Research On The Control Strategy Of Singel-Phase PV Grid-Connected System

With the shortage of traditional fossil energy and its endless environmental pollution problems, solar energy is paid more and more attention owing to its abundant storage, clean, safe and convenient expansion. Photovoltaic(PV) power generation accounts for an important position in the field of solar energy application. Especially, many remarkable results have been achieved on PV grid-connected power generation technology. Mainly taking into account the utilization efficiency of photovoltaic cells and the grid quality, the maximum power point tracking(MPPT) technology and the grid-connected control technology of single-phase PV grid-connected power generation system are researched in this paper.The utilization of solar PV power generation is illustrated firstly from the aspect of energy and environment. The present status of the development of photovoltaic power at home and abroad as well as PV grid-connected power generation are summarized. At the same time, the main research contents of the paper are shown. Secondly, the single-phase-two-stage topological structure is chosen based on the analysis of the PV grid-connected topologies under different classifications. The total control scheme of the system is designed, of which the DC/DC circuit realizes the MPPT control of the photovoltaic cell and the DC/AC circuit realizes both the grid-connected control and the stability of the DC bus voltage.In the MPPT control part, the analysis and simulation of photovoltaic cells model is carried on and the advantages and disadvantages of the commonly used MPPT methods are expounded. Then, a variable step size adaptive incremental conductance method is used and its superiority is verified by simulation experiment. In the grid-connected control part, the mathematical model of grid-connected inverter is analysed. After the scheme of current inner loop and voltage outer loop control being made, the current controller based on Quasi-Proportional-Resonant-Control and the voltage controller based on Auto-Disturbance-Rejection-Control are designed concretely.Finally, in order to verify the control effects of the single-phase PV grid-connected power generation system, simulation and experimental tests are completed. In the simulation test, by comparing the current control effect on PI control, PR control and quasi-PR control, at the same time, by comparing the voltage control effect on PI control and ADRC strategy, the rationality of the designed current controller and voltage controller is verified. In the experimental test based on hardware platform, the experimental results and simulation results are basically identical, proving the feasibility of the control methods.