Stability Enhancing Voltage Feed-Forward Inverter Control Method to Reduce the Effects of Phase-Locked Loop and Grid Impedance

Abstract

Phase-locked loop (PLL) and grid impedance easily negatively affect the stability of the grid-connected inverter system and even cause the system oscillation. To suppress this oscillation, a stability enhancing voltage feed-forward inverter control method is proposed to reduce the effects of PLL and grid impedance. Then, considering the effects of the frequency coupling characteristic, the admittance model of the grid-connected inverter with the proposed stability enhancing control method is established, and the admittance characteristic and the system stability of the inverters with the traditional control method and the proposed stability enhancing control method are compared and analyzed. Analysis results indicate that the proposed stability enhancing control method improves the system stability in different short-circuit ratio (SCR) conditions. What is more, the system with the proposed stability enhancing control method keeps stable under a relative larger PLL bandwidth, while the system with the traditional control method oscillates. Finally, the effectiveness of the proposed stability enhancing control method is verified by experiments.