Abstract: Direct-drive electrically excited synchronous motor（EESM）is obtained widespread utilization in

wind power generation system due to its advantages of simple construction and low cost. Firstly，a mathematical

model of EESM was derived and the direct torque control（DTC）algorithm for EESM was introduced based on the

mathematical model. Aiming at the characteristics of adopting back-to-back power converter to combine to the grid，dynamic response capability of the direct current componen（t bus voltage）was investigated during a sudden change of the load. To improve the dynamic response of bus voltage，a DTC-based control algorithm of product balance of torque and impulse time was studied. By analyzing the balance condition to stabilize the bus voltage in the process of sudden change of the load，optimal voltage vector series were calculated to stabilize the bus voltage by experiencing only one time control adjustment. Finally，the effectiveness of the proposed control algorithm was verified by simulation and experiments.

      Key words: electrically excited synchronous motor（EESM）；direct torque control（DTC）；product balance

of torque and impulse time ；wind power generation