SU748653A1 - Device for regulating reactive power in three-phase ac mains - Google Patents

Description

(54) DEVICE FOR REGULATION

REACTIVE POWER IN THREE-PHASE AC NETWORK

The invention relates to the field of distribution of electrical energy, namely, the regulation of reactive power in networks, and can be used in enterprises that consume electrical energy.

A device for regulating reactive power in AC networks is known, which contains a chain connected to an AC network from a series-connected capacitor, parallel-connected thyristors and a transformer l. A disadvantage of the known device is the low efficiency due to the heating of the secondary winding of the transformer. In addition, the known device is cumbersome. The closest technical solution to the invention is a device for controlling reactive power in AC networks, comprising a chain connected between the network phases of series-connected capacitors.

anti-parallel thyristors and throttles, which is included in the forced switching unit j2j.

A disadvantage of the known device is the low efficiency due to its complicated circuit and the large energy loss in the fossel.

The purpose of the invention is to improve the efficiency of the device.

Claims (2)

This is achieved by the fact that a power control device in a three-phase AC network, containing a series-connected capacitor connected to the interphase of the network, counter-parallel-connected tyriptora and a choke, connects sequentially-connected additional capacitor and counter-parallel-connected thyristors, which are connected in parallel to the main serially connected capacitor and anti-parallel thyristors. In addition, it is equipped with the second and third additional capacitors, which are connected in star with the first additional terminal and connected to the phases of the network without capacitors. FIG. 1 shows a circuit diagram of devices a, fig. 2 - timing diagrams of the voltage Uj.g of the network, voltage across the capacitor Jf. switched circuit, current through the switched circuit capacitor, voltage across the capacitor U of the additional circuit. A device for controlling reactive power in three-phase AC networks, between the two phases of a network, is connected in series to a capacitor 1, which connects thyristors oppositely in parallel. 2 and 3 and fossel 4. Condenser I and thyristors 2 and 3 form a switched circuit 5. Parallel to switched circuit 5, an additional circuit is connected from a series-connected capacitor 6 and counter-parallel connected thyristors 7 and 8. To the point of connection of the capacitor 6 to the thyristors 7 and 8, one plate of capacitors 9 and 10 is connected, the others are connected to the mains phases. In addition, the capacitance of the capacitor 1 is significantly greater than the capacitance of the capacitor 6. The device operates as follows .. Until the time point (see Fig. 2), when, for example, the polarity of the mains voltage corresponds to that shown in FIG. without brackets, the thyristor 3 is open and the capacitor 1 is charged from the mains through the choke 4 and the thyristor 3. At time t, the thyristors 2 and 8 are opened. From this moment the condensation begins to recharge. torus 6 along circuit + capacitor I - thyristor 8 - capacitor 6 - - capacitor of torus 1 and from the network through choke 4, thyristor 8, capacitor 6. When the capacitor 6 is recharged, thyristor 3 is quickly locked because its anode current flows lower the magnitude of the holding current, and the reverse voltage is applied to the anode of the thyristor 3. Throttle 4 as well. the network inductance prevents a sharp drop in the network voltage during switching. After locking the thyristor 3, the reverse voltage of the network turns on thyristor 2. Capacitor B continues to charge from the network through choke 4 and thyristor 8 to an amplitude value of the network voltage, at which the thyristor 8 is closed. In the period of time), the capacitor b part 50 is discharged (see curve 11 in figure 2 through capacitors 9 and 10 and the voltage across it approaches the phase voltage of the network (see curve 12 in figure 2). the voltage applied to the thyristors 7 and 8 also decreases, In my ment of times t, if the mains voltage is equal and the p and voltage across the capacitor 1 (Jf, turn on the thyristor 2, as a result, the capacitor 1 is connected to the mains phases again and creates a current flowing into the network. At time t, the voltage of the network U, and thus the voltage across the capacitor 1 U, is It goes to O, and TOKi is condensed in .1 flowing into the network reaches its maximum value. From this moment the capacitor 1 starts to charge (the polarity of the line voltage is shown in brackets in Fig. 1.) At time tg. and thyristor 7. From this point on, capacitor b recharges again and thyristor 2 is quenched similarly to time t ... At time tg, when the voltages U are equal, open thyristor 3, as a result of which the capacitor 1 is again connected to the mains. At time t -, the network voltage (and, thus, the voltage on the capacitor 1 and decreases to 0, and the current 1 through the capacitor 1 flowing into the network reaches its maximum value. From this moment the device returns to the state which is before the time ty |. The described processes are repeated, they are interrupted each time of the mains voltage. By selecting the turn-on and extinguishing voltages of thyristors 2 and 3, the time period when the capacitor 1 is connected to the mains and the average current through the capacitor I flowing into the network. In this case, the reactive power is controlled in networks. The proposed device has an increased efficiency as compared with the prototype, since it is simpler according to the scheme, Sfosel is used for much lower power and thyristors of lower voltage class are used. A device for controlling reactive power in a three-phase AC network, comprising a series-connected capacitor connected between the phases of the network, an anti-parallel 5,748, then the included thyristors and a choke, which distinguishes in that, in order to increase efficiency, it comprises a series-connected additional kontsensator and antiparallel connected thyristors, which are connected in parallel with the main condenser and connected in series-parallel thyristors vklk chennym. 2. The device according to claim 1, characterized by the fact that, in order to reduce the voltage of the thyristors, it is equipped with a second and third primary capacitors, which are connected in star with the first additional capacitor and connected to the phases of the network without capacitors . Sources of information taken into account during the examination 1. USSR author's certificate N9 275212, CL H 02 T 3/18, 1964. 2. USSR author's certificate number 574817, cl. H 02 T 3/18, 1977 (prototype). / -. . ; W oh L 3 g vn / ..J ± i -five