SEQUENCE IMPEDANCE MODELING AND ANALYSIS OF PMSG WIND TURBINES CONSIDERING THE ELECTROMECHANICAL COUPLING

With the continuous increasing installing proportion of the permanent magnet synchronous generators wind turbines (PMSG-WTs), oscillation issues in grid-connecting PMSG wind farms are observed frequently. Sequence impedance model has gradually become a widely used method to analyze grid-connecting wind power oscillation issues. The sequence impedance model of PMSG-WTs built before usually ignores the torsional interaction between the shaft mechanical subsystem and the electrical subsystem, as called electromechanical coupling effect. This paper investigates the impact of the shaft mechanical model on the output electrical impedance characteristic of the PMSG-WTs. The dynamic behavior of the shaft subsystem is modeled through two-mass-spring mechanical model. Then the output sequence impedance model of PMSG-WT considering the electromechanical coupling effect is obtained, reflecting the transfer relationship of the small-signal perturbation between the shaft mechanical subsystem and the electrical subsystem.