A novel virtual vector-based direct power control strategy to reduce common mode voltage in transformer-less two-level grid-connected VSI

Thanks to their various advantages in terms of reliability in addition to their low size and low cost, transformer-less PV inverters are widely used in several applications. Nevertheless, not using a transformer leads to an undesirable leakage current that can be generated by the high-frequency variation of the Common Mode Voltage (CMV). In this paper, a novel Direct Power Control (DPC) strategy is developed to reduce the CMV in a transformer-less two-level grid-connected VSI. The Proposed DPC (P-DPC) algorithm is based on the application of virtual vectors instead of original vectors in order to control the active and reactive powers and commonly to reduce the CMV variations. Consequently, the amplitude and variations of the produced CMV are effectively reduced, resulting in enhanced overall performance of the grid-connected conversion system. Numerical simulation and hardware implementation in an FPGA board prove the effectiveness of the P-DPC in terms of CMV and leakage current reduction as compared to conventional DPC strategies.