Characterisation of interaction in an offshore AC grid with large WPPs and VSC‐HVDCs

Abstract

To exploit the full and flexible capability of offshore voltage-sourced converter high-voltage DC (VSC-HVDC) lines, interaction studies in the offshore AC grid are required but are not well understood or reported. This study examines the interaction dynamics of an offshore AC grid for interconnecting large wind power plants (WPPs). The conventional eigenvalue analysis method has limitations which make the interaction analysis of such systems difficult. Hence, in this study, an impedance-based analytical approach is employed to investigate the interaction phenomena. The impedance model of a VSC-HVDC converter for both direct and vector control with outer and droop controls are derived along with the impedance model of the full-converter wind generator. The interaction dynamics of the offshore grid is predicted through the well-established Nyquist criteria and is validated using time-domain simulations. The analysis shows that the system stability is decidedly influenced by the control configurations and tuning of the VSC-HVDC lines.

A Framework for Analyzing System Loadability With Multiple VSCs Using a Hybrid Model

“…In past studies into interactions between VSCs, a wide range of outer controllers have been considered, including 𝑃 − 𝑉 𝑎𝑐 , 𝑉 𝑑𝑐 − 𝑉 𝑎𝑐 , 𝑃 − 𝑄 and 𝑉 𝑑𝑐 − 𝑄 [57], [60], [63], [64]. Although 𝑃 − 𝑄 control schemes are typically implemented in the VSC, the results from [57] showed that VSCs with 𝑃 − 𝑉 𝑎𝑐 are more prone to cause adverse interactions which can potentially deteriorate the system stability.…”

Advanced virtual inertia control against wind power intermittency

“…Extreme system operations demonstrate the dynamic effects of the actual operation of interconnected power systems and verify the reliability of the proposed control strategy for high-level WPPs. In other words, include penetration and changes in system inertia [21]. Therefore, the effect of REP penetration caused by changes in wind speed data will affect the overall frequency of the interconnected system indicated by a high-test contingency [22], [23].…”

Identifying Feasibility Region Boundaries in Power Systems With Multiple VSCs

“…Similar to instability studies on systems with one VSC, when multiple VSCs are considered, effort is typically invested into analyzing the instability mechanisms caused by interactions with only one or two parameters regulated for each scenario, as in [12]- [15]. An impedance-based modeling approach has been used in [13] to study the dynamic interactions between two VSC-HVDC converters in an offshore grid. The results and analysis suggest that system stability is largely influenced by the selection of control parameters.…”