The most detailed and accurate models of power electronic devices are not always necessary depending on the research objectives and scenarios in the power system simulation. Selecting appropriate models is of great significance for the speed and accuracy of simulations. Taking the controllable inverter as an example， the detailed model， switching-function model and average-value model of power electronic devices are discussed and applied in the simulation cases. By comparing simulation results of the three models， the appropriate application range of these models is presented.