Analysis and Calculation of the Control Winding Current During Crowbarless Asymmetrical Low-Voltage Ride-Through for Brushless Doubly-Fed Induction Generators

The present control winding (CW) current calculations are inaccurate due to the incomplete consideration of the output limitation of the machine side converter (MSC) during the crowbarless asymmetrical low-voltage ride-through (LVRT) of the brushless doubly-fed induction generator (BDFIG). Furthermore, there is a paucity of literature on the relationship between the peak CW currents and the time of the fault occurrence, which has a distinct impact on the analysis and evaluation of the effectiveness of the BDFIG LVRT control strategy. To address this challenge, this paper considers the transient process in the MSC, provides an innovative approximate expression for the CW flux linkage in SVPWM overmodulation, and derives an expression for the CW transient current considering the time of fault occurrence for the first time. From the expression, the CW current of the BDFIG prototype was calculated when the fault occurs at different moments. The calculation results indicate that the peak value of CW is closely related to the time of the fault occurrence and the maximum peak value of the CW current is more than twice the minimum peak value when the fault occurs at different times. Extensive simulation and experimental results under different asymmetrical short-circuit fault have validated the correctness and effectiveness of the proposed expression.