Dual Half-Cycle-Bridges Single-Phase Photovoltaic Inverter

In a transformer-less photovoltaic (PV) grid-connected system, there exists a galvanic connection between the grid and the PV array. Without any transformer in the inverter, common-mode leakage currents can flow through the stray capacitance between the PV array and the ground. This paper first analyzes the equivalent common-mode circuit of single-phase inverter, and compares several single-phase inverters with constant common-mode voltage. This paper then proposes a novel dual half-cycle-bridges (DHCB) single-phase PV inverter with low conduction losses. A novel hybrid SPWM modulation method is introduced to achieve the minimum switching losses under any power factor operation. Next, adding a neutral point clamped circuit to the DHCB inverter, the common-mode voltage can be clamped to half of DC voltage firmly. Finally, simulation and experimental results have validated the theoretical findings.