Dynamic performance improvement of a moving average filter based-PLL using PI and fuzzy controller

Abstract

In all grid connected applications, Phase locked loop (PLL) is used for synchronization. The main objective of PLL technique is to precisely fast estimate the frequency and phase, when the grid voltage is unbalanced. A variety of moving average filter (MAF) has been proposed in recent literature which helps in eliminating the effect of DC offset, characteristic harmonics, and unbalanced voltage. MAF is a linear phase finite impulse response filter which eventually acts as a low pass filter. After incorporating a Moving Average Filter into Phase Locked Loop, the open loop bandwidth is drastically reduced and it is proved by presence of lower order harmonics having a large MAF window width. A Differential MAF has been proposed which eliminate the lower order harmonics to narrow the MAF window bandwidth and it is achieved by adding a special component into MAF structure which online changes its value according to the frequency and it will not introduce any phase lag. DMAF helps in increasing the open loop bandwidth and improves the performance of MAF based PLL. In this work PI controller and FUZZY controller are implemented, and tested reducing the Total Harmonic Distortions, Because of using the Fuzzy system the THD is reduced which greatly improves the performance of MAF.