A more sophisticated Park equation-based synchronous machine model, used in harmonic load flow study, is proposed. From the physical interpretation of this model, it can be noticed that synchronous machines should also be considered as harmonic sources in power flow study, only if the power network is asymmetrical. This model is then incorporated with the extended ‘decoupling-compensation’ network model used for harmonic power flow analysis. Several cases are studied, including harmonics caused by asymmetry of transmission lines and nonlinear elements like static VAr compensators (SVCs). A computed result verifies the effectiveness of the proposed model and the conclusion that more sophisticated synchronous machine models should be employed to obtain the correct, full scenario of harmonics distribution in power system is drawn.