Due to some of their advantages, HVDC systems become more and more popular in power systems. Up to now, many HVDC models have been developing. Each HVDC model has its own function and control scheme base on purposes of application. Before practical application, these HVDC have to be tested for the feasibility of these HVDC models in term of technical criteria by using power system simulation programs such as Pss/e, EMTP and EMTDC. Pss/e is a popular commercial programme for power system simulation using RMS value. This paper will show you how to make an HVDC user defined model. The control scheme of the HVDC and the case study will be presented in this thesis.