弱电网下基于频率自适应的新型锁相环设计方法及其稳定性分析OA

To address the issue of decreased system stability caused by the coupling between the phase-locked loop(PLL)and grid impedance in weak grids,a novel frequency-adaptive PLL design method is proposed from the perspective of optimizing the control structure.First,a system output admittance model considering the influence of the PLL is established.Based on this model,the stability and dynamic performance of the conventional PLL and the decoupled phase-locked loop(DPLL)under weak grid conditions are analyzed.The results show that both PLL and DPLL exhibit reduced stability and degraded dynamic response as grid impedance increases or grid fluctuations intensify.Then,based on the DPLL,an inertial element and an outer-loop frequency tracking unit are introduced to construct a new frequency-adaptive phase-locked loop(NPLL)structure with frequency adaptability.By enhancing system damping and real-time frequency tracking capability,the proposed method improves overall control performance.Finally,simulation and experimental results demonstrate that the proposed scheme significantly expands the range of grid impedance adaptability and exhibits superior frequency tracking capability and dynamic response under grid fluctuation conditions compared to traditional PLL and DPLL,thereby effectively improving system robustness and grid-connected power quality.