Generation and Transmission Expansion Planning Model Incorporating Flexibility Metrics, Virtual Transmission Lines, and Unit Commitment Constraints

Abstract

Generation and Transmission Expansion Planning (GTEP) faces increasing challenges due to high penetration of variable renewable energy, transmission constraints, and demanding cost and reliability targets. This paper proposes a robust optimization framework that integrates Virtual Transmission Lines (VTLs), implemented through Energy Storage System (ESS) investments, to reduce and defer conventional transmission expansion while enhancing system flexibility across multiple timescales. The model incorporates coordinated Transmission System Operator (TSO) and Distribution System Operator (DSO) flexibility and adopts a data-driven distributionally robust optimization (DDDRO) approach to address uncertainty in demand and renewable generation. A multi-level structure jointly optimizes investment and operation, including unit commitment and ramping constraints through soft-linking procedures, ensuring operational feasibility. Network constraints are represented using a linearized AC optimal power flow model, and TSO-DSO flexibility interactions are explicitly embedded in the planning formulation.