| The selection of synchronous generator model is one of the most important issue in power system transient stability analysis.When it comes to industrial application,high-order detailed models are often replaced by reduced order models to improve the efficiency.However,the difference between detailed models and reduced order models can not be neglected.A damping term is often appended in the reduced order model to obtain a reliable result.For now there is no definite method to determine the damping coefficient,therefore the empirical value is often used.Aiming at the problems mentioned above,a compensation torque which can be appended to the equation of rotor motion is obtained by two different methods in this paper,while the voltage equations and flux linkage equations are kept unchanged.The main work of this paper are as follows:The seventh-order model and the fifth-order model of synchronous generator are taken as the reference standard.According to the two-time scale characteristic of synchronous generator and singular perturbation theory,the singularly perturbed model of synchronous generator is established.Utilizing two methods to make compensation for the reduced order model.The first one is boundary layer correction.By establishing boundary layer system which involves stator electromagnetic transient,the fast component of stator flux linkage can be corrected and therefore a compensation torque formula is derived.The second one is dynamic correction.Apart from restoring the fast dynamic of stator flux linkage,the restoration of the slow dynamics is also taken into consideration.Besides,the fast current component of rotor windings are replaced by equivalent d-and q-axis stator current increments which create the same flux linkage,and by which an expression of compensate torque is derived.These two methods mentioned above are operated in two systems under two different circumstances.According to the results of simulation,the influence of winding resistance energy consumption is disclosed and the relationship between compensation torque and damping torque is clarified.In the end,based on industrial requirements,a novel method of calculating piecewise compensation torque based on averaging method is proposed in the SMIB system. |
