Calculation of three-phase harmonic power flow in power systems with traction loads

The mathematical model of an SS4 type electric locomotive, made in China, is first introduced. By considering the harmonic source as a controlled current source, a new algorithm of solving three-phase asymmetrical harmonic power flow in power systems with traction loads is presented. In this scheme, the three-phase fundamental power flow is solved by the P-Q decoupled method in which sparse and symmetrical matrix handling technology and a three-phase factor table are used; thus memory is saved and computing quantity is decreased. The three-phase harmonic power flow is directly solved by the Gaussian elimination method with a linear nodal voltage equation and thus the convergence problem does not exist. The fundamental and harmonic nodal voltage and branch current are solved by the decoupled iteration of fundamental and harmonic power flow. Computation results of some typical examples show that this algorithm can effectively save memory and has good convergence