The Designment Of A T Type Three Level Inverter Used In Photovoltaic Power Generation System

With the development of economy, energy crisis and environment pollution is becoming worse. Developing and using new energy source have attracted more and more attention. T he hybird AC/DC microgrid is one of the important directions in new energy development. As the transmission medium between AC and DC bus, both the topology and control strategy of the bi-directional AC/DC converter need to be researched. Because the traditional NPC three-level inverter topology has the disadvantages of more switching devices and loss distribution balance. T herefore, the research of this paper is based on the T-type three-level inverter.Based on practices in engineering project, this dissertation presents the design of a system and analyze corresponding experiments according engineering standards. Firstly, the principle of the three phase T three level inverter is analyzed and its mathematical model is derived. By reducing the common mode voltage of the inverter, a modified SVPWM algorithm is proposed. The system used in the proposed method is introduced and analyzed, including Double closed-loop control mode, MPPT and Anti island protection. In order to d etermine the parameters of the proposed 50 k W three-phase three level photovoltaic grid connected inverter, the power circuit and drive control circuit are introduced and designing. The design of the power circuit includes Main switch device, DC bus support capacitor and AC side LC filter selection. T he drive control circuit includes Sampling circuit and protection circuit and so on. By constructing a experimental sample platform, the dynamic and stable performance of T hree phase inverter grid connected are examined and the corresponding data are recorded including Grid connected steady state and dynamic waveform and efficiency and so on.Finally, the electrical properties and electrical protection are tested by experiments with the Converter grid operation. T he Operation waveform are shown for stable state or fault state. The experimental results suggest that the proposed photovoltaic grid connected inverter works stably and effectively.