电网故障下双馈风电机组暂态电流评估及分析

Evaluation and analysis of transient current of a DFIG windgeneration system under grid fault

为了便于分析并网双馈风力发电机组低电压穿越(LVRT)运行的承受能力,有必要对电网故障下双馈风电机组的暂态电流进行评估。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机端短路故障和电网电压不同跌落程度时的定、转子暂态电流评估的解析表达式,并通过考虑风力机传动链柔性的机组暂态仿真结果验证了推导表达式的正确性。在此基础上,应用推导的表达式对双馈风电机组在不同初始输出有功功率、无功功率以及电网电压不同跌落程度时的定、转子暂态电流最大值进行了计算,并得到了不同运行工况对机组暂态性能的影响规律。

In order to analyze effectively the operational capability of the low voltage ride through （LVRT） of a gird-connected wind turbine with doubly fed induction generator （ DFIG）, it is necessary to evaluate directly the transient currents of a DFIG wind generation system under a grid fault. By using the transient principle of the stator and rotor flux of a DFIG, ~the expressions of the stator and rotor transient currents of the DFIG wind generation system are derived under both the terminal short-circuit fault and the different grid voltage drop faults. By considering the drive train flexibility of a DFIG wind generation system, the proposed expressions of evaluated transient currents are validated by the time-domain simula- tion results from the transient models. In addition, by using the presented expressions, the maximum val- ues of the stator and rotor transient currents are calculated under the different initial conditions of the out- put active power, reactive power and the different grid voltage drop. The effects of transient performances of the DFIG wind generation system on the different initial operational conditions are obtained.