SU1686688A2 - Electric drive - Google Patents

Abstract

The invention relates to electrical engineering, in particular to a controlled electric drive based on an asynchronous motor with a short-circuited rotor powered by a voltage inverter. The aim of the invention is to increase the reliability of the electric drive and reduce losses in an autonomous voltage inverter. To do this, each of the channels of the same type of block 8 for detecting the signs of current errors is equipped with an adder 16 and a high-pass filter 15 included in the feedback circuit of the relay element 14. At the same time, in a closed stator current control loop, the minimum width of control pulses fed to the inverter is limited. and, as a result, increased reliability and reduced losses. 5 il B

Description

The invention relates to electrical engineering, namely to a controlled meringue driven electric drive of an asynchronous squirrel cage rotor powered by a voltage inverter and is an improvement of the invention according to the basic author. St. Ms 1354380.

The purpose of the additional invention is to increase the reliability of the drive and reduce losses in an autonomous voltage inverter.

FIG. 1 shows a functional diagram of the drive; in fig. 2 is a block diagram for determining the signs of current errors; in fig. 3 and 4 — input – output characteristics of the block for determining the signs of current errors; in fig. 5 - time diagrams that show the work.

The drive contains an asynchronous motor 1 (Fig. 1) connected by a stator winding to an autonomous voltage inverter 2, a sensor 3 of the stator current of the asynchronous motor 1, the outputs of which are connected to the inputs of the block 4 of the linear stator currents, the outputs of which are connected to the first inputs of the comparison unit 5 , the second inputs of which are connected to the outputs of block 6 of the task, block 7 of calculating linear combinations of current errors, the inputs of which are connected to the outputs of block 5 of comparison, and the outputs through series The current error symbol determination unit 8 is connected to the first inputs of the driver 9 characters of control actions, the second inputs of which are connected to the outputs of the equivalent voltage vector meter 12 via the voltage signal determination unit 10 and the linear conversion unit 11 a control actions conversion unit 13, the first inputs of which are connected to the outputs of the imaging unit 9 characters of control actions, the second inputs of the control unit 13 are connected to the outputs of the meter 12 of the equivalent voltage vector, and the outputs of the control conversion unit 13 are connected to the phase independent inputs of the meter 12 of the equivalent voltage vector and the control inputs of the autonomous voltage inverter.

Block 8 of determining the signs of current errors contains six channels of the same type, each of which is made with a relay element 14 (Fig. 2), a high-pass filter 15 and an adder 16, the output of which is connected to the input of a relay element

14, the first input of the adder 16 forms the corresponding input of the block 8, the second input of the adder 16 is connected to the output of the high-pass filter 15, the input of which

combined with the output of the relay element 14 and forms the corresponding output of the named block.

The drive works as follows.

The stator current sensor 3 produces a signal IA, Ic. proportional to the phase currents of the stator of the asynchronous motor 1. These signals are fed to the inputs of the block 4 of the linear conversion of the stator currents, which converts the values of the phase currents of the stator into an orthogonal coordinate system fixed relative to the stator. The output signals ijL, 1) L block 4 linear conversion

the stator currents are fed to the first inputs of the comparison unit 5, to the second inputs of which signals are received, 1 1 from the task block 6. Comparison unit 5 generates output signals A, A | ;, the difference between the set and real values of the stator currents of the induction motor 1. From the output of block 5, the signals D, D | arrive at the inputs of block 7 for calculating linear combinations of current errors, which form

em output signals Sii, 821, Sm, 8211, Sun, S2IH, arriving at the block inputs in determining the signs of current errors, which forms the output signals slgnSn, signS2i, slgnSui, slgnSaii, signSim, slgnS2in according to the equations

TH 5 "t 5 ° ec u5 1 + 5; 9n511-H 0 l-Se.ecAwS sicjnS -Hd Os

b; o „521 (if 45; 9 5 n 1 0;, ecAn52i + s; 9n52l

5Цп5 Л + 5 ° if5 +5 Эи5ш -501есм15т45; дп5ш.

 4 + 5 ° eLi5gp + B p5gp J 2lt -So.ecAHSan SignSjn-Hj Oj

"" And with: if 5m, s; gr5, in-U, 9n1-1-101015, w 9n5n1)

S, qn5 G + 5o, if 5, gSh45 dp5v1i "gsh -50, if 5gsh 5 p521P,

 AND)

where So is a constant value; HIJ is a value characterizing the depth of the flexible positive feedback, covering the relay element 14 (Fig. 2), is a function of time and is determined by the parameters of the high-pass filter 15

u t & m 2

where a is the transfer coefficient; Ti, Ta are time constants, and Ti T2.

The input-output characteristic of a relay element covered by flexible positive feedback (Fig. 3, 4) has a hysteresis zone d, the size of which is determined by the depth of the feedback

dN So. (3)

When switching in any of the six channels of block 8, the determination of the signs of current errors g in this channel changes as a function of time exponentially (Fig. 5). Moreover, at the first time moment after the switch (p – co) hysteresis d is determined by the expression

(5 "ach lima lint So a ± i So, (4)

p - 00 P t

which corresponds to the characteristic of the relay element in FIG. 3; in steady state (p 0)

dust aS0. (5)

which corresponds to the characteristic of the relay element in FIG. four.

The minimum pulse width D (Fig. 5) at the output of block 8 for detecting the signs of current errors is determined by the coincidence of the values of the stator current error A is the induction motor 1 and the hysteresis of the relay element 14 (for the origin in Fig. 5 the moment of connecting the relay element 14 is taken to the new state under condition I, in all other cases the pulse width is greater than the minimum) and cannot be less than the value specified by the ratio of the parameters a, Ti, 1i of the high-pass filter 15 in accordance with (2) - (5).

From the output of block 8, the determination of the signs of current errors, the signals signSn, signSai, signSui, signSzii, sign Sun, signS2in arrive at the first inputs of the driver 9 signs of control actions that form the control actions of UL U2. Uz according to the control algorithm implemented in the basic invention. SignuiA, signUiB, signUic signals, which are signs of UIA, UIB, Uic signals, coming to the inputs of the unit 10 for determining voltage signs from the outputs of block 11 linear transformation of the components of the vector of equivalent voltage, the outputs of which receive signals C, and Ua from the outputs of measuring 5 bodies 12 of the vector of equivalent voltage proportional to the values of the components of the vector of equivalent voltage. These signals are formed in the meter 12 of the vector of equivalent voltage by filtering the output control signals U + i, U + 2, 11 + 3, which arrive at its inputs from the outputs of the converter 13 of control actions, the first inputs of which receive signals

5 controls Ui, U2, 11z from the outputs of the imaging unit 9 characters of control actions, the second inputs of the control converter 13 receive signals C, U /, from the outputs of the meter 12 of the equivalent voltage vector. The control actions converter 13 generates the output signals iTi. . U + 3, arriving at the inputs of the autonomous inverter 2 voltage.

5 Thus, the introduction into each of the six one-channel channels of the block for determining the signs of the current errors of the high-pass filter and the adder leads to an automatic smooth increase in the hysteresis zone by an exponential law with increasing amplitude of the specified currents. As the hysteresis zone increases, the sliding mode frequency in a closed loop automatically decreases.

5 wherein the frequency reduction occurs in such a way that the width of the shortest control pulses by the autonomous inverter is sufficient not to lead to an inversion failure than

0 is provided in comparison with the basic invention with improved reliability. The loss reduction is determined by the decrease in the switching frequency of the semiconductor key elements in

5 inverter while maintaining the optimal switching law.

Claims (1)

Invention Formula 0 Electric drive by bus. St. No. 1354380, characterized in that, in order to increase reliability and reduce losses, each of the six channels of the same type for detecting the signs of current errors, completed with a relay element, is additionally equipped with an adder and a high-pass filter with a transfer function of the form: H (p) a –J + 1, where a is the transmission coefficient, Ti, T2 are time constants, and the first input and the output of the adder are connected between the corresponding input of the named block and the input of the corresponding relay element, and the second input the adder is connected to the output of the high-pass filter, the input of which is connected to the output of the relay element.