Reserch On The Control System Of Variable Speed Rotary Hydropower Unit

With the widespread application of large-capacity wind turbines and the increasing maturity of variable-speed constant-frequency technology,this article introduces variable-speed wind power tcchnology into the traditional hydropower field,using water turbines as prime movers instead of wind turbines to realize variable-speed hydropower systems,Is an important means to improve the opcating conditions of hydropower units.China is rich in hydropower resources,and there are still many low head power stations that need to be developed urgently.At present,low-head power stations generally use rotary-propeller hydroelectric generating units.Because the water head of low-head power stations often changes with seasons or different water storage stages,and the water head changes relatively.Larger amplitude,the load will also change with the power balance of the power system.Conventional synchronous hydropower units can only operate at the rated speed.When the water head and load change,the unit will deviate from the optimal working conditions and the hydraulic efficiency will be significantly reduced.Cavitation and sediment wear are serious,and the pressure pulsation of the draft tube increases,which greatly limits the operating range of the unit and reduces the power generation efficiency.Therefore,in order to further improve the operating conditions of hydropower units,this article applies variable-speed power generation technology to rotary-propeller hydro-generator units,so that the hydro-generator units always operale in a higher efficiency area,and at the same time,the unit can improve the efficiency of the unit under grid-connected conditions.Response characteristics of load.The thesis first conducts a more in-depth analysis of the research status of variable-speed hydropower units at home and abroad,and proposes to take the rotary-propeller turbine generator as the research object,and select the comprehensive characteristic curve and working parameters of the rotary-propeller turbine model of a hydropower station to carry out the research;The comprehensive curve of the propeller turbine at each fixed blade angle is processed to obtain the model comprehensive curve under the combined working condition,and on this basis,the optimal speed curve is obtained according to the method of minimum unit flow under equal unit output;then the speed change is given.The overall block diagram of the control system of the rotary-propeller hydropower unit.The mathematical model of the governor,the elastic water hammer model of the water diversion system,the linear and non-linear model of the hydraulic turbine,the first and second order models of the generator,and the simplified full power change The model of the flow device,etc.;finally,a simulation model of the control system of a conventional fixed-speed and variable-speed rotating-propeller hydropower unit is built,and the dynamic characteristics of the system are simulated and analyzed in depth.The results show that:in the constant-speed operation mode,under the same adjustment parameters Compared with the nonlinear hydraulic turbine model,when the disturbance amplitude is small,the dynamic process of the linear and nonlinear hydraulic turbine model control system is basically the same.When the disturbance amplitude is large,the dynamic process of the control system is quite different.The nonlinear hydraulic turbine model The dynamic process varies significantly with the change of the disturbance amplitude;compared with the control system of the fixed-speed unit,the variable-speed unit can keep running at the optimal speed according to the change of operating conditions.It has a short power command response adjustment time,good stability,and can always maintain The advantages of operating in the high efficiency zone.