HVDC-based Fast Frequency Support for Low Inertia Power Systems

This paper analyses and compares different methodologies for supporting system frequency in low inertia power systems using HVDC interconnectors. Reduced system inertia, caused by the massive integration of converter-interfaced renewables and the displacement of conventional synchronous generation, can result in high values of rate of change of frequency (ROCOF), increasing the risk of frequency stability problems. In this paper, HVDC interconnections are analysed to determine their capability to provide support to the frequency stability between the Great British (GB) power system and the Continental Europe (CE) power system. Different frequency support control schemes (including droop control and the exchange of Frequency Control Reserves) are modelled and compared for a variety of cases. HVDC interconnector constraints including maximum power ramp rates and available capacity for frequency support have been derived by analysing historical operational data and incorporated into the analysis. Probabilistic uncertainty analysis considering variations in system inertia and the availability of interconnector capacity for frequency support has been performed. Studies are performed on a simplified frequency-based model of the future GB power system. The findings illustrate that droop control provides the best frequency support mechanism.