A Fast Positive Sequence Components Extraction Method with Noise Immunity in Unbalanced Grids

Fast and accurate acquisition of voltage components is the basic requirement for grid-tied inverters to realize various control under unbalanced grids. In view of this situation, a delay sampling period filter, which rapidly separates each voltage component by delaying two sampling periods in dq frame, is proposed in this article. In view of the noise interference, a delay operation period filter (DOPF) is proposed to scale the operation period and limit the noise to an acceptable range. The complete positive sequence components (PSC) extraction method based on the developed DOPF+ moving average filter (MAF) algorithm is presented, combing the advantages of DOPF and MAF for eliminating the double-frequency ac components and high-frequency noise, respectively. Finally, the feasibility and priority of the DOPF+MAF algorithm and PSC extraction method have been verified by the physical experimental results.