Subsea DC collection grid with high power security for offshore renewables.

This paper presents a subsea DC collection grid with renewable power parks which inherently has robust DC fault protection and flexible expansion capability. By virtue of the applied DC/DC converter and the proposed DJ-Index Clamping control, different sections of the subsea grid are functionally interconnected and in the meantime decoupled in the event of DC faults. The faults are selectively isolated without the need for fast DC circuit breakers and system recovery from the faulty DC intertie branch is achieved by a coordinated operation strategy on DC/DC converters and DC disconnectors (or standard AC circuit breakers). A 200-MW test system is presented which consists of two 100-MW renewable energy sources (tidal stream and wind) and DC collection/transmission grids. The simulation results confirm the N-1 security of the presented topology and good control performance over a range of DC faults. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]