction motor has the following advantages.

(1) The calculation of the excitation current command value and the rated torque current value are independent of each other, and the torque current value at the time of rating is calculated according to the rated output value of the motor. The set value can be changed only by changing the setting, and the setting for the derated operation of the motor becomes easy.

(2) Conventionally, when there is an error between the setting data of the excitation inductance and the leakage inductance and the actual machine constant, these data are changed, and after the adjustment is completed, the rated torque as a reference of the excitation current command and the torque current command value. The current data needs to be adjusted again. In this regard, in the present invention, the excitation current command and the rated torque current value are automatically changed by changing the constant data, and the adjustment is simplified.

(3) Conventionally, when the excitation current command value and the rated torque current value are set and input by ratio data with respect to the rated current (design value) of the motor, the error between the rated current value of the actual machine and the design value is the excitation current command value. However, in the present invention, the calculation of the excitation current command value and the rated torque current value does not use the rated current value of the motor, so that the error is eliminated.

(4) Even when there is an error between the set value of the excitation inductance or the leakage inductance and the actual machine constant, the motor voltage at the time of no load is controlled according to the set value. It will be easier.

[Brief description of the drawings]

FIG. 1 is a TI equivalent circuit of an induction machine.

FIG. 2 is a main part block diagram showing one embodiment of the present invention.

FIG. 3 is a configuration example of a vector control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Induction motor 2 ... Speed control part 4 ... Slip calculating part 6 ... Current control part 11 ... Excitation current setting part 12 ... Rated torque current setting part

Claims (1)

(57) [Claims] 1. A method according to claim 1 , further comprising the steps of:
From the difference, the torque current
Give the decree I _T, Oyo said torque current command and the exciting current command I ₀
In vector control system of induction <br/> guide motor for vector control of induction motor based on Bisuberi frequency, a primary inductance L ₁ of the induction motor, no-load terminal voltage V ₀ and one order at a base speed of the motor From the frequency F _n, Setting of the excitation current command I _{0 according} to
And parts, the rated torque current value I ₂ for the speed control unit obtains the torque current command I _T, the rated output P _ower the primary inductance L ₁ and the exciting inductance M 'and the terminal voltage V ₀ which the induction motor The following equation Vector control apparatus for an induction motor, characterized in that a rated torque current setting unit for setting in accordance with.