Research On Converter And Control For Photovoltaic Power Generation System

With the development of society economy, energy need is becoming more and more, traditional fossil energy is facing depletion crisis and causes serious pollution when consumed. Energy conservation and environment protection have been necessary conditions for sustainable human development. Solar energy as one of renewable resources with the advantage of inexhaustible, unlimited, clean, pollution-free has been paid great attention by government.The output characteristics of photovoltaic cells has a strong non-linear, and is influenced strongly by the environmental factors, so how to effectively use and improve conversion efficiency of solar energy has become an urgent problem and need to be solved. Maximum power point tracking control and the grid-connected converter control are two key technologies for photovoltaic power generation system. This paper makes main research on these two key technologies.The main contents of this article can be summarized as follows:First, made analysis on common structures of independent photovoltaic power generation system,indirect grid-connected photovoltaic power generation systems and direct grid-connected power generation system; Made research on the working mechanism of solar cells, established solar cells model and did simulation.Second, analyzed the theory and characteristic on constant voltage method,perturbation method and incremental conductance algorithm of maximum power point tracking control methods, made comparison and simulation verification on these three common methods of maximum power point tracking control.Third, analyzed the theory of three-phase PWM rectifier and space vector pulse width modulation; made research and simulation on three-phase grid-connected transient control of 50 KW photovoltaic power generation system.Finally, simulation waveforms of the converter control system were analyzed. Simulation results show that the three-phase voltage-type PWM pulse rectifier is achieving a high power factor operation, the converter's output power meets the needs of grid-connected requirements, the control system has a fast dynamic response in case of a sudden change of the electricity grid's amplitude.