Study On Modeling And Simulation Of UHVDC Transmission Control System

UHVDC transmission has developed rapidly in China in recent years,and it has come to the stage of nationwide networking and large-scale application.This makes the AC and DC power grid have a great influence on the operation characteristics of the whole network frame,so the large-scale AC / DC simulation of the power grid has become an urgent demand.The DC part is electromagnetic transient,and the grid part is electromechanical transient combination.The hybrid simulation can not only guarantee accuracy,but also ensure the computation scale.DC part model ing directly affects the accuracy of simulation.UHVDC has high controllability and can quickly change its running state through the control system.Therefore,it is very important to establish the accurate simulation model of DC control system for the influence of AC and DC power network characteristics.UHVDC power transmission control is divided into station control,pole control,and valve control.This paper describes the DC station control start stop control,power control,power control,reverse the specified reactive power control;voltage control calculation,current calculation,low voltage current limiting and power oscillation damping control valve;the trigger angle control valve group,start stop control principle,converter transformer tap control.Then introduces the characteristics and modeling methods of PSModel hybrid simulation software developed by EPRI,and takes it as the platform build the main control,reactive power control,frequency control,power oscillation suppression limit deviation control,power control,pole transfer current margin compensation control,low voltage current limiting VDCL module,minimum trigger angle control,prediction control,maximum firing angle control,Gamma0 control,transformer tap control model of commutation failure.A whole set of UHVDC transmission control system is set up according to the above stratified control principle.The model simplifies the part that does not affect the DC characteristics.It reduces the computational complexity and improves the simulation efficiency while ensuring the correctness of the simulation characteristics.At last,a system is established based on the operation of Fulong Fengxian + 800 kV UHVDC transmission project which has been put into operation,and the DC and AC power grid are connected through the interface.By comparing the curves between the simulation and the actual recorded wave,it verifies the effectiveness of the DC control system.The results show that the operating characteristics of the DC control system are in accordance with the actual conditions,and can be used in the study of DC characteristics and the mechatronics and electromagnetic hybrid simulation of large power grid.This work is of great significance to the modeling and AC / DC simulation of UHV DC control system.