Transient Stability Analysis Of Interconnected Power Systems

With the rapid development of electrical power industry makes the scale of power system grows increasingly, and the severity degree of power grid accident increases, a great number of power system security and stability problems emerge. Therefore, it is necessary that the factors affecting the stability of power system and the coordination of power system and power units be analyzed. In this paper, the influence of unit inertial time constants on interconnected AC power gird transient stability level is researched and the method of power system emergency control is studied and improved, then, the correctness of theoretical analysis results is verified by simulation researching.Based on transient energy function, by means of mathematical deduce for equivalent two-machine system and analysis on its transient stability, the influences of unit inertial changes at both terminals on transient stability level of the whole system under various operation modes are researched, and respective influences of terminal unit inertial changes on transient stability of the whole grid are compared, besides, it is found that the influences of unit inertial time constants on system transient stability level are relevant to load level and initial operating condition of the power grid. Based on theoretical analysis, simulation of concerned examples under various operation modes is performed and the correctness of theoretical analysis results is verified by simulation results.For improving the result of power system transient stability control, the control variable weights of optimal generator-shedding control are regulated reasonably in this paper. In this paper, the generator-shedding control variable weights are regulated based on the influence of the inertia changing on the transient stability level, then, the order of generator-shedding is changed, some generators may have priority to be shed, and some may avoid being shed, and when the generator-shedding control is finished, power system transient stability level could be raised. This method improves the result of generator-shedding control, and its physical meaning is definitive. The effectiveness of regulating the control variable weight according to the influence of generator inertia on power system transient stability level is verified by the simulation results of IEEE-39bus system.