Research On Control Method Of MPPT And The Grid-connected Inverter In Small Power Photovoltaic Power Generation System

With conventional energy shortage and environmental pollution problem are increasingly serious, the solar energy received extensive attention of people for its unique advantages. Photovoltaic grid-connected power generation as one of the main ways to use solar energy, rapidly becomes a current research hot spot. In order to improve the conversion efficiency and stability of photovoltaic power generation system, improve the output power quality of photovoltaic grid-connected power system, this paper made a more in-depth research aims to the two key questions of maximum power point tracking and grid-connected inverter control in photovoltaic grid-connected power generation systems.First, the classification and structure of photovoltaic power generation system are introduced, and pointed out that the PV array and photovoltaic grid-connected inverter are two important component of photovoltaic grid-connected power generation systems; introduced the work principle and mathematical model of photovoltaic cells in detail,and then analyzed the output characteristics of photovoltaic cells; the common classification and topology of photovoltaic grid-connected inverter are analyzed, discusses the working principle of each; analyzed the topological structure and the basic principle of the two kinds of photovoltaic grid-connected power generation system, and compared their advantages and disadvantages, thus the two stage photovoltaic grid-connected power system topology adopted by this paper.Secondly, analyzed the basic principle of the maximum power point tracking in photovoltaic power generation system, mainly discussed two kinds of commonly used maximum power point tracking control method of photovoltaic power generation system and their respective advantages and disadvantages. In view of the deficiency that the traditional MPPT control algorithms were used in photovoltaic grid-connected power generation system, proposed the MPPT control method based on artificial fish algorithm, the artificial fish school algorithm was appliedto the former MPPT control of photovoltaic grid-connected power generation system, selected PWM duty as an artificial fish individuals,by simulating swarming and following and other acts of the artificial fish to seek optimal values, and was compared with the traditional MPPT control method P&O. Simulation and experiment show that this method is able to stabilized and efficiently tracking the maximum power point of the PV array, achieve maximum utilization of energy.At last, analyzed the control mode of photovoltaic grid-connected inverter, introduced the control target as well as the interconnection requirements of photovoltaic grid-connected inverter in detail, probed into two kinds of models of the output current control method. In view of the output power quality problems of photovoltaic grid-connected inverter, on the basis of the traditional PI, put forward the output current control method of iterative proportional integral for grid-connected inverter, this method used the ITAE criteria as the objective function,and deduced the expression on iterative proportional-integral and transfer function of grid-connected inverter output current. Control accuracy and speed of inverter were improved through real-time setting its optimal proportional-integral controller parameters, thereby the quality of the output current was ameliorated. Simulation and experimental results show that this method is simple to calculate and can effectively make the grid-connected inverter output the sine wave current in the same frequency and phase as the power grid.