Converter Interaction Identification using Open-Loop Mode Transition Criterion

With the increasing application of converter-interfaced generating units in power systems, interactions between converters and grids have been observed at both high and low frequencies. Modal participation or bode plots are the techniques typically used to identify these oscillations. However, these interactions are influenced both by the system and controller parameters, leading to multiple eigenvalue calculations for parametric variation analysis in large power systems. To address this challenge, the paper proposes a method that instead utilizes open-loop modes transition criterion to identify interaction/coupling modes in power systems. The method uses the open-loop eigenvalues of segmented subsystems and their local interconnections to the grid to determine the eigenvalue displacement, avoiding the need for eigenvalue calculations of the entire system. The proposed method (PM) is also extended to compute the system’s eigenvalues with a coupling gain variation and is tested in a multi-terminal DC grid. Results obtained using the PM are compared with those from modal analysis of the combined system. The PM is effective for parametric variation analysis of the subsystems and provides an efficient approach to identifying interactions between converters and the power system.