The large number of renewable energy sources and the gradual adoption of AC and DC hybrid networks have become two major characteristics of modern power systems. Along with this, the problem of harmonics in the power grid has become increasingly prominent. In this case, three difficult problems of harmonic source modeling, traceability and control methods have attracted increasing attention from both academia and industry. This paper reviews the current common harmonic source modeling methods, and uses them to provide references for theoretical research and practice in the field of power grid harmonics. From the perspectives of mechanism modeling and data-driven modeling of harmonic sources, the current common harmonic source time-domain modeling methods and frequency-domain modeling methods are described, analyzed and compared, and various modeling methods are summarized. The advantages and disadvantages of the method, as well as the applicable scenarios of various harmonic source modeling methods are discussed. It focuses on the problems of mechanism modeling and data-driven modeling methods, and proposes corresponding solutions for each problem. Finally, the characteristics of common harmonic source modeling methods are summarized, and the development direction of harmonic source modeling technology in the context of renewable energy access is prospected. This work is supported by the National Key Research and Development Program of China (No. 2017YFB0902800).