Analytical model for DFIG stator interharmonic current induced by RSC disturbance voltage through stator and rotor flux

Abstract

With the arising penetration rate of wind power, subsynchronous interharmonic oscillations and voltage flickers in wind power systems are getting worse in practical engineering. The generating mechanism and magnitude-frequency characteristics of interharmonics in double fed induction generator (DFIG) are critical issues. In this paper, considering the rotor side converter (RSC) disturbance voltage generated in inverter side, according to the steady-state voltage equation and flux equation of DFIG, the mathematical model of DFIG interharmonic equivalent circuit is built; rotor and stator electrical parameters are unified in d-q synchronously rotating reference frame through coordinate conversion; then the analytical model of DFIG stator interharmonic current caused by RSC disturbance component is established through stator and rotor flux with coordinate inverse conversion and derivation. The PSCAD simulation examples verify the accuracy of the established model. Finally, on the basis of quantitative calculation with this proposed model, and the time-varying characteristics of stator interharmonic current induced by RSC disturbances with wind speed variation is analyzed.