Modelling robustness for a flexible grid-tied photovoltaic generation system

Robustness to modelling inaccuracy is a vital characteristic of a controller, because no matter how accurate a model is, modelling inaccuracies always exist. However, it is difficult to achieve satisfactory nominal and robust performance of a grid-tied photovoltaic (PV) generation system at the same time, using traditional controller design methods. To solve this problem, a μ-synthesis control method combined with the application of linear fraction transformation (LFT) is proposed in this study. The proposed method is designed with object transforming and implemented with DK iteration. The μ-analysis and simulation results prove that the objective can be achieved under various microgrid conditions, determined by factors such as grid connection point voltage, load conditions and component parameter perturbations. Compared with traditional controller design methods, the grid-tied PV generation system under μ-synthesis control exhibits comparatively large perturbation margin for nominal performance and robust stability, and simultaneously is capable of guaranteeing the preset perturbation range for robust performance.