宽范围电网下并网逆变器延时小信号建模及不连续稳定区间分析

SMALL SIGNAL MODELING AND DISCONTINUOUS STABILITY REGIONS ANALYSIS OF GRID-CONNECTED INVERTERS CONSIDERING CONTROL DELAY IN WIDE RANGE GRID

该文以光伏并网逆变器为例,借助pade近似方法,建立考虑控制延时环节的光伏并网逆变器状态空间小信号模型,利用特征值分析方法研究宽范围电网强度下考虑控制延时的光伏并网逆变器稳定性问题。算例仿真分析结果表明:在考虑控制延时的光伏并网逆变器系统中,当电网强度在较宽范围内变化时,系统存在不连续稳定区间;考虑控制延时的系统小信号模型要更加精确,对控制器参数的变化更加敏感;在极弱电网(短路比SCR≤1.6)下,锁相环和电流环相关振荡模式之间会发生交互作用和"借"阻尼现象,并引起系统不稳定。最后通过MATLAB/Simulink仿真和验证实验证明了理论分析的正确性。

This paper takes photovoltaic grid-connected inverter as an example,using the pade approximation method,a small-signal model of the grid-connected inverter state space considering control delay is established,and the stability of the grid-connected inverter considering control delay under a wide range of grid strength is analyzed by the eigenvalue analysis method.Through the overall system digital simulation,the results show that in the grid-connected inverter system considering control delay,when the grid strength changes,the system has discontinuous stable regions;the small signal model of the system considering control delay should be more accurate,and more sensitive to the changes of controller parameters and in the case of an extremely weak grid,there exist interaction and‘borrowing damping phenomenon’between the phase-locked loop and the current loop,which causes system instability.Finally,this article proves the correctness of the theoretical analysis through MATLAB/Simulink simulation and experimental verification.