In this paper, we propose a two-stage transmission hardening and planning (TH&P) model that can meet the load growth demand of normal scenarios and the resilience requirements of hurricane-induced damage scenarios. To better measure the resilience requirements, the proposed TH&P model includes two resilience assessment indexes, namely, the load shedding (LS) under the damage scenario and the average connectivity degree (ACD) at different stages. The first-stage model, which aims to meet the load growth demand while minimizing the LS, is formulated as a mixed-integer linear program (MILP) to minimize the total planning and hardening cost of transmission lines, the operating cost of generators, and the penalty cost of wind power and load shedding in both normal and damage scenarios. The second-stage model aims to further improve the ACD when the ACD of the scheme obtained from the first-stage model cannot reach the target. Specifically, the contribution of each transmission line to the ACD is calculated, and the next hardened line is determined to increase the ACD. This process is repeated until the ACD meets the requirements. Case studies of the modified IEEE RTS-24 and two-area IEEE reliability test system-1996 indicate the proposed TH&P model can meet the requirements for both normal and damage scenarios.

This paper presents resilience-oriented transmission expansion planning (RTEP) with optimal transmission switching (OTS) model under typhoon weather. The proposed model carefully considers the uncertainty of component vulnerability by constructing a typhoon-related box uncertainty set where component failure rate varies within a range closely related with typhoon intensity. Accordingly, a min-max-min model is developed to enhance transmission network resilience, where the upper level minimizes transmission lines investment, the middle level searches for the probability distribution of failure status leading to max worst-case expected load-shedding (WCEL) under typhoon, and the lower level optimizes WCEL by economic dispatch (ED) and OTS. A nested decomposition algorithm based on benders decomposition is developed to solve the model. Case studies of modified IEEE 30-bus and 261-bus system of a Chinese region illustrate that: a) the proposed RTEP method can enhance resilience of transmission network with less investment than widely used RTEP method based on attacker and defender (DAD) model, b) the influence of OTS on RTEP is closely related with contingency severity and system scale and c) the RTEP model can be efficiently solved even in a large-scale system.