In recent years, power variations and energy criteria have been the main motivations for developing regenerative drive converters for elevators . A better performing solution for power smoothing can be easily found by using a supercapacitor-based storage device, connected to the intermediary circuit of a variablespeed- drive system. In this paper, power and energy considerations are being accounted for in the design of the storage tank and regarding the maximum power demand from the feeding network. For the power-conversion circuit, which is necessary to compensate the voltage variations of the supercapacitors during charge and discharge, a high-efficiency converter topology is proposed, which allows the bidirectionnal energy flow under soft-commutation conditions. Additionally it offers a good flexibility for the optimal sizing of the supercapacitor voltage level. The typical behavior of the special converter is given, together with an analysis of the advantages related to the specific application.