Design Of 500W Photovoltaic Grid-connected Inverter

With the development of economic and industry, the energy crisis and pollution have become more serious. Now renewable energy resources are researched to solve these two problems. In those green energies, photovoltaic power generation attracts more attention because of its pollution-free and makes great progress.Under this background, the dissertation deeply researches the PV grid-connected inverter, which is the hard core of the system, and uses the XE164F to control the system in order to transform the solar energy into electrical energy maximally. It has significance to research and experiment on the PV grid-connected system.By analyzing and comparing the structures and control strategies, two stages structure of PV grid-connected inverter is adopted in this dissertation with the analyses of control strategy for the system. Then it analyses the PV array model and its output characteristics, and compares some usually used maximum power point tracking (MPPT) methods. A variable step size P&O (perturbation and observation) method was used in this system. The control strategy of MPPT in two stages structure inverter is given in this paper. Islanding effect should be well solved in grid-connected photovoltaic system. This paper presents the meanings and the criterion of the islanding effect, shows causations of islanding effect happened, shows its hazards, testifies the needed anti-islanding effect, analyses the active and passive detecting methods separately, an improved AFDPF which has a period current disturbance within the normal fluctuate of grid frequency is used in this system which is adapt to the actual operation of Chinese grid utility and overcomes the shortcomings of conventional AFDPF.By deep analysis and research, the design of the hardware and software of the whole system is introduced in detail, including the system structure, assignment of the control resource, the selection of the power devices, the design of the magnetic components, the design of key sample circuit and the protective circuit and the flow chart of the software of the system and all of the interrupt service. At last, the experiments for validating the theory are carried out. The result of the experiments validated the feasibility of the grid-connected photovoltaic system designed in this thesis.