OPTIMAL PLACEMENT AND SIZING OF UNIFIED POWER FLOW CONTROLLER (UPFC) FOR VOLTAGE STABILITY ENHANCEMENT (CASE STUDY: GERD TO HOLETA 500/400 KV TRANSMISSION LINE NETWORK)

Abstract

The GERD to HOLETA 500/400 KV transmission line network was assessed to determine the optimal location and size for a Unified Power Flow Controller (UPFC) to enhance voltage stability. Due to the long transmission path and rising load demand, system components have become overloaded, causing power outages. To evaluate the current power system conditions, the Newton-Raphson load flow technique was used in the power flow model. The voltage stability index shows signs of instability, and load flow analysis reveals that all bus voltages, except for the slack bus, fall outside the acceptable range. Active and reactive power losses on the transmission line are 0.491 MW and 0.4689 MVAR, respectively; while the systems rated capacity is 2591 MW and 1255 MVAR. The minimum required voltage is 0.95 pu, but the actual minimum voltage magnitude and stability are 0.872 pu and 0.5262 pu, respectively. UPFCs, as reactive power compensation devices, are proven to enhance voltage stability, power losses, and voltage profiles. The UPFC was sized and placed using Grey Wolf Optimization (GWO) to minimize power losses, improve voltage stability, and optimize the voltage profile. The optimal UPFC size is 757.5 KVAR, and the best location is bus 3. With UPFC compensation, the bus’s minimum voltage magnitude and stability improve to 0.9668 pu and 0.83477 pu, respectively, while active and reactive power losses decrease to 0.1655 MW and 0.03302 MVAR. After implementing UPFC compensation, the annual energy loss cost is reduced from 10.343 million Birr to3 .486million Birr, and the total cost of a 757.5 KVAR, UPFC is 5.708 million birr including installation cost for resulting in a savings of 1.142 million Birr and a payback period of 12 months. The economic analysis confirms the solution is both effective and cost-efficient