A Communication-less Voltage Balancing Strategy for Modular Isolated DC-DC Converter Based Platform-less Offshore Windfarm

In this paper, a DC collection system for offshore windfarms using modular isolated DC-DC converters with an input parallel-output series (IPOS) configuration is considered. The series connection at the output terminals of the converters forms the High Voltage DC (HVDC) link, which eliminates the need for an offshore platform to house a large step-up transformer. However, the unequal nature of the wind power inputs at different wind turbines (WTs) leads to an unequal voltage distribution among the series connected DC-DC converters, with some of their voltages becoming unacceptably high. This paper proposes a simple voltage balancing scheme of the IPOS structure by varying the input voltage of each converter in proportion to its output voltage. This approach eliminates the need for fast communication among controllers of different WTs and achieves voltage balancing of the DC-DC converters' input and output voltages.