Comparative evaluation of synchronization techniques for grid interconnection of renewable energy sources

This paper presents comparative performance evaluation of conventional SRF-PLL, existing adaptive notch filter (ANF) and an amplitude adaptive notch filter (AANF) based synchronization techniques used for converter-interfaced renewable energy systems. In addition, real time implementation and extraction of frequency and amplitude of the input grid voltage signal by all the three techniques has been presented. Comparative analysis has been done based on their ability in extracting amplitude and frequency variation of the input grid voltage signal under unbalanced and frequency variation condition. The single phase AANF provides high degree of accuracy than SRF-PLL and ANF in extracting appropriate signal information even for unbalanced and distorted grid condition. The important feature of the AANF is its amplitude adaptability, which improves its speed of response and accuracy when grid signal is of variable amplitude. Experimental results demonstrates better performance of AANF for frequency and amplitude detection than existing ANF and SRF-PLL, hence it can be used for wide range of applications such as converter interfaced distributed generation systems, islanding detection in smart grids, various fault detection techniques etc.