SU1443110A1 - Method and device for controlling induction motor - Google Patents

Description

(56) USSR Copyright Certificate No. 782114, cl. H 02 R 7/42, 1978.

Kovach K.II. and others. Transients in AC machines. - M.-L.: State Electrotechnical Publishing House, 1963, p. 744.

USSR Author's Certificate No. 1185526, 1.1.11 .84.

(54) METHOD OF MANAGING THE ASYNCHRONOUS MOTOR MOTOR AND DEVICE FOR IMPLEMENTING IT

(57) 1. A method of controlling an asynchronous electric motor, in which the rotor speed of an induction motor is measured, form the magnitude of the stator current frequency by summing the rotor speed with an additional frequency dw, and the stator current is adjusted as a function of the required torque M, while in the established Lee Rr / L

k is VM, characterized in that, in order to increase speed and control accuracy and increase the average torque of an induction motor by maintaining the constant phase shift mode of the stator current and the rotor flux linkage on t45 in transient modes, with a stepwise change in the required torque M, the value stator current ig and additional frequency Liz according to the laws:

where ./R(-; R (- I g is the electromagnetic time constant, resistance and inductance of the rotor;

 mutual inductance of the stator and rotor;

ZP is the number of pole pairs;

M - the initial value of the moment, is proportional to the initial S value of the input action.

(L

four;;

2. The device according to claim 1, comprising a torque setting unit, a driver with control actions with outputs for setting the magnitude and frequency of the stator current, a driver for setting the stator current phase signals, a power current converter and a rotor speed sensor

iCO

Scheni, installed on the shaft asynh- j

of the rotary motor and connected to the first input of the control driver, the second input of which is connected to the output of the torque command unit, the outputs of the tasks of the magnitude and frequency of the stator current of the driver, the control actions of the phase generator signals of the stator current, connected to the outputs of the control inputs of the power converter, the outputs of which are connected to the stator windings of the induction motor, while forming the control actions in the form of aperiod of a common link, two dividing elements and an adder, the first input and output of which respectively form the first input and output of the frequency setting of the control action generator, the second input of the adder is connected to the output of the first division element, and the input of the divisible second division element forms the second input of the control form generator the effects of the second dividing element are connected to the output of setting the stator current of the driver for controlling actions and are connected to the input of the divisible first dividing element, the inputs of teley both elements

the divisions are interconnected and connected to the aperiodic link output, which is different from the fact that, in order to improve energy performance by reducing losses in ac. synchronous motor, a proportional conversion element with coefficient I is inserted into the control driver, the input of which is connected to the output of the second the dividing element, and the output forms the output of setting the magnitude of the stator current of the control action generator, with this the input of the aperiodic link is connected to the output of the second division element.

one

The invention relates to electrical engineering, in particular, to an adjustable AC electric drive, and can be used to control the torque, control the speed and refine the movement of the working parts of industrial robots, machine tools and other machines and mechanisms equipped with asynchronous motors with a short-circuited rotor.

The purpose of the invention is to increase the speed and accuracy of control, increase the average torque of an asynchronous motor by maintaining the constant mode of phase shift of the stator current and the rotor flux linkage by ± 45 ° in transient modes, as well as improving energy performance.

Fig, 1 shows a structural diagram of a torque asynchronous electric drive; FIG. 2 is a structural diagram of a generator of equalizing effects; Fig. 3 is a vector diagram explaining the control method.

The device for controlling an asynchronous electric motor contains a torque setting block I (Fig. 1), a driver 2 of control actions with an output 3 setting a current value by a stator with an output 4 of a task, a frequency of a stator current, a driver of 5 phase setting signals, a cattor, a power current converter 6 and rotational speed sensor 7 mounted on the shaft of an asynchronous electric motor 8 with a short-circuited rotor and connected to input 9 of the driver 2 of control actions, input 10 of which is connected to the output of block 1 ta. The outputs 3 and 4 of the tasks of the magnitude and frequency of the current of the stator, respectively, of the driver 2, of the control actions are connected to the inputs of the generator of the 5 phase setting signals of the stator current connected by the outputs through the instantaneous regulators 11-13

5 phase currents with control inputs of the power converter 6 current, the outputs of which are connected to the stator windings of the asynchronous motor 8,

The shaper 2 of control actions contains an aperiodic link 14 (FIG. 2), the first 15 and second 16 division elements and the adder 17, the first input of which forms the input 9 of the shaper 2 of control actions. The output of the adder 17 forms the output 4 sets the frequency of the driver 2 control actions. Second

The Q input of the cy11atator 17 is connected to the output of the first dividing element I5. The input of the divisible second dividing element 16 forms the input 10 of the driver 2 for control actions. Output second

314

element 16, the division is connected to element 18 of the proportional transform. The output of which forms the output 3 sets the value of the stator current of the driver 2 of the control actions. The output of the second element 1-6 of the division is also connected to the input of the aperiodic link 14, the output of which is connected to the interconnected inputs of the dividers of the elements 15 and 16 of the division. A relay element 19 is connected to the image of adder 17.

The device works as follows. The input effect of the electric drive from the output of the moment setting unit 1 is fed to the input 10 of the driver 2 of the control actions. Magnitude

input effect of the drive is proportional to the magnitude of the required torque M.

In the control driver 2, the drive signals of the stator current is and the stator current frequencies w, -5 are generated, which are received from outputs 3 and 4, respectively, to the corresponding inputs of the driver of the stator current phase current signals i soo isfc -sc, which are fed to the control inputs tori 11-13 of the instantaneous phase currents and almost inertia-free work off the power current converter 6, for example, a transistor pulse inverter, using

negative feedback on the instantaneous phase currents supplied from the outputs of the power converter 6 current to the inputs of the regulators P-13 instantaneous phase currents. As a result of switching the key elements of the power converter 6 in the stator windings of the induction motor 8, the phase currents change in accordance with the set values of the instantaneous amplitude and instantaneous frequency depending on the input action M and the measured rotor speed and which value is measured using the rotational speed sensor 7.

To ensure torqueless control of the engine torque M in accordance with the required torque M proportional to the magnitude of the input action, i.e. to ensure equality, it is necessary to control the instantaneous amplitude of the stator phase currents ij and the instantaneous frequency of the stator phase currents Ug when

104

where the stator current phase (spatial angle of the stator current vector) and the rotor flux linkage phase (the spatial angle of the rotor flux linkage vector must be shifted by an angle that is either kept constant in the direction determined by the direction of the required moment, or is connected with the required moment M according to the law defined by the quality criteria of an asynchronous electric drive.

The control law for torqueless torque control in the dynamics is determined by the eus from the differential equations of the rotor chain, expressed in terms of the orthogonal components of the stator current vector in the x, y coordinate system, oriented relative to the rotor flux vector.

Orientation conditions are:

(one)

where (angular velocity of rotation of coordinates, is equal to the angular frequency of the flow of the coupling of the rotor; U) is the angular velocity (frequency)

rotor rotation;

Do) - additional frequency, equal to the slip of the rotor flux linkage relative to the rotor.

Slip the rotor flux linkage 3) equal to the rate of change of the angle between the flux vector

rotor C., and the axis of the rotor (li; 5d-)

O-b

At. following condition (1), the known differential equations defining the relation between the module of the rotor flux-coupling vector f, orthogonal components of the vector is is, igv) and the motor torque are

Lr dVr. ,, t h p-zg-

R dt

I-

M- - rj I, - o Zp -

(2) (3) (A)

Z 2 P L,

According to the vector diagram (fig. 3) is is-sin i /; I J- 51443 .1

The f-if angle in equations (5) and in the vector diagram (Fig. 3) is made between the spatial vector of the stator current ip and the spatial vector of the rotor flux linkage V and characterizes the phase shift of the stator current and the rotor flux linkage for each of the phases a , B, with asynchronous motor.

From the differential equation (2), taking into account (5), the transfer function for the modulus of the rotor flux-coupling vector is obtained

VP

where T is the electromagnetic constant of the rotor time; L is the inductance of the rotor; Rf, - active resistance

rotor. From equations (W) and (5) follows

M 2 ZP i.sini. (7)

Static transfer coefficient

on, moment for given quadratic

l the magnitude of the stator current ij given

(6) and (7) depends on the angle, the phase shift of the stator current relative to the rotor flux linkage

3 L 2 P bf os i sinfc. .

From (8.) it follows that in order to ensure the maximum moment at a given stator current, it is necessary to control the phase of the stator current with phase

(eight)

shift relative to the phase of the rotor flux linkage, satisfying the condition

L- .. 0 (9)

5T. c.

From equation (9) with regard to the orientation conditions (1), according to which the condition is true:

COSilf-70, (10)

the optimal control law of the asynchronous motor follows the maximum moment

II

F - + L L L - - T

(eleven)

 55

The + sign in the expression (11) corresponds to the positive direction of the engine torque.

.one

.106

The consequence of the optimal control law (11) is the equality of the values of the orthogonal components of the stator 1 current vector projections with orientation along the rotor flux linkage vector:

i5, ± is,. (12)

The projection of the stator current vector i does not change its sign when the direction of the moment changes and characterizes the stream-forming EO component of the stator current equal to the projection of the stator current vector on the axis, the direction of which coincides with the rotor flux linkage vector.

The component of the stator current i, orthogonal to this axis, characterizes the torque-forming component of the stator current, the sign of which is determined by the direction of the moment.

According to the vector diagram (Fig. 3), the angular frequency of rotation of the stator current vector relative to the stator axis

(About i + Ellf S dt dt dt at

(13)

0

0

five

0

five

where d is the stator current phase;

And - the angular position of the rotor; Particle phase shift of the rotor flux linkage relative to the rotor axis.

Since the shift angle between the phases ic and (is constant in magnitude is consistent with

BUT the control law (11) and g- 0,

about. and

Then, with optimal control according to the law and 1J, the stator current frequency is equal to the rotor flux linkage frequency, including in dynamic modes of torque variation:

(14)

instantly often amd

where 0.5 gta stator current and rotor flux linkage;

(l) angular frequency of rotation of the rotor;

yy is an additional frequency or slip of the rotor flux linkage, which characterizes the speed of relative rotation of the flux linkage vector of the rotor relative to the rotor. Stator current slip and rotor flow in control mode

(ll) are the same, in connection with which the optimal control mode of the stator current phase (11) can be implemented by controlling in polar coordinates by changing the stator current vector modulus (instantaneous stator current amplitude) and stator current vector argument (stator current phase) . The phase current of the stator 5 is formed by the driver 5 phase setting signals of the stator current -sfc sc and is processed by the power converter 6 current using negative feedback on the instantaneous phase currents and regulators 11-13 instantaneous phase currents

isc ((t) is ,, (t); isfc (t) i sb (t); i5c (t) i sc (t).

To eliminate feedback on the position of the rotor A in the torque asynchronous electric drive (Fig. 1), the stator current frequency control is used as the sum of the measured rotor speed u; (using speed transducer 7, for example, using a tachogenerator) and an additional Lee frequency) equal to the slip current of the stator and the rotor flux linkage, followed by conversion of the frequency setting signal WSB of the stator current phase 5 Su. (| t) dt.

At the optimal control (s), the additional frequency is determined according to equation (3) in proportion to the ratio of the torque component of stator current i to the rotor flux ratio equal to the modulus of the rotor flux vector is. (T)

. ,, Rf t

/ Ilu - - b

L (t)

(15)

When the moment M changes in mode (11) as a function of moment, both the amplitude of the stator current ig and the amplitude of the flux linking c) change due to the fact that according to equations (5) JQ

i - 1

v / t / t

 -St

S2

According to equation (b) value. rotor flux linkage v ,, (t)

It is delayed with respect to the change in the value of the stator current is (t). The time constant of the aperiodic process of changing the magnitude of the rotor flux linkage is equal to the electromagnetic time of the rotor TORCH-1N, T because with the time T DT, after the moment change, the magnitude of the flux linkage of the rotor reaches its fixed value, determined as a function of the moment according to the equation m (2), (4), (16) and (17):

(18)

where Lf is the steady-state value of the rotor flux linkage equal to the modulus of the rotor flux link vector. The steady-state value of the stator current is determined by the steady-state magnitude of the rotor flux linkage according to equations (2) and (16);

i,

(nineteen)

25 30

os 40

The transient process of changing the flux linkage of the rotor from one steady-state value to another steady-state value v makes it necessary to form to fulfill law (11). associated transients of variation in the magnitude of the stator current and the additional frequency 3c; as a function of the current value of the rotor flux linkage Vr (t).

Equations (4) and (17) imply the equation relating the processes of variation of the instantaneous amplitudes of the stator current and the rotor flux linkage as a function of time when the engine torque changes in the Zepkön control mode (11):

, - (tb- / 2. 3ZpL -GDP

(20)

Q

a from equations (15) and (17) follows the equation of the processes of variation of the stator current slip (additional Lie frequency) and the instantaneous amplitude of the rotor flux linkage

55

  R 2L M (t)

 G / sg vFtT

(21)

The stator current control processes according to the proposed method are described by equations (20), (14) and (21) and determine the processes for performing interrelated actions on the engine by changing the magnitude and frequency of the stator current when the input effect of the Momeite actuator M (t) M changes ( t).

To exclude information about the size of the rotor flux linkage that is difficult to measure, a solution of the differential equation (2) is used under the condition of fulfilling the optimal control law (11) and its consequence — the equality of the moment-forming and flow-forming components of the stator current 15, lij Nis / T.

It follows from equations (16) and (20) that, when controlled by law (11), the current-forming component of stator current ijy is equal to the projection of the stator current vector ij on the axis of the rotor flux vector V. torque of the engine to the current value of the flux linkage of the rotor 4 p (t):

, 2Lr M (t)

5.-, y; w

The required relationship between the magnitude of the rotor coupling flows 4 f and the motor torque M proportional to the input action is determined by substituting the expression for the current-generating component of the stator current into the right-hand side of the differential equation (2):

br.l. (j). ,, (...),., 23, whence, taking into account equality

% W .v. (T)

(22)

 H dt

(24)

get the differential equation for the quadratic value of the flow-chain-45 of the rotor when the moment changes in the control mode according to the law (11)

1 (l + i (t) bM (.t). (25) R atf J / jp

When the engine torque jumps from the initial value of Md to the final value M, the square value of the rotor flux linkage changes according to the law determined by solving the differential

Efficient Equation (25):

2t

V, (t) (M, -M), (26)

where M (j; is the initial value of the moment at the established initial value of the flux linkage poTofa, determined by the condition of the steady state (18).

As follows from equation (26), in the control mode according to the law (11), the transient change in the rotor flux magnitude occurs twice as fast as follows directly from equation (2), which is ensured by sharply increasing the stator current and the current-forming component of the stator in the initial period of time after the moment jump in accordance with Eqs. (20) and (22), followed by a rapid weakening of the forcing as the rotor's flux linkage increases to a new steady-state value. This provides invariant torque control regardless of the current values of the rotor flux linkage and the stator current in the transient process of forming the optimal flux link value of the rotor.

Substituting the law of variation of the rotor flux linkage from equation (26) into equations (20) and (2), we obtain the laws of invariant moment control at optimal maximum moment control of the rotor flux linkage for systems with phase-frequency-current control, starting from conditions of the moment invariance M (t) M (t):

(27)

(28)

The method of controlling the value of the stator current is (t) depending on the input action is implemented for the case of one polarity of the moment setpoint using the second division element 16, aperiodic link 14, proportional conversion element 18 and the described relations between them.

The instantaneous frequency of the stator current is controlled by the adder 17, the first input 9 of which receives a signal from the output of the rotational speed sensor 7 (for example, the output voltage of the tachogenerator), which is proportional to the rotor speed and). The second input of the adder 17 receives the output signal of the first division element 15, with which it controls an additional frequency of 3w equal to the slip current of the stator and the rotor flux relative to the rotor with the specified ratio of the dividend and divider for the first element 15 division.

The input signals and the output signal of the adder 17 can take both positive and negative values. The direction of rotation of the stator current and rotor flux vector vectors is set, depending on the sign of the output signal of the adder 17, using a relay element 19, the output signal / V

ten

The current of which O or I determines the direction of rotation of the vector ig, which is formed by using the shaper of 5 phase driving signals of the stator current, depending on the setting signal of the instantaneous amplitude of the stator current ig, coming from output 3, which is formed by the proportional conversion element 18, and depending on the signal sets the instantaneous frequency of the stator current Ujg, coming from the output 4, which is formed by the output of the adder 17.

When the input action of the torque electric drive, coming from the output of the block I of the torque setting, changes with the help of the driver 2, it determines the magnitude and frequency of the stator current.

-Sh

W

15

17 (Oh s

X)

si

from

-to

 Piie.2

Rotor axis

Stator axis

X

uz.3

Claims (2)

1. The method of controlling an induction motor, in which the rotor speed of the induction motor is measured, the stator current frequency is formed by summing the rotor speed with an additional frequency ώω, and the stator current i _{s is} regulated as a function of the required moment M ', while in steady-state operation Δω = R _r / L _r and i _s Mind ¹ , characterized in that, in order to increase speed and accuracy of control and increase the average torque of an induction motor by maintaining a constant phase shift of the stator current and rotor flux linkage by 145 ° in transient conditions, with an abrupt law of change in the required moment M ⁽ form the stator current value i _s and the additional frequency Δω according to the laws: J ^2L X JL37A __________ A ________ ^Lrn / m; + (m'-m}) (1st ⁴¹ ^ ^L f М '+ (М'-М') (le ^2tir ) where T _r = L _r / R _r ; R _r L _r is the electromagnetic time constant, active rotor resistance and inductance; L - mutual inductance of the stator and rotor; Z _p is the number of pairs of poles; is the initial value of the moment proportional to the initial sg value of the input action. 2. The device according to claim 1, comprising: · a unit for setting the moment, a driver of control actions with outputs for setting the magnitude and frequency of the stator current, a driver of phase driving signals of the stator current, a power current transducer, and a rotational speed sensor mounted on an asynchronous I shaft the motor and connected to the 'first input of the driver of the control actions, the second input of which is connected to the output of the unit for setting the moment, the outputs of the tasks of the magnitude and frequency of the stator current of the driver of the control actions are connected to the inputs of the driver of the phase driving signals of the stator current, connected by the outputs to the control inputs of the power current converter, the outputs of which are connected to the stator windings of the induction motor, while the control action terminator is completed in the form of an aperiodic link, two elements of division and an adder, the first input and output of which respectively form the first input and output of the frequency generator of the control actions, the second input of the adder is connected to the output of the first division element, and the input of the divisible second division element forms the second input of the driver of the control actions, the output of the second division element is connected with the output of the job value of the stator current of the driver of the control actions and by is connected to the input of the divisible first division element, the inputs of the dividers of both division elements are interconnected and connected to the output of the aperiodic link, characterized in that, in order to improve energy performance by reducing losses in the induction motor, an element of proportional conversion is introduced into the control shaper with coefficient? 2, the input of which is connected to the output of the second division element, and the output forms the output of the task of the stator current value of the shaper of control actions, When input of this delay element is connected to the output of the second division element.