First real-time implementation of DC grid protection strategy

This paper demonstrates the performance of a three-terminal DC grid test system modelled in a real-time digital simulator (RTDS) platform at ABB´s DC Grid Simulation Center. In this hardware-in-the-loop simulation arrangement, all the converter stations, AC network equivalents, transformers, cables and the DC switchyards including DC breakers are modelled inside RTDS following a dual time-step strategy. However, the entire control and protection system is implemented in the ABB´s MACH control and protection platform. The MACH system receives the measurement signals from the RTDS through analog and digital I/O cards and sends switching order to the converter valves and breakers. The selective and time-critical performance of the protection functions in case of DC faults is demonstrated in this paper through real-time simulation.