MODELING AND EXPERIMENTAL ANALYSIS OF VARIABLE SPEED THREE PHASE SQUIRREL CAGE INDUCTION GENERATOR

Induction machines have wide applications in renewable power system and particularly in wind turbine power systems. In case of standalone wind power system applications, for generating single phase electricity single phase or three phase induction machines can be used. Three phase induction generator can be used to generate single phase electricity at constant or above synchronous speed by using the two-series-connected-and-one isolated (TSCAOI) winding connection without an intermediate stage. In contrast with single-phase cage induction machines, three phase induction machines are significantly less expensive, more efficient, and smaller in frame size in comparison with their single-phase counterpart of similar power ratings. This paper introduces a novel cage induction generator and presents a mathematical model, through which its behavior can be accurately predicted. The proposed generator system employs a three-phase cage induction machine and generates single-phase, constantfrequency electricity at varying rotor speeds without an intermediate inverter stage. The technique uses any one of the three stator phases of the machine as the excitation winding and the remaining two phases, which are connected in series, as the power winding. The twoseries-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 at both sub and super-synchronous speeds with appropriate excitation to the isolated single winding at any frequency of generation. An Experimental analysis and dynamic mathematical model, which accurately predicts the behavior of the proposed generator.