The Broadband Adaptive Harmonic Resonance Suppression Strategy based on the Sliding-Window FFT Algorithm for the Grid-following Inverter

Abstract

The photovoltaic new energy power generation technology has developed rapidly, the increase of nonlinear devices in the electric grid leads to rapid permeability growth. The power grid presents the broadband variation of harmonic frequency and weak grid characteristics. The Harmonic current and harmonic voltage interact and generate each other through large power grid impedance, aggravating the risk of harmonic resonance in grid-connected systems. As the critical equipment, the grid-connected inverter should have the ability to fast and accurate grid signal acquisition. If the inverter harmonic suppression strategy has a particular structure and parameters, it will not be able to adapt to the situation of decreasing the harmonic frequency and changing harmonic content, thus aggravating the instability under the weak grid. This paper proposes a broadband adaptive harmonic resonance suppression strategy based on a sliding-window FFT algorithm to solve the above instability issues. The sliding-window FFT algorithm can obtain the multi-harmonic information with changing grid points in real-time at a higher rate. The structure and parameters of the harmonic resonance suppression strategy can adaptively change with the obtained multi-harmonic information, and it does not affect the control characteristics at other frequencies except harmonic frequency. Therefore, the harmonic suppression ability of the inverter under the weak grid is ensured. Finally, the rationalization of the strategy is validated through simulation experiments under two working conditions.