An Enhanced Fault-Tolerant DC-DC Converter with Redundant Circuit and Topology Reconstruction

Thanks to the advantage of high fuel efficiency and low emission, more electric aircraft (MEA) attracts increasing attention from modern aircraft. For MEA, power converters with high reliability which can remain normal operation after multiple unexpected faults, are highly demanded in electrical power system. In order to fulfill the high reliability requirement, a novel fault-tolerant LLC dc-dc converter is proposed for MEA in this paper, which can operate normally after twice shorted-circuit fault on switches. The first fault tolerance is obtained with the redundant circuit, and only two extra secondary diodes are added to achieve the second fault tolerance through topology reconstruction, contributing to low cost. Besides, the voltage and current stresses of primary switches almost remain unchanged in different operation modes and thus the circuit design is simplified. In this paper, operation process of the proposed converter is introduced in detail firstly. Then, the control strategy is provided, in which a soft mode transition method is employed to suppress current overshoot during the transition process. Finally, a 500W prototype is built and the experiment results are given to verify the converter effectiveness.