增强型调速器对中国云南电网超低频振荡影响分析

云南电网在部分水电机组中采用增强型调速器，会引发超低频振荡，并严重威胁异步电网频率安全。为揭示水电机组增强型调速器影响云南电网频率的原因，通过对系统频率偏差从不同方向穿越一次调频死区时的动力学行为进行理论计算和时域仿真，论证了增强型调速器在水电机组一次调频死区附近没有稳定平衡点，且当系统频率偏差缓慢穿回一次调频死区时，在超低频段引入约90°的相位滞后，进而降低系统频率安全稳定裕度。最后借助小扰动分析工具计算了包含水轮机、调速器、发电机模型的单机系统特征根，通过对比仿真，说明增强型调速器不仅与水锤效应在超低频段有相似的负阻尼效应，还是引发超低频振荡的扰动源头之一，使超低频振荡持续且无法衰减。

Analysis on Impact of Enhanced Governor on Ultra-low Frequency Oscillation in Yunnan Power Grid of China

Enhanced governors are adopted in some hydroelectric units in Yunnan power grid, which causes the ultra-low frequency oscillation and threatens the frequency stability of power grid seriously. In order to reveal why the enhanced governors of hydroelectric units affect the frequency of Yunnan power grid of China, the theoretic calculation and time-domain simulation are conducted on dynamic behaviors when the system frequency difference across the dead zone of primary frequency regulation from different directions. It is demonstrated that the enhanced governor does not have a stable equilibrium point near the dead zone of primary frequency regulation of hydroelectric generator, and when the system frequency difference slowly passes back to the dead zone, a phase lag of about 90 degrees is introduced in ultra-low frequency band, thus reducing the safe and stable margin of the system frequency. Finally, the eigenvalues of a single-machine system including hydro turbine, governor and generator models are calculated with the aid of small disturbance analysis tools. Through the comparative simulation, it is shown that the enhanced governor not only has similar negative damping effect with the water hammer in ultra-low band, but also is the one of the disturbance sources of ultra-low frequency oscillation, which keeps ultra-low frequency oscillation continuous and unable to attenuate.