Photovoltaic MPPT Control Method And Performance Analysis Based On State Space

Solar energy is a kind of new energy that is indiscriminate and inexhaustible.Solar power plays an important role in solving the energy crisis and environmental pollution problems facing human beings.This paper mainly studies the controller parameter design of DC-DC converter and the Maximum Power Point Tracking(MPPT)problem in complex situations such as shadow occlusion.This paper analyzes photovoltaic power generation system,DC-DC converter modeling,MPPT control method research and experimental platform construction.The main research contents of this paper are as follows:(1)Firstly,the basic principle of photovoltaic cells is analyzed in detail,and the mathematical model of photovoltaic cells is built according to theoretical knowledge,and a numerical simulation model is established.The photovoltaic cells were simulated under simulated environmental conditions,and their output characteristics were analyzed.Because of the influence of light intensity,ambient temperature and humidity,the output of the photovoltaic cells exhibited I-V and P-V nonlinear curves.Finally,several common MPPT algorithms are introduced and their advantages and disadvantages are analyzed.(2)Photovoltaic cells are affected by environmental factors during voltage output,and research is conducted to regulate the output of photovoltaic cells.Firstly,the Buck circuit is analyzed.The MOSFET is turned on and off to make the Buck circuit have two working modes.At this time,the mathematical model of the DC-DC converter is nonlinear and time-varying.Secondly,the state space averaging method is used.Mathematical modeling transforms the mathematical model of a DC-DC converter into a linear equation of state that can be controlled and analyzed using control theory.Finally,a numerical simulation model is built according to the photovoltaic power generation system which provides a simulation experimental platform for further research on voltage controller and MPPT algorithm.(3)By studying the transient response and steady-state response of the Buck circuit in photovoltaic power generation systems,it is found that its robustness is extremely poor.The PI and PID compensators are analyzed separately,and it is concluded that the compensator is not suitable as a compensator for the system.By introducing Lead-Lag to the parameter setting algorithm of the compensator,the experimental results are compared,and the ideal compensator parameters are finally obtained,so that the transient response and steady-state response of the system reach the specified standard.Based on the improved DC-DC converter,an improved variable step size perturbation observation method is proposed to achieve maximum power point tracking quickly in the case of shadow occlusion.The feasibility and effectiveness of the MPPT control scheme are verified by MATLAB/Simulink.(4)The Buck step-down converter is used as the hardware circuit of the MPPT control board.The team launches a micro-photovoltaic power station simulator based on the STM32F103ZET6 microprocessor,and controls the DC-DC converter through the MPPT main control board to realize the MPPT algorithm.Experiments show that the compensator after setting the parameters improves the output characteristics of the DC-DC converter,and optimizes the maximum power point tracking,which effectively improves the power generation efficiency of the photovoltaic cell.