Power and Speed Control of Brushless Doubly-Fed Induction Generators

The brushless doubly fed induction generator (BDFIG) with a partially rated converter has characteristics of a squirrel cage induction generator and a conventional synchronous generator. Its control is challenging due to the machine's complicated structure, which requires an effective controller to stabilize it within its normal speed range and under various steady state and dynamic operations. In this paper, a comprehensive nonlinear vector control scheme is proposed for BDFIGs, where the speed control is achieved through the model reference adaptive control (MRAC), while the reactive power and electromagnetic torque control are achieved through a hybrid controller by combining the sliding mode and proportional-integrator (PI) control. Simulations using MATLAB/Simulink indicate that the proposed nonlinear control structure yields superior dynamic response when subjected to input mechanical power and reference speed changes when compared to a linear PI controller.