Research On Grid-connected Single-phase Photovoltaic System And Islanding Detection Method

All the countries around the world are facing the energy crisis which is becoming more and more serious. With the continuous development of science and technology, the consumption of energy is also gradually increasing, but, the fossil energy storage capacity is limited, even if all the available fossil energy on the earth and behind the sea are mined, there is always a day that they are all consumed up. At this situation, Photovoltaic and other new energy is the key to solve the energy problem which is constraining the development of human, and it is also the key to alleviate the increasingly serious environmental crisis. In the context of energy demand and environmental improvement, in the paper following, the single-phase grid-connected photovoltaic system is carried on a thorough research, the various equivalent model of photovoltaic cells are analyzed, all kinds of common maximum power point tracking technology are discussed, the structure of the inverter control strategy of grid-connected photovoltaic system and some popular islanding detection strategy which are suitable for the grid-connected photovoltaic system are analyzed.Firstly, in this paper, a thorough analysist of the characteristic of photovoltaic cells and its working principle is carried on, on the basis of depth discussions on various equivalent circuit, a mathematical model for the photovoltaic cells is set up under the simulation software, simulate the PV cells under various environment variables, verify its relationship with the environment variables and correctness of the model.Secondly, in this paper, the various common maximum power point tracking algorithm is analyzed, with various elements considered, incremental conductance method is selected as the maximum power point tracking control strategy, and its reliability is verified by simulation.Thirdly, in this paper, the grid photovoltaic power generation system in the structure of the inverter system is analyzed, completed the construction of the mathematical model using the simulation software, its PI parameters are adjusted according to the structure of the system, the effectiveness of the proposed inverter system structure is proved with the simulation results.Finally, in this paper, the islanding detection methods which are suitable for grid-connected photovoltaic power generation system are analyzed and compared, the commonly used passive islanding detection methods and active islanding detection methods are mainly introduced, and put forward an improved active frequency drift method as the islanding detection method, the effectiveness of the proposed islanding detection method is proved with the simulation results.