Stability Evaluation Of Hydraulic Power Generation System Under Different Excitation

Hydraulic power generation system is a kind of complex nonlinear dynamic system with nonlinear,coupling and randomness.Mechanical,electromagnetic and hydraulic factors in the system influence and restrict each other.A complete hydropower generation system includes a hydro-generator system,a water diversion system and a speed regulation control system.Although these three important subsystems have different physical properties and different orders of parameters,they form a unified water-mechanic-electric coupling system through the coupling inside the system.The state change of any subsystem will affect the whole hydroelectric system through coupling mechanism.Taking hydraulic power generation system as the research object,considering that it is a typical water-machine-electric coupling system,the stability and dynamic response of the system will change with the time.The actual disturbance that affects the stable operation of the unit is transformed into the excitation form and then introduced into the model to analyze the stability and dynamic characteristics of the operation of the hydraulic power generation system under different excitation.The main contents and conclusions of this paper are as follows:(1)The stability of a hydro-turbine generator set can be characterized by the vibration,pendulum and pressure pulsation of the unit,among which vibration is the most direct and important index to measure the stability of the unit.The factors affecting the hydraulic stability are relatively complex,and the vortex zone of the tail pipe is one of the key factors affecting the stability of the hydraulic power system.In order to deeply study the stability and vibration characteristics of hydraulic power generation system under the influence of pressure pulsation,based on the coupling relationship between turbine governing system and shafting,a coupling dynamic model containing the regulating system and shafting was established and the pressure pulsation of the draft pipe was introduced as the hydraulic excitation.The nonlinear coupling relationship between different components of the system and the influence of different mechanical system parameters on the vibration characteristics of the system are revealed.The research results provide a theoretical reference for exploring the stability mechanism under the influence of pressure pulsation.(2)Time delay often occurs in many practical mechanical and electrical systems,such as power grids,process control systems and engineering systems.Although the time delay is very small in many engineering practices,it still has a great negative effect on the stability and controllability of nonlinear systems.Considering the influence of inertia and clearance in the mechanical system,time delay is introduced into the turbine governing system through system parameters,and the influence law of different time delay on the stability of turbine governing system is analyzed by numerical simulation.System in the operation process is not remained steady at a single point,but according to the network side need to adjust load and switch operation s,transfer coefficient is therefore changing in the process.Different time delay is studied and the dynamic response under different excitation intensity coupling system,and reveals mechanism of instability with the increase of excitation amplitude and time delay.(3)The stability of the hydraulic power generation system is jointly affected by the internal characteristics of the hydraulic power generation system and external operating conditions.Internal factors and external factors interact and influence each other,and obvious randomness will appear.Considering hydraulic random fluctuations,the transmission structure failure and mechanical error,the internal and external random excitation in hydroelectric power system of shaft system is introduced,and its transformation from the traditional though Lagrange system to energy system,the problem of random excitation in hydroelectric power system under in introduced into the analysis of single factor(energy).The stochastic model of hydraulic power generation system is represented by one-dimensional diffusion process by stochastic average method,and the stochastic stability of the system is analyzed by boundary analysis method.