Study On The Effect Of Static Excitation System On Power System Stability

More and more static excitation systems apply in power system, because their power get from the generator terminal, some scholars have a certain worry if static excitation systems get wide application. It has important significance to do the study on the effect of static excitation system on power system stability:Because of the power of the static excitation system getting from the generator terminal, the change of the generator terminal voltage will affect the performance of excitation. The thesis takes single machine infinite bus power system as the study object, in which one phase to ground fault and three-phase short-circuit fault which happen in generator terminal high voltage side is simulated, to analyze performance of static excitation system. Results show:when one phase to ground fault happens, the generator terminal voltage can keep in high level. After the fault removed, the terminal voltage can recover quickly. When three-phase short-circuit happens, the length of fault remove time delay has big effect on system stability. If the fault removes after a long delay, the generator excitation-loss protection may act in subsequent transient process, affecting the stability of the system.The static excitation system as a kind of fast and high gain excitation system, it is one of the important reasons for the low frequency oscillation. Therefore, the generators which adopt the static excitation system need to configure PSS to damp low frequency oscillation. In order to analyze this problem, taking a large area of interconnected power grid simplified network as the calculate object, analyzing the small disturbance stability base on eigen-analysis method when all the generators respectively adopt AC exciter excitation system and static excitation system. Analysis shows that, the system's small disturbance stability is bad when static excitation system without PSS, and worse than the situation that the grid adopt AC exciter excitation system. Since the static excitation system configures PSS, it can improve small disturbance stability of the system.In power system stable process, especially during power grid oscillation, the effect of static excitation system on system is widely concerned by people. In order to analyze the problem, based on an accident happened in a large area of interconnected power grid as the research object, the thesis builds the whole system simulation models by PCCAD/EMTDC, and does a simulation for this accident. The simulation results reappear certain phenomenon in the process of accident, such as power flow reversion, voltage fluctuation and power oscillation, which is helpful to further understand the accident. In this system, all the generators respectively adopt the static excitation (with PSS) and AC exciter excitation system. The simulation results show that, the static excitation system's ability in maintaining power system long-term stability is no worse than that of AC exciter excitation system. In grid oscillation process, the static excitation system can not cause voltage collapse and aggravate system oscillation, which have certain reference significance on the further understanding of the static excitation system's effect.