Improve the Voltage Profile in Transmission Lines by using Fractional Frequency Transmission System

This paper presents a low-frequency ac (LFAC) transmission system for 50/3HZ source. The LFAC system is interfaced with the main power grid with a voltage source inverter. The 50/3 supply voltage is connected to the load through the voltage source inverter. The LFAC system improves the transmission capacity and distance compared to the conventional AC solution at nominal frequency, e.g. 50HZ to 60HZ. And reduces the investment cost compared to the HVDC solution. In this project, comparative analysis is carried out for power transmission, for 1200km length at 50Hz and 50/3Hz. Test system of 765kV and 1200kV are selected as transmission voltage levels. Simulation is carried out on test system over Matlab simulink environment. Load at the receiving end is varied from 0% to 150% of Surge Impedance Loading (SIL) in steps of 25%. Also, computation has been carried out for sending & receiving end voltages, active power transfer capacity, reactive power transfer capacity, and compensation required for 1200km line. Results shows that for 50Hz test system of transmission line, power transfer is not possible without compensation, voltage profile and power transfer efficiency is out of the limit, but in FFTS, it is possible to transmit 5 to 6 times the rated power without any compensation and voltage profile and power transfer efficiency is within the limit.