A novel PLL system based on adaptive resonant filter

When connecting the grid-connected power electronics systems to the utility system, one of the most important aspects to be considered is the synchronization with the grid system in phase and frequency. The synchronized speed and accuracy depend on the technology used in the phase-looked loop (PLL) system. Different kinds of PLL technologies have been published in recent years. A novel PLL structure is presented in this paper. The proposed PLL is based on synchronous reference frame (SRF) with a simple structure comparing with other SRF strategies. By adding an adaptive resonant filter in the conventional SRF - PLL system, the proposed PLL system can track the grid frequency and phase angle accurately with high dynamic response. This PLL system can be used for the grid system with unbalanced and harmonic distortion. Another advantage of the proposed PLL system is that even there is phase fault the gird frequency and phase angle can be tracked accurately. Simulation results by Matlab/Simulink are given in this paper.