SU1210177A1 - Compensator of reactive power - Google Patents

Description

The invention relates to electrical engineering and is intended to regulate reactive power in electrical networks.

The purpose of the invention is to reduce the installed capacity of the equipment.

Figure 1 shows the basic circuit diagram of the reactive power compensator (CRM), figure 2 shows idealized time diagrams of currents and voltages that explain the operation of the compensator.

CRM (Fig. 1) consists of a three-phase thyristor bridge converter 1, formed from thyristors 2-7, a three-phase thyristor bridge converter 8, formed from thyristors 9-14, a smoothing droplet 15, the midpoint of which is connected to the short-circuited output direct current of a three-phase thyristor bridge converter 1, commuting thyristors 16 and 17 connected to the outputs of a smoothing throttle by 15 different electrodes, a storage capacitor 18, additional diodes 19 and 20, two control thyristors 21 and 22 of an additional capacitor 23 shunted by a diode 20, control throttle 24, an additional source 25 of direct current and an additional capacitor 26 shunted by a diode 19, with diodes 19 and 20 being switched according to the direction of the switching thyristors 16 and 1 a The polarity of the additional source 25 of the direct current is matched with the polarity of the commutating thyristors 16 and 17 and the source 27 of the direct current, to the midpoint of which the control choke 24 is connected

In addition, the axes are shown (fig 2): 28 - phase voltages U, U | v, Uc; 29 - phase currents from 30 - voltage U, (i and U, respectively, of capacitor-accumulator 18, capacitor-accumulator in the circuit of the known compensator 1I network, as well as the voltage value Ut and Urt, - the maximum voltage value of the network U; 31 - voltages and,; y, and and respectively on additional capacitors 23 and 26J 32 - voltages Ugi5 and, respectively, on the smoothing choke 15 and on the smoothing choke in the well-known compensator circuit.

772

The device works as follows.

Suppose that at time point b the thyristors 2-7 and 9-14 are locked, the throttle current is 15 | y, 5 is closed through switching thyristors 16 and 17 and an additional DC source 25, the voltage (Jc on the capacitor drive 18 is equal to the maximum The value of Ucm is negative, which corresponds to the polarity indicated in Fig. 1, the voltage of the capacitor 26 and the emf about / 5s the contractile throttle 15 is equal to its maximum value and opposite in the direction of Ucinf iShfl ft, the voltage of the additional source 25 of direct current, and the voltage Uci capacitor 23 equals about zero.

Let at time ti (Fig. 2) unlocking pulses are applied to thyristors 2 and 9. At the same time, under the action of a voltage dU - (Ucm-Uf, -UnO, where Ui-n is the network voltage between phases A and C at the moment time t, thyristors 2 and 9 will open and a switching current arises along the circuit: the middle point of the smoothing throttle 15, thyristor 2, phase A and C of the network, thyristor 9, capacitor-drive 18 and current circuit circuit section O, where the current will be pass along two parallel branches: point d, capacitor 26, switching thyristor 17, section bd of the smoothing other Scelle 15 and the point d, a capacitor 23, a switching thyristor 16, Cu smoothing choke portion 15, with the current values in each of the parallel branches are equal

As a result, the current in the switching thyristor 16 will decrease to zero and it will close, and the switching current in the da section will flow n next. two parallel branches m: point d, capacitor 26, switching thyristor 17, segment b. smoothing throttles 15 and point d capacitor 23, additional source 25 of direct current, switching thyristor 17, section L a smoothing (1 drossel 15, and switching current i (will be distributed in parallel branches depending on voltage across capacitors 23 and 26 J, which at this time will recharge until the voltage on the capacitor is 23

3

Uc-1 will not reach the value of l cirrr l-ft and the voltage of the capacitor 26Uc7. He will become equal; zero, and the entire current will be closed along the circuit: capacitor-accumulator 18, diode 19, commutating thyristor 17, section bd of smoothing throttles 15, thyristor 2, phase A and C of the network, thyristor 9, capacitor-accumulator 18. A recharge will begin the storage capacitor 18 and by the time t its voltage will change to a value.

At time 12, a triggering pulse is applied to the control thyristor 21, which opens under the influence of the voltage –UK and in the control throttle 24 a current io 2i 5 closes along the circuit: capacitor drive 18, diode 19, control thyristor 21, section (-) О

direct current source 27, control choke 24, storage capacitor 18. In this case, the total current of the storage capacitor 18 will be equal to the sum of the currents of the smoothing throttle 15 and the control throttle 24ig2 i ,, and therefore the process of recharging the storage capacitor 18 is accelerating. By the time tj, the voltage of the capacitor-accumulator 18 will change from -UK Lo + U (, and the control throttle current. (And therefore the control thyristor 21 will decrease to zero, the control thyristor 21 will close also during time ti, - tj, the voltage of capacitor 18 will vary only under the action of a smoothing throttle current 15.

. At time t (, when the voltage Uc on capacitor 18 reaches the value of the source, an unlocking pulse is applied to the switching thyristor 16, which opens and under the action of the voltage

uU - (Ucm T UVTI) in the above

. circuit: capacitor-drive 18,

774

the capacitor 23, the switching thyristor 16, the section of the smoothing throttle 15, the thyristor 2, fa, s and C of the network, the thyristor 9, the capacitor-drive 18 will generate a switching current of a different direction. As a result, the current in thyristors 2 and 9 is reduced to zero and they are closed, and the current of smoothing throttles 15 (415 is closed through commuting thyristors 16 and 17 and an additional DC source 25.

Similarly, including in turn the operation of other thyristor pairs 3 and 10, 4 and 11, 5 and 12, 6 and 13, 7 and 14, previously turning off the preceding thyristor pairs, as well as including equal periods of time LT, t, since In operation of each of the indicated thyristor pairs, control thyristors, and 22, we obtain the diagrams of currents and voltages presented in Fig. 2 in axes 29-32.

The regulation of the amplitude of the reactive current generated by the CRM is decelerated by changing the time of delivery of the opening IlCix pulses to the control thyristors 21 and 22.

In the process of operation of the compensator, the power consumed in the control circuit of the throttle 24 comes from the rectifier 25 and 27, and the sensibility is consumed in the chain of the throttle 15 directly from the supply network and from the rectifier 25.

The parameters of the additional capacitors 23 and 26 and the source 25 of the direct current are selected from the conditions of reliable switching. The installed value of additional condensates 23 and 26 does not exceed 5% of the installed capacity of the capacitor-accumulator 18 and, therefore, their inclusion of the circuit CRM does not lead to an increase in the total installed power of the power equipment and mass and size parameters.

ABC

Phage /

tj t2

FIG. 2

Claims (1)

REACTIVE POWER COMPENSATOR, comprising two three-phase thyristor bridge converters connected in parallel on the alternating current side, smoothing and controlling chokes, two switching thyristors, unlike electrodes connected to the terminals of the smoothing choke, a capacitor drive connected to the first three-phase short-circuit direct current output of the first end converters, two control thyristors and a direct current source, characterized in that, in order to reduce In order to reach the installed capacity of the equipment, it contains an additional DC source and two additional capacitors shunted by diodes, and the DC output of the second three-phase thyristor bridge converter is shorted and connected to the midpoint of the smoothing inductor, parallel to the other unlike electrodes of the switching thyristors are connected a chain of two additional capacitors connected in series with one another, with the diodes shunting them included o with switching thyristors, and an additional DC source connected in accordance with the polarity of the switching thyristors, moreover, to the other electrodes of the switching thyristors, in addition, opposite thyristors are connected by unlike electrodes, between the other electrodes of which an additional direct current source is connected, the polarity of which coincides with the polarity of the control thyristors, and the second end of the storage capacitor is connected to a common point of additional capacitors and the control choke is on chen between the midpoint of the DC source and the first end of the capacitor storage. SU <. „1210177