Research On MPPT And Island Detection Technology In Distributed Photovoltaic Grid-connected Power Generation System

With the deepening of China's modernization,the problem of energy supply in social development has become increasingly prominent.For a long time,China's electricity supply mainly relies on fossil energy sources such as coal and petroleum,which has made China's environmental protection problems increasingly serious.As the world's largest developing country,China needs to reform the existing energy structure,vigorously develop clean energy,and take the path of sustainable development.In recent years,the photovoltaic power generation industry has achieved rapid development in China.Distributed photovoltaic power generation has also gained market recognition for its advantages such as flexible and convenient operation.With the access of a large number of distributed photovoltaic power generation systems in the power grid,while bringing considerable benefits,many technical problems will also arise.This article takes single-phase distributed photovoltaic grid-connected power generation system as the research object,builds a photovoltaic grid-connected simulation model with the help of Matlab / Simulink software,and focuses on two key technologies of distributed photovoltaic grid-connected power generation: maximum power point tracking(MPPT)Research on island state detection technology.This article first introduces the development status of photovoltaic power generation at home and abroad,and the development status of distributed photovoltaic grid-connected power generation.Based on the analysis of photovoltaic power generation related theories such as the basic working principle of photovoltaic cells and the output characteristics of photovoltaic cells,the problems existing in photovoltaic grid connection are raised.Then,the photovoltaic grid-connected inverter structure and control strategy are studied.In this paper,a single-phase two-stage dual-loop PI-loop PI-loop controlled photovoltaic grid-connected inverter based on LCL filtering is selected to realize the grid-connected inverter function.Next,based on the research on MPPT technology of traditional photovoltaic cells,an improved fuzzy control algorithm was proposed,and a distributed photovoltaic grid-connected simulation model was built with the help of Matlab / Simulink software.Simulations were performed on the proposed algorithm and two traditional MPPT algorithms.Comparative study shows that the improved fuzzy control algorithm has obvious advantages in tracking speed and stability.Finally,the international common island detection methods and standards are described.Through a comparative analysis of commonly used island detection algorithms,an island detection algorithm based on adjusting the power output point is proposed.Using the grid-connected inverters for island simulation comparison experiments,the proposed algorithm does not need to add additional equipment,which can eliminate the island detection blind zone,improve the island detection efficiency,and meet the island standards set by the state.