This paper presents a control system of an isolated squirrel cage induction generator (IG), whose stator windings are connected to a PWM inverter/rectifier, using direct torque and rotor flux control (DTRFC) algorithm based on the sliding mode approach. Unlike the conventional vector control scheme, the proposed control strategy permits to directly control the flux and torque without resorting to the usually used current control loops. The three phase induction generator is modeled through a diphase approach and the magnetic saturation phenomenon is included both in the IG model and in the control algorithm via a variable magnetizing inductance, based on experimental tests. The control system should keep the dc voltage across the capacitor constant and equal to the reference value, regardless of changes in the rotor speed and load.

Keywords: Direct torque and rotor flux control (DTRFC), Sliding mode control, Autonomous induction generator, Magnetic saturation