Three-phase self-excited induction generators (SEIGs) are often used as energy conversion devices in micro-grids for renewable energy sources such as wind, pico-hydro, bio-gas, etc. A three-phase SEIG is modeled in this paper using the Alternative Transients Program (ATP), which is a version of the Electro-Magnetic Transients Program (EMTP) commonly used in universities and private/governmental power companies. The generator’s performance at different excitation, rotating speeds and loading conditions is to be studied. Although modeling of SEIG has been well documented in literature, few have reported the use of ATP to model the SEIG, leaving several important functions of this powerful tool untapped for renewable energy applications. To bridge this gap, examples of how to model and simulate an SEIG with balanced and unbalanced loading conditions are presented. Results obtained by the analytical model, experiments and ATP simulation will be compared.