Numerical Simulation And Analysis Of Speed Fluctuation Of The Steam Turbine Generator System

In this thesis,one isolated steam turbine generator system is researched.The speed fluctuation phenomenon of the system is analysed.Lumped parameter method is employed to establish the torsional vibration model of the steam turbine generator.The correctness of the torsional vibration model is verified by comparing with experimental results.Mathematical model of steam turbine speed governing system are derived.The coupling models of speed governing system and shafting with or without considering its elasticity are established.The simulation results show that the model considering the shafting elasticity could better reflect the speed fluctuation of the steam turbine.Then the shaft is replaced by a true multi-inertia and elastic model.Transient speed is treated as a feedback signal to the control system.Using the Simulink model of the steam turbine system,the different turbine speed fluctuation is simulated,which are caused by different governor parameters.It can be seen that speed fluctuation and the whole system oscillation instability will happen if governor parameters do not match well with the system.The simulated calculation results are verified by experiments.While adjusting the speed governor idle,speed fluctuation of steam turbine reduced to 6 rpm.The relationship between the dynamic characteristics of shafting and power fluctuation is also studied by the simple model.As can be seen through the experiment,when the generator connecting in parallel with system,it has impact on shafting,possibly excited shafting torsional vibration.By using this method can measure shafting torsional vibration.While increasing active load in experiment model,the electric currents presented fluctuation at low frequency,similar to the phenomenon of the isolated power station system.Using the simulation model,repeated the speed fluctuation at low frequency in the experiment site.