弱电网条件下LCL型三相光伏并网逆变器研究

LCL TYPE THREE-PHASE PHOTOVOLTAIC GRID-CONNECTED INVERTER UNDER WEEK GRID CONDITIONS

针对常规并网逆变器在弱电网环境下易出现不稳定情况,在考虑电网阻抗变化条件下设计LCL型滤波器网侧电流及电容电压双闭环控制策略。基于LCL型光伏并网逆变器拓扑结构,在dq同步旋转坐标系下建立数学模型,进行解耦及控制器设计。分析电网阻抗变化对LCL型滤波器的影响,给出一种考虑不同电网阻抗条件下锁相环扰动的系统参数设计方法。最后通过仿真验证理论推导的正确性和可行性,以及三相光伏并网逆变系统的稳定性和鲁棒性。

Conventional grid-connected inverters are prone to instability in a weak grid environment.A double-closed loop control strategy for grid-side current-LCL filter capacitor voltage is designed considering the impedance variation of the grid.Based on the LCLtype photovoltaic grid-connected inverter topology,a mathematical model is established in the dq synchronous rotating coordinate system to perform decoupling and controller design.The influence of grid impedance variation on LCL filter is analyzed.A system parameter design method considering phase-locked loop disturbance under different grid impedance conditions is presented.Finally,the correctness and feasibility of the theoretical derivation and the stability and robustness of the three-phase photovoltaic grid-connected inverter system are verified by simulation.