Anti-vibration Structure Optimization Design Of Underground Powerhouse For Pumped Storage Power Stations

As a clean and renewable resource,water energy is abundant in China.Hydroelectric generation,by using the resource of water energy,can effectively convert water energy into electric energy and is relatively economical,environmental-friendly and mature in technology.Pumped storage power stations are energy-saving and environmental-friendly with functions such as frequency modulation,peak clipping,valley filling and emergency use.Large-scale pumped storage power stations are often built with underground powerhouses.Once a pumped storage power station is set in motion,the water turbine is pushed to revolve by the water energy,which is then turned into electric energy by the electric generator.As the pump-turbine generator unit is installed in the powerhouse,its mechanical and hydraulic vibration may cause its support structure to vibrate violently,thus leading to a powerhouse vibration.The pumped storage power stations have the characteristics of having high water head,large capacity,high revolving speed and two-way flow of water,which can give rise to an even severe vibration to the powerhouse.Apart from the special working conditions such as starting,shutdown,no-load,accident,grid connection,sudden loading,isolated operation and sudden load reduction,the pumped storage power stations,compared with the traditional hydropower stations,also have other motion features to their own accord.All these can potentially increase the vibration of the structure of the powerhouse.In most cases today,though the influence of unit vibration on powerhouses can be optimized or avoided with low unit vibration frequency thanks to the gradual matureness in research and technology,the pressure of flow fluctuation in the channel,having a wide range of frequency distribution and often very difficult to estimate,can still exert a huge impact on the structure of the powerhouses.Zhanghewan Pumped Storage Power Station built in China has experienced violent vibrations and the vibrations were mainly caused by the fluctuating pressure.Therefore,it is of great necessity to optimize the structure design of this type of powerhouses.In this thesis,such parameters as the sizes and number of runner blades were collected from some underground powerhouses of pumped storage power stations with a capacity of around 300 MW that have been completed or being built in China.A complete unit block in the main powerhouse of a pumped storage power station with a capacity of 300 MW,9 runner blades and 20 guide vanes,similar to Zhanghewan Pumped Storage Power Station,was taken as the control model(the parameters of this model were close to the mean parameters values of the current same type of power stations).An ANSYS model was set up to calculate the global natural vibration frequency of the control model and that of each typical parts.With the same method,the vibration response of fluctuating pressure under the frequency of doublednumber of runner blades was also calculated.By modifying the thickness of the floor slabs,columns and stairs slabs of each floor of control model,18 modified structure schemes were set up and the global and every typical parts' natural vibration frequency and response of fluctuating pressure of the modified schemes were calculated.By a contrast analysis with the control model,the change law of natural vibration frequency and response of fluctuating pressure over the change of the sizes in each parts of the powerhouse was obtained.The study was intended to provide some reference for the optimization design of structure size of the same type of pumped storage power stations.The results showed that when the size of each part is changed,the natural vibration frequency of the part is greatly affected,while the natural vibration frequency of the other parts and the global structure is insignificantly affected.When the thickness of floor slabs of the generator floor was 1m,the floor slabs of the busbar floor 0.85 m,the floor slabs of the water turbine floor was 0.95 m,the floor slabs of stairs 0.35 and the section size the columns on both sides was 0.9m×0.9m,a relatively optimized structure size of the powerhouse was attained.