Influence of reactive power support control strategy on short-circuit current calculation and fault analysis method of DFIG

Abstract

More and more Doubly-fed Induction Generators (DFIG) have a low voltage ride through (LVRT) capability, which needs to provide reactive power for the grid during the low voltage ride-through period. Traditional short-circuit current calculation of DFIG ignore the influence of reactive power support on short-circuit current; it is assumed that the rotor current is zero when the Crowbar is input after the fault. This inaccurate short-circuit current will indirectly affect the protection’s operating characteristics and produce certain errors. Specially, in China’s new grid-connected wind power standards, DFIG need to output reactive current during fault to provide reactive power support for the system. At this time, the rotor-side converter should no longer be locked, and provide continuous reactive current during the fault. In view of the above issues, according to the input–output characteristic of rotor converter, the equivalent model of rotor converter and the transient model of DFIG were provided. The influence mechanism of reactive power support control strategy was analyzed. The short circuit current calculation model of DFIG was established. Based on RTDS the experiment platform with physical controller of converter was founded, the proposed short-circuit current calculation model considering the reactive power support control strategy has been verified. The fault analysis method for the grid with penetration of DFIG is analyzed. Result of this research is available for the study of DFIG influence on the protection characteristics.