IEEE paper: DC connections beat AC for large-scale inverter stability
Massive battery storage systems risk instability — unless you switch to DC links.
Researchers Qiang Fu, Wenjuan Du, Siqi Bu, and Haifeng Wang published a study in IEEE TRANS POWER SYSTEMS (2026) examining converter-driven stability (CDS) issues in large-scale bidirectional inverter-based stations (IBSs). These stations connect massive controlled DC resources — such as battery energy storage systems — to AC power grids through bidirectional inverters to balance power. The team compared the impact of AC versus DC connections on subsynchronous oscillations (SSOs) by varying three factors: the number of CDCRs, power flow direction, and inverter control parameters.
Their key finding: AC-connected IBSs can trigger instability as the number of CDCRs increases, irrespective of power flow direction. To maintain stability, the maximum power amplitude of the IBS was calculated. In contrast, DC connections significantly reduce these risks — provided the DC line resistance is much lower than the AC line reactance. Additionally, tuning control parameters proves more effective under DC connections for improving power-related critical stability. The authors conclude that DC-IBS is the preferred architecture for high-voltage transmission, validating their results across multiple network topologies and system scales.
- AC-connected IBSs induce subsynchronous oscillations as CDCR count increases, regardless of power flow direction.
- DC connections reduce instability risk when DC line resistance << AC line reactance.
- Tuning inverter control parameters is more effective for stability under DC connections than AC.
Why It Matters
Guidance for grid operators: use DC links for large battery storage stations to avoid oscillation risks.