Pmu-based Systems-of-step Splitting Research

The scale of power system interconnection has been increasing in recent years. When oscillation occurs in an interconnected power system, if there are no effective measures to identify and control, the oscillation will spread and result in blackout. It is an effective measure to split the system at proper spots to break off out-of-step state, and to prevent voltage and frequency collapse and ensure the stabilization of each subsystem. The split equipment is an essential device to prevent power system wide-area blackout when a serious fault occurs.Bus voltage phasors are important state variable which can be used to observe and judge stability of a power system. It is possible to realize real- time monitoring and control to power angles using GPS based PMU(Phasor Measurements Unit).In this thesis, changing characteristics of some electrical parameters of a power system during out-of-step is analysed. It particularly introduces traditional criterions. By analysising the buses voltage phase angles difference, which connect to the tie-lines in interconnection grid, an PMU based out-of-step criterion is proposed. Another method is also proposed to seize oscillation center based on the voltage phase angles difference of buses. Furthermore, the criterion that proposed in the paper is validated by emulator EMTDC and dynamic simulate experiment. In the end , it proposes split scheme based on PMU.