Sliding mode control of DFIG powers in the case of unknown flux and rotor currents with reduced switching frequency

This paper aims to implement a stator power control for a doubly fed induction generator (DFIG) with unknown flux and rotor currents. This goal is achieved based on a high-gain sliding mode control (HG-SMC) and by exploiting the fact that the flux remains near the nominal value. A new implementation scheme has been developed to achieve low switching frequency compared to the conventional method. The advantages of the new scheme over the old one are presented. Some interesting features of the new scheme are: (1) elimination of rotor's current sensor, which leads to lower cost and failure rate in the drive system; (2) simpler implementation because it does not require any modern method for the flux estimation; (3) longer lifetime of the rotor side-converter. The proposed control scheme is verified by simulations results and experiments on a 7.5 kW DFIG power prototype.