Performance evaluation of three phase SRF-PLL and MAF-SRF-PLL

Abstract

Synchronous reference frame phase locked loop (SRF-PLL) is a well established technique used for maintaining synchronism of a grid connected VSI with an electric grid. Many methods of PLL are present in the literature to achieve improved performance under nonideal grid condition. These solutions are based on SRF-PLL structure along with some modification to achieve improved performance. It is observed that faster and better performance are achieved at the expense of more computations. Moving average filter (MAF) SRF-PLL structure is one such solution that consumes less resources and gives a reasonably fast response. In this work the performance of a MAF-SRF-PLL structure is evaluated in terms of unit vector distortion and settling time under various nonideal grid conditions. Its performance is compared with that of two differently designed SRF-PLLs. This evaluation gives a clear idea about possible utilizations of these PLL structures under different possible nonideal grid conditions.