Research And Design Of Single-phase Two-stage Photovoltaic Grid-connected System

Solar energy is one of the most promising,most realistic,cleanest and renewable energy sources that can be exploited on a large scale in the world today.With the increasing environmental pollution and the increasing scarcity of energy,the development and use of solar energy has become an urgent task for human development.In recent years,great progress has been made in the use of solar energy to generate electricity.The main development method is the research of grid-connected photovoltaic power generation.Research and design of photovoltaic grid-connected systems have very important practical significance.This paper mainly studied single-phase two-stage photovoltaic grid-connected systems,and discussed and analyzed them in detail.Detailed analysis and research on the structure of photovoltaic grid-connected systems,basic principles of photovoltaic cells,selection of component parameters,tracking control of maximum power point,and inverting grid-connected control strategies.This paper discussed the development status and background significance of photovoltaic power generation systems at home and abroad,and studied and analyzed the specific structural principles and control strategies.First,the basic circuit principle and equivalent model of the photovoltaic cell were studied in detail.And in the MATLAB/Simulink environment,a photovoltaic cell simulation model was built,and the variation of the output curve characteristics under different external conditions was simulated to provide a theoretical basis for maximum power point tracking control.The Boost circuit was used in the front stage,and the components and parameters were selected through analysis and calculation.On this basis,the advantages and disadvantages of several common control methods for maximum power point tracking were studied and analyzed.Then,the shortcomings of several common methods were compared and analyzed.The original methods were improved,and the dual mode control using the two methods was combined.In the method,the maximum power point tracking simulation model of Boost circuit was built under MATLAB/Simulink simulation software.The simulation analysis and comparison of different methods were performed.The improved method improved the tracking speed and robustness.The rear stage adopted a single-phase full-bridge DC/AC inverter circuit to analyze and calculate the parameters of the components.By analyzing the traditional methods,the deficiencies in tracking without static errors were improved,and a virtual vector-based voltage and current double was proposed.The closed-loop control method controls the grid-connected inverter.The PI controller was used as the voltage outer loop,the quasi-PR controller was used as the current inner loop,and the single-phase SVPWM modulation method was used to trigger the inverter control,and the simulation model of inverter circuit was built.Through the simulation analysis and comparison of the control strategy,verified its correctness and validity.Finally,based on the theoretical analysis and control strategy research above,the hardware circuits of the system main control circuit,sampling circuit,etc.,as well as the main program of the system software,the cycle interrupt subroutine,and the capture interrupt program were designed.The entire simulation model was built for the single-phase two-stage photovoltaic grid-connected system,and the control strategy was simulated and verified.The feasibility and superiority of the method presented in this paper were verified from the aspects of bus voltage regulation and high-quality grid-connected current.