General steady-state analysis of three-phase self-excited induction generator feeding three-phase unbalanced load/single-phase load for stand-alone applications

A general steady-state analysis of a three-phase self-excited induction generator (SEIG) feeding a three-phase unbalanced load or single-phase load is presented. Symmetrical component theory is used to obtain relevant performance equations through sequence quantities. While the analysis of the system is inherently complicated due to unbalance and magnetic saturation, valid simplifications incorporated in the equivalent circuit for both forward and backward fields result in manageable equations suitable for computer simulation. Suitable nonlinear parameters are chosen corresponding to appropriate saturation levels. Using this technique a 7.5 kW, 415/240 V, four-pole, three-phase induction motor operated as a SEIG is analysed under different unbalanced loads and compared with experimental results. The feasibility of using three-phase machines for such unbalanced operations has been critically examined for stand-alone power generation.