High‐Gain Isolated Bidirectional DC–DC Converter for Hybrid Fuel Cell Electric Vehicles

ABSTRACT In fuel cell electric vehicles (FCEVs), a large number of fuel cell (FC) packs need to be connected in series to match the DC bus voltage, which can cause charging imbalance issues. FC is also unsuitable for storing the energy generated during deceleration events or downhill movement. To address these issues, FC in combination of ultracapacitor (UC) is interfaced with proposed isolated bidirectional DC–DC converter (IBDC). Proposed converter is a modified version of a single‐ended primary inductor capacitor (SEPIC) converter. It offers high‐voltage gain and a noninverted output, which provides proper matching with the DC link voltage. Galvanic isolation and continuous input current is also achieved with the proposed converter for better performance of the FC/UC source. Compared with isolated SEPIC (iSEPIC) for the same power rating, the proposed topology requires a lower coupled inductor (CI) size, which reduces the size and weight of the converter. Furthermore, bidirectional capability enables regeneration during deceleration and downhill movement. In addition, a nonideal analysis of the converter is presented and small‐signal modeling is developed for control design. A 200‐W hardware prototype is developed, and experimental results confirm the effectiveness of the proposed converter with 91.6% analytical and 90.9% experimental efficiency.