Harmonic power flow calculations for a large power system with multiple nonlinear loads using decoupled approach

Power flow calculation is normally carried out for fundamental frequency. Due to the extensive use of nonlinear loads, harmonic frequencies are present and need to be also considered. Unfortunately, unavoidable complexity and heavy computation burden are often encountered by involving nonlinear loads into the calculation. Multiple nonlinear loads typically employed in the real system will further weigh the computation down. This paper implements a decoupled approach to overcome the problem. The couplings between harmonics are rationally disregarded enabling separate calculations for every harmonic order. This will greatly reduce the complexity level and computation burden. However, the accuracy of this technique is somehow questioned due mainly to the neglected harmonic couplings. The accuracy of the implemented decoupled harmonic power flow (DHPF) algorithm is investigated by simulating the distorted IEEE 18-bus system and comparing the results with those generated by standard packages (e.g., HARMFLOW and ETAP). The implementation is then extended for the IEEE 123-bus system including multiple nonlinear loads.