A New Smooth Synchronization of Brushless Doubly-Fed Induction Generator by Applying a Proposed Machine Model

The Brushless Doubly-Fed induction Generator (BDFG) has a commercial potential for wind power generation, due to its low maintenance cost. For simplicity, the Cascaded Brushless Doubly Fed induction Generator (CBDFG) topology is usually applied as a model for BDFG. The BDFG-based wind turbines must be synchronized and connected to the grid, without inrush current. This paper purposes an improved Direct Torque Control (DTC) method for smooth synchronization of BDFG. Since BDFG has a complicated model, due to the resistance and voltage source in its rotor loop, finding proper references for smooth synchronization is difficult. To overcome this difficulty, a new model for BDFG is proposed. Appropriate flux and torque references for the DTC scheme are proposed based on this model, in order to achieve grid synchronization without inrush current. A 2-MW BDFG is simulated to show the efficiency and accuracy of this proposed method. The experimental results of a 3-kW laboratory scale BDFG confirm the efficiency of this proposed method.