Impedance Model of PMSG-Based Wind Turbine System And Stability Analysis Based on Routh Criterion

In recent years, with the increasing integration of renewable energy capacity, offshore wind power has entered a period of rapid development. Due to its large capacity, many offshore wind turbines employ permanent magnetic synchronous generator based (PMSG, i.e., Type-IV)wind turbines, leading to frequent occurrence of oscillation accident. Impedance-based methods are commonly used to analyze small-signal stability of grid-connected system. However, in the impedance modeling of permanent magnet direct-drive wind turbines, PMSGs are often simplified as Voltage Source Converters (VSCs), with the assumption that the DC capacitor is large enough. This simplification neglects the machine-side dynamics. This paper incorporates machine-side dynamics into the impedance modeling of PMSG. Frequency scan simulations are conducted to verify the accuracy of the model. Finally, the stability of the grid-connected system is assessed through the Routh criterion.