Abstract：The suppression of common mode current is a key technical issue in transformerless photovoltaic (PV) system. Firstly, the common mode model of the conventional transformerless grid-connected cascaded H-bridge PV system is established. The mathematical expression of the common mode current is derived. The major factors that affect the common mode current are discussed. The reason that the conventional cascaded H-bridge inverter fails to reduce the common mode current is explained. Secondly, a new cascaded H5 topology and its modulation strategy are proposed to solve the common mode current issue. Finally, a prototype with digital control is built. The experiment tests of cascaded H4 and H5 topologies are carried out. The experimental results verify the effectiveness of the proposed solution.
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2018, Vol. 33 
