A Method Of Tracking Power System's Oscillation Center Based On Wide Area Information And Its Application

With the development of smart grid and increasing connection of power grid, maintaining the power system operating safely and stable is more essential than before. As a usual form of unstable, power system oscillation may cause power flow changing, voltage fluctuation or even power system collapse. Therefore, it is necessary for us to further study on power system oscillation in order to find out an efficient scheme including oscillation distinguishing, oscillation center determining and out-of-step islanding control. Almost existing schemes only using local electric quantities and they cannot meet the safety and stability requirement of complex power grid.The using of Wide Area Measurement System(WAMS), Phasor Measurement Unit(PMU)and Fiber Optical Communication in power industry has make it possible to synthesize and conduct wide area data. Through providing wide area electric quantities, WAMS can improve the accuracy of oscillation recognizing and oscillation center determine. Using the wide area information obtained from phasor measurement units(PMU), a method to track the power system oscillation center is proposed. According to the phase relation between bus voltage phasor and line voltage difference phasor, the proposed method can determine the position of the oscillation center and track it in real-time, not affected by the drift of the oscillation center. When the oscillation center transfers due to the occurrence of cascading faults or continuous trip-outs, the oscillation center can still be recognized and tracked. On this basis, a criterion for asynchronous oscillation and an islanding control scheme are put forward, and a wide-area measurement system based strategy to unblock the oscillation blocking of distance protection is designed. The effectiveness of the proposed method is validated by simulation results.