Power electronic converters are increasingly used in power systems. However, they are vulnerable components and prone to aging failures, thus affecting overall system reliability. Therefore, their availability modeling especially in large-scale power electronic-based power systems is of paramount importance. This letter introduces four different approaches for converter availability modeling considering aging failures under different maintenance strategies. The accuracy and calculation burden of these approaches are illustrated by numerical analysis. It is shown that the method of device of stages and piece-wise approach are the most applicable methods in the case of corrective and preventive maintenance strategies respectively.