The control method for the squirrel cage induction generator system without speed sensor driven by wind turbine has been studied. The estimation of the generator speed is realized by feedback of torque component of the generator current. To determine the control gains, the transient responses of the system with respect to the change of wind velocity, are evaluated theoretically. As a result, it is clarified that the speed and torque response of the system is dominated by the time constant of the speed estimation divided by generator slip. The upper limit for time constant of the speed estimation is found, which limits the converter capacity and suppresses the strength of the generator shaft.
In this system, to eliminate the start-up failure due to the stall of the wind turbine, the generator must start from a running state of rotor, where the starting speed is determined by the terminal voltages generate from the residual flux of the generator.