A dynamic model of direct drive permanent magnet synchronous generator（D-PMSG） wind turbine is developed with ElectroMagnetic Transient Program/Alternative Transient Program（EMTP/ATP） software， on the basis of operational characteristics of D-PMSG with variable speeds. A novel coordinated control strategy of frequency and rotational speed is proposed to prevent second frequency variation caused by activation of rotational speed protection. Simulation results show that the proposed control strategy can capture maximum wind power in normal operation， and also minimize frequency variation following a sudden change of large load， which avoids second frequency variation and torque sudden change.