Abstract: Common averaging methods were studied for modeling the grid-connected converter in new energy domain to balance the accuracy and efficiency in electromagnetic transient simulation. A piecewise generalized state space averaging（P-GSSA） method was proposed for converters with the large-scale new energy connected to grid. The piecewise technique was applied to generalized state space averaging（GSSA） model of the converters in this method, which combines the time slot with similar operating characteristic together to study. And multi time scale modeling was successfully achieved in the grid-connected converter of new energy domain. An example was simulated according to the P-GSSA model proposed in this paper, and the simulation results show that the model can adapt to the efficient simulation of power converters in the domain of large-scale new energy connected to grid.