弱电网下多逆变器并网稳定性分析及提高策略OA

In weak grid environments,the larger grid impedance enhances the coupling between the grid and each inverter in a multi-inverter parallel system,resulting in decreased system stability or even instability.To address this,a strategy for improving the stabil-ity of multi-inverter grid-connected systems under weak grid conditions is proposed.Firstly,Norton equivalent models for single and multiple grid-connected inverters in weak grids are established.Secondly,from the perspective of grid-connected current stability,the stability criterion for the multi-inverter system is decoupled into that of a single-inverter system based on the concept of equivalent grid impedance,clarifying the mechanism behind the reduced system stability in weak grids.Subsequently,an improved control strategy to enhance the stability of the multi-inverter system is proposed,which increases the stability margin of grid-connected invert-ers by introducing an all-pass filter into the grid voltage feedforward loop and combines a harmonic controller to improve the system's ability to suppress background harmonics.Finally,simulation analysis verifies that the proposed strategy effectively enhances the stability of multi-inverter grid-connected systems under weak grid conditions.