Dynamics and vector control of wound-rotor brushless doubly fed induction machines

This paper proposes a Wound-Rotor Brushless Doubly Fed Induction Machine (WRBDFIM), an alternative Brushless Doubly Fed Induction Machine (BDFIM) concept for wind turbine applications. The WRBDFIM consists of two separate machine winding sets different in pole-numbers, whose rotor windings are connected together. Both of the winding sets are housed in the same machine frame. The separate winding set arrangement aims to eliminate the circulating current and suppress the undesired spatial harmonics created by the conventional BDFIM. The two-phase equivalent circuit of the WRBDFIM is derived by connecting the circuits of two conventional Doubly Fed Induction Machines (DFIMs). The electrical and mechanical dynamics are identified to form the machine model for the Direct Power Vector Control (DPVC), which is proposed to regulate the generated power of the WRBDFIM without rotor position sensors. Simulation results confirm the machine dynamic model and also prove the effectiveness of the DPVC scheme that provides accurate control and fast tracking capability.