Design and Control of the Brushless Doubly Fed Twin Induction Generator (BDFTIG) using dSPACE

The aim of this research is to present indirect vector control (IVC) for a Brushless Doubly Fed Twin Induction Generator (BDFTIG) for wind energy conversion. The system is anticipated as an advanced solution to the conventional doubly fed induction generator (DFIG) to decrease the maintenance cost and increase the system reliability of the wind turbine system. The proposed BDFTIG employs two cascaded induction machine sets, which consists of two wound rotor induction machines with their rotors connected in cascade to eliminate the brushes and copper rings in the DFIG. This new machine would ideally have one common rotor, and the two stators to be integrated within one housing. For the practical purpose of this research two separate DFIG’s were coupled together to a single prime mover. The dynamic model of the BDFTIG with the two machines’ rotors electromechanically coupled in a back-to-back configuration is developed and implemented using Matlab/Simulink. Based on the model, the control scheme for flexible power flow control in the BDFTIG with a bidirectional converter is developed. Independent control of the active and reactive power flow is achieved by a four-quadrant power converter under the closed-loop stator flux oriented control scheme. In the proposed control strategy, the generator speed tracks the reference speed very well, and thus the maximum power extract. Which is the optimum speed derived from the maximum power point tracking of the wind turbine.