highly reliable single-phase ac to three-phase ac converter with a small link capacitor

Single-phase ac to three-phase ac converters are needed in numerous applications, including motor drives used for residential applications. These converters, however, suffer from an inherent problem of mismatch between instantaneous input and output powers. Specifically, the instantaneous input power has a dc component along with an alternating component with double-line frequency; while the three-phase instantaneous output power is only dc.

 Conventional single-phase ac to threephase ac converters use large electrolytic capacitors to handle this mismatch of power. However, these electrolytic capacitors may have high failure rates, which contributes to reduced lifetime of the converters. Moreover, these capacitors can be bulky and heavy. 

This paper introduces a new single-phase ac to three-phase ac converter that uses a small film capacitor instead of large electrolytic capacitors. Despite using a small film capacitor, the double-line frequency harmonic does not appear at the input or output currents/voltages. The principles of the operation of the proposed topology are presented in this paper, and its performance is evaluated through both simulations.

Keywords—universal converter, ac-ac conversion, double-line frequency ripple, adjustable speed drives.