Research On Reduced Order Modeling Method Of Power Electronic Interface In Power System Based On Singular Perturbation Theory

Because of its flexible and convenient use,electric energy has always attracted many attentions.According to the current trend of rapid development of new energy,the "new power grid" presents a variety of forms of electric energy conversion and a large number of power electronic devices in the power electronics of the power system.Power electronics introduces more complex interactions,which are mainly reflected between electronic devices and the power grid.In the traditional sense,power grids generally include inductive devices and synchronous generators.The theoretical output voltage waveform of synchronous generators is a perfect sine wave.When there are fewer power electronic devices connected to the power grid,the traditional power grid can still assume the state of an ideal voltage source.However,now that grid-connected inverters are integrated into the grid on a large scale,the interaction between the grid and the converter and the interaction between the converters have become very complex and intense.At this time,it cannot be regarded as an ideal voltage source.How to carry out corresponding equivalent modeling for this kind of power electronic power system has been called a recent hot issue.In the process of reduced-order modeling research on power systems with power electronic interfaces,this paper mainly did the following work:First,compare the power characteristics of the power electronic interface with the power grid characteristics,and expose the power characteristics inside the power electronic interface.It also introduces the singular perturbation theory,which is the theoretical basis for system modeling of power systems including power electronic interface power supplies.It divides the different time scales in the electromagnetic transient model of power electronic interface power supplies,and divides each of them.The time scale of the state variables is simulated to distinguish between fast and slow dynamics,retain different degrees of fast and slow dynamics,and build classic differential reduced-order models and generalized differential reduced-order models.Secondly,taking the Neutral Point Clamp(NPC)(Neutral Point Clamp)three-level converter,which is widely used in the field of medium voltage and high power,as the research object,SVPWM is used when model control of the NPC three-level converter Carry out three-level control,and propose a more comprehensive and detailed control method.Then build an electromagnetic transient model and perform model reduction processing on it.Thirdly,using the hybrid characteristics of the NPC three-level converter,the inherent hybrid relationship between discrete events and continuous events is deduced in detail.Based on the theoretical basis of the Lyapunov stability criterion of hybrid systems,the reduced-order model is theoretically verified.The simulation model is built in the Matlab/Simulink simulation platform,and the simulation results confirm that this reduced-order modeling method has better tracking performance.Finally,on this basis,this theoretical model is applied to DFIG wind turbine modeling,and a reduced-order modeling method of DFIG is proposed.In the calculation simulation,the typical starting criterion of DFIG relay protection action in transient stability problem is analyzed,and the modeling principle of relay protection and low voltage ride through behavior is analyzed.Confirm the validity of this modeling model.