In view of the wide variety of HVDC controls, which can differ from one application to another, their simulation in transient-stability programs poses a specific problem. The simulation method described in this paper allows HVDC system representation in transient-stability programs by means of user-defined block diagrams for the control functions. The user enters the control specifications in the form of a data file which can be accessed by any users. Thus a bank of models is created which can be easily updated. An example of model creation using this method is also shown.