This paper presents a new formulation and algorithm for the problem of unit commitment with security constraints, which can obtain the worst case of transmission network line outage and solve the problem under such conditions. Optimal charging and discharging of electric vehicles, optimal charging and discharging of energy storage systems, and flexible loads along with renewable energy resources are considered in the problem of unit commitment. Uncertainty of energy resources is modeled as a scenario-based method. In this paper, a multi-objective function that includes reduction of operating cost, no-load and unit start-up/shutdown, load shedding costs, load shifting, unit pollution, optimal charging and discharging of storages, and the power cut of renewable energy resources is considered. The proposed formulation is a mixed integer linear programming (MILP) model whose absolute optimal solution is guaranteed by powerful Gurobi solvers. To validate the proposed formulation, several study cases and test 6- and 24-bus networks are analyzed. The simulation results show that the proposed algorithm is effective in identifying the worst possible line exit of the transmission network so that the objective function of the problem increases by about 8% after the worst-case line exit from the network.