With the deployment of renewable energy and the voltage source converter (VSC) based HVDC transmission systems (VSC-HVDC), the dynamic behavior of power systems has been greatly changed by the VSC sources, and the grid-forming (GFM) control framework of VSC is now widely concerned for the purpose of transient performance enhancement. In this paper, a HVDC and HVAC hybrid power system is constructed on PSCAD with the grid-following (GFL) and grid-forming (GFM) converters being connected and compared, where the GFM converter employs the virtual synchronous generator (VSG) control. The power system transient characteristics, including the swing angle, the bus voltage and system frequency characteristics during AC/DC fault scenarios are presented. The influence of GFL and GFM converters are compared and analyzed. In addition, an instability phenomenon caused by the current limiting link of the VSG control is discussed in the end of the paper.