Research On Design Method Of Power System Stabilizer

With power system expanding, low-frequency oscillation problems have become increasingly prominent. Power system stabilizer (PSS) has been widely used as an effective method of restraining low frequency oscillation. The design of PSS parameters plays a key role in operation. In this thesis, research on the design of PSS parameter is conducted in detail.The traditional theory of PSS is based on negative damping theory and Philips-Heffron model by increasing damping to improve the stability of power system. Theoretically, the phase lag can be got by calculating the angle between the reference voltages to the transient voltage of the generator. However, the phase of the voltage of the generator is commonly used to replace the transient voltage. It is worth to be discussed whether this replacement can fit all the situations. This paper studied the transfer function of the terminal voltage and the transient voltage of the generator. The influence of the reference voltage, the initial value of state variables and mechanical power was discussed separately, to provide reference for the existing running condition of PSS.The active type of PSS is flexible to restrain oscillation. However, it works well only when mechanical power hardly changes compared with electric power. When the condition is not satisfied, adjusting the amount of mechanical power would cause big changes of reactive power oppositely, which means anti-regulation. This thesis theoretically studied anti-regulation problem. The equation between the reactive power and electromagnetic power was deduced to explore the inherent mechanism, to support the test in work spot and the stable operation of the system.For some anti-regulation problems still exist, the paper established a function about generator terminal voltage and mechanical power and a function about reactive power and mechanical power. The internal mechanism of anti-regulation problems is analyzed. And then this paper discusses the effects of anti-regulation factors, measures to suppress anti-regulation factors by example.A new controller, symmetric root locus controller, is raised here, also referred to as SRL controller. It solves the anti-regulation problems and that transient potential and terminal voltage are not entirely consistent in phase compensation PSS fundamentally. Later, in order to further increase its feasibility in practical application, the dimension reduction to SRL controller has been carried to simplify control, which means only keeping the component corresponding to rotation speed which is easy to get access to. Through simulation results, it proves to function well to guarantee the control results basically. Compared with the phase angle compensation PSS, effect of the two methods are discussed, indicating that the controller is effective and achievable.