  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 the HAC concept in contrast to other grid-forming schemes i.e.,
power-frequency droop and matching controls. Our findings suggest that similar
to the ac-based droop control, \ac{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
advantages. Furthermore, we show how retuning certain control parameters of the
grid-forming controls improve the frequency performance. Last, as separate
contributions, we introduce an alternative control augmentation that enhances
the robustness and provides theoretical guidelines on extending the stability
certificates of \ac{hac} to multi-converter systems.
