A fundamental wave recursive DFT algorithm applied in the inverter´s pre-synchronization

This paper presents a voltage fundamental wave recursive DFT algorithm applied in grid-connected inverter pre-synchronization. The algorithm not only is able to reliably track the voltage fundamental phase, frequency and amplitude, but also reduces the calculating consumption to guarantee real-time algorithm. Based on the equal-angle interval sampling technique (EAISP), the algorithm can adjust the sampling interval according to the fundamental phase angle feedback. So it can achieve adaptive voltage-frequency tracking to reduce the spectral leakage and enhance the fundamental wave synchronization parameter accuracy. With respect to the traditional phase-locked loop synchronization method, the algorithm can precisely track the fundamental wave while harmonics and grid voltage zero-offset are serious to reduce the impact on the micro-grid and the inverter itself when grid-connected operation. The simulation results show its validity and feasibility.