Variable Resistance Crowbar Circuit and its Application in Improving Doubly-fed Type Wind Generator of Through Low Voltage Ability
Doubly fed induction generator（DFIG） is the first choice of model in wind power area.When grid voltage sagged,the wind generation into electric network must have Low voltage ride through（LVRT） ability,crowbar technology is improving LVRT ability of DFIG effective means.This paper analyzes when DFIG machine shorted the Crowbar resistance to the influence of transient processing and rotor current,and points out that the rotor maximum short-circuit current with the square of resistance are inversely proportional;Transient process lasting time with the size of Crowbar resistance are inversely proportional.Based on comprehensive considering the rotor side converter protection、 transient process duration and the network voltage support when cutting short circuit,then improving the existing Crowbar circuit form and putting forward the structure of variable Crowbar resistance circuit,researching the current characteristics and pulse width controlling method and simulation.The simulation results showed that the variable Crowbar resistance through pulse width controlling can realize effective controlling of the Crowbar equivalent resistance.
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