A Wide Input Voltage Range Converter With Input Voltage Autobalance in Medium Voltage Application

This article proposes a wide input voltage range converter with input voltage autobalance capability in medium voltage dc (MVdc) applications. The input voltage of each series-connected module is autobalanced by several series-connected half-bridges with balancing branches, and the current of each half-bridge is also autobalanced. By replacing the direct connection line with an LLC resonant tank and two clamping diodes between the bus capacitors and the balancing branch, both pulse frequency modulation (PFM) and phase shift modulation (PSM) are introduced to the converter without any additional active components. A wide input voltage regulation control scheme is proposed based on the topology. In addition, the converter is operated under a soft-switching state. Finally, a prototype with 3 kV dc input and 200 V/1 kW output is built to verify the feasibility of the proposed topology.