Synchronverter-based transformerless PV inverters

In this paper, a transformerless PV inverter is proposed, which is formed by adding a neutral leg into conventional half bridge inverter. It consists of one neutral leg and one inverter leg. The presence of the neutral leg enables the direct connection between the ground of PV panels and the ground. Two main benefits are then obtained. First, the common mode currents are completely eliminated because the stray capacitors between the PV panels and the grid neutral line are bypassed. Another benefit is the voltage of the PV is only required to be higher than the peak value of the grid voltage, which is same as that of conventional full bridge inverter. In addition, the synchronverter technology designed for three-phase inverters is extended to a single-phase case to design the controller of the inverter leg. As a result, the proposed inverter becomes more grid-friendly. The control of the two legs are independent with each other, which means the controller design much easier. The performance of the whole system is evaluated in detail with the provided real-time simulation results.