Bidirectional rectifier-inverter multilevel topology without DC-link passive components

A capacitor-less rectifier-inverter topology based on a fundamental frequency switched rectifier and a three-level flying capacitor is presented in this paper. The DC-link is free of any passive elements (capacitors, chokes or braking resistors). The removal of the large and bulky DC-link electrolytic capacitor, typically employed in rectifier-inverter topologies results in the elimination of a fault prone element and can have positive effects on the maintenance and operational life of a power electronics converter. The elimination of the DC components also affects the DC-link voltage, which is no longer constant, and makes the use of grid-side AC filters a necessity. The topology and operational principles of such a topology are also verified through simulation results.