A full frequency range average model for Vienna-type rectifiers

This paper presents a new mathematical model for three-level non-regenerative Vienna-type rectifiers exploiting the equivalence of this topology with three-level neutral-point-clamped (NPC) converters. Specifically, it models the rectifier operation using a positive- and one negative-rail switching function-the standard approach for NPC converters. This equivalent modeling renders the state space model of Vienna-type rectifiers structurally time invariant, enabling its conversion into the synchronous d-q frame, and its averaging over a switching cycle basis. The resultant model is consequently valid up to half of the switching frequency. An in-depth small-signal analysis is then presented showing that only the d-d channel and dc port of the rectifier present truly time-invariant dynamics, given the intrinsically pulsating power transfer between its ac and dc terminals; quasi-stationary small-signal analysis is thus mandatory for this type of topology. Simulation and experimental results with a 20 kW motor drive and 2 kW experimental prototype are used for validation purposes.