SU858175A1 - Method of increasing stability of electric systems - Google Patents

Description

one

The invention relates to power engineering, in particular, to emergency control of power systems, and can be used to improve the dynamic stability of a generator (power plant) in the event of a short circuit on a power line connecting a generator to a receiving power system, disconnecting it with relay protection devices and subsequent automatic reclosing Auto Recloser.

There are a number of methods for improving the stability of electrical systems by abruptly changing the voltage phase, according to which the phase change is carried out by alternately switching generators to adjacent transformers with a pre-selected connection group of windings or by switching phases on a damaged power line in the AR cycle, and then on other shunting power lines

and 2.

The disadvantage of these methods is their complexity and the need to install additional expensive equipment and switching equipment.

The closest in technical essence to the present invention is a method of increasing stability by phase control, which consists in increasing the possible deceleration site of a generator in a transient process during an outage and subsequent reclosing of one of the lines connecting the transmitting and receiving power systems by means of changing the winding junction group tori

The disadvantage of this method (as well as the previous ones) is the discreteness of the effect and the associated decrease in the efficiency of phase control by the transient process.

The purpose of the invention is to increase the efficiency of phase control,

20 The goal is achieved by setting the phase shift angle of the phase-adjustable transformer disconnected from the network in the pre-emergency mode to the position above the current generator load, and plugging it into the network during the dead time of the automatic reclosing. After the termination of the transient output, the phase regulator is gradually switched to the position of zero phase displacement - and then disconnected from the network. Phase regulating transformers with a mechanical switching system of adjusting windings have a relatively long switching time (compared to the dead time of the automatic reclosure). The time required for the transformer to move from the zero phase shift position to the desired position may exceed the reclose pause time. Therefore, the control system continuously monitors the load of the generator and in accordance with it sets the phase regulator to the required position. As a result of the proposed sequence of operations, a device with a relatively large intrinsic action becomes an element of a high-speed control system. FIG. Figure 1 shows a graph characterizing the stability conditions in the absence of phase control; in fig. 2 - the same, with phase management; in fig. 3 is one of the possible variants of the method implementation scheme. The initial mode is characterized by an angle corresponding to the cross point of the angular characteristic of the power P f () with the load direct P PQ (Figures 1 and 2). Angle 5 corresponds to the moment of automatic re-injection. When the mode is stable. With SfSnp, the stability of the mode is broken. The area of the figure abed describes the acceleration energy of the rotor), the area of the figure bef is the braking energy (). Angle (Control determines the angular mismatch of the rotor axis at the moment of AR, the system is on the stability boundary. The critical angle is dLj T, - tf-o. ), Boundary conditions of stability pr this follow from the following equalities

i V PmSinS) dS

The integration and subsequent algebraic transformations of this equality give

np.

The phase offset angle 0 as a function of the starting angle- (Jg (FIG. 2)) is expressed as

9% p-V tvl gf o)

After the switch 1 is turned off and the switch 2 is turned on, the phase-control circuit is ready for operation, at the moment the line is turned on again by the switch the angle characteristic

power is shifted by

angle 9.

At the end of the transition process, the phase control switch switches gradually to the 0 ° position, after which the switch 1 is turned on and the switch 2 is turned off. The control system of the switching contacts 4 and 5 again begins to work on function B f () and prepares the phase control circuit

Claims (3)

to the next cycle of action. From the comparison of FIG. 1 and 2, p, in the case of optimal phase control, is always greater. Due to this, the pause of the ARC can be increased and the speed requirements of the relay protection can be reduced according to the stability condition of the post-emergency mode. The phase impact circuit (Fig. 3) includes a switch 1, which is a switch of the switching mechanism, a switch 2, which is a switch of the circuit, a phase regulating transformer 3 with switching contacts 4 and 5. The phase control of the dynamic transition is carried out in the following way, the line switch is in the on state. In this case, the switch 1 is on, and the switch 2 is off. Thus, the phase-controlled transformer 3 is taken out of action, and its switching contacts are bounded by the contacts of switch 1. However, the control mechanism of switching contacts 4 and 5 operates, ensuring that their position corresponds to the phase shift angle & . Thus, the phase-shifter at any moment of time is prepared for switching on with angle © corresponding to a specific value of the generator load. In the event of a short circuit on the line, the linear switch is turned off, the switch 1 is turned off and the contacts 4 and 5 are disconnected to empty pause, and the switch 2 turns on and prepares the phase control circuit for operation at the angle of time prior to the accident. Switching on switch 2 is permissible only after switching off switch 1, since a phase-controlled transformer with shunted switching contacts set to a position providing an angle E, other than 0 ° F, represents a short-circuited circuit. Thus, the proposed method provides effective control of the generator transient in order to increase stability using a phase-controlled transformer. 1. Method for increasing the stability of electrical systems by creating a phase displacement to compensate for the angle of departure of the generator rotor during the dead-time reclosing period, in that, in order to improve the phase control efficiency, this phase clutch is provided by setting the phase-shifting phase-shifting angle transformer, disconnected in advance mode from the network, to the position corresponding to the current value of the generator load, and its inclusion into the network during the dead time period PT. 2, the method according to claim 1, so that after the completion of the Transient, the phase-controlled transformer is gradually shifted to the position of zero phase displacement, and then disconnected from the network. Sources of information taken into account in the examination 1. The author's certificate of the USSR 449419, cl. H 02 J 3/24, 1972. 2. Authors certificate of the USSR 508856, cl. H 02 J 3/24, 1973. 3. USSR author's certificate (And 176624, class H 02 J 3/24, 1964. PmStnf оfo. „$ Tn () / yV7 cz