基于Crowbar保护的双馈感应发电机暂态特性与参数设计

Transient Analysis and Crowbar Design of Doubly-fed Induction Generator with Crowbar Protection Under Grid Voltage Dips

双馈风力发电系统中,Crowbar(撬棒)仍是实现低电压穿越的常用方案之一,传统的分析方法忽略了定、转子磁链间的耦合,会带来较大的分析误差并遗漏一些暂态特性。从双馈感应发电机的数学模型出发,通过分析端口电压发生对称跌落、投入Crowbar后双馈感应发电机的暂态过程,推导出了定子磁链、定子电流、转子电流的解析表达式,并在表达式的基础上分析了各暂态量的幅值和变化规律等特性。在MATLAB/Simulink中建立了双馈感应发电机的仿真模型,结果证明了表达式的准确性。从复杂的数学表达式中抽离出Crowbar阻值与暂态特性的关系,分析了不同的Crowbar阻值对于故障期间系统的功率、电磁转矩的影响,并结合转子电流峰值计算及直流母线电压钳位效应的限制,给出了一种Crowbar电阻取值方案,该方案将有助于实际工程中选取合适的Crowbar参数。

An incorporation of a Crowbar is still the main method for the doubly-fed induction generator(DFIG)in low-voltage ride through.Generally,the mutual coupling between the stator and rotor flux is ignored during the transient analysis of DFIG with Crowbars,but this approximation has brought about obvious errors and even left out some transient characteristics. Through an analysis of the process of low voltage ride through (LVRT) based on a detailed model of DFIG,accurate expressions for stator flux,stator current and rotor current are deduced.Thus the characteristic of these variables are analyzed and the values calculated.An actual 10 kW DFIG is used for case study,the simulation results proving the accuracy of the expressions.From these formulas,the relations between the values of Crowbar resistors and the pulsation amplitude of electromagnetic torque,output power are revealed.Taking into account the DC-link clamp effect and influence on the performance of DFIG during LVRT,a new Crowbar resistance design method is proposed for reference in relevant engineering projects. This work is supported by National Basic Research Program of China (973 Program)(No.2012CB21 5 100),National Natural Science Foundation of China (No.5 1477064) and Lite-on Power Electronics Technology Research Fund (No.2013-04).