Research On Key Technology Of Low-power Wind Power Inverter

At present, fossil energies, such as coal, oil, natural gas, are still the main parts of energyconsumption. However the reserves of fossil fuels are falling gradually and will be mined outsomeday; while serious pollution problems caused by consumption of fossil energy havedrawn people’s attention. As a kind of green energies, wind power is increasingly attracted bypeople. Wind power generation, especially the grid-connected inverter for wind powergeneration has become the hot and difficult topic in the world. In the regions with rich windresources and low voltage power grid, small wind power grid system not only can improvethe wind power utilization, but also can bring certain economic benefits for users. Accordingly,small wind power grid system is an inevitable trend of wind development.A wind power inverter used in independent/grid dual mode is proposed in the paper,which analyzed the main circuit structure of dual mode inverter. Considering the reliability,cost and work efficiency, the article finally chose the main circuit topology structure with highfrequency transformer which is always used for small power grid inverter.The system was divided into two parts with boost and inversion which were analyzeddeeply. Based on the analysis of control methods, single polarity SPWM was chosen togenerate the control signals for inverter. According to the different system work model,different control strategies were taken. In order to ensure the local load voltage support whenthe system operated independently, voltage current closed loop was used to control outputvoltage. When the system ran in the combined grid, current double closed loop was adopted tocontrol output current.Voltage control mode was used in the independent operation mode by the inverter, whilecurrent control method is adopted in grid operation. So in switching process of two patterns,particularly important and sensitive load, it is necessary that the inverter works smoothly,automatically and reliably. Different switching methods were analyzed and a control methodused for two switching modes was given in the article. MATLAB/Simulink simulation fordifferent switching methods proved that the switching method could work well.The reasons, damages and the detection methods of island caused in grid inverter wereanalyzed. On the basis of active frequency drift (AFD), an improved AFD method that is nolonger subjected to the influence of the load characteristics was proposed. Simulation resultsshowed the validity of the improved AFD.Additionally, hardware and software design of 3kW wind power inverter which based onTMS320F2812 DSP were completed in the paper.