Conjoint analysis of crowbar switching scheme and its resistance based on statistical sampling for LVRT of DFIG

An active crowbar protective circuit is an effective and common approach for low voltage ride through (LVRT) of a doubly-fed induction generator (DFIG). The crowbar resistance value and its switching scheme both have crucial effects on safety recovery. The effects encountered are correlative dependence and interplay so that analyzing them from a single factor, as most existing LVRT control methods would do, obtains a partial optimal solution. This paper combines these two factors to analyze their coordination effects on the LVRT control, and to also investigate whether the global optimal performance of these factors can be achieved. The principles for resistance selection and the schemes for crowbar switching are discussed first. Next, the coupling relationship is analyzed based on statistical sampling simulation data with different resistance values and various switching schemes. The results demonstrate that their coordination has critical influence on rotor peak current, DC-link voltage and reactive power. The optimal coordination will be different according to specific requirements. Hence the global optimal combination could be achieved when all requirements are taken into consideration.