SU1354361A1 - Device for controlling thyristor rectifier - Google Patents

Abstract

The invention relates to a converter technique and can be used in control systems for controlled thyristor rectifiers. The aim of the invention is to reduce the influence of oscillations and the frequency of the supply voltage to suppress low-frequency harmonics. With an unchanged power supply voltage frequency, the output signal of the power supply frequency sensor 9 is constant. Frequency selector 6 It is tuned to the frequency of the low-frequency harmonic, set by ryu with setting 7, the frequency of the low-frequency harmonic. When the power supply frequency changes, the output signal of sensor 9 changes, which causes a change in the output signal of adder 8, under the action of which the resonant frequency of frequency selector 6 corresponding to the frequency of the suppressed low-frequency harmonic changes in accordance with the changed frequency of the supply voltage. This ensures the constant transmission coefficient of the frequency selector 6 with changes in the frequency of the low-frequency harmonic, which reduces the dependence of the suppression effect on changes in the frequency of the supply voltage. 4 il. with "S (L

Description

one

The invention relates to a converter technique and can be used in control systems with controlled thyristor rectifiers.

The aim of the invention is to reduce the effect of voltage fluctuations in the power supply network to suppress low-frequency harmonics.

Figure 1 presents the block diagram of the device; Fig. 2 is a controlled frequency selector circuit; Fig, 3 is a diagram of the frequency sensor; figure 4 is a diagram illustrating the operation of the frequency sensor.

The device contains in series Connected unit 1 current magnitude, the first input of current regulator 2 and the first input of system 3 of pulse-phase control, sensor 4 of rectifier current, the output of which is connected to the second input of current regulator 2, serially connected sensor 5 of output voltage rectifier and frequency selector 6, the output of which is connected to the second input of the system 3 of the pulse-phase control, the low frequency harmonic frequency adjuster 7, the output connected to one input of the adder 8, to the other input of which The output of the sensor 9 of the supply voltage frequency is connected, the output of the adder 8 is connected to the input of the frequency selector 6, the output of the rectifier 10 is connected to the load 11

The frequency selector (FIG. 2) contains an adder 12, a latitude-imp: a modulator 13, a series-connected resistor 14, a key 15, an integrator 16, a resistor 17, a key 18, an integrator 19 whose output is connected to one of the inputs of the adder 12 , the second input of which is connected to the output of the voltage sensor 5, the output of the pulse-width modulator 13 is connected to control inputs of the keys 15 and 18.

The mains voltage frequency sensor contains an integrator 20, shunted by switch 2, a short pulse shaper 22, a resistor 23, a switch 24, a capacitor 25, and a repeater 26.

The device works in the following way.

To the input of current regulator 2, a signal is set to set the current magnitude 1

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and a feedback signal from the current sensor 4. The output of current regulator 2 affects the pulse-phase control system 3. The output signal of the thyristor rectifier 10 through the voltage sensor 5 is fed to the information input (Fig. 2) of the frequency selector 6, which is based on the operational amplifiers 12.16 and 1. From the output of the frequency selector 6, the feedback signal in the form of harmonic oscillations frequency suppressed low frequency

15, the harmonics act on the second input of the pulse-phase control system 3. In this case, the decrease in the magnitude of the suppressed low-frequency harmonics is accomplished by changing

2Q of the time constant of the integrators performed on the operational amplifiers 16 and 19. The change of the time constant of the integrators is performed by means of pulsed conductivities,

25 such widths from series connected resistors 14 and switch 15, resistor 17 and switch 18, controlled by a pulse-width modulator. 13 The control signal of the frequency selector 6 is fed to its control from the output of the adder 18. The control The signal is obtained by summing the output signal of the frequency adjuster of the low-frequency harmonic 7 and the signal from the output of the frequency sensor 9 (FIG. 3).

The sensor 9 frequency consists of an integrator, performed on the operational amplifier 20, and the element

Q sampling memory, consisting of a key 24, a capacitor 25 and a repeater 26. To linearize the dependence of the output voltage of the sensor on the frequency of the supply network, it is covered

45 negative feedback from the output of repeater 26 through resistor 23 to the input of integrator 20. The depth of negative feedback is determined by the necessary degree of linearization and the magnitude of the tuning factor characterizing the change in the output voltage of the sensor depending on the change in the supply network. The key 21 serves to create

55 zero initial conditions of the integrator 20. The keys 21 and 24 are controlled by two sequences of pulses of duration t and tj, respectively. Both later 35

The pulse sequences are generated by the shaper 22, whose input is connected to the mains supply (signal and). The pulse sequence for controlling the key 2I is shifted relative to the sequence for controlling the switch 24 by time t,. Both sequences are formed at the moment the mains voltage passes through zero. Thus, their frequency varies synchronously with the frequency of the power supply network (Fig. 4).

The output signal from the sensor 9 frequency affects the second input of the adder 8. Get the output signal of the sensor 9 frequency in two stages. At the first stage, the integrator 20 integrates, from zero initial conditions, the difference signal between the reference signal Uj), which represents a constant voltage, and the output signal of the frequency sensor 9. obtained in the previous period of the mains

and, - ,,, (n-1),

 about

where Tu is the constant of integrator time 20; T - current feeding period

networks;

(t, + t2) integration time;

p - the number of the period of the mains. At the second stage, by closing the switch 24, the output signal of the integrator 20 is sampled. After the switch 24 is turned off, the output signal — output corresponding to the duration of the monitored period of the supply network changes, t. what causes10

15

The institute of the frequency of the supply time integrates the change in the output signal of the frequency sensor 9 and the corresponding change in the output signal of the adder 8, under the action of which the resonant frequency of the frequency selector 6 changes.

Suppose there was an increase in the frequency of the power supply network (figure 4) Reducing the period T of the supply network causes a proportional decrease in the output signal of the integrator 20 and a decrease in the signal at the output of the frequency sensor 9 at the close time of the switch 24. A change in the output signal of the frequency sensor 9 causes a decrease in the output signal of the adder 8, which acts on the control input (Fig. 2) of the frequency selector 6. In this case, the average value of the pulse-controlled conductances composed of 25 series-connected resistors 14, the key 15 of resistor 17, switch 18. A decrease in the time constant of the integrators 16 and 19 increases the resonant frequency of the frequency selector 6 in accordance with the changed frequency of the supply network. Similar processes occur in the device and with a decrease in the frequency of the mains supply.

Thus, the resonant frequency of the frequency selector 8, respectively

thirty

35

The frequency of the suppressed low-frequency harmonic, which changes automatically with a change in the frequency of the power supply, is remembered by the capacitor 25 of the power supply network. This ensures that the installed inlet repeat. l 26.

Simultaneously with the opening of the key 24, the key 21 closes, creating zero initial conditions on the OUTPUT of the integrator 20. After this, the circuit is ready for operation at the next period of the supply network. Since the integration time t is determined by the duration of the period T, the output signal of the frequency sensor 9 varies with the frequency of the supply network.

With a constant mains frequency, the output of the frequency sensor is constant. In this case, the frequency selector 6 is tuned to the frequency of the low-frequency harmonic, which is set by setpoint 7 of the frequency of the low-frequency harmonic. When the network changes, t ,. what causes0

five

The institute of the frequency of the supply time integrates the change in the output signal of the frequency sensor 9 and the corresponding change in the output signal of the adder 8, under the action of which the resonant frequency of the frequency selector 6 changes.

Suppose there was an increase in the frequency of the power supply network (figure 4) Reducing the period T of the supply network causes a proportional decrease in the output signal of the integrator 20 and a decrease in the signal at the output of the frequency sensor 9 at the close time of the switch 24. A change in the output signal of the frequency sensor 9 causes a decrease in the output signal of the adder 8, affecting the control input (Fig. 2) of the frequency selector 6. This reduces the average value of the pulse-controlled conductances consisting of 5 consecutively connected resistors 14 15 of resistor 17, switch 18. A decrease in the time constant of the integrators 16 and 19 increases the resonant frequency of the frequency selector 6 in accordance with the changed frequency of the supply network. Similar processes occur in the device and with a decrease in the frequency of the mains supply.

Thus, the resonant frequency of the frequency selector 8, respectively

0

five

the frequency of the suppressed low ratio of the transmission coefficient of the frequency selector 8 when the frequency of the low frequency harmonic changes, which reduces the dependence of the suppression effect 45 on changes in the frequency of the mains supply.

Claims (1)

Invention Formula A device for wiring a thyristor rectifier containing a series-connected current magnitude adjuster, one input of a current regulator and one input of a pulse-phase control system whose output is intended to be connected to a control input of a thyristor rectifier, a rectifier current sensor, an output which is connected to another input current regulator, rectifier of the output voltage of the rectifier and frequency selector, output connected to another input of the pulse-phase control system, characterized in that, in order to reduce the influence of the frequency fluctuations of the supply voltage to suppress low-frequency harmonics, the sensor frequencies mains voltage, low frequency harmonic frequency adjuster and adder, the output voltage frequency sensor output is connected to one input of the adder, the output of the low frequency harmonic frequency setting unit is connected to another input, the adder output is connected to the frequency selector frequency control input. FIG. 2 (Ls U8bti (9 -J- 25 Fig.Z 4J So Editor N.Lazarenko Compiled by A. Merkulova I. Tehred I. Popovich Order 5710/52 Circulation 659 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 . Production and printing company, Uzhgorod, Projecto st., 4 Proofreader M.Sharoshi Subscription