Impedance Modelling and Parametric Sensitivity of a VSC-HVDC System: New Insights on Resonances and Interactions

Abstract

Pervasiveness of power converters in the electric power system is expected in the future. Such large penetration will change the current power system dynamics leading to uncertain, unexpected, and potentially critical responses. This paper investigates the stability and resonance of a VSC-HVDC (Voltage Source Converter High Voltage Direct Current) link within an AC grid, whilst providing insights into resonances having a role on the grid. This is studied through the impedance-based modelling of the entire system (AC and DC grids), including controls of converters. Additionally, the impact of the different parameters of the hybrid AC-DC power system such as control systems and grid components on the system dynamics and stability is investigated. From this study, the impact of the system components and the controls of the converter on overall resonance response and stability is shown, including potential undesired sub-synchronous and harmonic resonances due to AC-DC system interactions. The analytical impedance-based models developed and obtained is validated through time-domain simulations, the physical model of the whole system is built in Simscape ™ Power Systems ™ and control systems in MATLAB/Simulink ® (R2017b). This has demonstrated the validity of the model to deal with and detect such dynamics.

Frequency Support Control of Multi-Terminal Direct Current System Integrated Offshore Wind Farms Considering Direct Current Side Stability

“…References [22,23] obtain an accurate impedance model of MMCs based on the harmonic state space and harmonic linearization method, but the order of the model is high, which is not conducive to the analysis of multi-terminal system stability. References [24][25][26] proposed several different DC side impedance models for the flexible DC transmission system based on the two-level voltage source converter, and these models were used for DC side resonance analysis. However, although the literature has achieved results on the modeling of MMCs and OWFs when participating in frequency regulation, the impact of frequency control coefficients of MMCs on the stability of MTDC systems has not been measured with a detailed analysis, and the design of the frequency control of OWFs and MTDC systems lacks supportive instruction.…”

Dynamic modelling and interaction analysis of multi-terminal VSC-HVDC grids through an impedance-based approach

“…However, in many of the studies with AC side as the focus, the impact of an interconnected DC side is often neglected. In [23,24], authors duly extended the modelling methodology to resonance analysis of the DC side of a complete point-to-point HVDC link with the aim of highlighting the impacts of AC grid impedance on DC side. However, in derivations it was assumed that either converter is in one of rectification or inversion, thus reducing the applicability to varying operating modes at each converter typical of a meshed HVDC networks.…”

Impedance-Based Interactions in Grid-Tied Three-Phase Inverters in Renewable Energy Applications

“…In grid-connected applications, the instability may take place, in principle, at any frequency depending on the behavior of the grid impedance, where the electrical resonances are of interest due to providing zero-degree phase behavior of the grid impedance at the resonant frequency [12,55,56]. The negative-incremental-resistance-like behavior of the grid-connected converter may reduce the damping of the grid and thus making it prone to electrical resonances, which may cause harmonic currents to appear [57][58][59][60].…”