Design, Control, and Analysis of a Fault-Tolerant Soft-Switching DC–DC Converter for High-Power High-Voltage Applications

A modular isolated soft-switching dc-dc converter that can offer two levels of fault tolerance is proposed. A typical application is the wind energy conversion system used in offshore series-dc wind farm concept. The converter consists of input-parallel-output-series (IPOS) connected modules. Each module is a full-bridge dc-dc converter with an active rectifier, which can achieve zero voltage switching for all primary side switches and zero current switching for all secondary side switches and diodes. Under normal operation, the converter is operated with secondary phase-shifted modulation. When tolerable fault occurs in certain module, reconfiguration method ensures uninterrupted operation for the system. Additionally, modular structure provides another level of fault tolerance. More benefits of IPOS structure include reduced input current and output voltage of each module, module shedding capability, reduced ripple content due to interleaving, intrinsic balancing, and scalable control method. Both normal and faulty operations are simulated and also verified by scaled-down prototype experiment.