Impact of forced and unforced system parameter variations on network stability and system economics of radial MTDC networks

This paper focuses on investigating the impact of system parameters uncertainty on voltage droop-controlled Multi-Terminal High-Voltage DC (MTDC) networks. The voltage droop typically controls the power-sharing among the receiving end-nodes for minimum transmission power loss. The hierarchical control layers are used to update the droop constants to cope with the system power/parameter variations. In this paper, a study is presented elucidating the effect of unforced system parameter variations, as transmission line resistance uncertainty and the power injection variation, on the droop characteristic settings for radial MTDC networks, from system economics and network steady-state and dynamic stability perspectives. Moreover, forced system parameter variations, such as those due to cyber-attacks, are addressed in this paper. Cyber threat with a malicious attack on the communication system in the hierarchical control layers is considered particularly during power variations to investigate the impact of falsifying the DC voltage droop characteristics. Towards generalization, two different droop-controlled radial MTDC networks, with optimal droop gains adjusted for minimum transmission loss, are employed for explicating and assessing the presented concept.