The integration of converter-based resources requires robust Fault-Ride-Through (FRT) capabilities. While current standards specify voltage magnitudes, phase jumps, and frequency deviations at the Point of Connection (POC), asymmetrical faults introduce non-uniform shifts across phases. Many existing grid codes remain mathematically underdetermined by defining requirements solely based on a single minimum line-to-line voltage magnitude.

This definition leaves the remaining two magnitudes and three phase angles as unconstrained degrees of freedom, bounded only by the HVRT threshold and the requirement that they do not undercut the defining minimum. This ambiguity fails to uniquely characterize the fault type or phase symmetry, resulting in a five-dimensional parameter space (two amplitudes, three phase-angles) of potential test cases. This complicates the deterministic verification of converter performance and necessitates a more rigorous definition of asymmetrical fault conditions. While previous research focused on hardware-side generation of these fault states, this work systematically evaluates the transient performance of Grid-Following (GFL) and Grid-Forming (GFM) converters within these parameters.

Based on original analysis using Electromagnetic Transient (EMT) simulations and laboratory data from Power Hardware-in-the-Loop (PHIL) testing, a set of test scenarios is applied to evaluate how the converters react to these varying conditions. Rather than merely observing stability, this work focuses on the resulting voltage and current profiles and their subsequent impact on the grid. The investigation utilizes a dual-track approach: commercially available converters are analyzed as black-box models to capture industrial performance, while self-developed algorithms allow for a more transparent, white-box assessment.

The results demonstrate that identical line-to-line voltage drops trigger fundamentally different transient responses, as the converter's behavior is dictated by the remaining degrees of freedom within the asymmetrical fault state. A key finding is that these converter-based responses are highly programmable and thus exhibit significant variability compared to classical synchronous machines. This paper proves that evaluating converter resilience requires a shift from one-dimensional magnitude checks to a multidimensional assessment framework. The proposed methodology provides a foundation for future grid code and testing enhancements, ensuring that converter-based resources contribute positively to grid stability under asymmetrical conditions.