Enhancing stability in renewable energy transmission using multi-terminal HVDC systems with grid-forming controls for offshore and onshore wind integration

This paper presents a thorough analysis of two-terminal VSC-HVDC links, and the effects of isolated faults have been extensively studied in multi-terminal HVDC (MTHVDC) networks systems that would enable the interconnection of substantial offshore wind farm energy resources to onshore power systems with emphasis on dynamic transmission performance during different fault and perturbation scenarios. The performance of the system was evaluated against three important scenarios: transient faults, sudden load drops, and wind speed changes. The work presented a comparative analysis of Grid-Following (GFL) and Grid-Forming (GFM) control strategies with a focus on their provisions in offering compliance with grid code requirements, particularly, in faults ride-through (FRT) performance. Transient stability and grid compliance has been performed through the study to take results as the GFM controller performance has been better as compared to GFL controller in the study. The GFM controller recovered more rapidly than its GFL counterpart, achieving voltage stability within 0.5 s and frequency stability within 0.6 s when subjected to fault and load disturbances, versus 1.2 s and 1.8 s for the GFL controller's voltage and frequency, respectively. The difference in voltage and frequency deviation between the GFL and the GFM system was less than ± 4% and less than ± 0.3 Hz respectively, further verifying that the GFM system far outperformed the GFL system, which demonstrated a voltage stability of ±18% and a frequency stability of ± 0.9 Hz under load disturbance. The results demonstrated the GFM controller's capability to stabilize power systems rapidly and fulfill grid code requirements even in the presence of compounded disturbances. The virtual inertia and dynamic dampness provided by GFM controller make the system resilient against fluctuations in both wind generation and grid faults. The results highlight the value of GFM-based MTHVDC systems as a dependable option for integrating offshore wind energy into the grid, creating a system with superior stability and efficiency in future large-scale renewable energy systems.