Study Of Arrangement Of Pressure Regulating Valve And Control Method In Small And Medium-Sized Hydropower Stations

With the development of hydropower industry,the safety of hydropower transient process is one of the key technologies for hydropower development.In this thesis,the simulation model of water conveyance is established,the same as Xianghe Hydropower Station generation system.The load variation,hydraulic disturbance and small load disturbance conditions of hydropower units are analyzed,which covers many representative working conditions,it may be involved in daily operation.The conclusion have reference value for relevant design,type selection,layout and control,protection prediction of hydraulic transient process of medium and small hydropower stations with pressure regulating valves,and have good applicability.The main contents are as follows:(1)The simulation model of diversion water generating system with pressure regulating valve as protection measure,which is introduced.The relationship between the control time of the pressure regulating valve and the change process of water hammer pressure in the system is studied.The inhibition effect of control time on the pressure of the end of the worm,and the rise of the speed are further analyzed.By establishing the simulation model of regulating valve after incorporating into tailwater,dangerous negative pressure phenomenon behind the valve during the transient process is studied,the particularity of multiple rotational speed wave peaks is emphatically analyzed.(2)The difference between power and frequency regulation during hydraulic interference is analyzed in detail.The pressure regulating valve and the initial opening of the guide vane caused drastic changes in output,as well as the dangerous processes.Such as the failure of the guide vane to move.When the frequency is adjusted,the bypass discharge of the pressure regulating valve is studied systematically.Then,the overload effect of the pressure regulating valve and the more complex output changes are analyzed quantitatively.(3)During the small load disturbance adjustment process,pressure regulating valve is difficult to participate.The difference of the parameters in the middle and low water conditions is summarized.The sensitivity of the system parameters is demonstrated,such as the unit's rotational inertia.Influence mechanism on the peak value and occurrence time of the indexes are analyzed,such as rotational speed and output.(4)Through the simulation calculation and analysis of many kinds of hydraulic transient processes,it is found that Xianghe river power station can still ensure the safe and stable operation of the system,when certain engineering construction and unit selection changes occur.After merging into the tailwater layout,protective effect of adopting the valve is better than that of connecting the valve into the lower reservoir layout.