Research On Grid-connected Photovoltaic Inverter Based On Improved PR Control Strategy

In recent years, photovoltaic power generation has become more and more widely applied. Photovoltaic grid-connected inverter is one of the key equipment in photovoltaic power generation system, which is used to convert the direct current produced by photovoltaic cells to the alternating current according to the power grid standard. Therefore, the research on the optimal control strategies of the photovoltaic grid-connected inverter can enhance the efficiency of photovoltaic power generation system and improve the quality of output power.Based on the analysis of the disadvantages for conventional Proportional Integral (PI) controller and Proportional Resonant (PR) controller, a improved PR controller of grid-connected inverter is adopted in this thesis. This improved PR controller has the following advantages:(1) the steady-state error of grid-connected current is small, and (2) the anti-interference ability to the grid voltage is strong. The variation of grid frequency can influence the operation of photovoltaic grid-connected inverter, and this problem can be solved by the proposed control strategy. Therefore, the proposed control strategy will enhance the output power quality and improve the efficiency of photovoltaic grid-connected system.The main contents of this thesis are as following:1. The research background information of the thesis is introduced which involves the development of the photovoltaic power generation system, photovoltaic grid-connected inverter and its control techniques. Then the future development prospect is analyzed, and the significance of study is presented.2. The main control strategies of the photovoltaic grid-connected inverter are introduced. Considering the grid-connected performance and efficiency of inverter, different control strategies are compared.3. An improved PR control is used in the grid-connected inverter in this thesis. This control strategy can effectively optimize the fluctuation of grid frequency.4. The experimental platform of 1KW photovoltaic grid-connected inverter is built.5. A simulation model of photovoltaic grid-connected inverter set up based on Matlab/Simulink. Many measure results are obtained in the experimental platform of 1KW photovoltaic grid-connected inverter in laboratory. The simulation and experimental results are provided to verify the effectiveness of the proposed control strategy. The research of this paper provides reference for engineering application of this kind of control strategy.