Study Of Real-time Monitoring Of Power System Oscillations

With the fast development of national economy, the power system scale is increasing rapidly which proposes new requirements to the power system stability. Wide area synchronized phasor measurement based on global positioning system (GPS) is a new technique developed in recent years which is called one of three front subjects in power systems. Power system oscillations may bring periodic swing of node-voltages and endanger power system safety and generation sets, even destroy the stability of synchronized operation. The real-time monitoring and eliminating of power system oscillations are very important for enhancing the stability of synchronized operation. We can watch the entire system state in real-time by monitoring phasors of voltage and current of all key substations. This provides a powerful technique support to analyze dynamic control characteristics, dispatch economically, operate stably and control power system.The meaning of synchronized phasor measurement is to measure state variables of some substations synchronously by high precision clock, and to transmit results to main-station used for real-time monitoring, relay and control. The new technique is promoted by GPS that can keep time in the whole global regions synchronous accurately. The biggest error of GPS is not more than 1μs which provides time label to power system. We can say that synchronized phasor measurement can be realized rely on GPS.This thesis summarizes the concept and framework of the Wide Area Measurement Systems firstly. Then introduces the theory of synchronized phasor measurement based on GPS. Furthermore, the GPS-R power system dynamic monitoring unit is particular introduced, which can monitor the power angle of different generators and buses combined with PMU so that realize the wide area monitoring and control of power system. In this thesis, several filtering algorithms for measuring the amplitude and frequency of power system oscillations are compared. The filtering algorithm based on the raised cosine filter is detailed introduced. The measurement accuracy and speed are discussed for different parameters to get the best. The ability to measure the lowfrequency oscillation and the error under varying system frequency are farther discussed in the thesis. Simulation results verify that the algorithm based on the raised cosine filter has higher accuracy and faster speed.