Study on software phase locked loop for single phase active power filter

Active power filter (APF) is considered the most viable solution for harmonic and reactive power compensation as well for other power quality problems. The reference current/voltage estimation is of utmost importance in APF and several harmonic extraction techniques require synchronizing signal in phase with the utility supply. The proper acquisition of synchronizing signal is significant for precise operation of APF. In this paper the software Phase Locked Loop (SPLL) based on time domain coordinate transformation to obtain synchronizing signal for single phase APF is considered. Orthogonal signal generation based on first order all-pass filter and band-pass filter is applied to PLL algorithm. The importance of synchronizing signal and the discrete implementation of orthogonal signal generation structure are also discussed. Simulation and experimental results validate the analysis and discussions presented.