考虑频率波动的水电孤网发电机自励磁研究

摘要

分析了发电机自励磁的物理过程,采用计及线路感抗的线路模型从理论上深入研究了频率对发电机自励磁的影响,推导出了发电机带空载长线时发生自励磁的临界频率表达式,指出当孤网频率超过临界频率的情况下,系统可能由正常状态过渡到发生自励磁的运行状态;并在临界频率的基础上推导出发电机在考虑自励磁后缩小了的运行极限,为避免水电机组孤网运行产生自励磁现象提供了理论依据.采用PSCAD/EMTDC进行仿真,仿真结果证明了所得结论的正确性.%The physical process of generator self-excitation is analyzed and the effect of frequency on generator self-excitation is theoretically studied based on the line model considering the line inductive resistance. The critical frequency expression of self-excitation for generator with unloaded long line is derived. It is pointed out that,system may transit from normal operation state to self-excitation operation state when the frequency of isolated network exceeds the critical frequency. Based on which,the modified generator operating limit considering self-excitation is derived to provide the theoretical basis for avoiding the self-excitation of isolated hydropower network. Results of PSCAD/EMTDC simulation prove its correctness.