Mechanism Analysis Of AC System Fault Influence On HVDC System Communication Failure

With the implementation of China’s “power transmission from west China to east China, mutual supply between south and north, nationwide interconnection”strategy, the rate of HVDC and UHVDC transmission project put into operation will further accelerate the pace in the next few years, the analysis of fault mechanism and the research of simulation accuracy about HVDC and UHVDC transmission system,which have important engineering and practical significance to further improve the stability of its operation and guarantee the safe and stable operation of whole system.The safe and stable operation of HVDC transmission system and the sending and receiving ends AC system are closely linked, commutation failure is the most common form of fault interaction system of AC/DC power transmission hybrid system. AC system fault, converter valve fault, DC line fault and so on are all easy to cause commutation failure in DC system. Therefore, the mechanism analysis for the influence of AC system Fault to HVDC system communication failure has practical engineering significance. Due to the randomness of the fault, the influence of initial fault voltage angle on system operation can not be ignored. In this paper, based on the theory of commutation voltage time area, analysis of the influence of initial fault voltage angle of commutation voltage time area, qualitative analysis and quantificational revelation the relationship between fault initial fault voltage angle and commutation failure, give the fault occurrence time which most easily cause commutation failure of DC system, ascertain the weak link of DC system commutation failure caused by AC system, and provide a theoretical basis for the research to avoid dc commutation failure measures and risk assessment commutation failure.Because the converter is a typical discrete switching element, and the DC control is very complicated, so the accurate modeling and simulation is one of the hotspots in the research of AC / DC system currently. Among them, the converterpulse triggering control system is a key component of DC control system, its accurate modeling and simulation is an important part of AC/DC systems modeling and simulation. In this paper, using the fast Fourier transform principle to extract the fundamental signal for phase voltage, filtering the interference and noise under the asymmetric fault conditions, improved the pulse triggering control module with CIGRE HVDC, so that it can still send equivalent interval pulse in the asymmetric fault conditions, and enhance the accuracy simulated the actual project.This dissertation is supported by Graduate Students Scientific Research and Innovation Project of Xinjiang(XJGRI2014030).