| Energy sources and environment is becoming a pressing problem for human living and development. Wind power has the abundant resources foundation in our country. The accumulative total installed capacity of China has jumped to the world’s first in2010, wind power has become a indispensable component of energy constitute.At the beginning of this thesis, the development situation of wind power is reviewed, then the development trend of wind power generation system is introduced. Based on the full power converter of the direct-drive wind power generation system that has greater overall efficiency and reliability, introduced the related multi-level converter technology.Second, this thesis presented a new wind power topological structure, which directly coupled the multiphase PMSG with the cascaded-multilevel inverter. At motor side, several three-phase PWM converters which have the same specification are used to adjust the reactive power of generator, supply the stable DC power for the cascaded-multilevel inverter at the same time. The cascaded-multilevel inverter of grid side transformed the DC power into high quality AC power at the required constant frequency, then input to the grid.Third, by comparison of several PWM control techniques that are used to the cascaded-multilevel inverter, the improved type of multilevel SVPWM control technology for cascaded-multilevel inverter is introduced. The described method simplified the complex voltage vector calculation, also increased the practicality in the engineering field.Finally, the simulation research of the cascaded-multilevel inverter is made by MATLAB/SIMULINK. The simulation results demonstrated the feasibility and advantage of the proposed strategy, laid the foundation for future research and practical work. |
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