The Effect of Excitation Capacitors on Induction Generators in Loss-of-Grid Events

Induction generators require reactive power for voltage generation. The reactive power can be supplied from the excitation capacitor installed in the generator terminal. The reactive power also could be fed from the grid when the generator is connected to the grid. Under off-grid operations, the voltage and frequency generated by the generator are strongly influenced by the reactive power of the excitation capacitor. On the other hand, under on-grid operation, voltage and frequency are influenced by the grid. This paper describes the effect of excitation capacitors in off-grid operations, and under transition from on-grid to off-grid operation especially in the event of loss-of-grid. The study was conducted on 500 W 380 V three-phase induction generator. Machine parameters are known by laboratory measurements. Those parameters are used to simulate the operating conditions of the induction generator by using SIMULINK-Matlab. The results show that the operating point after the loss-of-grid events are strongly influenced by the excitation capacitor value and the load power factor conditions.