Modeling, Analysis, and Suppression of the Impact of Full-Scale Wind-Power Converters on Subsynchronous Damping

This paper presents modeling, analysis, and suppression of the impact of a voltage-source converter (VSC)-based full-scale wind turbine (FSWT) on subsynchronous damping in power systems. First, a detailed output impedance model of the grid-interfacing VSC is presented and analyzed under different converter operating modes, control functions, and variations in operating point. Second, the output impedance model is used to analyze the impact of the grid-interfacing VSC on the electrical damping characteristics in the subsynchronous frequency range and interactions with an electrically nearby synchronous generator. The IEEE first benchmark for subsynchronous resonance studies is used for theoretical analysis and simulation results. It is found that the grid-interfacing VSC of the FSWT can have a negative impact on overall electrical damping and there is a risk of subsynchronous torsional oscillation especially at lower frequency modes. Third, to mitigate such interactions, an active damping controller is developed to reshape the output impedance of the interfacing VSC and yield positive electrical damping at torsional modes. Time-domain simulation results are presented to validate the theoretical analysis and show the effectiveness of the proposed active damping controller.