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. Due 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 HVDC power system stability studies by cascaded pi-section equivalents that neglect the frequency-dependent effects. This paper 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 paper provides a comparative example of the impact of the cable modelling on the small-signal dynamics of a point-to-point VSC HVDC transmission scheme.

A control scheme for utilizing energy storage of the modular multilevel converter for power oscillation damping

“…6. Test grid used for simulation [10] Effect of parameter inaccuracies using the frequency dependent model proposed in [11]. All converters are MMCs which are modeled using average arm capacitor dynamics [12].…”

PI Passivity-Based Control and Performance Analysis of MMC Multiterminal HVDC Systems

“…This model can be also found in [16], [18], [19] and is implemented using the Simulation results with this model are identified in the legend of the figures by "EMT". For the simulations, we assume that in the multi-terminal configuration all MMCs are characterized by the same parameters and that transmission lines can be represented by the frequency-dependent model detailed in [28], where the line inductance effect is neglected to simplify our tractation 4 . On the other hand, for the single-terminal configuration, we simply consider the case where one of such an MMC is connected to a constant dc current source, rather than the HVDC network.…”

“…In[28] it was shown that neglecting the inductive effect in transmission lines with only one parallel branch is a good approximation of the frequency dependent model. We adopt this approximation here to prove that the convergence rate of the MT-HVDC is uniquely related to the interconnection pattern and not to the cable states.…”

Flexible HVDC transmission systems small signal modelling: A case study on CIGRE Test MT-HVDC grid

“…For studies focused on low-frequency oscillations below 100 Hz, cascaded (say to be n) sections (and even single lumped) model is sufficiently accurate [11]. However, to analyze intermediate and highfrequency oscillations above 100 Hz, more elaborated frequency dependent models should be considered [16]. Indeed, the generality of modeling approach is preserved.…”