Abstract: Nowadays electromechanical transient simulations can no longer meet the simulation requirements of new power systems. However, electromagnetic transient simulations of large grids with numerous traditional electromechanical components, such as synchronous generators, would encounter a dimensional disaster. The simplification of synchronous generators is thus imperative. Firstly, a set of custom modeling scheme containing two equivalent circuits is proposed for the generator unit. According to the actual simulation requirements, synchronous generator models with different orders can be selected to simplify the simulation model. Secondly, in view of the fact that the generator set requires a lengthy starting time, rendering it unsuitable for electromagnetic transient simulation,a set of initialization methods suitable for custom modeling generator sets is proposed to ensure that the system can reach steady state at the beginning of simulation. Finally, the accuracy of the proposed custom modeling method for synchronous generators and its equivalent circuit, as well as the feasibility of the initialization method, are verified by building a single generator model and a WSCC three-generator nine-bus system model using PSCAD, respectively.