Algorithm of electrified railway three-phase voltage unbalance based on system transform method

Based on system transformation, this paper developed an algorithm to calculate electric railway three-phase voltage unbalance caused by using virtual nodes. The system transform method is illustrated. The transform matrix, the process of the transform and the virtual nodes are discussed in brief. According to the system transform method, a method is presented to deal with the virtual nodes. The modification of node admittance matrix and the dealing with turn phases are studied. The calculation results on CEPRI36 nodes system and a regional power grid show that the proposed algorithm is correct and has high practical value.