SU1370710A2 - Frequency-controlled electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in various sectors of the national economy. The aim of the invention is to improve the accuracy in transients by preventing the accumulation of the error signal in the rotational frequency. The goal is achieved by introducing into the frequency-controlled electrically-controlled drive key 17, the discriminator 18 of the operation mode and the delay unit 19. As a result, the accumulation of errors in the speed regulator 9 is prevented during the transition from brake to motor and from motor to brake, dynamic current surges and overturning of motor 1 are excluded. For block 19, it generates commands for unlocking key 17 when motor 1 transitions from one mode in another in the function of the discriminator 18 for a time equal to the half-period of a given rotation frequency. 5 il. from the next

Description

with

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The invention relates to electrical engineering, m ;: It can be used for automatic control by means of thyristor frequency converters based on autonomous current inverters by adjustable asynchronous electric drives of machines and mechanisms in various sectors of the national economy and is complementary to auth. St. No. 13343D7.

The aim of the invention is to improve the accuracy in transients by preventing the accumulation of the error signal in the rotational frequency.

FIG. 1 shows a functional diagram of a frequency-controlled electric drive; in fig. 2 is a diagram of the frequency correction node; in fig. 3 is a diagram of a driver of a logical signal of a given current; in fig. A - diagram of the delay unit; in fig. 5 shows an embodiment of a differentiation unit.

The frequency-controlled electric drive contains an asynchronous short-circuited motor 1 (FIG. 1) connected to a frequency converter 2 based on an autonomous inverto;) and the current with two inputs 3 and 4 for current and frequency is, respectively, phase sensors This is 5 and (voltages 6, block 7 of the rotation command, element 8 1: equilibrium, rotation frequency regulator 9 connected in series and current control unit 10, output connected to control input 3 for current 2 of frequency converter , frequency control unit 11 with driver 12 si flow clutch drives, the inputs of which form the first 13 and second 14 inputs of the frequency control unit 11 1, connected respectively to the outputs of the phase voltage sensors 6 and currents 5, and to the frequency correction node 15, the first input of which is connected to the output of the driver 12 the second input is connected to the second input 14 of the frequency control block, the third input of the frequency correction node 15 forms the third input 16 of the frequency control block 11 connected to the output of the rotation speed setting block 7 and to the first input of the comparison element 8 and the output of frequency correction unit 15 forms the output of block 11 frequency control j connected to control input 4 for frequency converter 2 often 10

you and with the second input element 8 comparison.

A variable key 17, an operating mode discriminator 18 and a delay unit 19 with two inputs are entered in a frequency-controlled electric drive, and the frequency correction unit 15 is provided with an additional fourth input 20 combined with the first input of the delay unit 18 and connected to the output of the operating mode discriminator 18. The second input of the delay unit 19 is connected to the output of the rotational speed setting unit 7, the output of the delaying unit 18 is connected to the control input of the control key 17 connecting the output of the comparison element 8 with its terminals to the RPO of the rotational speed controller 9, the output of which is connected to the input of the discriminator 18 mode

The rotational speed setting unit 7 can be made in the form of any source of electrical signal. The proportional-integral regulator of rotation frequency 9 is made on the basis of the amplifier of the amplifier. The current control unit 10, which represents the functional converter, can be made on the basis of an operational amplifier, covered by non-linear feedbacks using resistors and diode.

Frequency correction node 15 contains a key controller made at the operational amplifier 21 (Fig. 2) with resistors 22-24 and control keys 25 and 26 in the input circuit and in the feedback circuit 27 logical comparison element 27, driver 28 signals of a given current and driver 29 logical signals of the actual current. The outputs of the formers 28 and 29 are connected to the ladies of the logical comparison element 27, the outputs of which are connected to the control inputs of the terminal 25 and 25.

The shaper 7.B of a logical signal of a given current contains a pole of comparators 30-35 (Fig. 3) and three control keys 1–36, 38–8, and UPON; which are combined and form the control input of the shape-eating 28. Output) 11 ksm parator 30-35 are connected in pairs to the terminals of the corresponding controlled keys 36-18,

The delay unit 19 comprises an integrator 39 (FIG. 4) based on an operational amplifier, wide on the circuit.

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feedback control key 40, differentiation node A1, an output connected to the control input of the key 40, and a comparator 42, one input connected to the output of the integrator 39, and the other to the bias source E.

The differentiation unit 41 comprises an inverter 43 (FIG. 5), two resistor-diode circuits 44 and 45 and separation diodes 46 and 47 connected to the base of the transistor 48.

The discriminator 18 of the operation mode is a null indicator based on an operational amplifier with a logical output signal, which varies depending on the sign of the output signal of the speed regulator 9.

Variable frequency drive works as follows.

t5 y 20 M

The logical comparison element 27 compares the logical signals of a given 1 current and actual I current from the outputs of the respective formers 28 and 29 and extracts the phase error signal, which determines the deviation of the actual phase angle between the current and flow vectors of the motors 1 from the specified value. If the specified angle is less than the specified, the output of the logical comparison element 27 separates the signal B, and the signal and, consequently, the output frequency of converter 2 increases t5, the phase angle between the current and flow vectors of motor 1 also increases. If the actual angle is larger than the specified one, the element 27 of the logical comparison selects a signal of 20 m. Providing a decrease in the output frequency signal cc and the angle between the motor and current flow vectors.

Change signal oi at the output block

The output signal of the frequency setting unit 7 is fed to the input 16 of the frequency control unit 11, at frequency control node 25 11 leads to a correction which converts 15 to a change in the output of the regulator to the output frequency signal oi of the frequency converter 9 , the current control unit 10, the output current of the frequency converter 2, the electromaterial 2 frequencies. The signals CO, and ci compare) are found in reference element 8,

O

The logical comparison element 27 compares the logical signals of a given 1 current and actual I current from the outputs of the corresponding drivers 28 and 29 and extracts the phase error signal, which determines the deviation of the actual phase angle between the current and flow vectors of the engine 1 from the specified value. If the specified angle is less than the specified angle, the output of the logical comparison element 27 separates the signal B, and the signal and, therefore, the output frequency of converter 2 increases 5, the phase angle between the current and flow vectors of motor 1 also increases. If the actual angle is larger than the specified one, the logical comparison element 27 selects a 0 M signal, providing a decrease in the output frequency signal from the output frequency and the angle between the motor and current flow vector.

A change in the signal oi at the output of the frequency control block 11 leads to a change in the signals at the output of

ka 11 frequency control leads to a change in the output signals of the

l9 of rotational speed, current control unit 10, output current of frequency converter 2, electromagnet

at the output of the latter, the signal moment of the engine 1 is extracted. The change in the current and frequency converter control signals occurs until the output frequency signal tf equals the Oj signal, causing errors that, through the controlled key, which is closed in the steady state of the drive, 17 enters the input of the regulator 9 frequency

rotation The output signal of the rotation frequency control when the rotation frequency is equal to 9 (the signal of the moment of the actual phase angle between the motor 1) in the current control block 10 by means of a functional converter that implements the setpoint value (the signals B and M are absent) .

The torque-current bridge of the motor is converted into a reference signal for the output current of the frequency converter 2. The conversion of the voltage from the frequency setting into the output frequency signal oi of the converter 2 is carried out in the frequency correction node 15 due to the operation of the controlled keys 25 and 2b (Fig. 2) of the key controller based on the operational amplifier 21 under the influence of the correcting logic signals B (more) and M (less) from the output of the logical comparison element 27. Signal B closes KFUCH 25, contributing to an increase in the signal 0 in the code of the key controller relative to the input signal CO, the signal M closes the key 2b, contributing to a decrease in the signal оС relative to the signal (0л ,.

The current and frequency converter frequency control signals occur until the output frequency signal tf equals the rotation frequency setting signal Oj when the actual phase angle is equal between

com and the engine flux linkage to a given value (signals B and M are absent).

The logical signals 1 of the actual current of the engine 1 are produced by the shaper 29 of the frequency correction unit 15 from the output signals of the sensors 5 phase currents. Logic signals 1 of a given current are generated by shaper 28 (FIG. 3) of frequency correction node 15 from signals V of flux couplings, which, in turn, are produced by shaper 12 signals of flux couplings of frequency control unit 11 from output signals of sensors of phase currents 5 and voltages 6 .

Frequency-controlled electric drive can operate in two modes - in the motor and brake. Each mode corresponds to a certain polarity of the output signal of the speed regulator 9 (for example.

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positive in the motor mode and negative in the brake mode) and the sign of the phase angle between the motor current and flux vector vectors (positive in the motor mode and negative in the brake mode). Accordingly, in the imaging unit 28, two groups of logical sig5 and

at a time I, a given current is one at the outputs of the comparators 30, 32 and 34 for the motor mode, the other at the outputs of the comparators 31, 33 and 35 for the braking mode. This or another group of logical signals I is connected to the output of the imaging unit 28 by means of switches 36-38, controlled by the torque sign signal W, inputted to the frequency control unit 11 from the output of the operating mode discriminator 18 connected to the output of the speed regulator 9

When the drive moves from the motor mode to the brake element 27 of the logical comparison, a signal B is produced, which results in the inequality ui se, changing the polarity of the signal during rotation speed 9 and the logical signal, ai and the output of the discriminator 1B, are switched the switch 1 36 - 38 of the driver 28 logical signals of a given current, the phase of the signals I, at the input of the logical comparison element 27 jumps in the direction of lag by an angle close to TG rad, which leads to the separation of its output of the phase error signal is M; However, under the action of the transition signal M, selected when switching, the polarity of the output signal of the rotation speed controller 9 changes again, the logical signal changes at the output of the mode discriminator 18, the reverse phase jump of the signal Ij, the mode discriminator re-switches, and so on. etc., which does not correspond to the actual braking mode of the electric drive and leads to inrush current of the engine and its unstable operation. Duration of the transition process

I possibly rollover

tightened by engine.

At transition of the electric drive from a brake mode in motive the similar process takes place.

Thus, the signal overlaid by the logical comparison element 27 when the drive mode is changed is a signal

additional error for the regulator 9 speed, worsening the quality of transients. In order to prevent this by changing the operating mode of the drive to

a time approximately equal to the half-period of a predetermined rotational speed of the engine, the control key 17 at the input of the rotational frequency controller 9 opens, and the additional error signal does not pass to its input. The key 17 is controlled by a delay unit 19, which, at the moments of changing the mode of operation of the electric drive, generates a signal with a duration of about T rad the current frequency,

breaker key 17.

In block 19, the delay in a steady state under the action of the signal and, the capacitor of the integrator 39 is charged to the maximum voltage, the key 40

open, at the output of the comparator 42 a key closure signal 17 is generated. When the logical signal ω of the mode discriminator 18 changes from 0 to 1 or vice versa, the differentiation node 41 generates short-time closure signals of the key 40, as a result of which the integrator capacitor 39 discharges to zero, the comparator 42 switches and generates a signal of pa

The key of the key 17. At the end of the signal from the output of the differentiation unit 41, the key 40 is opened and the capacitor of the integrator 39 starts charging with a current proportional to the signal Co ,.

Upon reaching the output voltage of the integrator of the magnitude of K 1. lp displacement, the comparator P2 returns to the initial state and the key 17 locks. The time of the char.ch kondellas7 ora integra t of the mountain is back to the value of the signal Oj, and the parameters of the market are so that the ys are approximately equal — the axis of the duration of the half-period is set to the 1st frequency.

Thus, in the frequency-controlled electric drive controlled key included between the output element cf. denial and entrance

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Claims (1)

Claim Variable Frequency Drive St. No. 1334347, characterized in that, in order to increase accuracy in transient cutting errors in speed, a controlled key, an operating mode discriminator and a delay unit with two inputs are introduced, and the frequency correction unit g is equipped with an additional fourth input combined with the first input of the delay unit and connected to the output of the discriminator of the operating mode, while the second input of the delay unit is connected to the output of the speed reference unit, the output of the delay unit is connected to the control input of the managed key connected between the by comparison and a speed controller, the output of which is connected to the input of discrimination FIG. 3 FIG. if