Sub-Synchronous Oscillation Characteristics Analysis in Distribution Networks with UPS Clusters Based on Impedance Modeling

The widespread deployment of data centers and grid integration of uninterruptible power supply (UPS) clusters have intensified sub-synchronous oscillation (SSO) risks in distribution networks. Current research predominantly addresses SSO in renewable energy systems, with limited investigation of SSO caused by power electronics clusters in distribution networks. An impedance-modeling approach is proposed to analyze SSO in UPS-grid systems. Small-signal impedance modeling is employed to assess the impact of grid strength, UPS unit count, and control parameters on SSO. Case studies and simulations validate the theoretical framework. Results demonstrate that UPS-weak grid interactions increase SSO susceptibility. Additionally, higher UPS unit count not only lower SSO frequencies but also elevate oscillation risks. Reducing PI gains in the inverter’s voltage/current loops and rectifier’s current loop destabilizes the system, while increasing the rectifier voltage-loop PI gain enhances stability.