Generator self-excitation in isolated hydropower network considering frequency fluctuation

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.