Research On Analysis Of Fault Transient For HVDC Transmission Lines

With the further development of the regional power grid interconnection, the demand of long-distance and large- capacity transmission is gradually growing. The main problem with AC transmission systems is asynchronous stability, while the current source converter based HVDC technology is an excellent way of achieving a high-capacity, long-distance system interconnection, so it has been paid more and more attention.The protection of transmission lines is an important part of the control protection system in HVDC projects. In order to improve the operational performance of the DC line protection, more detailed analysis in DC line fault transient of HVDC systems need to be done, considering the impact of DC faults, AC faults, lightning, commutation failure and other factors.This paper focuses on fault transient analysis of HVDC transmission lines. The main contents are as follow:(1) The paper establishes HVDC system electromagnetic transient model, gives the modeling methods of AC system, the converter station equipment, control systems, DC transmission line modeling and lightning,to improve the electromagnetic transient model of DC system.(2) The paper studies electromagnetic transient characteristics of HVDC transmission line failure, analyzes the factors affecting the transient characteristics of DC transmission line fault transient and discusses the affects of fault transient lightning DC line and AC system faults, to provide technical support for the operation of relay protection.(3) The paper discusses the impact of commutation failure on HVDC transmission line fault transient analysis, conducts detailed electromagnetic transient simulation on commutation failure and analyses HVDC lines transient characteristics when commutation failure occurs.Finally, conclusions and the expectations of this paper are given.