Security constrained unit commitment with multi-stage corrective control of hybrid AC/DC power systems with VSC-MTDC

Security-constrained unit commitment (SCUC) is a practical approach for maintaining a satisfactory level of security while enhancing the cost-effectiveness of system operations. However, previous research has not sufficiently addressed the risks of N-1-1 cascade failures, making it challenging to interrupt cascading failures in the slow successive tripping stage. This paper proposes an SCUC approach, which introduces the voltage source converter based multi-terminal high-voltage direct current (VSC-MTDC) transmission system as a multi-stage corrective control measure to handle both emergency overloads and hidden failures of relay protection after the N-1 initial fault. First, an operation model of VSC-MTDC is proposed to fully exploit the VSC's flexible and fast adjustment capability. Then, a multi-stage SCUC model is formulated. The base state aims to schedule the power of generating units and VSC stations according to the load forecast. After N-1 contingency, the VSC-MTDC is used for fast short-term correction to mitigate network emergency overloads. Subsequently, coordinated with unit re-dispatch for long-term correction, the N-1-1 secure correction reacts to the hidden cascading failures by additional load shedding. Third, the proposed model is solved by an improved Benders decomposition-based three-level iterative algorithm. Finally, case studies are conducted to demonstrate the effectiveness of the proposed approach.