The Research Of Converter Based On Direct-drive Permanent Magnetic Synchronous Wind Power Motor

Direct-drive wind power generation system's control circuit is based on the stator.The frequency of current is changed into the same frequency with the AC power grid by converter.Therefore the converter rated capacity is the same of the Permanent magnet synchronous generator.The existing devices'voltage level did not achieve a breakthrough until multi-level technology appearance.Multi-1evel converter can reduce the harmonic content and be controled very flexible.It is very suitable for direct -drive wind power generation system.Therefore,the research on the multi-level converter in wind power system has a very broad application prospects.The technology of three-phase three-level neutral-point-clamped PWM rectifier was presented in this paper.The basic principle of space voltage pulse width modulation was analyzed,and the algorithm based on g-h coordinates was proposed.In the algorithm,the voltage vectors are transformed to xy plane,and then corresponding components are normalized. The selection of voltage vectors are determined by the decomposition of the reference vector,and then calculate the operating time of the selected voltage vectors in a control cycle.Compared to conventional algorithm which requires a complex discrimination of sectors and selection of redundancy states, the algorithm is with no selection of them,and also is general and simple to realize,needs small memory.Finally,the simulation model of wind turbine,permanent magnet synchronous generator,three level PWM rectifier,three level PWM inverter is set up by using Matlab\Simulink.Simulation results prove the merit of the algorithm in keeping neutral point voltage balance and resisting large load disturbance.