Research On Maximum Power Point Tracking Control Method For Photovoltaic Power System

With the rapid development of social-economic and the huge demand for energy,mankind must face and urgently solve the problems of the depletion of traditional energy resources and environmental pollution.In recent years,renewable energy has received widespread attention,of which solar photovoltaic technology has been rapidly developed.Due to the photovoltaic cell output voltage and current will be affected by external environmental factors(Illumination intensity,ambient temperature,etc.),with intermittent and randomness.Therefore,in order to improve the energy conversion efficiency of photovoltaic power generation system,maximum power point tracking control has become a crucial link.This paper focuses on the related theories and control methods of MPPT control of photovoltaic power generation system.The main contents are as follows:1.The mathematic model of PV cell is established,the current/voltage characteristic curve and power/voltage characteristic curve are analyzed,and the basic structure of photovoltaic power generation system is introduced.The research status and problems of maximum power point tracking control(single peak and multi-peak)of photovoltaic power generation system are analyzed.The basic principle of Active Disturbance Rejection Control Technique and its research status in various fields are expounded.2.The small-signal state-space equation of photovoltaic power generation system is established.The 1st order linear ADRC(2nd order ESO)is designed to decouple the PV cell's output voltage,inductor current and load voltage.Finally,the singular perturbation principle is used to prove the stability of the controller.In order to verify the effectiveness and universality of the proposed method,the optimum voltage method,conductance incremental method and perturbation method are respectively selected for simulation comparison test.The experimental results show that the proposed method obviously increases the maximum power point tracking speed and greatly reduces the power oscillation.3.The dynamic characteristics of the solar cell series circuit are analyzed.Taking two photovoltaic cells as an example,the number of peak values of the working mode and the power output characteristic curve of the series circuit are analyzed.This paper introduces the OIV-INC of the maximum power point dynamic range.The control strategy is improved to further improve the control performance and speed up the tracking algorithm.Simulation experiments use three photovoltaic cells in series circuit model,respectively,under uneven lighting conditions and uneven time-varying illumination under the conditions of its output power tracking performance comparison.Simulation results show the effectiveness of the proposed method.