Interleaved multi-phase ZCS isolated DC-DC converter for sub-sea power distribution

Power distribution in subsea oil and gas platforms is a challenging task. In addition to efficiency and power density, reliability and maintainability of the power conversion system are very important. A compact modular design can boost both reliability and maintainability of the power conversion system. Multi-phase soft-switching high-frequency isolated DC-DC converter is proposed to build DC links from high voltage direct current (HVDC) transmission line. Input-series output-parallel connection of DC-DC converters is proposed for increased voltage blocking capability and decreased current ripple in the intermediate capacitive DC link. Each phase module of the power conversion system is implemented by a current-fed zero-current-switching (ZCS) full-bridge phase-shift PWM DC-DC converter. Phase shift between switches of each leg of the full-bridge is adjusted to control power flow while phase shift between different phases (modules) is selected according to the number of phases in order to minimize ripple of the output voltage. To verify the proposed system design and analysis, experimental results on scaled-down laboratory prototype are presented for a three-phase ZCS DC-DC converter.