双馈感应发电机暂态性能精确计算及Crowbar电路参数优化

Accurate Calculation of DFIG Transient Performance and Parameters Optimization of Crowbar Circuit

随着双馈感应发电机(DFIG)的大规模应用及对其低电压穿越能力(LVRT)要求的提高,关于电网电压跌落时刻DFIG的暂态过程及LVRT改进措施的研究也越来越多;但是,之前的研究无论是用仿真方法还是数学手段,大都进行了一系列省略及近似,包括忽略定子电阻及认为定转子漏感相同等,这导致对DFIG暂态性能的研究及仿真计算的准确性受到不同程度的影响。文中首先从理论上对电网电压对称跌落后DFIG的暂态性能进行了精确计算和分析,揭示了定子磁链的暂态自然分量变化的本质规律,得到了转子参数对发电机各暂态衰减量的不同影响。然后,提出了一种新的Crowbar电路结构,并给出了Crowbar电阻和转子漏感的最优化参数设计方法。最后,采用MATLAB/Simulink对所提方案进行了仿真研究,验证了理论计算和所提方法的正确性及有效性。

With the increasing penetration of wind power into electric power grid,large scale integration of the doubly fed induction generator(DFIG)in wind farm and its low voltage ride-through(LVRT)capability stipulated stringently in the revised grid code have led to extensive researches on the detailed theoretical analysis of the DFIG dynamic characteristics and its LVRT enhancement capability.However,no matter whether mathematical analysis or simulation calculation was used in previous investigations,different kinds of negligence and assumptions have emerged,such as neglecting stator resistance or assuming the same leakage inductance between stator and rotor sides,which will result in different influences on the accuracy and validity of the dynamic characteristics analysis and the LVRT control design.In order to overcome these drawbacks,a completely accurate mathematical dynamic DFIG model is developed during the three-phase voltage dips without any negligence, and different interactivities between the generators rotor parameters and the damping speed and degree of the generators electro-magnetic variables have been derived.Based on the proposed calculation and analysis,the improved Crowbar circuit prototype and the optimal parameters design of the Crowbar are given.The simulation results in MATLAB/SimuLink have totally verified the validity and efficiency of the theoretical calculation and the proposed scheme.