Steady-state analysis and performance of a stand-alone three-phase induction generator with asymmetrically connected load impedances and excitation capacitances

This paper presents a steady-state performance analysis of a stand-alone three-phase induction generator self-excited with unbalanced capacitances and supplying unbalanced loads. Using the method of symmetrical components, the complex three-phase generator-load system is reduced to a simple equivalent passive circuit. A function minimization technique is employed to solve this equivalent circuit in order to determine the excitation frequency and magnetizing reactance. The proposed method enables practically all cases of unbalanced operation of the self-excited induction generator to be analyzed. Emphasis is next focused on single-phase loads and a special phase-balancing scheme, namely the modified Steinmetz connection (MSC), is investigated. It is shown that perfect phase balance of the SEIG can be obtained with an appropriate combination of excitation capacitances and loads. The theoretical analysis is validated by experiments on a 2.2 kW induction machine.