System stress with expanded use of interconnectors in the transition to net-zero

High Voltage Direct Current (HVDC) interconnectors will help enable net-zero energy systems by transmitting renewable energy from where it is abundant to where it is needed. They may also contribute to balancing services, for which there will be increased demand due to the expanded fleet of renewable generation. However, increased and more flexible use of interconnectors, along with changes in generator locations as renewables displace fossil fuels, may lead to congestion on existing AC transmission systems. In this paper, a transmission network model is used to investigate whether power constraints will restrict the use of HVDC interconnectors for flexibility services. A method, demonstrated on the GB transmission network (which is expected to accommodate increased HVDC interconnector and renewable generation capacity as it transitions to net-zero), is presented which explores interconnector activity and identifies which AC network assets limit the capabilities of the HVDC interconnectors and how often. Results showed that the number of constraints met on the GB network, when the interconnectors were operating at all combinations of full import or full export, reduces in future years. Therefore, the current GB transmission network is suitable for effective use of the planned increased number of interconnectors.