Flux weakening strategy of an induction machine driven by an electrolytic capacitor-less inverter

This paper presents a novel flux weakening strategy of an induction machine driven by an electrolytic capacitor-less inverter. In the electrolytic capacitor-less inverter, the DC-link voltage is fluctuating at six times of frequency of input three phase source due to its small DC-link capacitance. Hence, the decoupling of the fluctuation and maximum utilization of the DC-link voltage is the major issue in the electrolytic capacitor-less inverter. In this paper, the cost function is set to increase the voltage utilization of the inverter for the flux weakening operation of an induction machine. By the proposed cost function and flux weakening strategy, the operating speed of the induction machine is extended above base speed without any stability problem. The experimental results show the effectiveness of proposed strategy.