A bidirectional isolated DC-DC converter with low voltage stresses for energy storage systems integration

Abstract

Herein, a bidirectional isolated DC-DC converter with low voltage stress is introduced to utilise in energy storage frameworks. Two sets of coupled inductors (CI) and a transformer are utilized on the low-voltage side to increase voltage gain. Through the series connection of the secondary windings of the CIs with the primary windings of the transformer, the concluded voltage gain is improved by the multiplication of the turns ratios of CI and transformer. As a result, the voltage gains as well as the voltage stresses in both directions can be flexibly improved through three degrees of freedom, which are the turns ratios of the CIs, transformer and duty cycle. Clamp capacitors accomplish active clamping, and the energy saved within the leakage inductance is recycled. Additionally, some switches are performed with soft-switching and partially diminished switching losses. The steady-state analysis and extensive performance comparison of the proposed converter prove that the proposed converter outperforms the similar previous converters in the state-of-the-art. An 800 W 48 V/380 V prototype is developed to prove the performance of the proposed converter. The peak efficiency amounts of the proposed system in the high step-down and high step-up modes are 95.8% and 96.2%, respectively.