Comparison of CSI and VSI based modular rectifiers with magnetic AC coupling for large current and low voltage applications

Rectifiers delivering large DC currents (>1000 Ampere) at low voltages ( < 24 V) have significant conductive losses. Using controlled rectifiers to provide an output current following a reference increase those losses. An approach proposed in several works uses multi stage converters connected in cascade, where an AC/AC frequency changer is connected to an AC/DC diode based converter across a high frequency magnetic link. The AC/AC converter connected to the ac mains voltage boosts the frequency and provides control on the current delivered to the load. The DC converter delivers the output current at the load voltage. The main goal of these approaches is the reduction of conductive losses by performing the control on the AC/AC converter. Additionally, approaches using modular topologies offer additional advantages, especially in terms of reliability. This work presents a modular topology based on voltage source DC links. The topology is explained and simulations are presented in order to validate theoretical considerations.