A novel approach to integrating offshore wind power via the fractional frequency transmission system (FFTS) is briefly treated. The basic idea of FFTS is to improve the technical and economic performance of AC transmission systems by lowering the grid frequency

e.g. 50/3 Hz. FFTS is especially suitable for wind power transmission as the low frequency can significantly reduce the charging current. The basic structure and characteristics of a typical PMSG based FFTS offshore wind power system is described first. Then an example wind farm (300 MW

250 km) is used to compare the technical and economic pros and cons of the FFTS with the conventional approaches of HVAC and HVDC. The feasibility studies show that the performance of FFTS wind system is superior to that of HVAC and HVDC. The paper further analyzes the economical transmission distances for the above three integration approaches. The results demonstrate that the maximum transmission distance for HVAC is merely 80 km

and the critical transmission distance between FFTS and HVDC is 634 km. This result means FFTS suits most offshore wind farms

while HVDC is economical only for very long distance transmission. Therefore

FFTS is a very promising approach for offshore wind power integration.