双馈风力发电机故障穿越能力研究

Study on the fault ride-through capacity of doubly fed induction generator

在不对称电网故障下,为提高双馈风力发电机(DFIG)三相不平衡故障穿越能力,采用甘肃河西电网的实时数据,对双馈风力发电机发生不对称故障下穿越能力进行研究.在发电机出口串联采用改进控制策略的DVR,辅助DFIG风电机组实现故障穿越.为提高检测精度,首先,通过锁相环与pqr变换检测方法结合对电压跌落检测系统加以改进,为克服不平衡故障下负序分量对网侧和机侧的影响,在检测系统中加入基于对称分量法的正负序解耦算法;其次,利用四个PID控制器将参考电压的值与通过检测系统的结果值进行比较,分别调节每一相序,注入无功功率到电网中,保证待恢复的双馈风力发电机端口电压可以达到额定值,转速恒定,进一步保证系统的稳定运行.仿真结果验证了该方法的正确性.

To improve three phase unbalanced fault ride-through capacity of doubly fed induction gen-erator （DFIG） under asymmetric fault ,based on real-time data in Gansu Hexi Power Grid ,the fault ride-through capacity of DFIG under asymmetric fault was studied . The dynamic voltage restorer （DVR） with the improved control strategy was connected to the generator export in series assisting DFIG to realize fault ride-through .To improve the detection accuracy ,first of all ,the voltage sag de-tection system was improved through the phase-locked loop combined with pqr transform detection method .T he positive and negative sequence decoupling algorithm based on symmetrical component method was added to detection system to overcome the influence of negative sequence component to grid side and generator side under the unbalance fault .Secondly ,in order to ensure DFIG terminal voltage to reach rated value and keep the speed of generator constant ,with four PID （proportional-in-tegral-derivative） controllers ,the value of the reference voltage was compared with the results of posi-tive and negative sequence detectors respectively to control each phase sequence ,and reactive power was injected to the grid ,which could ensure the stable operation of the system .The simulation results show the effectiveness of the method .