VSC-HVDC power transmission system that connected long-distance high-capacity wind farm to the grid will be an important direction of the wind power technology development. The grid access solutions designed according to traditional AC grid structure could not fully reflect the advantages of the VSC-HVDC transmission. Firstly the typical grid solutions of VSC-HVDC based wind power system is analyzed briefly. And then, several new topology applied the wind farm internal DC bus and the Variable Speed DC (VSDC) power system that is suitable for those topologies are proposed. The operating control of VSDC is discussed and maximum wind power tracing is realized by simulation in the end.