Modeling and Analysis on the Reliability of Ultra-HVDC Security and Stability Control System Considering the Overall Architecture and Different Operation Modes

With the rapid development of ultra-high voltage direct current (U-HVDC) transmission systems, the security and stability control system (SSCS) plays an increasingly important role in ensuring the reliable operation of the power grid as the second line of defense for power system protection. To analyze the impact of SSCS overall architecture on the system reliability, firstly, a reliability analysis method for the SSCS is proposed to correlate the hardware, software and communication channel of the U-HVDC's SSCS under different U-HVDC's SSCS operation modes by establishing a fault tree model of the SSCS. Secondly, the sequential Monte Carlo method is employed to analyze the reliability of the U-HVDC's SSCC model considering the failure rate and maintenance time for each part of the SSCS. The proposed fault tree model and reliability analysis method is used to simulate a real case of the U-HVDC's SSCS commissioned in China. The result compares the reliability of the system architecture under different operation modes and provides significant insights on the selection rules of the U-HVDC's SSCS operation mode for system reliability improvement.