Research On Maximum Power Point Tracking And Control Strategy Of Grid-connected PV System

Energy problem is always intricate issues of the world. Currently, PV system has achieved a large of results. In this paper, two key questions based on the achievements of predecessors are deeply researched, one is maximum power point tracking (MPPT) issue and the other is the output current control of grid side. It is worthy improving the efficiency of MPPT and the tracking effect of current control methods.The source and significance of issues are illustrated firstly and the research conditions are described systematicly through home and abroad. At the same time, hot topics in PV research are also surveyed by camparing with the current research status of key problems.The basic principle of PV cell and the MPPT issue are analysed when output efficiency of PV cells is considered. Regular extremum seeking algorithm(ESA) has fluctuations problem at the optimal point up and down. Quadratic energy function based on improved ESA is presented. The disturbance will be decreased by judging in the specified threshold. Otherwise, the disturbance will be maintained and final purpuse is to reach the most optimal point. Through testing the steady and dynamic conditions, the simulation of proposed algortihm is superior to the rugular P&O and ESA method.The current control method of grid side is deeply researched in the control plane. Regular PI control has the steady error problem and PR control has the problem of controllor’s pamrameters and digital system accuracy. However, the proposed method can achieve the zero steady error, good robust and insusceptibility for parameters changing. Through changing the condition of output inductance and illuminance, three control methods are compared to simulate and find that sliding mode controller is better than proportion integral and proportion resonance control in case of tracking speed and total harmonic distortion.In order to vertify the feasibility of the proposed algorithm, the hardware and software of system are constructed. From the hardware plateform perspective of setting to study, hierarchical software system is designed in detail. The key hardware module and flow chart of software are presented, which lay the foundation of the debugging for the PV system.At last,the final result of experiment is analysed. The conclusion has two points. One is the MPPT algorithm which vertifies the feasibility of PV system, the other is the control method which proves the tracking effect, and have an advantage over regular PI and PR control methods.