An improved method of frequency detection for grid synchronization of DG systems during grid abnormalities

Renewable energy sources made a big impact to the world due to its un-limitedness. However for efficient consumption of power, proper synchronization of grid side inverter is essential. And the control of inverter largely depends on grid voltage parameters. This paper proposes an efficient way of synchronization for grid connected converter using an enhanced frequency locked loop (FLL). This method is useful in estimating the positive and negative sequence components of fundamental with more preciseness. The enhanced FLL is named as Auto-Adjustable Gain Frequency Locked Loop (AGFLL), as the gain is automatically adjusted by itself. It is first shown how the positive and negative sequence generated, and then the proposed AGFLL is hypothesized and investigated. Also there is a comparative study of AGFLL given with respect to different fixed gain SOGI-FLL. Finally the robustness of proposed algorithm was verified with Dual Second Order Generalized Integrator (DSOGI). The whole thing studied and examined in MATLAB/SIMULINK environment.