A predictive direct power control technique for transformerless grid connected PV systems application

Transformerless grid-connected PVs are more economical and efficient compared to transformer connected PVs; however, in this type of connection high leakage current flows between the PV arrays and the grid due to the parasitic capacitances of the system. This leakage current is one of the main culprits in causing electromagnetic interference in power system, saturation of distribution transformers and poses safety issues. Common mode voltage (CMV) is primarily responsible for the existence of this leakage current. To cope with issues which arise from omitting galvanic isolation (transformer), in this paper a predictive direct power control (PDPC) with reduced common voltage (CMV) called active zero predictive direct power control (AZ-PDPC) is proposed. Both theory and simulation show that the proposed method reduces the level of CMV along with general good performance. The proposed method's characteristics are compared with the PDPC technique.