交流电网故障时DFIG机组定转子暂态特性分析与仿真

Research on transient analysis and simulation of stator and rotor of DFIG under AC grid fault

针对电网对称及不对称故障,给出了估算定、转子暂态磁链和电流的方法。利用机理建模法建立了DFIG机组的数学模型,分析了电网故障下DFIG机组定、转子磁链的暂态特性,并推导出了定、转子暂态电流表达式。在理论分析的基础上,应用Simulink平台搭建了基于定子电压定向矢量控制策略的1.5 MW DFIG机组转子侧及网侧变换器模型,采用矢量轨迹图直观描述了定、转子磁链和电流的暂态变化过程,并提出一种结合基于双dq正、负序分解矢量控制与Crowbar电路的改进控制策略。通过仿真试验,验证了暂态电流表达式的正确性,并得到了跌落后电压值与定、转子电流最大值之间的关系曲线。此外,所提出的改进控制策略能够提高机组故障穿越能力。

A method is proposed to estimate the transient magnetic flux and currents of stator and rotor under the symmetrical and asymmetrical grid fault. By using mechanism modeling method, a mathematical model of DFIG is firstly built. Transient characteristics of the stator and rotor flux of the DFIG under grid voltage fault are analyzed, and the expressions of the stator and rotor transient currents are derived. After the theoretical analysis, the rotor side and the grid side converter of 1.5 MW DFIG are modeled based on stator voltage oriented vector control strategy in Simulink. In addition, the transient process of the stator and rotor flux and currents are described by the vector locus. A new control strategy which combines vector control based on double d-q positive and negative sequence decomposition with crowbar circuit is proposed. The results validate the expressions of the stator and rotor transient currents. Relation curves between the k and the maximum values of the stator and rotor currents are obtained. Furthermore, the capability of grid fault ride through of DFIG with proposed control strategy is improved.