Modeling line outages and transmission line expansion in REMix-MISO

Abstract

The growing share of renewable generation results in higher power imbalances in the energy system and more situations in which transmission lines are loaded close to their thermal limits. Therefore, the aspect of the security of supply and grid expansions gain significance. This thesis presents the modeling of the impact of transmission line outages on the network power flows, the implementation of mixed-integer linear programming (MILP) transmission expansion planning (TEP), and the development of a security-constrained line expansion method that considers critical outages in TEP (SC-TEP). A post-contingency critical lines (PCL) algorithm is developed based on the Line Outage Distribution Factors (LODF) to identify the critical lines, which cause the largest number of overloaded lines in the power system with their disconnection. The PCL algorithm is applied to the IEEE 24-bus system. The integrated method first calculates a relaxed version of TEP without security constraints to select the critical lines and then integrates the critical contingencies into the TEP. The MILP-TEP and the integrated SC-TEP method are applied to a modified version of the IEEE 24-bus system. The methods are implemented in the energy system optimization model REMix-MISO and validated with a reference model. Overall, the optimization results show the accuracy and efficiency of the PCL algorithm, the MILP TEP, and the security-constrained line expansion method. The consideration of critical lines only in TEP can result in some critical lines not being expanded. However, the numerical results demonstrate that the integrated SC-TEP method is much faster than the application of the full N-1 criterion in MILP-TEP. Therefore, the proposed method can be used as an accelerated approximation of a N-1-secure energy system.