Influence of phasor adjustment of harmonic sources on the allowable penetration level of distributed generation

•Voltage phasor is iteratively updated depending on DG size at PCC of power system.•Voltage angle referencing method is embedded into harmonic power flow modeling.•Single and long-term load profiles are included in the optimization process.•FCM clustering method is used to reduce computational effort in long-term planning.•Optimal DG sizes based on harmonic limits are obtained in different scenarios.