Small-signal stability is becoming crucial in Renewable Energy-based (RE) power plants since converter-based systems are prone to interact with the interconnected network and cause disturbances. Various methods have been introduced to evaluate the small-signal stability including impedance-based, transfer-function-based, eigenvalue-based, time-domain simulation and interaction risk screening methods.

The impedance-based stability analysis has become a trending method in the industry as it treats the power system components as black-boxed component, easy to apply and there is no need for exchanging of large amount of network data between different stakeholders. In this way, different TSOs such as TenneT, Svenska Kraftnät (SvK), Energinet and National Grid are imposing new requirements for the stability compliance to be fulfilled by the RE power plant developers.

However, the implementation of the impedance-based stability method in the industry has several challenges. Lack of harmonized compliance requirements, extensive work-load on impedance calculations in different stakeholders, immature evaluation criteria and difficulty in validation and mitigation of the critical findings. This paper introduces the main challenges in execution of the impedance-based stability study for an example wind farm and highlights the need for a framework among the industry to achieve small-signal stability and proper compliance procedure.

According to the presented results in this paper, the impedance-based stability compliance is a challenging requirement for the developers and a harmonized framework is crucial for a proper investigation, validation of critical findings and mitigation methods.