水电孤岛直流送出系统的频率稳定性研究

在考虑尾水管水压脉动的线性水轮机模型的基础上进行改进,设计了一种谐振函数来模拟尾水管的实际脉动情况,并建立了既考虑尾水管水压脉动又考虑弹性水柱的水轮机模型。采用时域仿真方法,验证了水轮机模型的准确性并分析了水力系统参数、调速器参数对送端孤岛直流送出系统频率振荡的影响。仿真结果表明,水力启动时间T_w、调速器参数K_D对送端孤岛系统的频率振荡影响较大,而弹性时间T_e对频率振荡的影响较小。在频率振荡的抑制方法方面,本文在原有的直流频率限制器模型的基础上进行改进,用二次低通滤波器代替一次滤波器并重新调整PI参数。由仿真图形可知,改进后的直流频率限制器抑制效果良好,可将送端频率有效地抑制在50Hz左右。

Research on Frequency Stability of Islanded Hydroelectric DC Sending System

In this paper, a resonance function to simulate pulsating situation of the tail pipe pulsation based on the linear turbine model is designed, and a novel water turbine model that considers the tail pipe water pressure pulsation as well as the elastic water column is built. By using time domain simulation method, the accuracy of the turbine model is verified, and the influence of the parameters of hydraulic system and the governor on frequency vibration in sending-end of islanded DC system is analyzed. Simulation results show that such parameters as the hydraulic startup time (T_w) and governor parameter (K_D) have great impact on frequency vibration in sending-end of islanded DC system with the exception of elastic time (T_e). Moreover, DC frequency limiter model is modified to restrain from frequency oscillation by using secondary low-pass filter instead of linear low-pass filter and regulating PI parameters. The results show that the frequency in sending-end will be controlled to about 50Hz, which verifies the validity of modified DC frequency limiter.