Bidirectional Isolated Half Bridge Three-Level Resonant DC–DC Converter and Optimized Modulation Strategy

In this article, a bidirectional isolated half-bridge three-level resonant dc–dc converter is proposed, where the voltage stresses of all power switches are limited to half of the input or output voltage. Only eight power switches are used in the proposed converter and the system volume and cost are decreased. The corresponding universal modulation strategy with the ability of auto-balance of the dc side split capacitors voltages is proposed and the steady-state characteristics is analyzed. In order to improve the efficiency, a multivariable coordinated optimization modulation strategy is proposed to realize the full-range quasi-minimum current trajectory and the full range zero voltage switching. The switching loss, conducting loss, and current stress are all reduced. The correctness and feasibility of the proposed converter and its optimization modulation strategy are verified by the detailed experiment results.