Study On Power System Out-of-step Oscillation Based On Oscillation Energy Flow

More and more interconnected and larger networks nowadays not only make contribution to resources’ proper scheduling and power system stability, but also raise new challenges to the synchronous operation of the whole system. When the disturbance is too severe for the system to maintain its integrity, it’s vital to prevent the total black outage, damp the oscillation and guarantee the continuous power supply for critical loads. As a significant part of the third and also the last line of defence for power system, out-of-step separation strategy has been widely used in China.Out-of-step oscillation problem belongs to problem of large disturbance transient stability. During out-of-step oscillation process, electrical quantities vary too dramatically that traditional analysis methods for small signal stability are no longer appropriate. Taking advantage of direct method, this paper investigates dynamic interaction between out-of-step clusters and migration rules of out-of-step center from the perspective of energy. At first, energy structure is briefly introduced, from witch oscillation energy flow is derived between two out-of-step clusters. Then, a further study is performed on the connection between variation rules of oscillation energy flow and power system stability in two-cluster and multi-cluster cases. At last, a novel out-of-step criterion is proposed based on oscillation energy flow. The separation criterion proposed in this paper is convenient to apply in reality and capable of capturing out-of-step interface correctly, which will sure make contribution to the stable operation of power system. Real network simulation proves the validity of the criterion proposed.