Frequency Multiplier Algorithm Based Fundamental Active Current Extraction and Phase Locked Loop for the Control of 3-Phase Shunt Active Power Filter

Control of shunt power active filter (SAPF) necessitates estimation of the fundamental active component (FAC) of load current and unit voltage templates (UVTs). In this paper, a frequency multiplier based FAC and UVT extractor is proposed, wherein the $\alpha-\beta$ quantities of load current and supply voltage undergo frequency multiplier action to obtain the respective components with fundamental frequency four times the power frequency. With the band pass filtering of these signals, the components corresponding to four times the power frequency are determined. Thus obtained current components are further processed to extract the FAC of load current. Similarly obtained voltage signals are used by the synchronous reference frame theory based phase locked loop for accurate UVT extraction with the help of the designed synchronizing logic. The comparative analysis performed using an experimental setup demonstrates faster dynamic response and accurate estimation with a developed extractor compared to earlier reported schemes. The performance of SAPF controlled with the proposed extraction algorithm is investigated in PSIM software. Further, experimental validation is also presented. The SAPF operation with the proposed control scheme ensures unity power-factor operation and adherence to total harmonic distortion (THD) limits by drawing sinusoidal currents from the grid.