Research On String Type Transformerless Photovoltaic Grid-Connected Inverter

Development and utilization of clean energy sources is gaining attention and has become one of the main development themes of the international community. Solar energy has been one of the clean energy that be focused on all of the word because of its clean and efficiency. The photovoltaic power generation is the most important form of the utilization of solar energy, and thus the photovoltaic power system research has become more and more significant.The traditional centralized grid-connected inverters and string-type grid-connected inverters are compared in the beginning of the paper. The first stage DC/DC converter topologies of the string-type transformerless grid-connected inverter system are analyzed. Next, the small signal modeling analysis of interleaved dual Boost circuit is given for regulator design. The interleaved dual Boost topology as the first stage of string-type photovoltaic grid-connected to reduce the input current ripple is extensively studied, and then it is verified by PSIM simulation.As for AC stage, the paper gives the small signal modeling analysis and the design of the PR controller. Meanwhile, the paper studies the common mode leakage current of the string-type transformerless grid-connected inverter system. Based on this, the suppression of common mode leakage current of H5 topology is analyzed. And then, the control block diagram and design parameters are given. Finally, the performance of the disigned inverter is verified by a 2.5KW experimental prototype, and the maximum power point tracking(MPPT) is achieved with different output power as well as common mode leakage current suppression.