A Multi-level Pseudo Single Active Bridge (PSAB) DC-DC Converter for Offshore DC Wind Turbines

The three-phase single active bridge (SAB) converter suffers from large second harmonic currents in the ac-link, low transformer utilization, and large required dc-link capacitors. This has led to a focus on the dual active bridge (DAB) converters in the literature, even for unidirectional applications like dc wind turbines. In these applications, the load-side transistors of the DAB converter transfer power for a small fraction of the fundamental period. This means investment in chips that are not used to the maximum of their potential. This paper proposes a hybrid of the SAB and DAB converters to solve this issue. The proposed converter can be controlled by phase shift modulation and performs similarly to a DAB converter. It is shown that this converter's total installed transistor apparent power is 40% and 45% less than that of conventional dual active bridge (DAB) and multi-level DAB converters, respectively.