A model for a novel variable speed cage induction generator

This paper presents a novel cage induction generator and a mathematical model, through which its behavior can be accurately predicted. The novelty of the generator is due mainly to the constant frequency electricity generation, without an intermediate inverter stage, by a 3-phase cage induction machine operated at varying rotor speeds. The technique uses any one of the three stator phases of the machine as the excitation winding, and the remaining two phases, connected in series, as the power winding. The two series-connected and one isolated (TSCAOI) phase winding configuration magnetically decouples the two sets of windings, enabling independent control. Electricity is generated through the power winding with appropriate excitation to the isolated single winding at any desired frequency, using a simple single-phase square-wave inverter or a reversible rectifier, when the rotor is driven at variable speed. The mathematical model, which accurately represents the proposed generator, is implemented in Matlab/Simulink. Simulations of the TSCAOI power generation under various operating conditions suggest that the proposed technique is viable, and is expected to gain popularity being simple, low-in-cost and not requiring output filtering for grid-integration.