Large-scale photovoltaic (PV) plants may be destabilised by the large grid impedance introduced by transformers and long transmission lines. When considering the digital control delay of grid-connected inverters, the problem will become more serious. In this study, the equivalent impedance model of digitally controlled large-scale PV plants is established, considering that the values of the parameters of the LCL filter follow Gaussian distributions. Then, the system stability can be analysed conveniently, and the stability analysis shows that the digital control delay will make the system robust to large grid impedance worse. To enhance the stability-robustness of the system, an H _∞ robust controller is proposed in this study. By properly selecting the weighting functions, the desired tracking error performance and robustness are achieved on the basis of the mixed-sensitivity optimisation control design. Compared with the traditional dual current loop control strategy, the H _∞ robust controller improves significantly the system stability-robustness against large grid impedance. Finally, simulation and experimental tests are carried out in this study, and the results demonstrate the effectiveness of the proposed H _∞ robust controller.

中文翻译：

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数控大型光伏电站的建模和鲁棒控制

大型光伏（PV）工厂可能会因变压器和较长的传输线引入的大电网阻抗而不稳定。考虑并网逆变器的数字控制延迟时，问题将变得更加严重。在这项研究中，考虑到LCL滤波器的参数值遵循高斯分布，建立了数控大型光伏电站的等效阻抗模型。然后，可以方便地分析系统稳定性，并且稳定性分析表明，数字控制延迟将使系统对较大的电网阻抗变得更鲁棒。为了增强系统的稳定性，H _本文提出了_∞鲁棒控制器。通过适当地选择加权函数，所希望的跟踪误差的性能和鲁棒性的混合灵敏度优化控制设计的基础上实现的。与传统的双电流环控制策略相比，H _∞鲁棒控制器大大提高了系统抗大电网阻抗的稳定性。最后，在本研究中进行了仿真和实验测试，结果证明了该方法的有效性。H _∞鲁棒控制器。