A Modified Droop Control Framework for Multi-Terminal VSC-HVDC System with Improved Power Sharing and Voltage Regulation

Resumen

In this paper an adaptive droop control strategy is proposed for voltage source converter based multi-terminal direct current (VSC-MTDC) systems to achieve a higher power-sharing accuracy, DC voltage regulation, and operating robustness during converter failures. The scheme integrates the robustness of voltage margin control with the distributed balancing capability of conventional droop regulation in a way that converters operating under constant power mode initially can switch automatically to droop mode at any time DC voltage differences exceed pre-set operating thresholds. Event-driven adaptability enhances synchronized inter-terminal response, enables equitable power readjustment, and mitigates voltage instability under heavy transient disturbances. A ±400 kV four-terminal VSC-MTDC system was planned and rigorously simulated in PSCAD/EMTDC for comparing the proposed method with conventional fixed-slope droop control. Quantitative results confirm that the proposed method realizes 45–60% reduction of peak DC voltage excursions, 40–55% reduction of active power overshoot, and 35–50% improvement in voltage settling time. Additionally, the passive converters in conventional schemes deliver up to +65 MW of extra support, thereby preventing the remaining terminals from being overloaded and maintaining safe operating margins. The dynamic coordination with advanced capabilities allows solid post-fault operation for single as well as multi-converter outages without protection-led shutdowns and improves the entire system's resilience. The demonstrated voltage stability, fault tolerance, and converter utilization enhancements confirm the adaptive droop control as a viable approach for the next-generation resilient, large-scale HVDC microgrids with high-penetration renewable energy integration.