This research work expose the advantages of HVDC technology for synchronization of two interconnected thermal power grid of 12 areas when load disturbance occur in power grid-1. Three types of tie-lines HVAC–1HVDC parallel tie-line, HVAC– 2HVDC parallel tie-line and HVAC–3HVDC parallel tie-line are applied for synchronization of 12 area two interconnected thermal power grid. For synchronization purpose of power grid this research work shows the HVAC–3HVDC parallel tie-line is better as compare to the HVAC–2HVDC parallel tie-line and HVAC–1HVDC parallel tie-lie. This research work also shows the HVAC–2HVDC parallel tie-line is better as compare to the HVAC–1HVDC parallel tie-line. Quality of all three types of tie-line is judged by the frequency deviation of two interconnected power grid of 12 areas when load disturbance occur in power grid-1. The biggest advantage of this research work is that the two interconnected thermal power grid of 12 areas is Synchronize by HVDC technology with traditional integral controller.