Fast and accurate evaluation method of commutation failure in line‐commutated converter‐based high‐voltage direct current systems considering probability characteristics

Abstract

Abstract Line‐commutated converter‐based high‐voltage direct current (LCC‐HVDC) systems suffer from commutation failure (CF) when receiving‐end AC grid faults occur, which is a major drawback and threatens the security and stability of power systems. This paper presents a fast and accurate evaluation method of CF for the LCC‐HVDC systems, considering the CF probability characteristics. Firstly, based on the analysis of the CF probability characteristics from the view of short‐circuit impedance, the CF tolerance index (CFTI) and CF vulnerability index (CFVI) are proposed to quantitatively evaluate the LCC‐HVDC systems' risk of the possible‐ and inevitable‐occurrence CF, respectively. Secondly, four factors, that is, commutation voltage, fault occurrence time, DC current and firing angle command, are considered to calculate CF evaluation indices (CFEIs) and identify the CF risk area boundaries based on the theoretical analysis. Moreover, the relationships among short‐circuit impedance, fault position, and extinction angle are established based on the AC/DC decoupling method, which helps realize the decoupling of multi‐factors affecting CF during fault. Compared to earlier methods, this evaluation method combines the advantages of the accuracy of the electromagnetic transient simulation method and the rapidity of theoretical derivation. Finally, the validity and accuracy of the evaluation method are verified in the CIGRE HVDC benchmark model and IEEE 39‐bus system.