SU773824A1 - Method of control of static reactive power source - Google Patents

Description

(54) METHOD OF MANAGEMENT OF STATIC SOURCE OF REACTIVE POWER

one

The invention relates to high-power switching devices with artificial switching and can be used to compensate for reactive power in power systems, in particular for the inverter part of an MHD generator.

A known method of controlling a static reactive power source is to unlock the auxiliary valve, lock the main valve of the previous phase, unlock the main valve of the subsequent phase, and close the auxiliary valve 1.

There is also known a method of controlling a static source of reactive power, which consists in opening the auxiliary valve of the previous phase, closing the main valve of the same phase, unlocking the next main valve, and closing the auxiliary valve of the previous phase 2.

These control methods have the disadvantage that with artificial switching on a switching capacitor, the voltage reaches twice the value, which reduces the reliability of the equipment and increases its installed power.

The closest in technical essence and the achieved result is a method of controlling a static source J of reactive power with artificial switching containing a main three-phase valve bridge connected to an AC network, to the terminals of which are connected shunt capacitors and an auxiliary three-phase valve bridge 10 connected through series capacitors to AC bridges of the main bridge, and the poles of both bridges are connected to a smoothing reactor, consisting in that they unbolt the whether auxiliary bridge at the beginning of the commutation interval, lock gates main bridge 3.

However, this control method has a disadvantage: at the moment of switching the valves, the voltage on them reaches twice the value compared to the nominal value, which reduces reliability and increases the installed power of the equipment.

The purpose of the invention is to increase reliability and reduce installed capacity.

The goal is achieved by the method of controlling a static reactive power source with artificial switching, containing a main three-phase valve bridge connected to an AC network, to the terminals of which are connected. Shunt capacitors and an auxiliary three-phase valve bridge connected via serial capacitors to the AC terminals of the main the bridge, and the poles of both bridges are connected to a smoothing reactor, consisting in that the auxiliary bridge valves are ortpirated the switching interval, lock the auxiliary bridge valve of the subsequent phase, lock the main bridge valve of the previous phase, control the polarity of the voltage on the auxiliary bridge valve of the previous phase, unlock the auxiliary bridge valves of the previous phase at the moment of polarity change and applied to it voltage, control the polarity of the voltage on the valve of the main bridge of the subsequent phase, unlock the valve of the main bridge at the time of changing the polarity of the voltage applied to it p., lock the auxiliary bridge valve of the subsequent phase, lock the auxiliary bridge valve of the previous phase.

FIG. I shows the power part of the reactive power source; in fig. 2 - summary waveforms of currents and voltages for one of the modes of the source of reactive power; in fig. 2a — voltages of a three-phase AC network, brought to the valve winding of the transformer; in fig. 26 - dependence of the smoothing reactor current on time t; in fig. 2c, d, d, are valve currents for phases c, a, respectively; in fig. 2e - voltage on the smoothing reactor equal to the potential difference Рд - f к; in fig. 2 the dependence of the voltage at the valve of the serial-phase bridge of the subsequent phase on time t; in fig. 2c shows the dependence of the voltage on the downstream serialized capacitor as a function of time t; in FIG. 6i shows the dependence of the voltage on the lock valve of the shunt bridge of the previous phase on time t; in fig. 2k - voltage dependence on the lock valve of the previous phase series bridge on time t; on fip. 2L is the voltage dependence of the serial phase capacitor of the previous phase; in fig. 2 m - voltage at the next valve of the shunt bridge of the subsequent phase; in fig. 3 - equivalent circuit of locking the main bridge valve at the beginning of the switching interval; in fig. 4 - equivalent circuit of locking the auxiliary bridge valve in the switching interval; in fig. 5 - diagrams of changes of potentials of points A, a, 8 in the switching interval.

In the drawings, the main valve bridge 1, auxiliary bridge 2, control unit 3, matching transformer 4, smoothing reactor 5, valves 6–8 of the cathode group of the main bridge, valves 9–11 of the cathode group of the main bridge, valves 12–14 of the anode group of the auxiliary bridge are indicated , valves 15–17 of the cathode group of the auxiliary bridge, shunt capacitors 18–20, series capacitors 21–23, voltage sources 24–26

 AC networks of phase A, B, C, respectively, the equivalent of 27 DC circuit and phase circuit, which in a given time interval does not participate in switching processes, with the generally accepted

assumption of unlimited inductance of a smoothing reactor, EMF

28 of the previous phase of the energy system, reduced to the valve winding, EMF

29 of the next phase, the inductive elements 30, 31 in the circuits of each phase, the presence of which is due to the dissipation current of the matching transformer, the inductance of the connecting lines and the current-limiting reactors.

Consider a sequence of operations in a single switching interval.

At the beginning of the artificial switching, the valves 13 of the auxiliary bridge of the subsequent phase are unlocked. In this case, a series-connected serial capacitor 22 and a shunt capacitor 18 of switched phases are connected to the valve 8 of the main bridge of the previous phase. A reverse voltage is applied to the lockable valve 8, equal to the difference of the voltages on the indicated capacitors due to the charges from the previous switching.

The reverse voltage action closes the valve 8 of the main bridge of the previous phase. The polarity of the voltage at the auxiliary bridge valve 14 of the previous phase is then monitored. At the time of changing the polarity of the voltage on the valve 14 from negative to positive, said valve is unlocked. The second switching stage starts, characterized by the fact that two valves are open simultaneously

 13 and 14 auxiliary bridge switched phases. The polarity of the voltage on the valve 7 of the main bridge of the subsequent phase is further controlled. At the time when the polarity of the voltage applied to the fan 7 from negative to positive is changed, the valve is unlocked. A series-capacitor 22 is connected to the valve 13 of the auxiliary post-phase bridge, on which a blocking voltage is created by the current and the valve 13 is closed. In addition, serially connected by a shunt capacitor 18 switched phases and a serial capacitor 21 of the previous phase are connected to the valve 14 of the previous phase. Under the action of a reverse voltage equal to the difference of the voltages of the two capacitors, due to the charges from the leaking switching, the valve 14 is closed at the end of the switching interval. The use of this invention reduces switching overvoltages, which increases reliability and reduces installed equipment power.

Claims (3)

1.Poese A.V. Schemes and modes of DC power transmissions. L., “Energie, 0 1973, p. 243-248. 2.Venikov V.A. and others. Static sources of reactive power in electrical grids. M., “Energie, 1975, p. 80-86. 3. USSR author's certificate for application No. 2324221/07 dated July 31, 76. i U2.t