Research On Modeling And Simulation Of Unified Power Flow Controller

As the power grid has entered the new stage of large scale system,EHV long distance transmission and network inter-regional.Complex grid structure and large-scale access of new energy need higher demanded of safety,stability,efficiency and flexibility to power grid.The Jiangsu power grid unif ied power flow controller(UPFC)project put forward higher requirements for the simulation and modeling technology of large-scale power electronic equipment.This paper established the modular multilevel converter(MMC)electromagnetic transient model,considering the modular multilevel converter based UPFC(MMC-UPFC)based on actual engineering requirements and simulation,study the modeling and Simulation of MMC-UPFC,the specific work is as follows:(1)The development of flexible AC transmission is introduced.On this foundation,the research status of UPFC,UPFC converter,UPFC mathematical model and UPFC control strategy are introduced,and significance of UPFC is expounded.(2)Based on a large number of references,basic principles,control characteristics,application of topology and development of UPFC integrated control mode are introduced in detail.(3)Modular multilevel converter(MMC)is the most critical in UPFC,the basic principle the mathematical model of MMC are mainly studied,three kind s of electromagnetic transient model of MMC are introduced,and the efficient electromagnetic transient model of MMC based on Thevenin equivalence are established,three kinds of modulation strategy of MMC are analyzed,and finally the nearest level modulation are choosen as modulation strategy.the simulation of three kinds of modulation strategy are analyzed,and the output characteristics under different modulation strategies are compared;(4)After the electromagnetic transient model of MMC is establish ed,with the MMC-UPFC double loop decoupling control strategy,start the MMC sub module capacitor pre charging,starting control method,the nearest level modulation,the use of the MMC circulation control and current limit control,the simulation of the MMC-UPFC is implemented in PSD-PSModel.The simulation analysis shows that the simulation model of MMC-UPFC established in this paper can simulate the operation of the actual project correctly,and ensure the accuracy of simulation,at the same time,improv e the simulation speed of MMC-UPFC.It can better simulate the actual engineering operation,and has a good effect.