弱电网下光伏并网逆变器的数字H∞鲁棒控制器设计

针对弱电网下光伏并网逆变器可能发生的失稳现象，提出一种光伏并网逆变器的数字H_∞鲁棒控制器设计方法。首先建立传统控制策略下光伏并网逆变器的控制模型，并分析其在弱电网条件下的稳定性。为了提高LCL型光伏并网逆变器对电网阻抗变化的鲁棒性，考虑数字控制延时的影响，通过建立离散域下光伏并网逆变器的标准H_∞控制模型，并设计加权函数，求得光伏并网逆变器的数字H_∞控制器。与传统的双闭环控制策略相比，理论分析与仿真和实验结果均表明，所设计的数字H_∞控制器可显著增强弱电网条件下光伏并网逆变器的稳定性。

DESIGN OF DIGITAL H∞ ROBUST CONTROLLER FOR PHOTOVOLTAIC RID-CONNECTED INVERTER IN WEAK GRID

Due to the influence of grid impedance, the photovoltaic（PV） grid-connected inverter may be unstable under the weak grid. This paper proposes a digital H_∞ robust controller design method for PV grid-connected inverter. Firstly, this work establishes the control model of PV grid-connected inverter under the traditional control strategy, and analyzes its stability under weak grid. In order to improve the robustness of LCL-filtered PV grid-connected inverter against the variation of grid impedance, the standard H_∞ control model of PV grid-connected inverter is established in discrete domain with considering the influence of digital control delay. And the digital H_∞ controller is designed by appropriately selecting the weighting functions. Compared with the traditional dual current loop control strategy, the simulation and experimental results in this paper prove that the designed digital H_∞ controller significantly enhances the stability of PV grid-connected inverter in weak grid.