Shafting Structure Of Double-ended Driving Turbo-generator And Its Torsional Vibration Suppression

With the increase of single-unit capacity of steam turbine generator sets and the increasing complexity of power grid,the risk of torsional vibration fault of steam turbine generator sets is intensified.The torsional vibration of turbo-generator sets not only affects the output characteristics of the generator,but also causes torsional fatigue damage of the shafting,and even damage the unit,which seriously threatens the safe and stable operation of the unit and the power grid.Therefore,it is of great significance to carry out the research on the suppression of the torsional vibration of turbo-generator sets.The shafting structures of existing turbo-generator sets are single-ended driving shafting structures,and the shafting torsional vibration suppression of turbo-generator sets mainly depends on the controller.For impact torsional vibration,even if there is a controller,the torsional vibration amplitude of the unit shaft is still large within a very short period of time after the torsional vibration occurs,and it is even possible that fatigue damaged or even damage has occurred to the unit shafts before the control action has taken effect.Therefore,it is still difficult to suppress the shafting torsional vibration in conventional turbo-generator sets.In this paper,the shafting torsional vibration is restrained by the shafting structure of the turbo-generator set,and the shafting structure of the double-ended driving turbo-generator set is proposed.The proposed shafting structure of the double-ended driving turbo-generator set is: steam turbines are arranged at both ends of the generator,and a steam equalizing mechanism is designed behind the regulating valve,and the steam is evenly distributed to the left and right steam turbine cylinders through the regulating valve,so that the steam turbine power regulation at both ends of generator shaft is synchronous and with the same strength.For the proposed double-ended driving turbo-generator set with double end drive shafting structure,taking a domestic 600 MW unit shafting as a reference,this paper preliminarily constructs the rotating shaft of the double-ended driving turbo-generator set and carries out modal analysis,discusses the reduction method of the shafting model,and analyzes the response characteristics of the shafting torsional vibration under fault.Considering that the connecting shaft between generator and turbine is prone to torsional damage,the shafting of double-ended driving turbo-generator set is simplified into three mass blocks.Based on the three-mass block shafting model,the shafting torsional vibration control system of a double-ended driving turbo-generator set is established,and the shafting torsional vibration controller is designed by using the multi-index nonlinear control design method.The simulation results show that under the condition of constant excitation current and constant valve opening,the double-ended driving shafting structure has a good performance of suppressing torsional vibration.Under the shafting torsional vibration controller,the shafting torsional vibration can be further suppressed effectively,and the system also has good system output characteristics,which indicates that the shafting torsional vibration controller designed by the multi-index nonlinear control design method is effective.In addition,the structure model of double-ended driving and dual-excited turbo-generator set with dual-axis excitation structure is proposed,the shafting torsional vibration control system of double-ended driving and dual-excited turbo-generator set with 3-mass block shafting model is established,and the shafting torsional vibration controller is designed by using the multi-index nonlinear control design method.Compared with double-ended driving and single-excited turbo-generator set,the simulation results show that dual-axis excitation has better torsional vibration suppression effect,and can greatly improve the output characteristics of the system.In the simulation of shafting torsional vibration,in order to accurately analyze the torsional vibrations of connecting shafts between adjacent cylinders and connecting shaft between cylinder and generator rotor,each turbine cylinder is usually regarded as an independent mass,so a 9-mass blocks shafting model of double-ended driving turbo-generator set can be obtained,and then the shafting torsional vibration control system of the doubleended driving turbo-generator set is established.Considering that the shafting torsional vibration control system established is a high-dimensional system,and the calculation of the shafting torsional vibration controller designed by using the multi-index nonlinear control design method is complicated,therefore,the shafting torsional vibration controller of the double-ended driving turbo-generator set with a 9-mass block shafting model is designed by using the nonlinear control method with objective holographic feedback in this paper.Simulation results verify the effectiveness of the controller.In addition,the nonlinear control scheme of shafting torsional vibration of the double-ended driving turbo-generator set with a9-mass block shafting model is also presented.The simulation results also show that dual-axis excitation has better torsional vibration suppression effect,and can greatly improve the output characteristics of the system.Finally,considering the uncertainties of some parameters and external disturbances in the shafting torsional vibration control system model,a robust adaptive control design method with objective holographic feedback is proposed and applied to the design of shafting torsional vibration controller of double-ended driving turbo-generator set.The simulation results show that the shafting torsional vibration controller designed by the robust adaptive control design method with objective holographic feedback not only has a good suppression effect of shafting torsional vibration,but also eliminates the influence of system parameter uncertainty and various external disturbances on the system,so that each target physical quantity of the generator set has good dynamic and static characteristics.