Offshore HVDC transmission systems are increasingly used to integrate large-scale renewable generation into weak or converter-dominated grids, where stability is governed by converter control dynamics, synchronization, AC/DC coupling, fault recovery, delay effects, and network strength. Although impedance-based analysis, small-signal modelling, and EMT simulation are widely used for stability assessment, practical grid integration is often organised around compliance-oriented EMT test procedures defined by transmission system operators. The link between converter-driven phenomena, test procedures, observable signals, and diagnostic metrics is therefore still not always explicit.

This paper proposes a compliance-oriented EMT test matrix for offshore HVDC systems. The matrix maps dynamic phenomena to test objectives, observable signals, diagnostic metrics, key parameters, and relevant HVDC architectures. Although developed for offshore HVDC grid-integration studies, where offshore power-plant behaviour, export-cable dynamics, and weak onshore connection points may interact through the HVDC link, the matrix is formulated as a general test-selection and interpretation framework for converter-dominated HVDC integration scenarios.

The approach is demonstrated using a representative point-to-point VSC-HVDC EMT model in MATLAB/Simulink. Four selected matrix entries are analysed: phase-angle steps, voltage-magnitude steps, a three-phase fault, and a measurement-delay case, corresponding to synchronization response, voltage-disturbance and AC/DC coupling, fault recovery with converter-current stress, and delay robustness. The results show that the tests provide complementary diagnostic evidence and should not be treated as interchangeable stability indicators. Severe fault tests alone are therefore insufficient for assessing weak-grid-related stability issues. The study is simulation-based and intended as a framework demonstration, not as a complete validation campaign.