This paper presents a phase shifted triangular carrier pulse width modulation technique for control of modular multilevel converter (MMC) based HVDC system. This switching modulation technique has reduced average switching frequency when compared to conventional method where switching state changes in each sampling period or control cycle. A dq reference frame based circulating current controller (CCC) is implemented to suppress the double line frequency arm circulating currents of MMC. Details regarding the outer loop power control and DC bus voltage control for transmitting desired amount of power through HVDC system are also discussed. A detailed matlab simulink model of eight submodules (SM) per arm MMC based HVDC system was developed and the corresponding simulation results are presented. Simulation studies with and without CCC are carried out and the corresponding variation in arm currents, SM capacitor voltages are also discussed.