Space Vector Modulation for Leakage Current Reduction in Transformerless Four-Leg Split Source Inverter

Transformerless systems play an important role in many applications, such as photovoltaic (PV) generation systems and motor drives, since they feature reduced size and greater efficiency. However, common-mode voltage (CMV) can produce leakage currents in transformerless systems. Although leakage current arises in many applications, PV systems are particularly problematic, due to the high parasitic capacitance in the silicon panels. Furthermore, PV systems with low input voltage usually employ a boost converter. The Split Source Inverter (SSI) emerges as a topology that adds boost characteristics with low switch count, simplifying the power conversion stage. However, conventional modulations strategies applied to the inverter can generate high leakage currents. To overcome this problem, many techniques have been proposed in recent years for three-phase inverters. Yet, only a few solutions have been proposed for three-phase four-leg inverters. This paper proposes a new Space Vector Modulation (SVM) strategy to reduce the CMV, and therefore the leakage current, for a four-leg SSI transformerless PV inverter. A comparison is presented with existing modulation strategies in terms of CMV, total harmonic distortion (THD), and maximum modulation index. Finally, simulations and hardware-in-the-loop results demonstrate the benefits of the proposed technique.