Power controller for a wind-turbine-driven tandem induction generator

An analysis of the performance of a three-phase squirrel-cage induction motor with two independent sets of stator windings run in generator mode, termed a tandem induction generator, is made and the conclusions verified by tests. The two sets of stator windings are fed from a three-phase supply with opposite phase sequences. By physically rotating one set of stator windings, a phase shift between the applied voltages is introduced, resulting in the ability to control shaft torque. The authors propose a control scheme for extracting maximum power from a wind-turbine-driven generator. The scheme relies on the tandem generator´s ability to feed power to a grid at variable shaft speed and constant frequency, and on the great ease in executing shaft torque control