Research On Electromechanical Characteristics Of Turbine Generator Under Large Disturbance

Synchronous generators are important components in power systems.The strong shocks caused by faults such as short circuit and loss of excitation may endanger unit safety and reduce their operating life.Therefore,it is of great significance to study the electromechanical characteristics of synchronous generators under large disturbance and their effects on system stability.The main work of this article is as follows:(1)Based on the single-machine grid-connected equivalent system of a synchronous generator,a machine-field-circuit-network coupled time-step finite element simulation model of a 300 MW turbo-generator was built.The generator uses a two-dimensional transient time-step finite element model,which fully considers the effects of eddy current loss,skin effect,and nonlinearity of the core material.The rotor shafting model of the generator’s mechanical input takes into account factors such as the torque transmitted by each shaft segment and the different changes in the speed of each mass.In the model,the traditional damping structure was improved,and the rotor slot wedge was divided into a multilayer structure.At the same time,the damping effect of the small rotor teeth and the large rotor teeth adjacent to the rotor slot wedge was considered.The rationality of the damping parameters of the improved damping model was verified using the principle of stator and rotor AC impedance.The current in each damping winding was analyzed through a three-phase short-circuit fault at the machine end,which verified the accuracy of the verification method.The accuracy of the finite element model was verified under rated operating condition.(2)A simulation of a sudden three-phase short-circuit fault and its removal at the turbine end of a 300 MW turbo-generator was performed.The main physical quantities of the generator’s electromechanical system during slip-pole operation of the unit under two damping models were analyzed.The fault limit removal time was calculated.The fatigue life loss of the shafting system caused by the large disturbance was calculated,and the number of slip-pole of the unit was calculated.The results validated the effect of the damping model on the calculation accuracy of generator electromechanical characteristics during large disturbances.(3)Based on the new finite element simulation model,the excitation fault of a300 MW turbo-generator with a rated load was simulated.It verified the effect of the model calculation by comparing the results of the real machine excitation fault.