Research On The Technologies Of Single-phase Two-stage Grid-connected Photovoltaic Inverter

With the development of the world economy, the energy crisis and environmental protectionhave become increasingly attracted attention in the field of new energy power generation.Solar powerhas become one of the most important part. Photovoltaic grid as the main form of solar energyutilization will surely develop rapidly, and thus gradually replace traditional energy.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 ofgeneral MPPT methods. The thesis also has a good study on the technology of the grid-connectedinverter. Based on the establishment of system models, the dual-loop control parameters are designedwith the root locus. A new dual-mode time-sharing control of one-phase two-stage grid-connectdPhotovoltaic Inverter is simulated. The simulation results show that at any time a single switch workin the high-frequency switching state which helps to improve the efficiency of the system.Besides, the paper presents the integrated design of the grid-connected PV system, including thesystem structure, topology selection, assignment of the control resource, the selection of the powerdevices, the design of the magnetic components and the design of key sample circuit and theprotective circuit. A3KW grid-connected PV inverter is built, and some experiments are carried out tovalidate the above theory design.At last, a method of fast fault detection of the Micro-Grid system isintroduced.