An assessment of Transient Assistive Measures using HVDC for special protection schemes: Case on the GB transmission system

Given the pressing need for additional transmission capacity to accommodate renewable generation, a range of advanced, technically effective and economically efficient corrective (or post-fault) actions that can release latent network capacity of the existing system, has been proposed. However, the increased use of corrective control to manage post-fault transmission overloads, for instance, in the form of generation and demand curtailments, has raised concerns related to angular and voltage stability of transmission systems and the reliability of the communication infrastructure on which the control relies. In this context, this paper proposes three Transient Assistive Measures (TAM) to supplement the generation and demand curtailment (intertrip) actions, which help in ensuring stability during the immediate post-fault period. The effect of communication delays is also considered. The proposed methods are analysed on a dynamic system model representing the GB transmission network. A 2 GW High-Voltage Direct-Current Link with Current Source Converters (CSC-HVDC) is modelled in DIgSILENT PowerFactory and incorporated into the full dynamic model of the Great Britain (GB) system to represent the planned western bootstrap. The proposed TAM are (i) a HVDC Power Oscillation Damping (HVDC-POD) controller, (ii) an adaption of the HVDC power order, and (iii) switchable reactive support devices. We demonstrated, based on studies performed on the GB transmission network, that without the proposed transient assistive measures, the benefit of corrective control is compromised and the risk of transient instability due to possible communication delays (in intertripping generation/demand), is significantly higher. It is shown that the proposed HVDC-POD is more economical and technically efficient, compared to the alternatives, even w