SU1674306A1 - Device for automatic control of reactive power - Google Patents

Abstract

The invention relates to electrical engineering and is intended to increase the power factor of consumers having multi-zone thyristor rectifier-inverter converters. The purpose of the invention is to improve the accuracy of control of reactive power and reliability. This is achieved by the fact that the synchronization unit 14, which provides the signal at the moment when the supply voltage passes through zero, regardless of the degree of distortion of the latter, is connected to the output of the voltage transformer 2 by its input, and the output to the clock input of the pulsed-phase control unit 10 and to the counting input the trigger 20 of the control unit 13, the input of which is connected to the output of the current transformer 3, and the output to the control input of the unit 10 of the pulse-phase control. This makes it possible to obtain an automatic adjustment of the clock phase. 6 Il.

Description

The invention relates to electrical engineering and is intended to increase the power factor of consumers having multi-zone thyristor rectifier-inverter converters.

The aim of the invention is to improve the accuracy of control of reactive power and reliability.

FIG. 1 shows a functional diagram of a device for automatic control of reactive power; in fig. 2, 3. 4 - timing charts of the synchronization unit; in fig. 5, 6 - timing charts of the control unit.

The device contains a network mode sensor 1, which includes a voltage transformer 2 connected to the supply network, and a load current transformer 2 connected to the load circuit 4, which uses multilink thyristor rectifier-inverter converters, a source of reactive power 5, connected parallel to the supply network and consisting of series-connected inductors 6, capacitance 7 and two anti-parallel connected thyristors 8 and 9, the control electrodes of which are connected to the output of the unit 10 imp lsno-phase control, comprising connected in series faeosdvigayuschy node 11 and the generator-distributor 12 pulses, input unit 10, a pulse-phase control output connected to control unit 13 and the exit 14 synchronization. Block 13

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control, the input of which is connected to the output of the current transformer 3. contains a phase shift regulator 15, one of the passes of which is connected to the output of the phase shifter 16, and the other to the output of the first logical element OR 17, whose inputs are connected to the outputs of the first and second logical elements are NOT 18 and 19 connected by the first inputs to the inputs of the trigger 20, and the second input of the element is NOT the IP connected to the output of the zero-body 21 and p / ode the first element NOT 22 connected by the output to the second input of the second element V: NOT 19 , Input zero-organ 21 podkl It is controlled through the filter 23 of the first current harmonic to the output of the current transformer 3. The synchronization unit 14 includes a first voltage harmonic filter 24 connected in series with the first null organ 25, a controllable delay element 26, and a synchronization signal generator 27, the output of which is connected to the phase shifter 11 of the pulse phase control unit 10 and the counting input of the trigger 20, the second null-organ 28, connected by the input to the output of the voltage transformer 2 and connected in series with the first logic element AND 29, the second logic element OR 30, differential m amplifier 31, the second input of which is connected to the output of the controlled delay element 26, and the integrator 32, the output of which is connected to the second input of the controlled delay element 26, the outputs of the zero-organs 25 and 28 also included through the elements HE 33 and 34 to the inputs of the logical element And 35, and the input of the third element HE 33 is connected to the second input of the element 29.

The Da6oidt i device is as follows.

When adjusting the load current 4, a phase shift occurs between the output voltages of the transformers 3 go and voltage 2, which characterizes the measure of reactive power consumption by the load 4.

For automatic compensation of reactive power consumed by the load 4. The device provides for the regulation of the opening angle of the thyristors 8, 9, the source 5 of reactive power, depending on the magnitude of the specified phase shift,

The synchronization unit 14, to the input of which signals are received from transformer 2, provides for receiving signals exactly at the moment of zero crossing of the supply voltage, regardless of the degree of phase and amplitude distortion of the postpair, which are used to synchronize the unit 10 of pulse-phase control and to fix the moment start measuring the phase shift of the load current relative to the supply voltage in the control channel 13.

Receiving a signal exactly at the moment of The passage through the zero voltage supply is as follows,

The supply voltage Ui (Fig. 2-4) through the measuring voltage transformer 2 is fed to the input of the first harmonic filter 24. That controls the operation of the zero-body 25. At the output of the zero-body 25, square-shaped pulses U4 ( Fig. 4 shows the process for one half period, therefore the pulses are unipolar), the duration of which is equal to the duration of the half period of voltage U2 behind filter 24, and the phase of the leading and trailing edges is determined by the moment of transition of this voltage through zero. The pulses U-q are then used to trigger (synchronize) the reference voltage generator, which is switched on at the synchronization input of delay element 26. At the output of the delay element 26, rectangular-shaped pulses Us are formed, the leading edge of which coincides with the front of the pulses, i.e. with the moment of changing the sign of voltage 1) 2 behind the filter 24, and the duration L is set so that the falling front coincides with the moment of changing the sign supplying the voltage Ui. Signals are formed on the falling edge of the pulses Us by block 27, which are then used to synchronize the pulsed control unit 10 and the thyristor control channel 13 for opening the thyristor source 5 of the reactive power source 5 by setting a certain duration of the pulses Us (i.e. the delay in the start of the formation of the synchronization signals; and the output of the delay element 26 is compensated for the effect on the synchronization accuracy of the constant phase shift — the amount supplied by the supply voltage Ui and the voltage behind the filter U2, the magnitude of which Only the parameters of the used transformer 2 and filter elements 24 are associated with conditions. However, as noted above, under operating conditions, the phase shift is determined not only by the selected characteristics of the filter 24, but strongly depends on the frequency variation and the degree of distortion of the supply voltage Ui, temperature and technological changes in the parameters of the elements of the device circuit.

directly proportional to the change in the magnitude of the phase shift will change the phase of the synchronizing signals, which reduces the performance of the source 5 of reactive power .-

In order to compensate for the influence of the phase shift instability on the synchronization accuracy in the proposed device, the output voltage of the measuring transformer 2 is also supplied to the input of the null organ 28 (Fig. 1). At the output of the zero-organ 28, rectangular-shaped pulses are formed, the duration of which is equal to the half-period duration of the supply voltage Ui, and the front and rear edges coincide with the points of transition of this voltage through zero (Fig. 2 ... Fig. 4).

The zero-body reacts only to a change in the sign of the input signals and, therefore, the duration and shape of the pulses does not depend on a decrease in the supply voltage in the zone of switching angles. The pulses are compared in duration and phase with the output pulses LU of the zero-body 25. In one half-period of the supply voltage, the comparison is made by the coincidence element performed on the AND 29 logic element, and in the second half-period And 35, the inversion is pre-made logical elements HE 33, 34 The phase of the leading edge of the comparison signals at the output of the matching elements 29 and 35 is determined by the phase of the leading edge of the signals U, and the falling edge coincides with the falling edge of the signals at the output of the zero-body 28. In accordance with To them, the duration of these comparison signals corresponds to the true (current) value of the phase shift - (FIG. 2 ... 4) between the supply voltage LH and the voltage Us behind the filter. Comparison signals from the outputs of elements AND 29 and 35, the passage through the logical element OR 30, are fed to the direct input of the differential amplifier 31, to the second (inverse) input of which are pulses Us from the output of the controlled delay element 26. When the amplitudes of the signals Ue and Us are equal, the output of the differential amplifier 31 produces pulses of rectangular shape U, the duration of which is equal to the difference between the actual (true) phase shift lf of the voltage U2 behind the filter and the set value of the delay Log of the beginning of the formation of synchronizing signals, , if Yes - p, the pulses U are negative and are formed at the beginning of the second half-wave of the supply voltage Ui, if

Yes pt p- they are positive and are formed by the end of the first half-wave Ui (Fig. W., Fig. 4). Subject to the equality l - p output eg. The designation of the U differential amplifier 31 is zero (FIG. 2). Here, it is not only the magnitude of the difference between the phase shift l - p of the voltage downstream of the filter 24 and the magnitude of the delay Yes that the synchronization signals start to form, but also the sign of this difference. The pulses from the output of the differential amplifier 31 are fed to the input of the integrating element 32, for which the following relationship holds:

 / U7dt.

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where UBUX is the voltage at the output of the integrating element;

r is the integration time constant;

U is the amplitude of the input signals.

From the above relation it follows that with a constant amplitude of pulses Uv, the output voltage of the integrator 32 is proportional to their duration averaged over time g. Averaging the duration of the signals Uy, which are formed using the signals at the output of the null organ 28, is also equivalent to averaging the time when the supply voltage Ui passes through zero. The output voltages of the integrator 32 are supplied to the control input of the delay element 26. Depending on its value, the magnitude of the delay of the formation of the clock signals varies. The steady state of the circuit occurs if, during the quantization period I, which is equal to the duration of the half-period of the supply voltage, the sum of all the signals at the input of the integrator 32 is zero. These equilibrium conditions occur only when there is a temporary coincidence of the signals Us and U6 at the input of the differential amplifier 31, when there are no pulses U at its output. In this case, Yes, the moment of the formation of the falling edge of the pulses Us at the output of the delay element 5, and, consequently, the moment of the formation of the synchronizing signals at the output of the shaper 6 coincide with the moment of the transition of the feeding heat through zero (Fig. 2). Any changes in the duration of Da pulses Us at the output of the delay element 26 or phase n - (/ voltage U behind the filter 24 leads to the violation of the specified steady state, i.e., the conditions of the circuit shown in Fig. 3 or fig. four.

At the output of the integrating element 31, voltage varying in magnitude appears, under the action of which the duration D of the output pulses Us of the delay element 26 begins to change. This change continues until the duration of the Yes signals again becomes equal to the magnitude of the phase shift — f. Regardless of the distortion of the shape of the power supply voltage Ui curve of the synchronization unit of the pulsed-phase control unit 10 and the control unit 13, the average moment of transition of this voltage through zero value will be performed. It should be borne in mind that in the absence of phase distortions of the shape of the supply voltage curve, the moment of formation of the synchronizing signals will coincide with the current value of the moment of transition through the zero of this voltage.

In control unit 13, the phase of the first harmonic of the current relative to the synchronizing signals is measured and a signal proportional to the phase is fed to the input of the phase shift controller 15 as feedback. As the setpoint of the controller 15, the signal from the setting device 16 is used, providing, at zero signal of the feedback connection, the phase shift of the opening of the thyristors 8 and 9 in Tg (Fig. 5). Correspondingly, a voltage appears at the output of the regulator 15, the level of which provides the phase shift of the thyristor control pulses 8 and 9 from the end of the half period to the beginning by such a value that compensates for the reactive power at each particular time of load operation. This is provided as follows.

At the output of the filter 24, a sinusoidal voltage (Fig. 6b) of the first harmonic of the current is shifted in phase by an angle p with respect to the synchronizing signals (Fig. 6a), corresponding to the transition times of the supply voltage. The voltage of the first harmonic of the current is fed to the input of the zero-organ 21, at the output of which two-polarity square-wave signals are formed, the duration of which is equal to the duration of the half-period of the voltage of the first harmonic. These signals are fed to the inputs of the AND-NE logic gates 18 and 19, and to the element 18 - directly, and to the element 19 - through the inverter 22 to measure the magnitude of the phase shift in both half-periods. Signals (FIGS. 5, 6 g) of rectangular shape from the outputs of trigger 20, the duration of which is

Oh - l. and the initial fas-e is determined by synchronizing cm; signal supplied to the counting input of the trigger 20 At the RYHODEKH of the elements AND- NOT 18 and 19 signals are formed

(Fig. 6e) direct 1) of the cognitive form, the duration of which is equal in phase between the voltage and the load current in different half-periods of the supply voltage. These signals arrive at the inputs of the logical

element OR 17, on which rectangular impulses are formed, which are rakish in length by input but shifted relative to each other by half the period of the supply voltage h (Fig. 6 e}. These signals are used in the cache; its feedback signals of the shift regulator 15 phases.

The output voltage of the regulator 15 is applied to the input of the bg.pka 10 of the pulse-phase control, where it is shown (Fig. 5, B).

f) with a saw-tooth voltage, synchronization of which is carried out by a pulse and synchronization, coming from -. 4 (Fig. 5, 6 a). At the time of comparison, OC; the voltage of the regulator 15 with a sawtooth

unit 10 pulse-b;; of your own sound, you generate a signal post / tchayuschayu control electro; common power thyristor (8 ipi 9); consistent with reactive power, and o (Fig. 5 b, and changing the output voltage reg / l legal): ib spawns the phase shift of the control signals of Gyrtsfig. 6 g) 8 and Г h.technical.cd active power 5. providing the cost of reactive mosh-capacity

Receiving is more stable, corresponding to tsegs momei. g / crossing the supply voltage zero, eliminates the failure of the thyristors of the reactive power source, which increases the power of the Ksocirb device and allows you to accurately measure the phase shift of the load relative to the supply voltage i fa., evoke control action,. lighter: hiding the true shift,, oey ,,,) by: the accuracy of regulation, Besides the ogp, the phase shift regulator excludes oscillatory processes in the system: the network - the source of reactive power - the loads, and thus

prevents overvoltage on load cells and a source of reactive power, which also increases the reliability of the device.

Claims (1)

Invention Formula A device for automatic control of reactive ESSENCE, comprising a network mode sensor, including transformers, power and load, an impulse-phase control unit. a phase-shifting node, the output of which is connected to a control pulse distributor connected to the input of a reactive power source, having leads for connecting to the supply network, and a synchronization unit, characterized in that, in order to improve the accuracy of control of reactive power and reliability , it is equipped with a control unit consisting of a phase shift controller, a phase shift controller, an OR gate, two NAND gate, a NOT gate, a trigger, a zero-organ, and a filter The first harmonic of the first harmonic is connected to the output of the load current transformer, and the output through the null organ is connected to the first input of the first NAND element, the second input of which is connected to one of the trigger outputs, the output of the first AND element NOT connected to the first input of the OR element, the second input of which is connected to the output of the second NAND element, the first input of which is NOT connected to the zero output through the element, and the second input to the second output of the trigger, OR output connected to the first regulator input phase shift, the second output of which is connected to the output of the phase shift adjuster, the output of the phase shift regulator is connected to the control input of the phase-shifting unit of the pulsed-phase control unit, the reactive power source consists of series-connected inductances, a capacitor and two opposite-connected thyristors whose control electrodes are connected to the input of a source of reactive power, their common point, as well as an amplifier, the inductance terminal is connected to the terminals for connecting the network, and the synchronization unit is made of a first voltage harmonic filter, two zero-organs, a control delay element, a synchronizer signal generator, two logical elements NOT, two logical elements AND, logical element OR. differential amplifier and integrator, the output of the first voltage harmonic filter is connected via the first null-organ to the inputs of the first element AND, the first element NOT and the controlled delay element whose output is connected to the first input of the differential amplifier and the input of the clock signal generator whose output is connected to the input of the phase-shifting unit of the pulsed-phase control unit and with the trigger input of the control unit the output of the second zero-organ is connected to the input of the second element NOT and the second input of the first AND element whose outputs are connected to the first input of the OR element, the second input of which is connected to the output of the second element AND, two inputs of which are connected respectively to the outputs of the first and second elements NOT, the output of the OR element is connected to the second input of the differential amplifier whose output is connected via an integrator to the second input of the controlled delay element, the filter inputs of the first voltage harmonic and the second zero-organ are connected to a voltage transformer. its ui TO ut and. at ..I-Y h and, 6Jf Loos Uc L-y CJ uk Ojt about, "Jt FIG. 2 chl M v - I- b) t V Oya a) t Act (Jt s Cjt I v ut Ji-v (Jt (Jt (Jt u; P "Jf F "/ g5 FIG L II IIfl well II Schi 5 L P FIG. 6