Improved Frequency Estimation Algorithm Based on the Compensation of the Unbalance Effect in Power Systems

This article proposes a frequency estimation algorithm that effectively cancels the effect of unbalance in a three-phase power system. Precise frequency estimation under unbalance conditions is very difficult to achieve since a negative-sequence component distorts the spectrum of the phasor of three-phase voltage signals. In this article, two parameters of the negative-sequence component are analytically compensated by introducing a modified periodogram, i.e., the phase parameter is removed, and the magnitude parameter is converted into a scaling factor. Rapid and precise frequency estimation is achieved by applying an iterative spectrum peak searching method to the modified periodogram. To verify the performance of the proposed algorithm, computer simulations were performed with various unbalanced and transient reflected signals. The results of the simulations confirm the accuracy and rapid convergence performance of the proposed algorithm.