Research On Single-phase Two Stage Photovoltaic Grid-connected Inverter

Solar photovoltaic power generation is an important form of utilization of solar energy, which converts light energy into electrical energy by the use of solar cells. With the development of technology, solar photovoltaic power generation will be one of most promising power generation technology. The thesis focuses on the single-phrase grid-connected photovoltaic system, which includes the topology of photovoltaic grid-connected system, maximum power point tracking (MPPT) method of photovoltaic arrays and grid-connected inverter control strategy.Firstly, topological structure of two kinds of single-phase grid-connected is analyzed and compared in detail. The whole control strategy of system is described. The advantages and disadvantages of two kinds of the control strategy are discussed.Secondly, the simulation model of photovoltaic cells is established. Simulation waveform shows the output characteristics of photovoltaic array. On this basis, three kinds of commonly used maximum power point tracking method are analyzed and compared. This thesis proposes a variable step size control method. The simulation experiment result shows that the new method is better than others.Thirdly, grid-connected inverter control strategy of voltage and current double closed-loop base on grid voltage orientation is introduced. The mathematical model is established. Then this thesis introduces three kinds of full bridge inverter SPWM modulation. In the Matlab/Simulink simulation environment, the simulation of single-phase two level photovoltaic grid-connected system is created. The simulation results verify the feasibility of the control strategy.Finally, the photovoltaic grid-connected system hardware and software have been designed. Based on the test platform, The maximum power point tracking control method of different contrast experiment and grid-connected inverter experiment have been finished. Experiment results have validated the feasibility and reliability of the designed photovoltaic grid-connected system completely.