Fault Clearance and Transmission System Stability Enhancement using Unified Power Flow Controller

Fault current introduces voltage and reactive power imbalances which are major problems in power systems. This study shows the ability of Unified Power Flow Controller (UPFC) to clear a single line to ground fault and improves transmission system stability. The device under review is one of the most advanced classes of Flexible Alternating Current Transmission System (FACTS) devices. A 30-bus transmission line system is modelled with MATLAB/Simulink software. Two cases were simulated to evaluate the performance of UPFC. In Case 1, the 30-bus network system is modelled and simulated without a compensating device whilst Case 2, the system is modelled with UPFC. The system models are designed to have a single line to ground fault with resistance 0.010Ω and ground resistance of 0.001Ω occurring at bus 1. The fault is expected to cause instability in the system and be cleared after 0.04s in both cases. The simulated results of the two cases were compared to determine the performance of UPFC in improving the voltage stability and power profile of the system. The results show that UPFC has the ability of stabilizing voltage and power profile of transmission system. The study has thus, increased insight on the use of the device in transmission system stability and control.