SU1480014A1 - Method for compensation of exchange and reactive power - Google Patents

Abstract

The invention relates to the field of power engineering and electrical engineering. The goal is to expand the functionality of reactive power control in circuits with non-sinusoidal forms of currents and voltages. When compensating for exchange and reactive power, a compensator is connected in parallel to the consumer so that between the generator, on the one hand, and the compensator and the consumer, on the other, there is no or minimum energy exchange, i.e. the subsystem, consisting of a compensator and a consumer, must consume from the generator either only active energy or exchange energy in a generator-compensator section and the consumer is reduced to a fixed value. Reactive power is determined by the exchange energy, i.e. energy stored in the reactive elements at intervals when a transfer from the generator to the consumer occurs, or at intervals when there is no return to the generator. The exchange energy and reactive powers, assuming a constant intensity of the converter of electromagnetic energy to other types, are calculated using the formulas given in the description of the invention. The choice of the type of compensated exchange energy and reactive power depends on the mode of operation of the system and the requirements for energy compensation. 1 il.

Description

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The invention relates to power engineering and electrical engineering, in particular, to the compensation of reactive loads in general industrial and autonomous electric networks using static valve compensators.

The purpose of the invention is to expand the functionality when adjusting reactive power in circuits with non-sinusandal forms of currents and voltages.

The drawing shows a structural diagram of the compensation device that implements the proposed method.

The compensator circuit contains generator 1, consumer 2, voltage sensor 3, current sensor 4,

blocks for isolating zero values of voltage 5 and current 6, multiplier 7, calculator 8, subtraction unit 9, reference voltage source 10, pulse shaper 11, key elements 12-15, accumulator 16.

The method of compensating for exchange and reactive power is as follows.

When compensating for exchange and reactive power in accordance with the proposed method, the compensation is performed using a device connected in parallel to the consumer so that between the generator, on the one hand, and the compensator and the consumer, on the other, there is no or minimum energy exchange. i.e. the subsystem, consisting of a compensator and a consumer, must consume from the generator either only active energy or exchange energy in a generator-compensator section and the consumer is reduced to a fixed value.

The widespread use of valve converters in power supply systems and power supply systems leads to a significant distortion of current and pressure of the power supply network, which significantly complicates the work of both other consumers and electromagnetic energy generators. The development of reactive power compensation methods based on real, physical processes in a system with valve converters, which allow to take into account the generation and consumption of reactive power not only on the main, but also on higher harmonics of the signal and described by fairly simple integral relations, circuits with non-sinusoidal currents and voltages are important and relevant.

It is advisable to create a reactive power compensation method on the basis of the determination of reactive power in accordance with the exchange processes in the scheme. Then the reactive power is determined by the exchange energy, i.e. energy stored in the reactive elements at intervals when energy is transferred from the generator to the consumer (t), or at intervals when energy is not returned to the generator (t + t °). The exchange energies Ma & , WoM, W06a and jet powers

O, Of, Q, assuming a constant intensity of conversion of electromagnetic energy into other types, are calculated by the formulas

W D6 - (1) W 06, P (t + .t °) - (2)

W

Of, 1

P t - P (t + t °); (3)

5 0 5

0 from 0 $

0

five

and Јttoe. 0 "XojH.

H t h 1 t 2 t

(four)

where P is the average for the period the value of the positive instantaneous power;

Р - the average for the period value of negative instantaneous power;

t is the sum of the time intervals at which the instantaneous power is positive; t is the sum of the time intervals at which the instantaneous power is negative; t ° is the sum of the time intervals at which elements of the system are disconnected from each other; T is the instantaneous curve period

power; T t + t ° + t. If the exchange power W oe characterizes the exchange processes in the system in the absence of the interval t °, whereas the contents W 55,, W os characterize the exchange processes from the generator or the consumer, respectively. The choice of the type of compensating exchange energy and reactive power (expressions (1) - (4)) depends on the mode of operation of the system and the requirements for energy compensation. The compensation of the exchange energies W og, W of,, Wo6i and the corresponding reactive powers Q, O ,, O g is identical. Consider the compensation of W 66 and 0 values (expressions (1), (4)).

To determine the integral characteristics of the compensation, it is first necessary to measure the instantaneous values of the consumer current i (t) and generator voltage U (t). Using the obtained functions i (t) and U (t), the instantaneous power values (P (t) U (t) i (t)) are calculated. The function is integrated

5G

instantaneous power P (r) over time intervals tr and t corresponding to positive and negative values of instantaneous power. In this case, the averaged signals P + and P corresponding to the result of integration are stored, and the stored values of the signal are stored during the integration intervals. The time intervals tf and t, corresponding to the positive and negative values of the instantaneous power, are determined by the moments of transition through zero voltage and current.

Next, the calculation of the exchange energy W 06 by the formula (1), as the difference of the stored signals over the integration intervals, is performed. The reactive power O is determined by formula (4) over the period of the instantaneous power curve. The calculated integral values are compared with the reference ones and get the values 4W for W06 w OB but 0; l Q Q Q Number 7 0. In the particular case

her how

 Oh Q

mo "

 0

If O ko / i (Q zero,) 2 0, then partial compensation of exchange (reactive) power is performed; if w is OB WHO (WHO) °, then full compensation of the exchange (reactive) power is made. For full or partial compensation of exchange and reactive power, it is necessary to use a cumulative element that, at intervals of negative instantaneous power at the terminals of the consumer, receives energy from the consumer and at intervals of positive instantaneous power at the terminals, the bittel transfers energy to the consumer. The storage device should include measures that exclude energy consumption from generators. The duration of switching on the storage device in the modes of consumption or generation of electromagnetic energy is determined by the value of HYOR, the speed of charge and discharge of the storage device. Consequently, in accordance with the compensation method, energy is stored at intervals of negative instantaneous power and recovers accumulative energy at intervals of positive positive power of the consumer.

8001 4b

In case you can put

t + h..r

P3 “p (t) dt EH-PCP L z.p awo6;

of

Yu with „m + -t Р05р

S PPa (t)

 cp pasp fl 06

MPS

five

0

five

0

five

0

five

0

five

p.

pa er

where tpj (t me) is at the beginning of the charge (discharge) accumulator;

t,. (t D "5p) duration of time

3 p / N

charge (bit; accumulator;

(t) is the instantaneous power of charge (discharge) of the storage ring;

psr. cf (roroere) average values of charge power (discharge) of the accumulator.

In order to improve the harmonic composition of the current and voltage, it is necessary to vary the times t Hi and t and the RP, the choice of which is determined by the specific type of consumer and generator. In this case, the intervals t3ap and t pa5p may consist of several subintervals that are not interconnected. The elimination or reduction of the energy consumed by the generator leads to the fact that the harmonic composition of the currents and voltages in the power supply system improves.

The invention is illustrated by the following embodiment of the device shown in the drawing and implementing the proposed method of compensating exchange and reactive power.

The cross section of the system comprising generator 1 and consumer 2 includes voltage sensors 3 and current 4 of the proposed compensation device.

The entered sensors 3 and 4 carry out galvanic isolation, matching the levels of the power circuits and the measuring part of the device, as well as the instantaneous values of the voltage U6x (t) and current ig) (t) at the input of the consumer 2. The output voltage of the sensor is 3 U ", . „(T) proportional

f /

measured voltage (Uewx} (t) ° Ui et (O) and 4 U Bb sensor | X4 (t),

proportional to the measured current

(U BHxttt) L; The inputs from the sensor outputs also go to the input of the multiplier 7, at the output of which a signal is proportional to the instantaneous

power P (t) about (4 MUU) A i l / s) “The output signal of the multiplier 7 enters the transmitter 8, which programmatically calculates the exchange energy by the formula (1). If it is necessary to compensate the exchange energies W 06, ..., W 061, then the calculator 8 implements the calculation programmatically using expressions (2) and (3). The output signal from the calculator 8 is fed to the non-inverting input of subtraction unit 9, the inverting input of which receives a signal proportional to W 06 пю # (in the particular case of W 06 num 0, the value of this signal is zero). The magnitude of the signal, proportional to W06 NOL1, is set with the help of source 10 of adjustable voltage.

The output signal from the dWe6 subtraction unit 9 is fed to one of the inputs of the shaper 11 pulses, to the other two inputs of the puller 11, the output signals of the voltage zero and 5 current extraction units 6 are received.

In accordance with the information received at the inputs of the pulse former 11, as well as information about the values of tW3, t3ap, tMps, t ro19p entered in advance in block 11, and also depending on the type of consumer 2, accumulator 16, and possible operating modes of the consumer 2 , at the outputs of the pulse generator 11, control signals are generated for fully equalized key elements 12-15. The key elements 12-15, according to signals from block 11, control the mode of operation of accumulator 16, which, in a particular case, relative to its output

terminals can be represented by a current generator. In accordance with the state of the key elements 12-15, the accumulator 16 either accumulates energy (the key elements 12, 15 in the conducting state, 13, 14 in the non-conducting state), or transfers energy to the consumer (the key elements 13, 14 in the wire state, 12, 15 in non-conducting state).

Claims (1)

Invention Formula The method of compensating exchange and reactive power, which measures the instantaneous current values of the consumer, the instantaneous values of the generator voltage, multiplies the instantaneous values of current and voltage, determines the value of the instantaneous power, integrates the product of these signals over time intervals positive and negative values of the instantaneous power, remember the averaged signal corresponding to the result of the integration, store the stored values of the signals for and integration intervals, characterized in that, in order to extend the functionality of controlling reactive power in circuits with non-sinusoidal forms of currents and voltages, time intervals corresponding to negative and positive values of the instantaneous power are determined by the transition moments through voltage and current zero, determine the value of the exchange energy as the difference of the stored signals over the integration intervals determine the reactive power over the period of the instantaneous power curve, store energy at the intervals of negative instantaneous power and return the accumulated energy at the intervals of the positive instantaneous power of the consumer.