Stator field oriented control of doubly-excited induction machine in wind power generating system

Optimal operation of a wind power generating system is featured by the variable-speed constant-frequency mode in which maximum-power capturing from the wind turbine and constant-frequency interfacing with the power system are the primary concerns. A slip power recovery system with a doubly excited wound rotor induction machine is attractive in this situation. Field orientation control for doubly excited induction machines is studied. Since the operational condition and control objectives of the variable-speed constant-frequency generating system are significantly different from those of a variable-speed drive system, the implementation strategy of field orientation control of induction machines must be reexamined. A stator field orientation control method suitable for the doubly excited induction machine in a wind power generating system is developed. Digital simulation was carried out showing that the doubly excited induction generator with the proposed control strategy can track the optimal torque-speed profile of a wind turbine very well. In addition, flexible reactive power control was also accomplished