Influence of Stray Parameters for High-frequency Resonance of MMC-HVDC Systems Based on Digital-analog Hybrid Simulation

The damping characteristics of flexible DC transmission system based on modular multilevel converter (MMC) change greatly during operation mode switching. When the impedance of DC system changes, it is easy to cause high-frequency oscillation due to the interaction of stray parameters in AC system. In this paper, a simplified frequency impedance model of the converter is established based on the topology and control logic; Secondly, combined with the frequency impedance characteristics of AC system before and after the operation mode change, the possible oscillation risk points under the interaction of AC and DC system are analyzed in principle; Finally, a full real-time electromagnetic transient simulation of the high-frequency oscillation caused by the change of AC system operation mode is carried out in the YU-E south channel model built in the Hypersim simulation platform to verify the correctness of the proposed theoretical model.