A Redundant Design and Control Strategy for Hybrid Dual Active Bridges Based DC Transformer

In this paper, a hot-standby redundant design and its control strategy are proposed for hybrid dual active bridges (HyDABs) based DC Transformer (DCT). This configuration of DCT is characterized with two types of isolated dc-dc converter, phase-shifted DAB (PSDAB) and series-resonant DAB (SRDAB). To achieve high reliability of SRDABs, several controllable PSDABs are connected with SRDABs in parallel. Moreover, the redundant PSDABs are operated in a flexible and controllable power mode under the normal conditions. Meanwhile, they share partial power with parallel SRDABS. If the HB converters in SRDABs are blocked due to inner faults, such as over-current, over-temperature, over-voltage and so on, the redundant PSDABs are employed to bear the whole power. Due to the hot standby method, there is no excessive voltage shock and current impact during the removal of the faulty SRDABs. The feasibility of proposed redundant design and control strategy is validated by the computer simulations on a 2250V/750V HyDABs-DCT.

I. Introduction

DCT is the core circuit in the high-frequency isolated power conversion system, such as dc distribution, electric locomotive traction and so on. Similar to the conventional ac transformer, it is capable of fulfilling different voltage transformation and galvanic isolation [1]–[2]. Due to extensive power semiconductor devices, it challenges the system efficiency and operational reliability of the system. Recently, efficiency optimization and high-performance protection have attracted a great deal of attention from researchers, along with its large-scale application.