Research On MPPT Technology Of Photovoltaic Power Generation System Based On Fuzzy PID Control

In recent years, with the rapid economic development, the global energy is facing a deficit and the environmental problems is becoming increasingly serious. As a new type of green energy, solar energy is clean, renewable and inexhaustible. Thus,it is attracting more and more attention. At present, the main problem facing photovoltaic power generation systems is that the output of solar cells has a strong non-linearity and the light conversion efficiency is very low. Therefore, by adding a maximum power tracking controller between the photovoltaic cell and the load, the efficiency of using solar energy can be improved. The object of this paper is the tracking problem of the maximum power point of solar photovoltaic cells. The main contents are as follows:Firstly, this paper introduces the principles and working characteristics of the solar cell, and analyzes its engineering model on the basis of the equivalent circuit of the photovoltaic cell. The mathematical model of the photovoltaic cell is built by MATLAB/Simulink simulation software. The writer operated the mathematical model and got the output characteristic curve. According to the curve, the writer summerized the changes of the maximum power point of the photovoltaic cell under different environments.Secondly, this paper mainly introduces the principles of the maximum power point of the solar cell. After studying the features of common maximum power point tracking methods, such as Constant-voltage Transformer, Conductivity Increment Method and Perturbation Observation, their advantages and disadvantages are summerized. In consideration of the disadvantages, this paper is based on PID control and introduces a strategy for maximum power point tracking . In addition to that, this paper also created a model of PID controller.Thirdly, this paper gives an analysis of the features and basic principles of fuzzy control and the design process of the fuzzy control controller. The writer proposed a new maximum power point tracking method which is based on fuzzy control. This paper untilized the fuzzy logic toolbox of MATLAB and built a simulation model for fuzzy controller of photovoltaic cell.Fourthly, in the light of instability of fuzzy control in tracking MPP, the writer integrated fuzzy control with PID control and designed a fuzzy PID controller. The simulation model created the output power curve of the photovoltaic cell under fuzzy PID control. A comparison of the tracking performance of MPP was made under Perturbation Observation, traditional fuzzy control and fuzzy PID control.The simulation results show that when the external condition changes violently,the low disturbance velocity led to slow tracking speed and poor stability. The simulation result which is based on traditional control shows that although the tracking speed of the maximum power point is improved slightly, however, its ability of preventing vibration of the system is low. When the external condition changes violently, the PID-based control method can track the maximum power point quickly,and the tracking performance is stable which can meet the needs for engineering practice.