Control of induction motor drives equipped with small DC-Link capacitance

The paper deals with control of induction motor drives equipped with a diode rectifier and a small DC-link capacitance. Neither an AC choke nor a DC choke is used. It is necessary to use DC-link stabilization control if the mains inductance is not very low. Conventional DC-link stabilization controllers rely on the current controller. If no input choke is used, however, the natural frequency of the DC link is higher than the current-control bandwidth, and the conventional stabilization methods cannot be used. This paper proposes a control algorithm based on direct manipulation of the stator voltage reference. Furthermore, a recently proposed field-weakening controller is modified to better suit the oscillating DC-link voltage. Design recommendations for the proposed scheme are presented. Simulation results of a 110-kW drive show that the proposed scheme stabilizes the DC link and the dynamic performance is comparable with that of the conventional drive.