Probabilistic assessment for action conditions of the 100Hz protection in a multi-infeed AC/DC system

The malfunction of the 100Hz protection in an HVDC system has severe effects on the safe and stable operation of the power system. In this paper, in combined with the improved converter switching-function model and the short circuit calculation of the ac system, a practical method to calculate the dc side 100 Hz current under ac faults is proposed. The computing efficiency is greatly improved by this method, and the effects of ac background harmonic and the asymmetric switching behavior of the converter and are also included. Based on this method, a probabilistic assessment method, in which the Latin Hypercube Sampling technology is used, for action conditions of the 100 Hz protection in a multi-infeed AC/DC system is presented. The proposed methods are verified by a demonstration with the case of southern China power grid in the year 2009. The results indicate that the proposed methods are accurate and effective, and have great practical significance to the relaying and control coordination in the multi-infeed AC/DC system.