Simplified Droop-Based Distributed Control for Single- and Three-Phase Compatible AC-DC Converters with Series Connectivity

This paper proposes a single- and three-phase compatible AC–DC converter with a simple distributed control scheme. The proposed system consists of independently controlled single-phase AC–DC converter modules, connected in series and/or parallel. This modular architecture enables flexible configurations with scalable capacity for both single-phase and three-phase operation, without requiring high-speed communication. In conventional series-connected systems, interactions among current controllers can cause overmodulation. To address this issue, the proposed control strategy extends droop control to the current control loop, enabling uniform load sharing even in series-connected configurations. A common control strategy is employed for both singlephase and three-phase operation, eliminating the need for control system modifications. The proposed architecture was experimentally validated using six 1.2-kW AC–DC converter modules. A 7.2-kW three-phase AC–DC converter, configured with two modules in series on the AC side and six modules in parallel on the DC side, operated successfully under rated conditions without overmodulation. Moreover, the distributed control scheme maintained continuous operation without any additional control actions even in the event of a failure in a series-connected module.