The Research And Design Of High-frequency Flyback Single Phase Inverter For AC PV Module System

In recent years, along with the declining production of the fossil fuels, there has been a growing interest in exploring renewable energy resources internationally. Solar energy, wind energy, geothermal and tidal energy can be used by human. The solar power with its rich resources, wide distribution, renewable and pollution-free advantages are highly valued by scholars. The solar energy are converted into electricity directly through PV effect. Solar photovoltaic technology as a new type of power generation technology is gained more and more usage. In recent years with the development of photovoltaic energy, the photovoltaic power system inverters as the main research object are researched by scholars widely.The topological structure of photovoltaic inverter is varied. In the past, the centralized inverters are mainly considered. Presently, the application of group tandem vibratory inverters and tandem vibratory inverters is more and more. A concept of the AC photovoltaic module system as a new technology is developed recently. In this system, pv module and inverter are integrated together as an AC PV module, and the AC modules are connected in parallel with the grid. Because the inverter and pv module don't match, the power loss is inevitable in the traditional inverter. The AC PV module system can overcome the defect.Based on AC PV module technology, a 200W single-phase photovoltaic (pv) grid inverter prototype is designed in this paper. The major works are as follows:(1). Summarized the background and status of photovoltaic power generation; Analyzed its advantages and disadvantages, and common problems in its research process to find the breaking point of this project.(2). According to the requirements of this system, and combining with the advantages and disadvantages of previous topological structure, this paper presented topological structure of the single-phase high-frequency flyback grid inverter applied to the AC PV module system, and control strategy combing the multilevel pulse sequence control technology with peak current control technology. Its working principle and states were also analyzed. (3). Through photovoltaic cell's characteristics and the equivalent circuit model, this paper analyzed the maximum power point tracking(MPPT) principle, and several common maximum power point tracking algorithms. Based on the principle of balance of power, this paper put forward the MPPT algorithm to track the maximum power point rapidly in this topology.(4). Designed simulation model of the single-phase high-frequency flyback grid inverter based on multi-level pulse sequence control and peak current control with MATLAB. Comparing and analzing the simulation results of the load and gird, this paper proved the feasibility of topological structure and provides theory basis for the device selection of the subsequent inverter.(5). Designed hardware circuits of power switch, flyback transformer, LC filters, DSP controller, sampling circuit and drive circuit, and also DSP's software based on the multi-level pulse sequence control and peak current control.(6) Combining with the 200W photovoltaic inverter prototype, this paper designed an experiment operated independently, and get the test waveforms. It was proved that main circuit parameter is reasonable. This inverter can realize the conversion from DC low voltage to the gird AC voltage with high efficiency, stability and reliability.