Self-excited induction generators driven by regulated and unregulated turbines

This paper discusses the steady-state analysis and performance of self-excited induction generators (SEIG) driven by regulated and unregulated turbines. The basis of the analysis is the nodal admittance method as applied to the equivalent circuit model. For constant-speed operation, a simple iterative technique is used for the determination of the electrical frequency. When the turbine speed is regulated to give constant-frequency operation, a direct solution is possible by solving a quadratic equation in the per-unit speed. In the case of an SEIG driven by an unregulated turbine, a two-level iterative procedure is required for determining the operating speed and torque. The Secant method is found suitable for the additional level of iteration and convergence is fast. Experimental investigations on a 2 kW three-phase induction machine confirm the accuracy of the proposed methods of analysis.