Abstract

The necessity of power system security optimization of the Nigerian 330kV transmission is ever increasing. To this end, the optimal placement and control of FACTS devices are proposed for power system security optimization. The optimal placement of the UPFC in the power system is to ensure stability and voltage level improvement. The objective function for the formulation of the optimization problem is to find the opti¬mal placement of the UPFC that ensures voltage stability, minimization of Voltage Collapse Point Indicator (VCPI) and active power loss. The MATLAB/ SIMULINK model of the case study of Nigerian 330KV, 48-bus power system was created. In the simulations carried out, the system was subjected to transmission line and power plant outage contingencies. Findings showed that the instability due to the power plant outage contingency was more severe than that due to the transmission line outage contingency. Without the placement of the UPFC, in the case of transmission line outage contingency, the voltage level of the critical bus (bus with lowest damping ratio) fell from 0.813 p. u to (and oscillated around) 0.3934 p. u. Whereas in the case of power plant outage contingency without UPFC, the critical bus voltage fell from 0.813 p. u to (and oscillated around) 0.2785 p. u. The system was found to be unstable as all the real parts of the system eigenvalues (in the case of the power plant outage contingency) and most of the eigenvalues (in the case of the transmission line outage contingency) lies on the right-hand side of the S plane. However, with placement and control of the UPFC the voltage transient oscillations (in the cases of the transmission line and power plant outages) were effectively damped out and the voltage level of the critical bus was restored to within the 5% voltage drop requirement. Hence the optimal compensation by the placement of the UPFC enabled the power system to recover from the contingencies and continued to provide quality power supply thus ensuring power system security.