水轮机组与电网耦合对电网动态稳定的影响

电网多次发生水轮机组参与的功率低频振荡现象,产生机理不明,严重影响电网的安全稳定运行.本文以江西柘林水电厂为例,首先分析其水轮机组尾水管水压脉动情况以及对输出机械功率的影响,其次根据尾水管水力系统物理特性,建立考虑尾水管压力动态的水轮机组模型.采用时域仿真方法,探讨了水轮机组水力系统与电网之间的耦合作用,研究了水轮机组尾水管水压脉动对电网动态安全稳定的影响.仿真结果表明:当水轮机组尾水管水压脉动频率与其发电机所在电网中的自然振荡频率相同或接近时,有可能发生共振而引发电网的功率振荡,造成电网动态稳定的破坏.研究结果对分析电网低频振荡产生原因具有一定的参考价值.

Effect of the Coupling Between Hydraulic Turbine Set and Power Grid on Power Grid Dynamic Stability

Low frequency ocillation phenomenon in which the hydraulic turbine sets participate occurred on power system many times. They have unknown mechanism, which has seriously affected the security and stability operation of power grid. In this paper, taking the Zhelin hydropower plant of Jiangxi Power Grid as the example, the states of water tail pressure pulsation and the influences for the output mechanical power are analyzed firstly. Then the hydraulic turbine set model considering the water tail pressure dynamic is established based on the physical characteristics of the draft tube hydraulic system. The effect of water tail pressure pulsation on the power grid dynamic security and stability is studied and the coupling between the hydraulic turbine set and power grid was investigated. The simulation results indicate that power oscillation in power grid might be caused by the water tail pressure pulsation because of resonance, when the water pressure pulse frequency is consistent with or close to power system natural oscillation frequency. Power oscillation causes the dynamic instability of power grid. The conclusion can provide reference to research into the causes of power system low frequency oscillations.