Wide-area frequency control during power system restoration

Abstract

One of important subjects in power system restoration that already is not addressed is frequency control. Operators are often concerned with the size of load and generation, which can be safely increased. With the emphasis on higher utilization of power systems, monitoring of its dynamics is becoming increasingly important. This requires information with higher accuracy and update rates faster than those usually provided by traditional SCADA systems. In addition, it must be synchronized over a wider geographical area than that provided by traditional protection systems. Nowadays, the introduction of Phasor Measurement Units (PMU) and Wide Area Monitoring Systems (WAMS) as well as advances in communication and computational equipment make it technically possible to monitor the stability of the power system online, using a wide area perspective. In this paper a novel method for frequency control during restoration is presented. Simulations were carried out on 39 bus New England system to verify the effectiveness of the proposed method. A single-machine equivalent for each power system island is computed online using PMUs. Using this model the progression of frequency stability after a disturbance is predicted, so suitable amount of load pickup or generation increase can be determined for the supervised island of the power system.