As distribution system (DS) flexibility becomes crucial for transmission system operator (TSO) network management, data privacy concerns hinder effective interoperability. The notion of feasible operating region (FOR) has emerged as a promising privacy-preserving concept. However, effectively leveraging FOR in TSO operations remains challenging due to three key factors: its accurate determination in large-scale, meshed DS networks; its tractable analytical representation; and its economic valuation. The present paper proposes an AC optimal power flow (OPF)-based method to construct a three-dimensional PQV-FOR that explicitly accounts for voltage variability and diverse flexibility-providing unit (FPU) characteristics. The construction process employs a two-stage sampling strategy that combines bounding box projection and Fibonacci direction sampling to capture the FOR. Then, an implicit polynomial fitting approach is introduced to analytically represent the FOR. Furthermore, a quadratic cost function is derived over the PQV domain to monetize the FOR. The resulting framework enables single-round TSO-DSO communication without iterative exchanges. Case studies on meshed DS with up to 533 buses, integrated into TSs, demonstrate the method’s efficiency compared to standard AC-OPF. On average, the proposed approach yields negligible cost deviations of at most 0.058% across test cases, while reducing online computation times by up to 58.11%.
Dindar et al. (Mon,) studied this question.