Research On Influencing Factors Of Regulation Quality Of Small Fluctuation In Hydro-power Station With Surge Tank

As crucial backbone power sources in the power grid,the main task of the hydro-electric power units are the frequency modulation and peak modulation task.So,it is important to ensure that they have good regulation quality and high quality power output.In the small transition process,hydro-electric power units often exist in the speed of the tail wave attenuation rate is too slow and other problems caused by the surge tank water level fluctuation,so that the impact of regulatory quality.And these questions have always been the focus of attention.In order to improve the regulatory quality of the system,people often set the surge tank near the location of the turbine in the project,but also bring the problem of the tail is more serious,even increase the surge tank area to reduce the impact of tail waves,making a substantial increase in investment in engineering.Therefore,it is of great value to study the influence of various factors on the regulation quality of the small transition process for the hydro-power station with the surge tank.First of all,the fifth-order mathematical model of the regulating system is established in this paper,which includes diversion tunnel,surge tank,pressure pipe,hydro-electric generating unit,governor,etc.Then,since the five or more equations can't find the analytical solution,so the original five-order system needs to be simplified.In this paper,the influence of each factor on the speed of the unit during the transition process is analyzed by theoretical derivation and numerical simulation.It is found that the change of the turbine head pressure caused by the pressure wave of the pressure pipeline has little effect on the flow characteristics of the t urbine.The speed of the unit is very close to the original system unit speed fluctuations proces s.According to this principle,the original model can be simplified to a fourth-order model.The decomposition of the characteristic equation of the fourth-order model is obtained by the superposition of two second-order links,which represent the main-wave characteristics and tail-wave characteristics of the rotational speed.By analyzing the two second-order links,we get the analytic expression of the regulatory quality index such as overshoot and adjustment time.And the correctness of the analytical formula is verified by an engineering case.The results of this research provide a reference for similar power stations.Finally,Based on the theoretical expression of adjusting the quality indexes,the influence law of various factors on the regulation quality of small fluctuation is studied,including the pressure chamber position,the surge tank section area,the governor parameters,Ta and eg and so on,and through the numerical simulation of the comparative verification.