Active DC-Link Split-Battery Quasi-Single-Stage Inverter: Architecture, Modulation, and Flexible Management of Battery Modules

Reyhaneh Eskandari, Alan J. Watson, P. Venugopal, Patrick W. Wheeler, T. B. Soeiro

This article provides a systematic investigation of active DC-link split-battery inverter, a three-phase quasi-single-stage topology that synthesizes a multilevel, pulsating DC link by integrating multiple split-battery modules into a cascaded half-bridge string connected to the three DC terminals of a three-phase neutral-point clamped inverter working as a voltage selector stage. Herein, a synergetic modulation scheme is used to coordinate the battery converter strings and voltage selector so that the high-voltage-rated switches operate only at low frequency with zero voltage switching transitions, while the low voltage-rated devices commutate at high frequency. Owing to its multilevel voltage-source behavior, it improves output power quality and electromagnetic interference, easing filter requirements. In addition, this study provides modulation strategies for the cascaded strings that enable flexible battery module management, including symmetric and asymmetric module voltages operation, an analytical semiconductor current-stress model under level-shifted pulsewidth modulation, and a comparative assessment against related split-battery architectures. The proposed architecture and modulation approaches are validated in simulation and experiments.