Research On Photovoltaic Grid-connected Inverter

The maximum power point tracking control and inverter control are two key issues for photovoltaic grid-connected inverter,to study which can improve the efficiency of power generation and photovoltaic grid-connected inverter power supply quality. At present, the commonly used control method of maximum power point tracking many, but there are still tracking precision and light mutation conditions prone to error problem, which needs to carry on the further research and improvement; in addition, the traditional direct power control strategy is simple, convenient control, but at the same time, the switching frequency is not fixed and voltage inaccurate orientation problem, which should be improved and enhanced.This paper first analyzes the equivalent circuit of the photovoltaic cells, and use mathematical models to build simulation models, using this model to analyze the output characteristics of photovoltaic cells. Secondly, the analysis and comparison of four typical DC-DC converter, selecting the boost converter as the PV DC-DC converter, and then analyze the incremental conductance method, perturbation and observation method, the constant voltage method and self-adapt to the perturbation method works and the advantages and disadvantages,Design a dual-mode control method based on the constant voltage method and the adaptive disturbance, to solve the several control methods in the presence of the tracking precision and light mutation conditions prone to error, and MATLAB was used for modeling and simulation, to verify the feasibility of the design.Subsequently, in-depth study and analysis of the traditional direct power control strategy, aimed at the existing problems, the corresponding improvement, using a phase locked loop instead of sector selector, guaranteed output current and voltage have the same frequency and phase, solves the inaccurate orientation problem; space vector SVPWM instead of hysteresis comparators and the switching state table, solves the switching frequency is not fixed the problem, and at the same time to improve the control precision and stability, effectively reduce the harmonic content; in active power parameter settings are improved, so that the system can real-time adjust the output current according to the energy changes, the intermediate bus voltage stability in a set value, so as to protect the front stage maximum power tracking function smoothly, and MATLAB was used for modeling and simulation, to verify the feasibility of the design.Finally, the PV grid-connected inverter using MATLAB simulation, to verify the feasibility of the design program.The conclusions of this paper provides guidance to the research and design of photovoltaic grid-connected inverter.