Simulation Analysis On Torsional Vibration Of Turbogenerator Shafting Under Wind-thermal-bundled Power Transmission

The power transmission mode combined wind power and thermal power not only meets the long-distance transmission of traditional energy and renewable energy,but also greatly alleviates the problem of wind power absorption,and gradually becomes the mainstream form of wind power transmission.However,the access of the wind farm also brings new instability inducing factors to the power grid,which may cause electromagnetic oscillation of the power grid,and then excitated the torsional vibration of shafts and electromechanical interaction,affecting the safe and stable operation of the turbine generator.In this paper,the simulation analysis of torsional vibration of turbo-generator shafting under wind-thermal-bundled power transmission is carried out.Firstly,the mathematical model of each part in the wind-thermal-bundled power transmission system is conducted,including doubly-fed wind turbine,turbo-generator unit,and high voltage direct current transmission system.At the same time,the inherent characteristics of the torsional vibration of the steam turbine unit shafting model are analyzed,which lays a foundation for the following research.Secondly,based on the mathematical model of wind-thermal-bundled power transmission system,the model unified electric and mechanic is set up with the electromagnetic transient simulation software PSCAD/EMTDC.The influence of the ratio of wind power and thermal power,the control parameters of the wind turbine converter and the different bus faults on the torsional vibration of the turbo-generator shafting is discussed.The simulation results are analyzed in the time domain and frequency domain.The results illustrate that the integration of doubly-fed wind turbine can restrain the torsional vibration of the turbo-generator shafting to a certain extent,and the higher the ratio of wind power and thermal power,the more obvious the restraining effect is;the gain coefficient of the converter of the doubly-fed wind turbine will affect the torsional vibration of the turbogenerator shafting,while the integral time constant have little impact;on the whole,the shafting torsional vibration excited by three-phase short circuit fault is more serious than that excited by two-phase short circuit fault.Finally,a time-frequency analysis method of shafting torsional vibration signal based on variational mode decomposition and hilbert transform is proposed to further discuss the relationship between the time and the modal components of the shafting torsional vibration signal.The results show that the method can effectively separate the modal components contained in the torsional vibration signal,and get the relationship between the modes and time.