Bipolar Short Circuit Fault Location of DC Transmission Based on Iterative Soft Threshold Compressed Sensing Theory

At present, the fault location method for DC transmission lines was mainly the traveling wave method, but in this method there were such defects as hard to capture the wave front and difficult to determine the wave velocity, and so on. For this reason,a DC transmission bipolar short circuit fault location method based on the iterative soft threshold compressed sensing theory is proposed.The steps of the proposed method were as follows: firstly, according to the preset positioning accuracy the virtual nodes were defined in DC transmission line; secondly, according to the equivalent impedance between the two virtual nodes and the two modular multilevel converters at each end of the DC transmission line, the nodal admittance matrix of DC transmission line was listed and combining with the measured high frequency current component value of the fault voltage measured at the measuring point on the transmission line, the underdetermined nodal voltage equation was written; thirdly, the current injected into the ground from the fault point was equivalent to the injecting current at one or two virtual nodes nearest to the fault point; finally, by means of compressed sensing algorithm the sparse current vector was solved, therein the global optimal point or the local optimal point could be recognized as the fault point. Simulation results show that using the proposed method the fault point can be accurately located, and the obtained result is stable and adaptable to the transition resistance.