换相失败后水轮发电机的频率响应特性分析

Frequency response characteristic analysis of hydraulic turbine after commutation failure

针对高压直流输电系统换相失败引发送端系统发电机频率和功角不稳定的问题,文中建立了包含发电机、调速器、水轮机等元件的频率分析模型,考虑故障后暂态过程中调速器对机械功率的调节效应,将换相失败后发电机的功角特性分为失稳模式和非失稳模式,两种模式与换相失败的持续时间和直流输送容量有关。其次,分析了非失稳模式下水锤效应时间常数对于系统频率特性的影响,由于水轮机传递函数是非最小相位系统,在调速器和水轮机的降机械功率控制中呈现出负调节效应,其水锤效应时间常数越大,负调节效应越明显,换相失败后的频率峰值越高。BPA不同模型仿真结果验证了相关结论。

Aiming at the stability problem of frequency and generator angle after commutation failure in HVDC sys- tem, this paper analyzed the mechanism of commutation failure in detail based on the commutation process. Consider- ing the moderating effect of governor on mechanical power in transient process after faults, the power angle character- istics of the generator are divided into unstable mode and stable mode based on equal area rule. The two modes are relative to the commutation failure duration and DC capacity. The influence of water hammer time constant on system response after commutation failure is analyzed in stable mode. The mechanical power control of the governor and hydraulic turbine shows a negative regulation effect for the transfer function of hydraulic turbine is non-minimum phase system. The relative conclusions are verified by different BPA model simulations.