AC/DC Power Flow Calculation Method for Metro System Considering Harmonic Power

Being different from the AC/DC power system,metro's traction power supply system(TPSS) is an AC/DC hybrid system,in which the difficulty of load flow calculation lies in the decoupling and iteration method of AC/DC system.In this paper,the bus nodes of traction substations(TSSs) in the AC side were regarded as PQ nodes of AC system,and the nodes in the DC side were regarded as constant voltage nodes of DC system,thus the AC/DC system was decoupled.In DC system,the nodes were divided into P nodes and V nodes in order to adapt to the characteristics of DC traction network and improve convergence speed.In AC system,crossed frequency admittance matrix was used for the harmonic modeling,and the forming of the harmonic voltage and current relation matrix for rectifiers units.Using harmonic power of AC harmonic power flow,the PQ nodes were corrected,which improved the accuracy of AC power flow.This hybrid power flow algorithm organically combined AC fundamental power flow,harmonic power flow and DC power flow and its convergence and adaptability are good.Test on an actual system verified the effectiveness of this algorithm.