Stability Analysis of Real-World Subsynchronous Oscillations via Black-Box EMT Models

In this paper, we demonstrate methods to extract $dq$ admittance for a solar photovoltaic (PV) farm from its black-box model used for electromagnetic transient (EMT) simulation. Each $dq$ admittance corresponds to a certain operating condition. Based on the $dq$ admittance, analysis is carried out to evaluate how grid strength and solar irradiance may influence stability. Two types of stability analysis methods (open-loop system based and closed-loop system based) are examined and both can deal with $dq$ admittance's frequency-domain measurements directly and produce graphics for stability analysis. The findings based on $dq$ admittance-based analysis are shown to corroborate EMT simulation results.