双馈风力发电机Crowbar电阻优化设计研究

The Research on Optimization Design of DFIG Crowbar

应用Crowbar保护电路是实现双馈风力发电机组低电压穿越广泛应用的手段,而Crowbar电阻的选取对穿越过程有着决定性的作用。目前,针对Crowbar电阻的设计虽已有很多研究,但大都是得到Crowbar电阻的大概选择范围,然后在这范围内用试凑法进行Crowbar电阻选取,从而难以到达最优设计效果且效率不高。本文提出一种基于模糊隶属函数的Crowbar电阻设计方法来提高Crowbar电路的设计效率并获得更高满意度的低电压穿越过程,首先分析电网发生三相短路时双馈风力发电机的故障特性,然后分析了Crowbar保护电路中阻值选取的约束条件,采用隶属度函数方法建立了Crowbar阻值选取目标函数,在Matlab仿真软件平台上对所选方法进行了仿真验证,仿真结果证明了基于模糊隶属函数的Crowbar电阻设计方法可以提高设计效率并获得更好的低电压穿越过程。

A widely used way to realize LVRT is adding a crowbar circuit to the DFIG, however, the choice of crowbar resistance is difficult and it has a key influence on LVRT during the grid faults. In recent years, there have been many studies on the choice of crowbar resistance, however, these studies generally give a broad resistance choice scope, and the designer can only choose the crowbar re-sistance by trial and error method to get a better LVRT process, hence, the efficiency is not high. In this paper, a crowbar resistance design method based on fuzzy membership function is proposed, it can improve the design efficiency of crowbar circuit greatly and achieve a higher degree of sa-tisfaction during LVRT process. This paper analyzes the change process of stator and rotor fault current, obtains the constraints relation of crowbar resistance with rotor side current and DC-link voltage, then transforms the crowbar resistance constraint equations into the fuzzy membership function, and finally establishes a DFIG model with Crowbar circuit on the Matlab simulation soft-ware platform. The simulation results which verify this crowbar resistance design method can get the satisfy result on the maximum balance and improve the efficiency of selection of the crowbar resistance greatly.