Research On An Adaptive Power System Stabilizer

With the development of national economy, the number of long-distance transmissionlines and large-capacity power plants is increasing day by day. The size of the powersystem is growing, and closely linked. Accordingly, this induced the problem oflow-frequency oscillations which have a very bad effect on stability of power system.Power system stabilizer (PSS) is important equipment for damping low-frequencyoscillations. In order to get the damping requirements, PSS needs complex online tuningwork. But this online setting has a certain degree of operational risk, and cannot guaranteethe optimal damping at various frequency bands. Therefore, an adaptive power systemstabilizer (APSS) is developed in this paper. APSS consist of the parameter estimator andthe controller. Using the measurement data of system input and output, the estimatorestimates the system output, and determines the operation changes of the system bycompared with the actual output. Using the recursive formula to calculate the systemparameters, the estimator achieves the purpose of the system parameters identification. Atthe same time, the controller which is supplied continuously with values formed by theestimator, reconfigures the poles of the closed loop system by the automatic correction ofthe pole shift factor, and attempts to generate the controller signal required for optimumdamping. The APSS continually identify the system parameters that are as close aspossible to the real system, and automatically adjusts the controller output to achieve thebest optimum damping.In this paper, a contrastive simulation between the APSS and a conventional PSS iscarried out on a single machine infinite-bus power system under different disturbance. Theexperimental results have illustrated that the APSS can restrain the low-frequencyoscillating effectively and stabilize the power system when the system suffered from thosedisturbances. In this way, the design of this APSS has practical values.