System-level performance and robustness of the grid-forming hybrid angle control

Abstract

This paper investigates the implementation and application of the multi-variable grid-forming hybrid angle control (HAC) for high-power converters in transmission grids. We explore the system-level performance and robustness of HAC concept in contrast to other grid-forming schemes i.e., power-frequency droop and matching controls. Our findings suggests that, similar to the ac-based droop control, HAC enhances the small-signal frequency stability in low-inertia power grids, and akin to the dc-based matching control, HAC exhibits robustness when accounting for the practical limits of the converter systems. Thus, HAC combines the aforementioned complementary advantageous. Furthermore, we show how retuning certain control parameters of the grid-forming controls improves the frequency performance. Last, as separate contributions, we introduce an alternative control augmentation that enhances the robustness and provide theoretical guidelines on extending the stability certificates of HAC to multi-converter systems.