Experimental investigation on steady-state and transient performance of a self-excited induction generator

This study presents a novel approach to determine the steady-state performance of a self-excited induction generator (SEIG). The method gives an intuitive understanding of the effects of loading on the steady-state performance of the SEIG, without requiring any major mathematical effort. The steady-state no-load voltage of the SEIG is determined as the intersection between the generator no-load curve and the capacitor characteristics. The proposed method extends this approach to a loaded generator by replacing the no-load characteristic by a new generator-load curve. The method is initially applied in a lab environment, but a suitable algorithm to be used instead is also introduced. The algorithm has been validated through laboratory measurement showing an excellent agreement between theoretical and experimental results. Furthermore, an experimental investigation of the demagnetisation process of the SEIG is performed, showing how remanent flux depends on applied fault or load resistance. This analysis reveals some issues not previously reported in the literature. The relationship between remanent flux and speed at which self-excitation occurs is shown to contain a discontinuity, above which a fixed minimum speed is required for re-excitation given a certain capacitance. Below the discontinuity the minimum re-excitation speed is dependent on how the generator was demagnetised.