Research On The Grid-Connected Photovol Taicpower Generation System

Along with the continuous development of economy, the world is facing energydepletion dilemma. As an emerging green energy, photovoltaic power-generation hasbecome an important part of today's energy, and also will become one kind of the mainused energy in future. This paper research on the grid-connected PV system, includingphotovoltaic grid-connected system the topology of photovoltaic grid-connectedsystem,the control strategy, the relevant parameters,the methods to realize themaximum power point tracking,the control of grid-connected current, and anti- islanddesign.Firstly, study the design of two-links circuit, using a simple topology DC-DCconverter circuits (Boost converter) to realize MPPT; and using full bridge inverter torealize grid-connected.This paper also does the research on Constant Voltage Tracking Algorithm, Perturb &Observe Algorithm and Incremental Conductance Algorithm. And compare ImprovedIncremental Conductance Algorithm and Incremental Conductance Algorithm by MatLab.Full-bridge inverter circuit is fit for the structure of grid-connected system, whilePLL based on DSP is designed to control the output current and grid voltage to maintainthe same frequency and phase. To reduce the THDI, PI control and repetitive controlstrategies are selected, the results show that the control strategy can effectively improvethe quality of output.Islanding detection has an effect on the safty of electrical equipment and thepersonnel involved, so islanding protection must be high reliability. This paper verifiesthe principles of passive methods, and experimentally demonstrates the short of passivemethods. Based on the passive method, a positive feedback of frequency shift part isincreased as the active detection part. The experiment proved that this method detectfaster, with smaller NDZ. It can quickly cut off the connection between the power gridand photovoltaic power generation system.Finally, this paper made conclusions of the research has been done and shows thedirections for further research.