变阻值Crowbar电路及其在提高双馈式风电机组低电压穿越能力中的应用

Variable Resistance Crowbar Circuit and its Application in Improving Doubly-fed Type Wind Generator of Through Low Voltage Ability

双馈风力发电机的低电压穿越能力较差,Crowbar技术是提高双馈风力发电机低电压穿越能力的有效手段。分析了DFIG机端短路时Crowbar阻值对转子电流和暂态过程的影响,指出传统Crowbar电路采用固定的阻值,无法兼顾低电压穿越过程中各阶段对该阻值的不同要求。为此提出了一种变阻值Crowbar的电路,采用这种电路只要控制脉宽就可以改变Crowbar电路的等效电阻,在电网发生地电压故障后,可以根据保护过程不同阶段的特点及时调整Crowbar电路电阻,提高双馈风力发电机的低电压穿越能力。为了验证调整效果对新设计的Crowbar电路的调整效果进行了仿真。仿真结果表明,变阻值Crowbar能够通过控制脉宽实现对Crowbar等效电阻的有效控制。

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.