Analysis of SDFT based phase detection system for grid synchronization of distributed generation systems

A fast and exact detection of phase and fundamental frequency of grid voltage/current is essential for calculating accurate reference signal in order to implement the control algorithm of inverter-interfaced distributed generation (DG) system and realize precise harmonic compensation. However, the methods adapted in the literature based on phase locked loop (PLL) exhibits large phase error, be difficult to implement, and their performance is also indistinct under conditions where the grid frequency varies or the supply is distorted with low frequency harmonics. This paper explores an improved phase detection system for DG system based on Sliding Discrete Fourier Transform (SDFT). The proposed SDFT based phase detection shows a robust phase tracking capability with fast transient response under adverse situation of the grid. Moreover, SDFT phase detection system is more efficient as it requires small number of operations to extract a single frequency component, thereby reducing computational complexity and simpler than DFT. The superior performance of proposed SDFT phase detection system is analyzed and the obtained results are compared with Discrete Fourier Transform (DFT) filtering to confirm the feasibility of the study under different grid environment such as high frequency harmonic injection, frequency deviation, and phase variation etc.