Sliding Mode Control of a Doubly Fed Induction Generator Supplying an Isolated RL Load

In this paper the authors present preliminary results concerning 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. This kind of system has already been considered in the past by other researchers, mainly by using PI-type regulators. However, it must be reminded that in electrical machines the existence of parameter changes (caused by several reasons like winding temperature variation, hysteresis and saturation, amongst others) is well recognized, but rarely accounted for. For this reason, a non-linear control strategy, namely 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 a controller for regulating amplitude and frequency of the voltage generated by a DFIG, which is a wound-rotor induction generator. First simulation results are presented as well. Finally, the conclusions of the work are given and future activities are described