Determining and implementing an approach to system frequency and inertial response in the Ireland and Northern Ireland power system

Ireland and Northern Ireland have policy objectives to have 40% of total electricity consumption to be provided by renewable sources by 2020. Approximately 37% of the total energy will be supplied by windfarms. As a separate synchronous power system, the operational challenges to achieving this securely and effectively are significant. In particular, it has not yet been established to what level a synchronous power system can be operated with non-synchronous generation including windfarms and HVDC interconnectors. In this regard a suite of ten distinct technical issues were examined employing time domain dynamic, transient and frequency response techniques with respect to increasing system non-synchronous penetration (SNSP) levels up to 100%. This paper concentrates on the system frequency and inertial response following the loss of significant in feeds. The modeling, based on data consistent with the Grid Code standards in Ireland and Northern Ireland, suggests that the security of the power system is compromised for frequency response with SNSP in excess of 50% if the current operational practice and performance from generators and windfarms continues. However a range of mitigation strategies examined including emulated inertia, alterations to the loss of mains protection for distribution connected windfarms and improved reserve from conventional plant is presented and their impact on the overall efficient operation of the power system.