Space Vector Modulation Techniques for Common-Mode Voltage Reduction in Three-Phase Transformerless Split-Source Inverters

Abstract

Photovoltaic (PV) systems with low input voltage usually employ an input boost converter and an output inverter. Regarding to this issue, the split-source inverter (SSI) provides a single power conversion stage which aggregates boost capability with low switch count. On the other hand, conventional modulation strategies applied to the grid-connected SSI can result in large high-frequency common-mode voltage (CMV). Depending on the parasitic path, the CMV synthesized by the inverter can give rise to large leakage current which must be limited for security reasons. This paper proposes two space vector modulation (SVM) strategies to provide the reduction of high-frequency CMV in transformerles SSI. The first strategy is based on the selection of specific voltage vectors whereas the second strategy employs virtual vectors which correspond to the combination of existing voltage vectors. Furthermore, it is performed an analysis in terms of CMV, leakage current, total harmonic distortion of line-to-line voltages and the maximum achievable modulation index. In addition, a comparison with existing techniques is presented to demonstrate the features of the proposed strategies. Finally, simulations and hardware-in-the-loop results demonstrate the benefits of the proposed techniques.