State-feedback-with-PI control for NPC three-level inverter

A discrete state-feedback-with-PI control scheme is proposed for NPC three-level inverter. The discrepancy between two approaches to design the controller, one in continuous domain, the other in discrete plane, is discussed. By means of continuous transformation, a load current feed-forward decoupling strategy (LCFF) is successfully proposed in this paper to make feed-forward possible for the discrete state-space controller. Based on transfer function analysis and comparison of discretized and continuous system, comprehensive verification is provided to verify the effectiveness of the derivation of the LCFF path. Simultaneously, the robustness analysis of the proposed strategy to the output impedance is also performed. Finally, experimental results are provided to verify the feasibility and validity of the proposed strategy.