In this paper the authors consider the Sliding Mode Control (SMC) of a Doubly Fed Induction Generator (DFIG), supplying an isolated RL load in a Variable Speed-Constant Frequency (VSCF) generation system. It must be reminded that in electric machines the existence of parameter changes, caused by several reasons like winding temperature variation, hysteresis and saturation, is well recognized, but rarely accounted for. For this reason, SMC has been considered. SMC has various attractive features like order reduction, robustness, disturbance rejection, and, sometimes, simple implementation. In this paper, some ideas of SMC applied by Utkin et. al. for controlling the speed or torque of a squirrel-cage induction motor are used to design two families of controllers for regulating amplitude and frequency of the voltage generated by a DFIG. First simulation results are presented as well.

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