Research On The Key Technologies Of Grid-connected Photovoltaic Power System

Photovoltaic (PV) power generation has become a very important part of future renewable energy in China. With the continuous research on the Grid-connected PV system it will play a more and more important role in the energy structure adjustment. It is made of the two parts that include the MPPT controller and the inverter for the household-type grid-connected PV system. This paper based on the grid-connected PV system has studied the characteristics of PV array, Maximum Power Point Tracking (MPPT) method, the control technology of the grid-connected inverter and so on. It also gives a relatively complete design of the grid-connected PV system, experimental prototype and experimental results.The thesis analyzes the working mechanism of photovoltaic array and its output characteristics, illustrates the principle of maximum power point tracking (MPPT), and gives a system introduction of general MPPT methods. And the common MPPT method of perturb and observe (P&O) is detailly discussed, include the reason of the failure estimation, optimized design method and arithmetic is introduced, and simulation anaysis are presented to verify the correctness. The thesis also has a good study on the technology of the grid-connected inverter. Based on the establishment of system models, the dual-loop control parameters are designed with the root locus. The hybrid control strategy with mixing repetitive control and PI control is studied because of the drawback of traditional PI control.Besides, the paper presents the integrated design of the grid-connected PV system, including the system structure, topology selection, assignment of the control resource, the selection of the power devices, the design of the magnetic components and the design of key sample circuit and the protective circuit. At last, a 500W grid-connected PV inverter is built, and some experiments are carried out to validate the above theory design.