Challenges in small-signal stability compliance process for renewable energy-based power plants and a framework proposal for industrial application

Small-signal stability is becoming crucial for Renewable Energy-based (RE) power plants since converter-based systems are prone to interact with the grid subsystems and cause oscillations. Various methods have been introduced to evaluate the small-signal stability including frequency-domain and time-domain methods. The impedance-based stability analysis has become a trending method in the industry as it treats the power system components as black-boxed models and there is no need for exchanging of large amount of network data among different stakeholders. Hence, different TSOs are imposing new requirements for the stability compliance to be fulfilled by the RE power plant developers including impedance-based stability and additional time-domain studies. Despite the benefits of the stability compliance requirements, the execution of the studies and achieving a realistic outcome are very difficult and time-consuming due to the limitations in data sharing among stakeholders, validity of the models, unclear roadmap and workload. This paper proposes a framework to investigate the stability requirements involving all stakeholders and highlights the challenges over the stability compliance process. In addition, the stability study toolbox, which is developed internally within Vattenfall, is introduced and two case studies on an exemplary RE power plant are presented.