Research On Over-standard Vibration Characteristics And Start-up Optimization Control Of High-head Hydropower Station

People have been always concerned about the safe and stable operation of hydropower stations.For this reason,relevant standards have been formulated at home and abroad to specify the vibration limits of key parts of hydroelectric unit.When the unit is operated in a non-recommended operation area or under transient conditions such as start-up,it is prone to over-standard vibration,which will cause damage to the hydropower station or even cause serious safety accidents.For example,when the “8·17” accident occurred in the Sayano–Shushenskaya Hydropower Station,the vibration amplitude of head cover bearing of turbine exceeded the allowable value by four times.In this paper,the over-standard vibration is analyzed systematically in depth by means of prototype observation,theoretical derivation and numerical calculation.What’s more,the optimal control of the unit’s start-up method is studied.The corresponding results are as follows:(1)Type identification and response characteristics of over-standard vibration of hydroelectric sets were studied.Firstly,the classification and identification method of over-standard vibration were proposed.Then the unit vibration of a high-head hydropower station was identificated and analyzed.The results showed that the over-standard time of fixed load condition was longest,lasting for 779 min,and the maximum vibration peak-peak value was 294μm,which was 4.2 times of the allowable value of 70μm.Start-up was the type of over-standard vibration with the largest vibration amplitude.Its maximum vibration amplitude reached 582μm,which was 8.3 times of the allowable value of 70μm.After that,the head and load characteristics of various types of over-standard vibration were conducted.Finally,a fitting formula for hydraulic turbine efficiency was established and verified.(2)Based on the proposed new methods of vibration signal processing,research on the structure vibration characteristics of hydropower plant under fixed load conditions was carried out.Firstly,the main vibration source components were determined by the theoretical calculation and test data analysis about the structure vibration of the hydropower plant for an actual project.Then,the adaptive variational mode decomposition method for non-stationary signals and the sub-signal standard deviation calculation method based on autocorrelation function for stationary random signals were applied to analyze the change law of the plant structure vibration in detail with the head and load under the action of multi-vibration sources.Finally,the intensity-correlation degree was established to evaluate the importance of each vibration source.(3)Single-objective and multi-objective optimal control researches on the start-up process of hydroelectric unit were conducted.Firstly,the time-frequency characteristics of the plant structure vibration during the start-up process were analyzed.It was determined that the maximum vibration of the plant structure occurred during the process of the vane opening to callback.Then,on the basis of considering the unit quickness and hydraulic stability,the correlation between the three influencing factors and the four control indexes of the open-loop start-up process was studied.After that,the single-objective optimal control of the open-loop start-up process was performed by using genetic algorithm for an actual project.The obtained results could reduce the maximum pressure fluctuation by 14.9% without extending the start-up duration.Finally,the non-dominated sorting genetic algorithm with elite strategy was applied to conduct the multi-objective optimal control of open-loop start-up process.The Pareto secondary dominant solution sets optimization method was proposed.The corresponding start-up process could reduce the maximum pressure fluctuation by 18.36%~31.14%,the start-up duration was shortened by 1.13%~19.63%.