Research And Application On Fault Current Limiting Technology Of HVDC-Light Transmission System

DC transmission and distribution technology has been widely used in high voltage direct current transmission,DC power distribution,subway and shipbuilding.When a short-circuit fault occurs in the DC transmission and distribution line,the current rise rate of the line is high and the current amplitude is large,which makes it difficult for the DC circuit breaker to break the fault current.The technology to limit the short-circuit current has become an important guarantee for the reliable operation of the DC system.In this thesis,the topology of a DC fault current limiter is designed and applied to a DC system represented by a HVDC-light transmission system to limit the rising rate and amplitude of the short-circuit current.First of all,this paper introduces in detail the structure,working principle and operation mode of the HVDC-light transmission system,and summarizes the advantages and problems of the HVDC-light transmission system.Then,a model of a HVDC-light transmission system with passive load is built on the Simulink simulation platform.The voltage and current waveforms of the system under normal operation are obtained through simulation.Then,the fault-generating module is used to manufacture the single-pole ground fault and the double-pole short-circuit fault at the near,the middle,and the end of the direct current transmission line.the short-circuit voltage and current waveform on the DC side are obtained from the simulation.Dased on summarizing the characteristics of the existing DC fault current limiter,this paper designs a topology of a improved DC fault current limiter and introduces the structure and working principle of the fault current limiter.This paper builds a model of the improved DC fault current limiter on the Simulink platform and the current limiting function of the DC fault current limiter is verified by simulation.The current limiter uses the current transfer principle to transfer the short-circuit current to the limit value branch,using the chopping control method to limit the amplitude of the short-circuit current.After changing the parameters of the internal components of the current limiter,the current limiting function of the current limiter is simulated again to determine the influence of each component on the performance indicators of the current limiter.Then,this paper designs a specific scheme for the current limiter to be limited and exited.Finally,the model of the improved DC fault current limiter is placed in the model of the HVDC-light transmission system to verify the current limiting effect of the current limiter in the DC system.