2. Wound-Rotor Doubly-Fed Induction Generator (DFIG) Figure 1 shows a typical DFIG scheme employing voltage source converters. With the aid of power flow diagrams, power-slip graphs and equations, explain the generating mode of operation at (a) sub-synchronous and (b) super-synchronous speed. Rotor Gearbox DFIG Current sensing Converter A DC link Controller Figure 1 Converter Transformer Current sensing Mains grid (30 marks)

Fig: 1