Protection of large partitioned MTDC Networks Using DC-DC converters and circuit breakers

Abstract

This paper proposes a DC fault protection strategy for large multi-terminal HVDC (MTDC) network where MMC based DC-DC converter is configured at strategic locations to allow the large MTDC network to be operated interconnected but partitioned into islanded DC network zones following faults. Each DC network zone is protected using either AC circuit breakers coordinated with DC switches or slow mechanical type DC circuit breakers to minimize the capital cost. In case of a DC fault event, DC-DC converters which have inherent DC fault isolation capability provide 'firewall' between the faulty and healthy zones such that the faulty DC network zone can be quickly isolated from the remaining of the MTDC network to allow the healthy DC network zones to remain operational. The validity of the proposed protection arrangement is confirmed using MATLAB/SIMULINK simulations.

Enhanced Control of Offshore Wind Farms Connected to MTDC Network Using Partially Selective DC Fault Protection

“…Highly selective protection system in which DCCBs can isolate faulty DC lines in less than 5 ms without the need for converter blocking provides a viable technical solution for handling DC faults in MTDC grids. However, the high cost of DCCBs has led to quest for low-cost alternatives such as partially selective DC fault protection strategies that use a combination of reduced number of DCCBs and slow ACCBs to clear DC faults while retaining some of the pre-fault power transfers [26]. Nonetheless, the slow partially selective DC fault protection strategy requires significant modifications to WTC control, particularly, to maintain offshore AC voltage and frequency for extended period of time in the orders of several seconds after the blocking of offshore MMC.…”

Review of DC fault protection for HVDC grids

“…To rationalize the cost and reliable system operation, network partitioning of a large DC network is proposed in Liangzhong, Jing, Lie, and Rahman (), Rahman, Xu, and Liangxhong (), and Rahman, Xu, and Yao (). As shown in Figure , fast acting DCCBs or DC‐DC converters are only equipped at strategic locations which partition the large DC system into a number of small DC network zones.…”

Control of Offshore MMC During Asymmetric Offshore AC Faults for Wind Power Transmission

“…o date, there are large amount of offshore wind powers already installed in Europe and many new plants are under construction or at planning stage [1]. Among several transmission system technologies, voltage source converter (VSC) based high voltage DC (HVDC) transmission technology offers a cost-effective solution for connecting remote offshore wind farms (OWFs) and a number of such schemes are already in operation [2,3].…”