Virtual Synchroscope: a novel application of PMU for system restoration

Power system restoration is well recognized as one of the key technologies to improve the reliability of power systems. Generally, the restoration process is divided into several stages as preparation, system restoration, load restoration, synchronization and inter-connection. Currently, re-closure of breakers is done by field crews with synchroscope. A novel methodology, entitled as “virtual synchroscope”, is proposed in this paper. By utilizing Phasor Measurement Units (PMUs), the proposed methodology compares phasors of voltages at connection points from the two islands with the accurately time-stamped measurements. By adjusting voltage magnitude, frequency, and phase angle in the control center, all the requirements for synchronization are satisfied and the synchronization can be implemented. A case study on a power system is presented to validate the feasibility of the proposed method. It is proved that the proposed method can meet the requirements of all standards and resulting in smooth synchronization.