Impact Assessment of FCUC on Optimal Design of UFLS Settings in Island Power Systems

A frequency constrained unit commitment (FCUC) formulates the non-linear, non-convex frequency dynamics to obtain the generation dispatch of island power systems (IPSs). Even with FCUC, under frequency load shedding (UFLS) is inevitable for sufficiently large contingencies. The objective of this paper is to assess how generation dispatches obtained by FCUC affect and change optimal settings of UFLS schemes and the associated dynamic performance. By using a real-world Spanish island, the UFLS scheme is optimally tuned for both the standard unit commitment (STUC) and the FCUC. The dynamic performance of both UFLS schemes are compared in terms of average shed load and frequency nadir values after each generator outage. Results show that FCUC increases the IPS cost by 10.8%, but the improvement in the dynamic frequency response is not fully exploited unless the UFLS scheme settings are re-tuned for the new optimal dispatch.