Probabilistic Reliability Evaluation Under High Renewable Penetration: Evolution from Generation Planning to Transmission Planning

초록

This paper presents a new probabilistic adequacy evaluation methodology for composite power systems that integrate wind turbine generators (WTGs) into a conventional Hierarchical Level II (HLII) framework consisting of generators and transmission lines. To explicitly quantify the adequacy impact introduced by variable renewable energy sources (RESs), a new index termed Renewable Adequacy Impact (RAI) is proposed. The proposed method adopts a fully probabilistic modeling approach: conventional units and transmission lines are represented using two-state forced outage rates (FORs), while WTGs are modeled using multi-state representations derived from wind-speed probability distributions and corresponding power-output characteristics. An effective load model for HLII systems is developed to simultaneously incorporate generation outages and transmission constraints. The methodology is demonstrated using a two-bus sample system, showing how WTG uncertainty propagates through composite-system contingencies and affects adequacy indices such as LOLE, EENS, and EIR. The results indicate that the proposed HLII + WTG model enhances both the accuracy and interpretability of reliability assessment under high renewable penetration. Furthermore, the newly introduced RAI index provides a meaningful quantitative measure of renewable-driven adequacy impacts, offering practical insights for future Generation Expansion Planning (GEP) and Transmission Expansion Planning (TEP) in increasingly uncertain power systems.

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