Coordination Strategies for Securing AC/DC Flexible Transmission Networks With Renewables

This paper studies key aspects of preventive and corrective security strategies to coordinate flexible transmission network infrastructure. To do so, we propose a two-stage stochastic optimization model that can efficiently coordinate available preventive and corrective control actions (pre- and post-contingency) from flexible network technologies, generation, and demand, while explicitly considering the likelihood of postcontingency events and wind/solar uncertainty. This stochastic/probabilistic model constitutes the counterfactual against which current deterministic, preventive operational practices are compared. Flexible network equipment such as HVDC and FACTS devices are efficiently modeled through a tight MILP representation and network losses are also included through a linear representation. Through several case studies, we demonstrate the advantages of probabilistic, corrective security to improve coordination of HVDC and FACTS setpoints and thus reduce network congestion and reserve holding levels, improving the overall efficiency of the system operation. We also quantify the value loss associated with current deterministic, preventive control operational practices when coordinating setpoints of flexible network equipment, demonstrating that adding flexible network technology could even increase system costs under a preventive security approach.