Interfacing a fixed-pitch-angle wind turbine with a double-output induction generator

We describe the performance of a variable-speed, constant-frequency, double-output induction generator (VSCF—DOIG) that is being driven by a fixed-pitch angle wind turbine. The induction generator is run according to a control strategy that forces the generator to extract more than its rated stator power output from the wind without being overheated. Since, in the steady state, the mechanical power developed by the wind turbine is balanced by the electromechanical power developed by the generator, the interfacing problem may be solved by representing the wind turbine performance curve Cp = f(λ) as a polynomial function of the induction generator slip and wind speed. Using this approach, the induction generator outputs that correspond to a given wind speed can easily be calculated. This procedure is superior to previously used trial and error methods.