Stability margin definition for a converter-grid system based on diagonal dominance property in the sequence-frame

Amico, Gabriele and Egea Alvarez, Agusti and Xu, Lie and Brogan, Paul (2019) Stability margin definition for a converter-grid system based on diagonal dominance property in the sequence-frame. In: 21st European Conference on Power Electronics and Applications (EPE2019), 2019-09-02 - 2019-09-06.

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    Abstract

    The increased presence of power converters in power networks has set new power system stability chal-lenges. New methodologies have been proposed to analyse these systems and one of the most promisingis the impedance-based stability criterion. To date using this method the grid interfaced converter is repre-sented in terms of impedances and it is assumed that the converter impedances within the sequence-frameare decoupled. However, coupling between the components of the sequence-frame converter impedanceshave been observed, and different studies have shown how relevant this might become to the stability per-formance. Hence, a stability margin that takes such coupling into account is presented in this paper. Thisresults in a more conservative measure of the stability robustness of the system, compared to the gainand phase margin figures employed in the impedance-based stability criterion. The presented study hasbeen used to assess how the relative stability of a VSC system connected to a weak grid varies with itsoperating point, and experimental data have been used to support the analytical study.