Frequency‐dependent cable modelling for small‐signal stability analysis of VSC‐HVDC systems

Abstract

State‐of‐the‐art time‐domain models of power cables account for the frequency dependency of physical parameters to enable accurate transient simulations of high‐voltage transmission schemes. Owing to their formulation, these models cannot be directly converted into a state‐space form as required for small‐signal eigenvalue analysis. Thus, dc cables are commonly represented in high‐voltage direct current (HVDC) power system stability studies by cascaded pi‐section equivalents that neglect the frequency‐dependent effects. This study demonstrates how the conventional cascaded pi‐section model is unable to accurately represent the damping characteristic of the cable and how this can lead to incorrect stability assessments. Furthermore, an alternative model consisting of cascaded pi‐sections with multiple parallel branches is explored, which allows for a state‐space representation while accounting for the frequency dependency of the cable parameters. The performance of the proposed model is benchmarked against state‐of‐the‐art cable models both in the frequency domain and in the time domain. Finally, the study provides a comparative example of the impact of the cable modelling on the small‐signal dynamics of a point‐to‐point voltage‐source converter (VSC) HVDC transmission scheme.