To integrate large-scale intermittent wind power greatly challenges the power system operation on security analysis, active power dispatch and voltage control. The conventional centralized architecture of energy management system (EMS) could not satisfy the requirement to mitigate the wind power’s fluctuations, especially on network modeling, information communication, real-time analysis and flexible control. As part of a new distributed-centralized architecture, a distributed EMS for wind farm is proposed, as well as the key technologies that include network modelling of wind farm grid, state estimation, wind power forecasting, 3-D monitoring, security assessment, AGC and AVC, etc. An application example of wind farm voltage control is presented to illustrate the operation effects of the distributed EMS.