Long-term Clustered Unit Commitment Considering Lack-of-Inertia and Lack-of-Flexiramp Requirements

Long-term unit commitment (LT-UC) is the essential tool for operators to estimate the feasibilities of weekly/seasonal electrical production and operation processes. With the increase of renewable resources integrating into the power system, finding a suitable schedule commitment through LT-UC for maintaining adequate ramping reserve and frequency reserve against dynamic net-load fluctuations in low inertia gird becomes challenging. To solve this problem, this paper designs a refined LT-UC model to cope with multi-period requirements, including lack-of-inertia capabilities and lack-of-flexiramp ones, resulting from various net-load variabilities and uncertainties. In particular, a recognition method concerning lack-of-inertia and lack-of-flexiramp event screening is designed; then, associated security constraints concerning lack-of-inertia and lack-of-flexiramp connected to relevant intervals are extended. An improved LT-UC model is carried out by incorporating these derived constraints into LT-UC. Furthermore, to accelerate the computational time of the proposed model, a concise clustered LT-UC model that treats homogenization units into a clustered unit is re-constructed. Results are conducted based on a modified version of the IEEE 6-bus test system and the IEEE 30-bus test system, and the feasibility and effectiveness of the proposed model are tested by comparing it with existing empirical models.