Accurate Phasor Estimation During Power Swing

Modulation of voltage and current signals with low-frequency components during power swing creates difficulty in accurate phasor estimation. Sequence component-based relaying principles are therefore being affected. In this paper, fundamental and modulating frequency components are incorporated in phasor estimation formulation to improve accuracy. The method estimates the two frequencies first and then the phasor using the least-squares technique. As an application of the proposed method, the sequence component of current is used for the detection of an unbalanced fault during power swing. The method is tested for numerous power swing and fault conditions of a WSCC 9-bus system and compared with conventional methods.