Flexibility Optimization in Robust Co-Optimization of Combined Power System and Gas Networks Using Transmission Lines’ Switching

Abstract

The operational flexibility in electricity networks with a high penetration rate of renewable resources has received a great deal of attention. In several research works, gas network constraints have been studied in operational flexibility studies because specific characteristics of the gas-fired units play a major role in procuring flexibility. However, the literature shows that the interval range of the uncertainty set has been assumed to be deterministic in most of the available research works. This paper tries to fill the research gap about stochastic modeling of the interval range of the uncertainty set. It considers the uncertainty set’s interval range an uncertain parameter, allowing optimal scheduling with less conservative assumptions. In addition, transmission lines’ switching is considered to optimize the network topology when the N-1 reliability measure is adopted. As a nonconvex problem, the recourse decision level would be a mixed-integer program (MIP), for which an exact nested column-and-constraint generation algorithm is used to find the best solutions. The proposed method was applied to IEEE six-bus and 39-bus test systems, interconnecting their corresponding gas networks. The test results infer that in a specified risk level for the IEEE six-bus and 39-bus test systems, with a rather slight increase (7.3% and 065%) in the operation cost, a large reduction (89% and 99%) in the out-of-sample cost could be obtained, respectively. The test results illustrate the advantages of the proposed method, using the variable interval range of the uncertainty set and corrective transmission lines’ switching. In addition, it was shown that if transmission switching is not considered, the total cost rises up to 18.8%.