SU1494110A1 - Device for compensation of power of distortions - Google Patents

Abstract

The invention relates to electrical engineering and can be used in networks of industrial enterprises and autonomous power supply systems containing powerful non-linear loads. The goal is to improve the quality of compensation by reducing the level of higher harmonics due to modulation, and reducing switching losses. A distortion power compensation device (ACMI) contains a step-down transformer 1 with two primary windings, with the beginning of one winding 2 connected to the end of the other winding 3, and the other opposite terminals are connected, respectively, through a pair of parallel-connected thyristors 5, 6 and 7, 8. Ko The secondary winding of the transformer 1 is connected to an energy storage device, which is a series-connected reactor 11 with a capacitor 12. The eigenresonant frequency of a series oscillatory circuit formed by ary winding 9 of the transformer 1, the reactor 11 and the capacitor 12 exceeds the frequency of the highest harmonic load current to be compensated. In addition, the device contains a control unit 13 and its associated network voltage sensors 15, load current 14, compensation current 4 and oscillating circuit current 10. Turning on the thyristors, the oscillating circuit is excited and energy is stored in it. In this case, the amplitude of the resonant current reaches the value specified by the control unit. Due to the EMF induced in the primary windings of the transformer from the flow of this current, the conditions of thyristor switching are provided in both rectifier mode and inversion mode. The control unit selects the reactive (orthogonal) component of the load current and generates thyristor control pulses with an adjustable delay relative to the phase oscillation of the current in the circuit. As a result, at the output of the MCI, a current is formed, which is formed from opposite-polarity pulses with a variable amplitude and duration, which are fragments of sinusoidal oscillations. The envelope of this current is the required compensation current. In each half-period of the supply voltage between the oscillatory circuit and the network, a complete cycle of energy exchange occurs. To eliminate the influence of the mains voltage on the shape of current pulses, the control unit provides for automatic change of the slope of the leading edge of the reference pulses. A predetermined level of current in an oscillating circuit is maintained by an automatic control circuit including a loop current sensor. To improve the accuracy of compensation, feedback feedback has been applied. 6 ill., 1 tab.

Description

31А9

Distortion (UCMI) contains a step-down transformer 1 with two primary windings, with the beginning of one winding 2 connected to the end of the other winding 3, and the other opposite terminals are connected, respectively, through a pair of counter-parallel-connected thyristors 5, 6 and 7.8 o To the secondary winding of the transformer 1 an energy storage device is connected, which is a series-connected reactor 11 with a capacitor 12. The self-resonant frequency of a series oscillatory circuit formed by the secondary winding 9 of the transistor the reactor 1, the reactor 11 and the capacitor 12 exceeds the frequency of the highest harmonic of the load current, compensating compensation,. In addition, the device contains a control unit 13 and associated network voltage sensors 15, load current 14, compensation current 4 and oscillating circuit current 10 By switching on the thyristors, an oscillating circuit is excited and energy is stored in it. At the same time, the amplitude of the resonant current reaches the value set by the control unit. Due to the emf induced in the primary windings of the transformer from the flow of this current.

ABOUT

The switching conditions of the thyristors are provided in both the straightening mode and the inverting mode. The control unit selects the reactive (orthogonal) component of the load current and generates control pulses with thyristors with an adjustable delay relative to the current oscillation phase in the circuit. A current is formed, which is formed from opposite-polarity pulses with variable amplitude and duration, which are fragments of sinusoidal oscillations. The envelope of this current represents the required compensation current. At each half-period of the supply voltage between the oscillatory circuit and the network, a complete energy exchange cycle occurs. To eliminate the influence of the network voltages on the current pulse shape, the control unit provides for an automatic change in the slope of the leading edge of the reference pulses. in the oscillatory market, it is supported by an automatic control circuit, including, and a loop current sensor. Dp according to the accuracy of compensation, feedback on compensation current was applied 6 or less, 1 tab.

The invention relates to electrical engineering and can be used to improve voltage quality and reduce power losses in industrial networks and autonomous power supply systems containing powerful non-linear loads.

The purpose of the invention is to improve the quality of compensation by reducing the level of higher harmonics in the compensation current caused by modulation and reducing switching losses.

Fig. 1 shows a block diagram of a distortion power compensation device (MCMI); Fig. 2 is a functional block diagram of the control unit; in fig. 3 - timing diagrams that explain the formation of compensation current; Figures 4 and 5 are timing diagrams explaining the formation of reference pulses in the control unit; FIG. 6 are timing diagrams explaining the operation of the pulse distributor. FIG.

UKMI contains a step-down transformer 1, in which the beginning of one primary winding 2 and the end of the other primary winding 3 are connected and through the sensor 4 current compensation connected to one of the supply wires

network, and other opposite conclusions, each through a pair of anti-parallel-connected thyristors 5-6 and 7-8, are connected to another power supply wire, and the beginning of the secondary winding 9 is connected to reactor 1I via sensor 10 of the reactor current and the capacitor is connected in series with it 12, its second output connected to the end of the secondary winding of the transformer 9, control unit 13, the inputs of which are connected to the outputs of load current sensor 14, network voltage sensor 15, compensation current sensor 4, and sensor

5U

10 current reactor, and the outputs are connected to the control electrodes of thyristors 5-8 s

The control unit (Fig. 2) contains a block 16 for extracting the reactive (orthogonal) component of the current, the first input of which is connected to the output of the load current sensor 14, the second input is connected to the output of the network voltage sensor 15, and the output through the inverter 17 is connected to the first input the first adder 18, the second input of which is connected to the output of the sensor 4 compensation current, and the output is connected to the input of the aperiodic link 19, the first rectifier 20, whose input is connected to the output of the sensor 10 of the reactor current, and the output through the smoothing filter 21 is connected to the first ohm second adder 22, the second input of which is connected to the output of the source 23 of the reference voltage, the multiplier 24, the first input of which is connected to the output of the sensor 15 of the supply voltage, the second input is connected to the output of the second adder 22, and the output is connected to the third input of the first adder 18 , voltage divider 25, the input of which is connected to the output of voltage supply sensor 15, and output to the second rectifier 26, the third adder 27 and the fourth adder 28, the first inputs of which are connected to the output of the second rectifier 26, and the second inputs with the output of the voltage source 23, the first comparator 29, the first input of which is connected to the output of the second rectifier 26, the second input connected to the output of the smoothing filter 21, and the output to the first input of the first starting and resetting circuit 30 of the integrator, the second comparator 31, the input of which is connected to the output of the reactor current sensor 10, and the output is connected to the first input of the second integrator starting and zeroing circuit 32, the first integrator 33, the first input of which is connected to the output of the third adder 27, and the second input is connected to the output of the first The second integrator launch and zeroing circuit 30, the second integrator 34, the first input of which is connected to the output of the fourth adder 28, and the second input connected to the output of the second integrator starting and zeroing circuit 32, the fifth adder 35, the first input

0

five

0

five

I

0

five

0

five

0

five

Ш6

porn is united by a walk of 33 and 33, and PTFR is proud of a source with 73 source NLP support, simple with a florist 3f-), the first input of which is integrated with the second integral 34, L of the second connection with the output of the output, and an output switch. voltage, the third compiler 37, the input of which is connected to the output of the fifth adder 35, l output is connected to the second input of the first integrator 38, the input of which is connected to the output of the sixth total 36 l output is connected to the second input of the circuit 32 run and reset integrator, the third rectifier 39, whose input is connected to the output of the aperiodic link 19, and the output to the first inputs of the fifth 40 and sixth 41 complators, the seventh comparator 42, the input of which is connected to the output of the aperiodic link 19, the eighth compiler 43, whose input connected to the output / hum of the voltage supply sensor 15, the distributor 44 pulses, the first input of which is connected to the output of the seventh comparator 42, BTOpofi - with the output of the fifth comparator 40, the third input connected to the output of the eighth comparator 43, the fourth input is connected to the output of the sixth comparator 41, the fifth input is connected to the output of the second comparator 31, the pulse generator unit 45, the flow of which is connected to the output of the pulse distributor 44, l output is connected to the control electrodes of the thyristors 5-8, and the second input of the fifth comparator 40 is connected to the output of the fifth adder 35, and the second input of the sixth comparator 41 is connected to the output of the sixth adder 36,

The illustrated diagrams of the time diagrams fy on the axis are shown: 46 - mains voltage U and load current 1 „; 47 is the signal i of the compensation current and the compensation current i 48 is the voltage across the thyristors 7 and 8; 49 - voltage U j on thyristors 5 and 6; 50 is the current of the relay 1 (; 51 is the nominal, the conductor of the conducting thyristors. Figure 4 shows the diagrams for the axes: 52 is the reactor current; 53 is the sequence of reference pulses for the inversion mode (GBS); 54 is the sequence, the reference pulses for straightening mode (ORj)

In FIG. 5, reference numeral 55 denotes signals at the input of the first comparator 29.

FIG. 6 shows diagrams along the axis: 56 - signal at the output of the eighth comparator 43; 57 - signal at the output of the seventh comparator A2; 58 - the signal at the output of the second comparator 31; 59 - the signal at the output of the sixth comparator 41; 60 is the signal at the output of the pth comparator 40; 61 — thyristor control pulses 7; 62 — thyristor control pulses 8; 63 — thyristor control pulses 6; 64 - thyristor control pulses 5c

The device works as follows with

Initially, energy is stored in the oscillatory circuit formed by the secondary winding of the transformer 9, the condenser 12 and the reactor 11. In this case, the mains voltage turns on the thyristor 8 or 6 and the current in the secondary winding of the transformer is energized frequency equal to the resonant frequency of the oscillating circuit

H

eleven

(L + L2) C

where L is the inductance of the reactor 11;

L is the inductance of the secondary winding of the transformer 9; С - capacitor capacity 12о

Further, the unlocking of the thyristors is performed synchronously with the current oscillations in the circuit. Moreover, if during the positive half-period of the mains voltage Up the current in the reactor i increases, the thyristor 8 opens; if the current i L decreases, it removes the thyristor 6c when changing the polarity of the network voltage Uc, the thyristor 5 is unlocked at intervals of the current rise of the reactor i, and the thyristor 7 at all times the moment of switching is provided by a direct voltage, which is equal to the sum of the voltage U j, and the DDS of one ich of the primary windings of the transformer induced by the flow of the oscillating circuit along the secondary

the control winding 9, in the control unit 13, the phase shift of the control pulses relative to the transition of the reactor current i through zero is formed so that the current consumed by the MCMI in the energy storage mode in the oscillatory circuit is close to the sinusoidal current in the oscillatory

0 circuit is monitored by sensor 10

reactor current After the amplitude of the reactor current i reaches the value specified in the control unit, the MCMI switches to compensation mode.

In the compensation mode, the work of the MCMI is based on the energy exchange between the oscillatory circuit and the supply network with, and in the exchange of participation 20 W, only a part of the energy stored in the oscillatory circuit. The direction of energy transfer is determined by the choice of the thyristor, and its quantity is determined by the magnitude of the network voltage at the moment

25 switching and time delay

of this moment relative to the phase of the current oscillation in the secondary winding of the UKMI transformer generates a current opposite to the reactive (orthogonal) component of the load current. Therefore, the energy / output from the oscillating circuit (entering the oscillating circuit) is half a period

It / 2

 supply voltage W j Uj, ij ,,

about

The energy exchange cycle is completed every half-period of the supply voltage; the average value of the energy of the oscillating circuit remains unchanged

Depending on the required power of the MCMI, the amplitude of the reactor current 1 1 is set. The inductance of the secondary winding 9 of the step-down transformer 1 and its transformation coefficient are chosen so that for a given amplitude of the current of the reactor IL, the amplitude of SG (C, inducted by Q in each of the primary windings 2 and 3, was approximately two times more than the amplitude of the amplitude of the network Up, this is necessary for reliable unlocking of the thyristors in compensation mode. The inductance of the secondary winding 9 is several times smaller than the inductance of the reactor 1I (approximately 10 times) so that the changes in the amplitude of the current in the oscillatory circuit n compensation mode do not lead to unstable operation of ACM1.

Processing the signals from the load current sensor 14 and the sensor 15 of the control voltage 13 generates such a signal i at the compensation current 1 c, so that in total with the load current 1 c it generates a current in the transmission line 1 d, in accordance with the voltage of the PS network . For example, for a sinusoidal voltage and load current shown in timing diagram 46 in FIG. 3, the compensation current signal 1 has the form 47 of FIG. 3. Such a compensation current is generated as follows.

Suppose at the initial time t, the reactor current has a phase such as in diagram 50 in FIG. 3 At time t, the thyristor 7 is unlocked, at which at this moment the voltage is positive due to the emf induced in primary winding 3 (diagram ma 48 in fig 1.3). In this case, a current pulse flows through the open valve 7 through the primary winding 3 of the step-down transformer (Figure 47 in Fig.3). The pulse has a negative polarity with a positive polarity of the voltage of the network Uj., Toe. the current was inverted due to the energy output from the oscillatory circuit, V, the next, second, half-period of current i. an unlocking pulse is applied to the thyristor 5 at the time t2 with some delay relative to the moment of current transition in the oscillatory circuit i, zero, proportional to the change of the compensation current signal i. In this case, a current pulse of smaller amplitude and duration flows through the primary winding 2 of the step-down transformer. After the signal i, is passed, at the instant tj through zero, at the output of the MCMI, positive current pulses of about Dp form. In the positive current half-periods ii thyristor 8 enters into operation, and thyristor 6 enters into negative current, Since the current direction ik and polarity the network and with the same, there is a process of rectifying the current associated with the storage of energy in the oscillating circuit. In diagram 51, the numbered tees are shown on p and the corresponding conductivity intervals.

where r

Ristoro, incl. 1 hlm my TP of the current curve of i iC all lilzso not including the interconnection of the HRT of the moment t when the voltage is applied to the network voltage.

Thus, by choosing one of the two oppositely connected primary windings 2 and 3 of the first transformer 1 and supplying the triggering pulse to one and two oppositely connected thyristors of this winding at the output of the MCMI. current pulses of both polarities are formed when the polarity of the mains voltage U is polarity. By deducing the thyristor control pulses with respect to the instant of current i L through zero, the amplitude and duration of current pulses i c at the output of the MCMI, the envelope of which is glare to signal i, produced by the control unit 13,

The signal i of the compensation current in the control unit 13 is generated as follows

The first input of the reactive (orthogonal) component is Jup, the current 16 is supplied i from the load current sensor 14, the second input of this block is supplied with the signal Uc from the network voltage sensor 15, the output signal is a reactive (orthogonal) component load current ip, defined as the difference of load current i, and its active component i ,,:

 RN

moreover, the active component of the load current iD is determined in accordance with the expression

R

1 rt Gt l

P Ti

and.

where r

active power, the average for the period value of the product and s and i

Uc and

De-ping network voltage value Signal i P passes through inverter 17; At the first input of the first adder 18, a signal is applied To the output of the first adder 18, an aperidic link 19 is connected, the smoothing signal and the restricting region of the compensating load current iu are compensated. Next, the compensation current signal i is sent to the first input of the comparator through the first compensation signal i AO and first input of comparator 41 for comparison with control pulses of control unit,

And, due to active losses in an oscillatory 1M circuit, the reactor current i | gradually fades out. To stabilize this current and cover the active losses in the main circuit of the MCMI, there is a following circuit in the control unit. The signal from the current sensor of the reactor 10 is fed to the input of the first stage of the cylinder 20, from which the pulsating form signal passes through a smoothing filter 2 s. The output signal IL, which is proportional to the amplitude of the current of the reactor, is fed to the first input of the second summator. 22, the second input of this adder is supplied with the signal T of the source of the reference voltage 23, proportional to the given amplitude of the current of the detector. The difference signal c - Lm from the output of the second adder 22 is fed to the second input of the multiplier 24, to the first input of which a signal is given l from the voltage sensor of the network 15c At the output of the multiplier 24, a signal is generated that is proportional to the change in the amplitude of the reactor current i | and replicates the form of the network voltage (active component of the load current) In the oscillating circuit excitation mode, this signal determines mainly the form of current consumed by the UKMI from the network

The formation of reference pulses in the control unit occurs through two channels, separately for the inversion mode and the rectification mode with. The reference pulses for inversion are formed as follows.

The second inputs of the fourth 28 and sixth 36 adders receive a TO signal of the reference voltage source 23 o. At the moment the reactor current IL passes through zero from the output of the comparator 31 to the first input of the second starting and zeroing circuit of the integrator 32, the second integrator 34 the signal at its output begins to increase, expressed on the sixth adder 36 of the signal If ,. The signal OP from the output of the sixth adder 36 is supplied to the second input of the sixth comparator 41 At the time of the transition of the reference signal OP through

zero from the fourth comparator 38 to the second start-up and zeroing circuit of the integrator 32 receives a signal for the second integrator 34 to obtugle. In this case, the reference signal OPU has the form shown in time diagram 53 (FIG. 4) by a solid line. Diagrams 48 and 49 show that the voltage on the thyristors in the adjacent half-periods of the current i is different, and this difference is greater, the greater the voltage value of the network and, therefore, when the thyristors are turned on, there is a constant delay with respect to the moment of transition of the reactor current i through zero, but when the network voltage U changes at the output of the MCMI, current pulses i ,, are slightly different in amplitude and mean value. Moreover, in the inverting mode with (J s they are minimal and in the straightening mode maximum). and the adjusting characteristic of the UKMI in the whole range of variation of the mains voltage changes the slope of the edge of the reference pulses as a function of PS, With a maximum value of Ur P.

- P1

the front of the reference pulse OP should take the position shown by punk-; by the tyr line in diagram 53 (FIG. 4) c. This is achieved in the following way. The signal from the voltage sensor of the network 15 is fed through the voltage divider 25 and the second starter 26 to the first input of the fourth adder 28; the higher the level U,., the steeper the voltage at the output of the second integrator 34 is, Fig 54 shows the formation of reference pulses for the rectifier mode (OD). The formation channel of these pulses includes the third adder 27, the first integrator 33, n the adder 35, the third comparator 37, the circuit 30 also works as described, but the launch delay of the first integrator 33 with respect to the transition of the reactor current ij is additionally introduced, through zero, proportional to the voltage level of the Uco network. This is done using the first comparator torus 29, to the first input of which a pulsating current signal from the capacitor is output from the first rectifier 20, and to the second input is a signal proportional to the pulsating voltage of the network from the second rectifier output

13U

26o At the moment of intersection of these signals, the signal la comes-the launch of the first integrator 33. The process of forming the start-up delay time of the first integrator 33 is illustrated by the diagram 55 of FIG. 5, which shows the signals at the inputs of the first comparator 29; t, and t 3 are the delay times for two half-cycles of the reactor current i. In Figure 54 of Fig. A, the maximum delay time t is noted.

The pulse distributor 44 is made on the H-HJDi-HE logic elements and performs the function of selecting the orig or OP cc working thyristor depending on the polarities of the network voltage Uc, reactor current i | and the compensation current signal i. The logic of the pulse distributor is explained in the table.

Figure 6 shows timing diagrams illustrating the operation of the pulse distributor. Diagram 56 shows the signal at the output of the eighth Comparator 43, carrying information about the polarity of the mains voltage U (., Diagram 57 shows the signal at the output of the seventh comparator 42, carrying information about the polarity of the compensation current signal, and diagram 58 shows the output signal the second comparator 31 carrying information about the polarity of the current of the reactor 1, in diagram 59 - the signal at the output of the three-way comparator 41, which is formed at the moment when the leading edge of the reference pulse OP1 reaches the value of the pulsating signal at the output of the third inverter l 39, to the input of which signal i is applied to the current com

Q

50

five

0

five

0

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five

101 i.

Pengakia, on diagr tmr 6P - with igpl at the output of the p that kom1llltp -1, h 4P, on

which takes place GrLNKOIIO P1-HCPL | Pgo signal block 39 s. optics pulses Orig. On the l; 1m, lr 61-64, the output pulses are indicated by thyristors at the output of the formers of the pulses 43, connected to the circuit of the distributor of 44 pulses,

To improve the accuracy of compensation of the reactive (orthogonally) component of the current ip in the MCMI, we also provide feedback for the other way, for this, the signal from the current compensation sensor 4 subtext to the second input of the first total is 18,

The device for compensating the power of the distortion forms the tech- nology (amplification with the help of pulses, measured in width and amplitude, ”In this case, the level of harmonics of low-order frequencies (close to compensated higher harmonics) is lower than at

Thus, in the long-legged device, the expansion zone of compensated higher harmonics is expanded, i.e., e, the accuracy of compression is increased. Furthermore, the use of a cluster (the LC circuit allows for the use of natural switching thyristors, reducing switching losses,

Claims (1)

Invention Formula A distortion power compensation device containing a step-down transformer, a reactor, a control unit, the inputs of which are connected to the outputs of a load current sensor, a network voltage sensor and a reactor current sensor, and the outputs are connected to control electrodes of switching devices, which are compensation quality by reducing the level of higher harmonics in the current compensation due to modulation, and reducing switching losses, a compensation current sensor, a capacitor, and a single output soedinennsh reactor, and the other - with the secondary winding of the transformer, the second end of which is connected via a reactor current sensor to the second terminal of the reactor, wherein the commutator that ioknye apparatus vtolneny on tiristorlh transformer formed with two pergshchnymi windings in which the beginning of one and the end of the other are connected and through compensation current sensors are connected to one ug of the mains supply, and other opposite types are connected to another input of the mains through a pair of counter-parallel connected thyristors, the compensation current sensor output is connected to the input a control unit consisting of a reactive current isolation unit, the first input of which is connected to the output of the load current sensor, the second input is connected to the output of the network voltage sensor, and the output through the inverter is connected to the first input of the first adder, the second input of which is connected to the output of the compensation current sensor, and the output is connected to the input of the aperiodic link, the first rectifier whose input is connected to the output of the capacitor current sensor, and the output through the smoothing filter is connected to the first input The second adder, the second input of which is connected to the output of the voltage source, the multiplier, the first input of which is connected to the output of the network voltage sensor, the second input is connected to the output of the second adder, and the output from The one is connected to the third input of the first adder, the voltage divider whose input is connected to the sensor output of the network voltage, and the output to the input of the second terminal, the third and fourth adders, the first inputs of which are connected to the output of the second rectifier, and the second inputs The first comparator, the first input of which is connected to the output of the second rectifier, the second input is connected to the output of the first miter, and the output is connected to the first input of the first start-up and zeroing circuit of the integrator, the second comparator op, whose input is connected to the outlet of the reactor current sensor. and the output is connected to the first input of the second starting and zeroing circuit, the first integrator is the first 5 0 5 0 s About 0 the input of which is connected to the output of the third adder, and the second input is connected to. the output of the first starting and zeroing circuit of the integrator, the second integrator, the first input of which is connected to the output of the fourth adder, and the second input is connected to the output of the second starting and zeroing circuit of the integrator, the fifth adder, the first input of which is connected to the output of the first integrator, and the second input is connected with the output of the reference voltage source, the sixth adder, the first input of which is connected to the output of the second integrator, and the second input is connected to the output of the reference voltage source, the third comparator, the input of which is with the output of the fifth adder, and the output is connected to the second input of the first starting and zeroing circuit of the integrator, the fourth comparator, the input of which is connected to the output of the sixth accumulator, and the output is connected to the second input of the second starting and zeroing circuit of the integrator, the third rectifier whose input is connected with the output of the aperiodic link, and the output is connected to the first input of the fifth comparator and the first input of the sixth comparator, the seventh comparator, the input of which is connected to the output of the aperiodic link, the eighth comparator, the input of which with the output of the network voltage sensor, pulse distributor, the first input of which is connected to the output of the seventh comparator, the second input is connected to the output of the fifth comparator, the third input is connected to the output of the eighth comparator, the fourth input is connected to the output of the sixth comparator, the fifth input connected to the output of the second comparator, a block of pulse formers, the input of which is connected to the output of the pulse distributor, and the output connected to the control electrodes of the thyristors, the second input of the fifth comparator connected to the output house of the fifth adder and the second input of the sixth comparator connected to the output of the sixth adder t four( 45 47  WT V /, i, t3 2 J7 Z5 V I4 (4 ( d} ig2 (rigz "./ five fuf S6 fi.b 97 n n n n to II and n fig.c