The development of fully controlled power semiconductor devices has paved way the path for Voltage Source Converters (VSC) based High Voltage Direct Voltage (HVDC) transmission systems. For these high voltage applications, Modular Multilevel Converter (MMC) is a good candidate which utilizes interconnection of several Sub-Modules (SM). Furthermore, it provides several advantages including flexibility, scalability, better voltage quality etc. However, the MMC can be vulnerable to the DC short circuit faults. Different Sub-Module (SM) topology based MMCs exists which can suppress the DC short circuit current. The MMCs can be modelled with different modelling technics. This paper presents a comparative study of a point to point (PTP) MMC based HVDC system with feed-forward current control based on detailed and averaging modelling technics. Furthermore, the DC short circuit handling capabilities of Half Bridge SM (HBSM) and Full Bridge SM (FBSM) topologies are examined. Real time simulation results are provided to demonstrate the results of the study on FPGA based MMC support unit from Real Time Digital Simulator (RTDS).