Phase Estimation of Harmonically Distorted Grid Voltage by Frequency Lock

A novel method of synchronization is proposed for the estimation of the phase of the fundamental component of harmonically distorted power line voltage. Whereas commonly used phase synchronization techniques depend on a multiplier to measure phase discrepancy, which results in frequency components causing ripple in the output phase estimation, the proposed method measures the phase error by directly subtracting the incoming signal from a one-cycle delayed copy of the signal. For a harmonically distorted signal, this produces a zero steady state error signal, and a ripple-free estimate of the line voltage phase. The principal feedback loop in the proposed method aims only at frequency tracking, whereas a sliding correlation is used to extract an estimate of the line voltage fundamental component, resulting in faster overall response, because the output estimate is not itself used in any feedback loop. Simulation results are presented to validate this proposed method.