Technical performance of different DC CB technologies for future HVDC Grids

Abstract

Multiterminal dc (MTDC) network is preferred due to its reliability, security of supply and flexibility. However, MTDC network also comes with the protection challenges resulting from dc faults. Hence, the dc circuit breaker (DC CB) is imperative in such a network. In these recent years, several DC CB technologies have been proposed and demonstrated by different manufacturers. Besides, these DC CB technologies differ from each other in terms of the speed of operation, interruption capability and costs. Hence, for the optimal performance of the MTDC network, a study of the co-ordinative operation of different DC CB technologies is required. In this thesis, two typical types of DC CBs are modelled in detail and implemented in a 4-terminal MTDC network in PSCAD environment, by considering operation time, interruption capability and interruption characteristics. The obtained results are used for DC CB’s selection optimization methodology for the future MTDC networks. Similarly, a scaled model of DC CB has to be analysed in terms of its interruption capability in MTDC network considering various scenarios. Therefore, in this master thesis, technical performance of DC CB technologies is conducted for a test and multiterminal dc network in EMT based software environment.

The DC CB is the key to unlock the reliable operation of a Multi-terminal direct current network, whereas fast, effective and accurate models are frequently needed for system-level studies. Due to higher subsystem components in DC CB, a detailed DC CB model creates a bottleneck in the network analysis. This thesis also proposes and compares, an average model with a detailed model of Voltage source converter Assisted Resonant Current (VARC) and Mechanical DC CB in MTDC Network in terms of their performance and computation time for two typical simulation cases. The average and detailed model is modelled and simulated on the PSCAD/EMTDC electromagnetic transient platform. Decisively, this thesis concludes by presenting an accurate response of the average model during the fast transient event, showing additional computational advantage.