双馈电机电压跌落暂态过程分析

The Transient Process Analysis of Doubly-Fed Induction Generator During the Voltage Sag

为了便于研究并网双馈风力发电机组低电压穿越运行的控制策略,有必要对电压跌落时双馈风电机组的暂态特性进行分析。本文利用双馈发电机定转子磁链的暂态变化机理,推导并提出了双馈风电机组在电网电压骤降时的定子暂态电流和电磁转矩的解析表达式。在此基础上,通过对表达式的分析得到影响电压跌落电磁过渡过程的本质因素。在理论分析基础上,为了验证所提电磁过渡过程的正确性,建立了1.5MW双馈电机低电压穿越控制模型,仿真结果表明:电网电压跌落时,双馈电机定子侧电流和电磁转矩与理论分析基本一致,因而可以说明本文电压跌落的分析方法能够正确地反映电压跌落过程中的电磁现象,可以为双馈电机LVRT控制策略的研究提供足够的理论依据。

In order to analyze the control strategy of the low voltage ride through（LVRT） of a gird-connected wind turbine with doubly fed induction generator （DFIG）, it is necessary to analyze the transient performance of a DFIG wind generation system under a grid fault. In this paper, use the transient mechanism of stator and rotor flux to derive the transient analytical expressions of stator current and electromagnetic torque during the voltage sag. On this basis, through the analysis of the expression to get the essential factors of electromagnetic transition. Based on theoretical analysis, in order to verify the correctness of the proposed electromagnetic transition, to establish a DFIG control model of 3MW, the simulation results show that the stator current and torque with the theoretical analysis are consistent during grid voltage dip. It illustrates that the voltage drop analysis method can accurately reflect the voltage drop in the process of electromagnetic phenomena. I t can provide adequate theoretical basis for double-fed motor control strategy of LVRT.