A Novel Bidirectional Five-Level Multimode CLLC Resonant Converter

In order to widen voltage gain of bidirectional on-board charger to meet requirements of electric vehicle with different voltage levels, a novel bidirectional five-level multimode CLLC resonant converter is proposed by combining the CLLC resonant tank module (RTM) with the five-level cascaded neutral-point clamp active bridge which is composed of two three-level neutral-point clamp (3L-NPC) bridge arms. Furthermore, the converter can, respectively, establish three voltage gain modes of high, medium, and low to effectively widen voltage gain adjustment capabilities through the fixed-frequency plus phase-shift hybrid modulation independently adopted in each 3L-NPC bridge arm, while soft-switching is realized by phase control between resonant current and input voltage of RTM. Meanwhile, the key parameters of RTM would be symmetrically designed to make bidirectional power transmission characteristics, which become consistent based on soft-switching and monotonic voltage gain control. Finally, according to the simulation platform and experimental prototype, it can be shown that the practical voltage gain is close to the theoretical design gain and converter has good dynamic performances after realizing soft-switching in each mode.

Automated summary

In this paper, a novel bidirectional five-level multimode CLLC resonant converter is proposed to widen the voltage gain for electric vehicles with different voltage levels. The converter combines the CLLC resonant tank module (RTM) with a five-level cascaded neutral-point clamp active bridge. It establishes three voltage gain modes of high, medium, and low through fixed-frequency plus phase-shift hybrid modulation, while achieving soft-switching through phase control between resonant current and input voltage of RTM. The symmetric design of key parameters of RTM ensures bidirectional power transmission characteristics and consistent voltage gain control.