H2D4-Type Single Phase Transformer-Less Inverter with Reactive Power Control for Grid-tied PV System

Transformer-less inverter is popular for grid-tied photovoltaic (PV) system due to low cost, smaller size and higher efficiency. However, one of the technical challenges, which need to be handled carefully, is the issue of leakage current. Moreover, an inverter must be capable of controlling the reactive power to a certain extend to maintain the power factor (PF) close to unity. Therefore, many inverter topologies have been proposed. In this paper, a new four diodes and two IGBT switch based H2D4-type highly efficient transformer-less inverter is proposed that can handle the issue of leakage current maintaining low total harmonic distortion (THD) and higher PF where the common mode (CM) voltage is maintained constant. As a result, the leakage current deceases and the conduction loss as well as size of the system is decreased due to minimum number of IGBT switches. Furthermore, two control systems are proposed to control the reactive power with desire PF. The comparison among proposed H2D4 topology and conventional neutral point clamped (NPC) and H6 topology have been analyzed in this paper. To validate the accuracy of the theoretical analysis, the compared topologies are simulated in MATLAB/Simulink software. It is found that the PLL and PI closed loop control based H2D4 inverter topology controls the reactive power maintaining a low current THD with higher efficiency and high PF as compared to the system with only PI control based topology.