A Security-Aware and Cost-Effective Preventive Control Strategy Against Cascading Failures in Hybrid AC/DC Power Systems with a Bi-Level Optimization Framework

To ensure economic dispatch and suppress cascading failures in hybrid AC/DC power systems, this study proposes a security-aware and cost-effective preventive control strategy based on a bi-level optimization framework. First, given the limitations of existing indicators and simulation methods in accurately characterizing commutation failures, the transient characteristics of such failures are analyzed using electromagnetic transient simulations in PSCAD. A classification approach based on Particle Swarm Optimization–Support Vector Machine (PSO–SVM) is developed to identify and categorize commutation failure scenarios. Then, both system security and economic performance are jointly assessed by considering the AC/DC security margin and total operating cost. A bi-level optimization model is constructed, in which the lower-level optimization model aims to obtain the system security margin, while the upper-level optimization model minimizes the total operational cost. To solve this model and determine the optimal generation dispatch strategy, an Improved Particle Swarm Optimization (IPSO) algorithm is employed. Finally, case studies on a modified IEEE 39-bus system verify the feasibility and effectiveness of the proposed strategy in mitigating cascading failures while achieving economic dispatch in hybrid AC/DC power systems.