Introduction: The GB electricity network is setting a fast pace of transition towards a net-zero carbon energy network. The system inertia and fault level are expected to decline continuously over time. Furthermore, the level of power electronic converters integrated into the electricity transmission network from renewable energy (e.g., wind turbines and photovoltaics), HVDC (High-Voltage Direct Current) links, traction loads, battery storage and FACTS (Flexible Alternating Current Transmission System) devices is going to increase dramatically and this will pose new risks to the electricity transmission network in terms of instability in the sub-synchronous and near synchronous frequency range. This is associated with transmission network resonant modes with power electronic converters time delay and control dynamics.  The aim of this project is to understand the phenomena and assess the risk of sub-synchronous and near synchronous instability resulting from controller interaction with the sytem in future low carbon energy scenarios and develop an innovative mitigation measure to address it.

Objectives: The objective of the proposed work is to develop an indepth understanding of the different forms of sub and near-synchronous oscillations and the associated instability risk in the future GB sytem. The work will provide recommendations on a suitable modelling approach and analysis methodology. Nevertheless, the work is also aimed at exploring an active mitigation measure which is capable of reducing multiple frequency oscillations to mitigate the instability risk in the transmission network.