Digital predictive current control of multi-level four-leg voltage-source inverter under balanced and unbalanced load conditions

This study investigates the experimental validation of finite control set-predictive current control (FCS-PCC) of a multi-level four-leg voltage-source inverter (VSI) operating under balanced and unbalanced conditions. The proposed topology is a combination of conventional four-leg VSI with an additional four switches circuit serving as dc voltage synthesiser. Unification of both circuits can supply energy to unbalanced three-phase loads by providing the path for a zero-sequence load while maintaining appropriate load voltage to the system. The proposed control strategy takes advantage of the discrete nature of the power converter system to predict the future behaviour of the output current. FCS-PCC is based on an optimal approach that selects the most accurate switching signals among 48 valid switching states by computing cost function and applying switching state that minimises the tracking error to the next sampling time. The proposed control has been experimentally verified to assert the robustness of the control. The prominent outcomes of the experiments confirm the ability of independent load current reference tracking with harmonics distortion lower than the conventional eight switches VSI.