Different from traditional power system， power electronics devices are widely used in microgrid to connect distributed generation（DG） to the power grid. As a result， many new problems are founded in the microgrid simulation. One of the most important problems is the interfaces design of DGs. This paper introduces the inverter interface model， equivalent voltage source interface model and equivalent current source interface model. The design and analysis of the three methods are given with PV as an example. Details of these methods such as response characteristics， calculation speed and precision are compared using PSCAD/EMTDC. The application of the three interface models are given as the conclusion.