Research On Photovoltaic Grid-connected Inverter

As the world's rapid population growth, social economic development and people's living standards improve, the global demand for energy increases, while the traditional exploitation of fossil fuels is limited, global is going to face energy crisis, in addition to the serious pollution of the environment, so the development of new energy is very important. Has abundant resources of solar, renewable and clean, etc., is the ideal alternative energy. While the photovoltaic grid-connected power generation is the main development trend of solar energy utilization, the photovoltaic grid-connected inverter is the middle part of the PV display and the power grid, has a vital role.The two keys of Photovoltaic power generation system are the maximum power point tracking of cells and photovoltaic grid-connected inverter control, this thesis focus on the two parts to research, mainly to do the following work:Firstly, the development background of photovoltaic grid-connected power generation technology, domestic and international photovoltaic grid-connected inverter developments and trends are introduced in this paper. Compare and analysis of several circuit topology, and ultimately determine to use the DC-DC and DC-AC two steps photovoltaic grid-connected inverter. The first stage DC-DC is the Boost circuit and the last stage DC-AC is the full-bridge invert circuit, and the principle of two circuit is analyzed.Secondly, the basic principle and working characteristics of PV cells are introduced in this paper, several common maximum power point tracking methods are analyzed in detail, such as constant voltage tracking, perturbation and observation method and incremental conductance. Proposed a new perturbation and observation method——based on curves comparison of the perturbation and observation method, which is proved to reach the maximum power point accurately and quickly by MATLAB simulation. In the last inverter part, with the control of output current, analysis and comparison of several common current control strategies, this paper uses a space vector pulse width modulation (SPVWM) method, simulation result shows that output current and grid voltage with the frequency and phase by MATLAB establishing simulation model, to achieve the control goal.Finally, the hardware of the 1.5kW PV grid-connected inverter is designed in this paper, including the parameters of the main circuit design and test circuit and drive circuit, for similar photovoltaic grid-connected inverter design provides some reference.