A Doubly Grounded Transformerless PV Grid-Connected Inverter Without Shoot-Through Problem
Zhilei Yao, Yubo Zhang
Abstract
As conventional transformerless PV grid-connected inverters have shoot-through problem and common mode leakage current issue, a doubly grounded transformerless PV grid-connected inverter is proposed. The proposed inverter consists of a buck converter and a buck-boost converter, which operates at positive and negative half-line cycles, respectively. There is no shoot-through problem in the proposed inverter, so dead-time in gate signals is not required. As grounds of the PV array and the grid are shorted, the common mode leakage current can be eliminated. No current flows through the body diodes of switches, so there is no reverse recovery issue of the body diodes of switches. Only one switch operates at high frequency in each half-line period, so efficiency of the system is improved. Operating principle of the proposed inverter is elaborated in detail. The control strategy is given. The control method is simple and the grid-connected inverter is a single-stage system in each half-line cycle. Loss calculation and example is given in detail. Finally, simulation and experimental results of the proposed inverter validate the theoretical analysis.