A New Phase-locked Loop Design Method and Stability Analysis Considering the Coupling Effect of Grid-connected Inverter Under Weak Grid
In response to the issue of mutual coupling leading to system instability among the current loop,phase-locked loop,and grid impedance of the grid-connected inverter under a weak grid,a mathematical model for the grid-connected inverter under weak grid conditions is established.The coupling principles between the phase-locked loop and the current loop are analyzed.Based on zero-pole distribution and the Nyquist stability criterion,the primary reasons for the decrease in system robustness when the grid impedance and the bandwidth of the phase-locked loop change are revealed.A new phase-locked loop control structure is proposed by constructing a pre-link to reshape the phase-locked loop transfer function and providing a specific parameter design method.Theoretical analysis indicates that the proposed new phase-locked loop can eliminate the impact of phase-locked loop bandwidth on system robustness,decoupling of phase-locked loop bandwidth and current loop,and enhance the system's adaptability to weak grids.Finally,simulations and experiments are conducted to verify the effectiveness of the proposed new phase-locked loop design method.
万方数据
维普
