New Monolithic Modular DC-DC Converter for Constant Current Offshore Interconnection With VSC HVdc Network

The rapid growth in HVDC (High Voltage Direct Current) grids has shown the falls of point-to-point connections. Several challenges such as the requirement of DC (Direct Current) fault blocking capability, interfacing of different grounding schemes, offering multi-vendor interoperability, and difficult to achieve high DC voltage stepping, represent serious issues to deployment of HVDC grids. DC-DC converters are considered the optimum candidate to overcome these challenges in HVDC grids interconnection. In this paper, a novel isolated hybrid monolithic modular DC-DC converter is proposed that interconnects LCC/VSC (Line Commutated Converter/Voltage Source Converter) based HVDC networks. It achieves smaller count of semiconductors, lower conduction losses and DC fault blocking. Detailed mathematical analysis, design, and control of the proposed DC-DC converter are illustrated. Also, both simulation model and experimental test rig are built to validate the proposed DC-DC converter under different normal operational and fault scenarios.