METHODS OF IMPROVING TRANSIENT STABILITY
Methods that improve the transient stability
The transient stability of power systems is a nonlinear problem, from the past the power system was only confined to planning and design but now a days the transient stability studies are important both in operational planning as well as real-time operation. “Transient” means changing.
So for transient stability the system stage is changing where if the transition is considered from one equilibrium to the other then due the large disturbances occur. So improving the transient stability is the main requirement.
THERE ARE VARIOUS METHODS OF IMPROVING TRANSIENT STABILITY THESE ARE :-
By the Joint Usage of DC System
In parallel ac-dc systems the stability problem generally occur so the researches has been done and according to that results are obtained by an experiments on the artificial ac and dc transmission facilities were the dc power of steady state is more as compared with the ac power, with improved transient stability. The transient stability is improved if the dc power is rapidly increasing in case of faults in the ac system. In 3-phase short circuit the sending ac system results in a serious decrease of the dc power which causes the generator to accelerate at the sending end. Two control methods are present for the countermeasure.
By using UPFC
This paper mainly gives the answer to the following question: How to unified power flow controller (UPFC) parameters and how it should be controlled in order to achieve the maximal desired effect for solving first swing stability problem. These types of problems mainly appear for bulky power systems with long transmission lines. There are various methods of reference identification of the series part, in order to improve the transient stability of the system based on: optimal parameters, state variables and also injection models were studied. Finally, a method based on state variables and using the local measurement was proposed.
By using multiple models and switching
Most common problem in adaptive control is the poor transient response which is observed when adaptation is initiated. Here a stable strategy is developed for improving the transient response by using multiple models of the plant for controlling and switching between them. These models are identical except for initial estimates of the unknown plant parameters and control is applied to determine at every instant by the model which best approximates the plant. Result which we get after simulation indicates the improvement in performance that can be achieved.
Transient Stability Simulation by the Waveform Relaxation Methods
In this a new methodology for power system dynamic response calculations is presented. This technique is known as the waveform relaxation which is extensively being used in transient analysis of VLSI circuits and it can take the advantage of new architectures in computer systems such as parallel processors and gives the computational results.
By the phase-shift insertion
The computational studies of transient stability of synchronous machines are connected to an infinite bus bar by a double-circuit transmission line and are used to illustrate the effect of relative phase-shift where the insertion between the machine and its associated power system takes place. This method of obtaining a change in the effective rotor-excitation angle and thus the power transfer is described together with an outline of possible methods of implementation by a phase-shifting transformer in a power system..