计及低电压穿越控制的双馈风力发电机组短路电流特性与故障分析方法研究

Study on Short Circuit Current and Fault Analysis Method of Double Fed Induction Generator with Low Voltage Ride-through Control Strategy

近年来双馈风力发电机组并网容量不断增加,且现有双馈风力发电机组普遍具备了低电压穿越能力,在故障期间低电压穿越控制策略将对双馈风力发电机组的短路电流特性造成很大影响,而不精确的短路电流计算将会影响故障分析的结果,进而使保护动作特性的评估产生误差。针对上述问题,基于变流器的输入-输出外特性等效变流器的数学模型,进一步给出考虑控制策略的双馈风力发电机组故障期间暂态模型,分析低电压穿越控制策略对短路电流的影响机理,最终建立双馈风力发电机组短路电流计算的等效模型。采用RTDS建立含双馈风力发电机组实际控制器的物理实验平台,验证了所提出的等效模型具有较高的准确性。并在此基础上对含双馈风力发电机组接入的电网故障分析方法进行了探讨与分析。研究结果为进一步分析双馈风力发电机组接入对保护动作特性的影响奠定了基础。

The enlarged scale of doubly-fed induction generator（ DFIG） is connected to the power system and mostly DFIG units generally have a low voltage ride through（ LVRT） capability recently. The LVRT property will have notable influences on the short circuit currents in DFIG＇s fault. Then the imprecise short-circuit current calculation may affect the results of system fault analysis and thus contribute considerable errors to the evaluation of the protection action characteristic. In this paper,according to the input-output characteristic of the converter,the equivalent model and the transient model of DFIG are provided. The influence mechanism of the LVRT control strategy is analyzed,and the short circuit current calculation model of DFIG is established. Based on the real time digital simulator（ RTDS）,the experiment platform with physical controller is founded,by which the proposed short-circuit current calculating model is validated. The fault analysis method for the grid with penetration of DFIG is analyzed. Results of this research are available for the study of the influence of DFIG on the protection characteristics.