Research On Diode Clamped Three-level PV Grid-connected Inverter

With the continuous growth in the society and the economy, the traditional useof fossil energy can no longer meet the requirement of sustainable development.More researches began to focus on the new clean energy, in particular the solarenergy. The technology of photovoltaic power generation, as the most efficientmethod of exploiting solar energy, has matured over the years. Currently PVgrid-connected inverter is still focusing on the traditional two-level inverter, whererequired high voltage is achieved by cascading multiple inverters. Three-levelinverter presents advantages of less requirements on pressure endurance, lowharmonic voltage output, and has started to draw attention in the photovoltaicpower industry. The technology of three-level inverter will become the mainemphasis of large power PV grid-connected inverter research.This paper focuses on the research on diode-clamped topology of three-levelPV grid-connected inverter. It starts with the introduction of the working principlesof the diode clamp topology three-level inverter and commutation mode of theinverter. It then discusses the three-level modulation strategy based on themathematical model of the universal modulation constraints, with rigorouscomputation and analysis. After addressing the theories, the second part of thepaper explains the hardware circuit architecture and software system frame of theDSP experimental prototype in detail, including the selection of the power moduleand building various parts of the platform, as well as the selection of the controllerchip of the software and achieving the functional program.The final part of the paper describes the related experiments and their resultsfrom the laboratory prototype, outlined the issues encountered in the experimentsand provided with analysis and solutions, and concluded a preliminary validation ofthe feasibility of the use of three-level inverter in PV grid.