Investigation of Modular CLLC DC/DC Converter using Bypass Control for Wide Output Voltage Regulation

Abstract

With the recent emerging demands in power electronics and electric grid of the future, resonant converters like CLLC converter are gaining popularity in applications like dc microgrids because of their advantages like high efficiency and bidirectional operation capability. However, one limitation of such converters is their limited voltage range which makes it hard to interface wide output voltage range loads like electric vehicle charging. Using additional power conversion stages solves this issue but it comes with added cost and reduced efficiency. This paper proposes a novel converter topology referred to as modular partial power architecture that has reduced power conversion stages and a novel bypass control strategy which allows it to have wide voltage range. Using the bypass control method, full voltage range of 0-100% is possible with bidirectional power flow by bypassing or turning on the modules based on voltage requirement. The detailed design considerations for this converter have been analyzed for a specific design case, and it is shown that the device losses can be reduced by up to 60% at full load. The working of the converter and the control strategy have been verified both in simulation and hardware.