The Research On Grid-Connected Control Of Photovoltaic Power Generation System And Its Transient Process

With the increase of energy depletion and the environment crisis, the utilization of new energy has become to a major theme in the world. Because of the advantages of economy, clean and convenient over conventional power generation, solar photovoltaic power generation has developed rapidly and received people's universal approval and attention. Following the trend of photovoltaic power generation, from the perspective of large-scale grid-connected in the future, the main work in this paper was the research on grid-connected control of photovoltaic power generation system and its transient process.Summarizing the development of solar photovoltaic power generation system, analyzing the grid-connected principle of photovoltaic power generation system, reviewing the topology and control technology of grid-connected inverter in the current, after comprehensive comparison, selecting two state photovoltaic power generation system as the research direction. Adopting dc converter completed the maximum power tracing, using inverter to sustain the stability of the voltage in the dc side and power inverter. In addition, the article gives a detailed analysis and discussion on the selection of the parameters of some important components in the system.Analyzing the characteristics of photovoltaic cells, hunting for the establish principle of the PV mathematic model, achieving to track the array's maximum power point by the help of Incremental Conductance Method. The tracking performance of the system was tested when the external conditions changed, Simulation results show that: the design is reasonable, meeting the requirements on the photovoltaic power station.Completing the grid-connected control of two-stage photovoltaic power generation system, With a LCL filter, the stability of the system is poor. Pole assignment based on state feedback and Repetitive Control were used to realize the Grid-connected control of the system. Since the order of outer loop in the system is high, the controller design is difficult. In order to sustain the stability of the voltage in the outer loop, root locus method was adopted to design the controller.Finally, in order to find out measures to improve the photovoltaic generation system's transient stability, the characteristics of grid-connected photovoltaic power generation system and the transient process under a large disturbance were analyzed.