Preventing loss of synchronism of droop-based grid-forming converters during frequency excursions

• Published in: International journal of electrical power & energy systems 2023-06, Vol.148, p.108989, Article 108989
• Main Authors: Collados-Rodriguez, Carlos, Westerman Spier, Daniel, Cheah-Mane, Marc, Prieto-Araujo, Eduardo, Gomis-Bellmunt, Oriol
• Format: Article
• Language: English
• Subjects: Droop control; Grid-connected converters; Grid-forming control; Loss of synchronism; Voltage source converters
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2023.108989

•The instability mechanism related to the loss of synchronism of droop-based GFOR converters during frequency excursions is detailed.•A modified droop control is presented to ensure converter synchronisation for any grid frequency condition as well as maximising the frequency support of the converter.•A comparative analysis between the proposed control and existing methods is performed, highlighting their advantages and disadvantages.•The proposed droop control has been validated under different case studies as- suming various VSC penetration levels and compared with conventional droop control. This short communication addresses the risk of synchronisation loss during frequency excursions for droop-based grid-forming converters when active power limitations are considered. The synchronising capability of this control approach is based on the converter’s active power exchange, which is used to generate the internal frequency of the converter control. The power available in the resource or converter ratings can impact the synchronising capability during frequency deviations. The analysis is restricted to droop-based grid-forming converters, but it could be extended to other active-power-based synchronising methods. A droop-based control is proposed to extend the operation frequency range of grid-forming converters. The performance of the suggested method is also compared to alternative ones presented in the literature. Finally, the proposed control is validated in the IEEE 9-bus system with different VSC penetration levels through EMT simulations developed in PSCAD.