Research On Transient Characteristics And Affecting Factor Of Doubly-Fed Induction Generator Connected To Grid

Wind power generation is the most development potential and development prospects of new energy power generation in China. Wind power generation is showing rapid growth trend in the world, and double-fed induction generator (DFIG) is the most widely used in farms. The fault characteristics of existing analysis methods are no longer applicable on the DFIG. It has not yet formed a mature failure analysis methods and mathematical calculation model. This makes the relay setting calculation difficulties.Firstly, this paper analyzes operation principle of doubly fed wind power generator and improvement measures on the low voltage ride through, based on space vector, establishing the positive, negative sequence mathematical model of DFIG. Secondly, in consideration of the initial operation state of DFIG, it deduces the analytic expression of the DFIG with Crowbar protection under the symmetric and asymmetric voltage drop through mathematical analytic method. Thirdly, according to the crowbar protection circuit with different time delay, the whole failure process into two phases. By analysis of short circuit current of two process calculation, to research the properties of short circuit current of DFIG which crowbar protection action time effect on. Finally, the effect factors are studied in detail which is on the frequency and amplitude of short circuit current.In this paper DFIG failure mechanism and transient characteristics are more in-depth study in the grid failure, based on simulation analysis calculation method extends in the direction of further failure mechanism and failure calculation method. The fault characteristic of DFIG from the crowbar protection circuit instantaneous action to crowbar protection circuit delay action areas expands on. The proposed calculation method for the failure of DFIG which takes into crowbar protection circuit delay action account has clear physical meaning, more accurate results. And provide a theoretical support for the applicability of current relay principle in the study of large-scale wind power grid.