Study On Parameter Identification Of Transmission Line And Thevenin Equivalent Based On PMU

The mathematical model of power system has been widely applied in power system planning and designing, operation and control, the inaccurate parameters of model would affect security and stability of power system. With the fast development of China’s electric power system, ultra/high voltage, large capacity and long distance transmission, interconnection network becomes more complex. For traditional methods to obtain model parameters such as theoretical calculations or off-line testing, et al, that could no longer meet the requirements. With the development of phasor measurement unit (PMU) and wide-area measurement system (WAMS), it opens a new path for on-line parameter identification. In this paper, parameter identification of transmission line and Thevenin equivalent is studied based on PMU data. Through analyzing the feasibility of π model for positive sequence parameter identification, robust recursive least square (RRLS) algorithm is proposed. For too many identification results, Kernel density estimation and point estimation is suggested to obtain statistical characteristics and the impact of the noise and errors in the measurement is discussed in detail. This paper studied the factors that affect the credibility of results, including the availability of practical PMU data, the impact of measurement error and high resistance, then the program is proposed by monitoring the voltage angle difference of both sides for transmission line identification. Meanwhile, two-step identification method is proposed for unsymmetrical transmission line by discussing the deviation of parameters and identifiability. At last, an improved deviation correction algorithm to track Thevenin equivalent parameter, four machine two area system and practical PMU data verify the effectiveness of the proposed method.