In recent years

the issue of high harmonic due to wide application of power electronic device is widely discussed

but the study for the transmission characteristic of ultra-high harmonic of wind power generation is still insufficient.In this paper

the representative double-fed fan and direct-drive fan connection system is selected to set up mathematical model of its ultra-high harmonic transmission and define its ultra-high harmonic frequency separately.The harmonic distortion rate is adopted for quantitative discussion of both main frequency distribution range and overall contents of ultra-high harmonics.The single unit wind farm unit system is extended to the multiple units wind farm system and the current amplitude characteristic of ultra-high harmonics of wind farm in case of series connection of multiple units at various wind velocities.The correctness of related conclusion is verified by the PSCAD simulation.