Research On The Vibration Characteristics Of The Hydropower Generation System

Safe,efficiency and stable operation has always been the focus of construction and maintenance of the hydropower industry.The hydropower generation system is the main part to ensure the power generation,transmission and regulation of hydropower station.Studies of its stability characteristics of the key to ensure the stable operation.From the perspective of external interference,as the unstable large installed capacity of clean energy is connecting to the power grid,the stochastic disturbance from the power grid is enhanced,which in turn affects the stability of the hydropower system.For the internal vibration,the nonlinear dynamic behavior of the complex water-mechanical-electric coupling system and the complex forces of the hydro-generator shafting system will lead to significant change in the vibration state of the system.Therefore,it is necessary to establish a reasonable and accurate stochastic model of hydropower systems to analyze the stability characteristics of system operation under stochastic disturbance.Meanwhile,From the perspective of vibration characteristics,a coupled hydroelectric power generation system model is needed to study the interaction between the complex nonlinear dynamic behavior and vibration state,and the evolution characteristic of the vibration.This paper is organized as the following aspects:(1)For the effects of the external stochastic disturbance on the operation of hydropower system,a stochastic factor is introduced and the stochastic mathematical model of the turbine regulation system is established by the orthogonal polynomial approximation method.The accuracy of the deterministic stochastic model obtained by the orthogonal approximation method depends on the maximum number of adopted orthogonal polynomials,and the maximum number directly affects the computational strength of numerical simulation.Therefore,the obtained model is firstly analyzed from the aspects of accuracy and feasibility.By studying the variation law of the system dynamics under different adopted orthogonal polynomials and different random intensities,the number of adopted polynomials that satisfy the numerical simulation accuracy and facilitate of the simulation calculation is obtained.On the other hand,based on the above research results,numerical simulation is carried out to analyze the stability of the system under stochastic disturbance of different intensity.(2)Due to the multi-scale structure of time between the various components of the hydropower generation system,the caused various nonlinear dynamic behavior affects the stable operation.A coupled nonlinear mathematical model of the hydropower generation system is established to couple the hydro-turbine governing system with the hydropower generation unit.The fast-slow factor is introduced to the obtained model to analyze the vibration characteristics under the fast-slow effect.The vibration characteristics under the influence of fast-slow effects are studied from three aspects: the relationship between the evolution law of the fast-slow effects of different fast-slow frequencies and the vibration characteristics of the unit shafting;the influence of fractional order on the vibration of fastslow effects;the relationship between stability and fast-slow frequency.(3)Research on the evolution law of vibration characteristics of hydropower systems.Since the fractional order can more accurately describe the nonlinear dynamic behavior of complex systems than integer order,a coupled nonlinear model of fractional-order hydroelectric power generation with elastic water hammer is established.Firstly,the dynamic behavior of the coupled system under different excitation current is analyzed by numerical simulation.In view of the influence of excitation current on system stability,the evolution law of the vibration characteristics of hydropower generation unit under different fractional orders is analyzed.The evolution characteristics of the unit vibration with the fractional order in the horizontal and vertical directions are obtained.