Studies On Fault Diagnosis Of Commutation Failure In HVDC Transmission

Because of the unique technical and economic advantages, the high voltage direct current(HVDC) transmission technology has made a very wide range of applications, in thelong-distance high-capacity transmission and regional networking. Commutation failure isone of the HVDC transmission system common faults, affecting the safe operation of theentire power system. Accurate and rapid diagnosis of commutation failure is the premise ofthe control of commutation failure.First, this article describes the HVDC transmission system and its Current Situation ofcommutation failure fault diagnosis, and points out that the shortcomings of fault diagnosismethod.Secondly, this paper analyzes the commutation failure of HVDC transmission systemsand the mechanism and influencing factors of the commutation failure，and describes thehazards and control measures of commutation failure. In addition, this article describes a faultsimulation method of commutation failure based on PSCAD/EMTDC, and builds a simulationmodel by using PSCAD/EMTDC.Based on the wavelet energy spectrum and grey comprehensive relationship degree, afault diagnosis method of commutation failures in the HVDC transmission system ishighlighted; the wavelet energy spectrum is used to quantify fault characteristics, and then thefault reasons are identified according to the grey comprehensive relationship degree. First, ituses arc extinguishing angle to determine whether the commutation failures occur or not; then,the wavelet analysis of DC current fault signals is conducted to obtain the wavelet coefficientson every scale and calculate the wavelet energy spectrum; the wavelet energy spectrum andthe reference sequence of failures are analyzed based on grey comprehensive relationshipdegree, and thus the fault reasons are identified according to the principle of maximumrelationship degree. The simulation of Yun-Guang±800kV DC transmission system showsthat the method can accurately diagnose commutation failures.