Reliable simple method for suppression of leakage current in grid-connected CHB inverters

In this study, a method for suppression of common-mode current in the transformerless cascaded H-bridge (CHB) photovoltaic inverter is proposed. The proposed approach reduces the leakage current in the transformerless 5-level CHB inverters to a negligible value. By adding an ac switch to the structure of the CHB inverter, a new redundancy state for synthesising the zero voltage is obtained. Using this new redundancy state and available switching redundancies, the common-mode voltage is kept constant and the leakage current is reduced. The performance of the proposed approach is compared with the already existing approach for reduction of leakage current, in the MATLAB/Simulink environment. Experimental investigations are also provided to verify the theoretical and simulation results.