SU1094129A1 - Rectifier converter control device - Google Patents

Abstract

A DEVICE FOR CONTROLLING A VENTILATED CONVERTER, containing in each phase a series-connected relay element, the first input of an adder, an integrator, an amplifier whose output is connected to the second input of an adder, the third and fourth inputs of which are connected respectively to the source of control and reference voltages, the driver of control pulses, designed to connect to the control electrode of the corresponding valve, / current and load voltage sensors, the push-button closure contact, which input a source connected to a first reference voltage, wherein. In order to increase the reliability of the valve converter, it is equipped with a differentiating element, a demodulator, a key element with a dead zone and a HE element, the first OR element, a key element, the EQUIPMENT common to all phases, and the second reference source in each phase. voltage, RS-trigger and the second element OR, the input of the differentiating element is connected to the output of the relay element, and its output through the demodulator, the key element and the element NOT to the first input of the first el OR, the second input of which is connected to the output of the RS flip-flop, the first input of which is connected to the output of the push-button contact, and the second input is connected to the output of the second OR element, the first and second inputs of which are connected respectively to the output of the sensor the output of the amplifier is connected to the first input of the EQUALITY element and with the closing contact of the key element, the second input of the element EQUALITY through the diffuser; 4i the contact of the key element is connected to the second source of the reference voltage, and The input input is about; the key element is connected to the output of the element OR, the output of the element EQUALITY is connected to the input of the corresponding control pulse generator.

Description

The invention relates to electrical engineering and can be used in power thyristor converters of automatic systems, controlling electric drives of technological installations, for example, rolling mills. A known system of pulse-phase control of a converter, containing in each phase an adder, an integrator, an amplifier and a pulse shaper of control pulses. thyristors of the power block, and the output of the amplifier is connected to the second input of the adder, the third and fourth inputs of which are connected to tvetstvenno to sources ku kntsego control signal. reference voltage xq lj. However, the device has low reliability due to the possibility of a false actuation of the pulse shaper by controlling the thyristors of the power unit under the influence of external interference, for example, from the supply voltage side. The closest to the invention in technical essence and the achieved effect is a device for controlling a valve converter containing in each phase a series-connected relay element, the first input of the adder, the integrator, an amplifier, the output of which is connected to the second input of the adder, the third and fourth inputs of which are connected respectively to the source of the control and reference voltages, the control pulse driver intended to be connected to the control electrode of the corresponding vein yl, current sensors and voltage load button normally open contact having an input coupled to a first reference voltage source 2J. A disadvantage of the known device is low reliability due to the possibility of false triggering of the driver for controlling pulses. In addition, in known devices, when the synchronizing signal disappears (the voltage of one of the phases), the SIFU of the corresponding phase enters its own self-oscillation mode, when the fronts of its output signal are not fixed in time with respect to the supply voltage. When the voltage of the corresponding phase appears, a random control impulse may be applied to the thyristor of the power block, which will cause an error of the processes regulated in the system, or the inoperability of the converter. The aim of the invention is to improve the reliability of the valve converter. The goal is achieved by the fact that the device for controlling the valve converter, containing in each phase successively connected relay element, the first input of the adder, the integrator, an amplifier, the output of which is connected to the second input of the adder, the third and fourth inputs of which are connected respectively to the source of the control and reference voltage, control pulse shaper, designed to connect to the control electrode of the corresponding valve, current sensors and load voltage, push-button The closing contact, the input of which is connected to the first source of reference voltage, is provided with a differentiating element in each phase. a demodulator, a key element, with a dead zone and an element NOT, the first element OR, a key element, the EQUITY element common to all phases, a second source of reference voltage, an RS flip-flop and a second element OR, the input of the differentiating element is connected to the output of the relay element, and its output through the demodulator, the key element and the element are NOT to the first input of the first element OR, the second input of which is connected to the output of the RS flip-flop, the first input of which is connected to the output of the push-button contact, and the second The second input is connected to the output of the second element OR, the first and second inputs of which are connected respectively to the output of the current and voltage sensors, the output of the amplifier is connected to the first input of the EQUALITY element and to the closing contact of the key element, the second input of the EQUALITY element is connected via the breaking contact of the key element the second source of the reference voltage, and the control input of the key element is connected to the output of the OR element, the output of the EQUALITY element is connected to the input of the corresponding generator control pulses. FIG. 1 shows a functional diagram of the device} in FIG. 2-4 timing charts of his signals. The device contains series-connected relay elements 1-3, adders 4, -6, integrators 7-9, amplifiers 10-12, elements 13-15. Equality, drivers 16-18 of control pulses, valve block 19, loads 20, blocks 21-23, differentiating element 24, demodulator 25, key element 26 with dead band and a logical element NOT 27, each of. Blocks 21-23 include 28–30 input and 31–33 output terminals, key elements 34–36 first elements OR memory 39, current sensor 40, voltage sensor 41, second element OR 42, trigger 43, button contact 44 , terminal 45 for connecting control signal Hz, terminal 46 for connecting source X {j of reference voltage, terminals 47 and 48 for connecting sources of reference signal X ,, X, input terminals 49 and 50 of current and voltage sensors, respectively, the device works as follows in a way. Sensors 40 and 41 (Fig. 20.5) directly include the transducers 51 and 52 of the monitored parameter (current, voltage), for example, an analog signal, cascades made according to the modulator-demodulator principle with a separation transformer ( in FIG. 2b) and output threshold elements 53 and 54 with the characteristic shown in FIG. 32. The trigger threshold of the links 53 and 54 corresponds to the maximum permissible current level and voltage in the load circuit of the valve converter Relay elements 1-3 (Fig. 1) have zero threshold values; They are intended to convert: 3 the voltage of the corresponding phase of the power supply (Fig. 2e) to a signal like a square wave with an average zero value (Fig. 2G). The cascades formed by adders 4-6, integrators 7-9 and amplifiers 10-12 represent systems that in the initial state operate in self-oscillation mode, the frequency of which is normalized by the inertia of integrators 7-9 and amplifiers 10-12. - 12 have a non-inverting characteristic. Under the action of the output signal of the relay element 1 (Fig. Za), the links 4, 7, 10 are transferred from the auto-oscillation mode to the forced synchronization mode with the phase voltage C, In the time interval t (Fig. З5) the change in the output signal Y7 (t ) of the integrator 7 occurs under the action of the difference of the signals Y (t) (Fig. 3A) and) (Fig. 35) .. At the time of changing the sign of the signal at the output of the relay element 1 (Fig. 1 and 3A), the sign of the derivative of the output signal changes integrator 7. Amplifier 10 is switched at the time t of the transition output the first signal of the integrator 7 zero. At intervals tJ, t4, the development of the unfolding function Y7 (–b) occurs in a similar way. As a result, the output of the amplifier 10 generates a signal (Fig. 36) with a period T equal to the period of the mains voltage (Fig. 3c (), but lagging behind it in phase by an angle of about 60-80 electrical degrees), which depends on a54plitudy the synchronizing signal at the input of the adder 4. Under the action of the control signal (Fig. 3b) supplied to terminal 45 (Fig. 1), the output signal of the integrator 7 is shifted vertically relative to the zero of the device, and in the direction opposite to the sign of the control action (Fig. 3g) This changes the position in time of the fronts of the output The signal of the amplifier 10 with respect to the synchronizing effect (voltage of the corresponding phase). Using the reference voltage XQ connected to terminal 46 (Fig. 1), an initial angle is set at which the corresponding gate of the unit 19 opens. The sign of the output signal of the elements 13 - 15 corresponds to the product of the signs of the signals at their inputs. In the initial state of the keys 34 - 36 shown in FIG. 1, to the second input ele. Copies 13 8–15 are connected to the source of the reference signal X (Fig. 1, terminal 47) of positive polarity. This ensures the formation at the output of elements 13-15 of signals, which completely replicate the shape of the output pulses of the links 10-12.

S10

The formers 16-18 are made on the basis of single vibrators, which can be synchronized from both the front and rear edges of the output pulses of the amplifiers .10-12. The output signals of the formers 16-18 are fed to the control electrodes of the corresponding thyristors of the block 19 (Fig. 1, in order to simplify the figure, there is no communication line between the block 19 and the network voltage). The time constant of the differentiating element 24 is chosen in such a way as to transmit with minimal distortion to the input of the demodulator 25 a variable component of the output signal of the relay element 1 (FIG. 4, 1).

In demodulator 25, the output of differentiating element 24 (Figs. 5 and 6) is rectified (Fig. 4B) and is amplified so that. its amplitude during normal operation of the device would exceed the dead zone C of the key element 26. In this case, the output of the key element 26 generates a signal of the constant level (Fig. 4d), which provides a zero value of the voltage at the output of the element 27 (FIG. four). Suppose that at time t 0 the voltage of phase C turned out to be zero. Then the output signal of the relay element 1 takes a fixed, for example, positive value (Fig. 46). This leads to a decrease to zero of the output signal of differentiator 24 and demodulator 25 (Fig. 4g). When the condition YUJ () C is fulfilled, the key element 26 is closed (Fig. 4g), and a signal appears at the output of the HE element 27 (Fig. 3A), under the action of which the key element 34 is switched. As a result, both inputs of the element 13 are connected to output 10. Pin 10. However, regardless of the pulse signs at the output of the block 10, the output signal of the element 13 takes a positive value, which eliminates the possibility of generating control pulses of the valves at the output of the block 16.

96

When the voltage of phase C appears, the key element 34 returns to its initial state after that, as the transient synchronization process ends in the control phase. This is achieved by an appropriate choice of the time constant of block 21. The operation of blocks 22 and 23 is similar to that considered.

Thus, the device eliminates the supply of false thyristor control pulses when the corresponding phase of the converter supply voltage disappears.

The second element of RSHI 42 and RS-flip-flop 43 serves to turn off amplifiers. 10 - 12 from shapers 16 -. 18 if the output coordinates of the converter (current, voltage in the load circuit) exceed the permissible levels. At the same time, at the output of the second element OR 42, a signal of logical 1 is formed, which translates RS trigger 43 into a state in which logical 1 is also input to the input of the first elements OR 37 - 39.

This leads to switching of the key elements 34-36 and fixing the output voltage of elements 13-15 at a positive level, when the possibility of starting the shapers 16-18 is excluded. To transfer the RS trigger 43 to the initial state of the logic O, the button contact 44 and the reference signal source Xg-f (Fig. 1, K. pemma 48). The output signal of the second element OR 42 can also be supplied to the disconnecting circuit of block 19 from the mains voltage.

Thus, the proposed device is characterized by higher reliability when operating in process control systems. This is achieved by eliminating the possibility of forming thyristor control pulses when the voltage of any of the phases disappears and disconnecting the converter from the network while simultaneously removing the voltage from the control electrodes of the thyristors of the power VP block.

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Claims (1)

DEVICE FOR CONTROLLING A VENTIAL CONVERTER, containing in each phase a relay element connected in series, a first adder input, an integrator, an amplifier, the output of which is connected to a second adder input, the third and fourth inputs of which are connected respectively to a control and reference voltage source, a control pulse shaper designed for connecting the corresponding valve to the control electrode, / current and load voltage sensors, push-button make contact, whose input is connected In order to increase the reliability of the operation of the valve converter, it is equipped in each phase with a differentiating element, a demodulator, a key element with a dead zone and an element NOT, a first element OR, a key element, an element INDIVIDUALITY, common to all phases, the second source of the reference voltage, RS-flip-flop and the second element OR, with the input of the differentiating element connected to the output of the relay element, and its output through the demodulator , the key element and the element NOT to the first input of the first OR element, the second input of which is connected to the output of the RS-trigger, the first input of which is connected to the output of the push-button contact, and the second input is connected to the output of the second OR, the first and second inputs of which are connected respectively to the output of the current and voltage sensor, the output of the amplifier is connected to the first input of the IDENTITY element and to the NO contact of the key element, the second input of the IDENTITY element through the NC contact of the key element is connected to the second the source of the reference voltage, and the control input of the key element is connected to the output of the OR element, the output of the UNIVERSITY element is connected to the input of the corresponding control pulse shaper.