General Methodology for Analysis of Sub-Synchronous Interaction in Wind Power Plants

This paper presents a general methodology for analysis of sub-synchronous interaction in wind power plants. These include appropriate frequency scanning method for the assessment of the sub-synchronous control interaction, and calculation of the electrical damping provided by the wind turbine generator for investigation of the sub-synchronous torsional interaction. A general formulation of both methods applicable to any given wind turbine and network is presented. A dynamic frequency scanning method for the turbine side is developed which takes account of the turbine nonlinearities and its active behavior. Various aspects that need to be considered when injecting a voltage or current signal into the system for dynamic frequency scanning are discussed in detail. The veracity of these methods is confirmed against electromagnetic transient analyses. The application of these tools and techniques is demonstrated on a practical power system comprising type 3 wind turbines and series compensated lines.