A Synchrophasor Estimation of Power Systems Considering Three-phase Amplitude Imbalance

Abstract

When the distribution network occurs fault or the three-phase load is unbalanced, the measurement accuracy of the phasor measurement unit (PMU) will decrease due to the influence of the unbalanced current/voltage signal. Accordingly, a synchrophasor measurement algorithm considering three-phase amplitude imbalance is proposed to improve the estimation accuracy under three-phase amplitude imbalance. Firstly, the discrete Fourier transform (DFT) is used to identify the amplitude imbalance phase and pre-estimate the amplitude imbalance coefficient. Then, by expanding the Taylor model and combining the mathematical transformation, the Negative-Twice-Frequency Component (NTFC) generated by DFT is eliminated. Finally, an accurate phasor measurement result is obtained through offline matrix calls and error correction steps; The signals defined by IEEE Standard C37.242-2013 are adopted to verify the performance of proposed algorithm. The simulations show that the proposed algorithm is valid under three-phase amplitude imbalance, and the measurement fluctuation is significantly reduced with a reasonable increment in computational burden.