OPTIMAL CAPACITOR PLACEMENT AND SIZING FOR LOSS MINIMIZATION IN NIGERIAN POWER GRID USING FUZZY LOGIC TECHNIQUE

Abstract

In this paper, the existing Nigerian 330kV grid network within the south-south geo-political region was examined. The performance of the existing transmission system must be increased in order to enhance the efficiency of the power grid. To achieve this, power loss minimization and voltage profile improvement are the two most important strategies. The network consists of seven (7) generating stations, sixteen (16) buses, and nineteen (19) transmission lines. The network was modeled in electrical transient analyzer program (ETAP19.1) to determine the voltage performance index and loss sensitivity index using Newton Raphson power flow algorithm. Also, the fuzzy logic inference system toolbox in MATLAB/Simulink environment was used to determine the capacitor suitability index (CSI). The result from the base case shows that Bus 12: 93.07% and Bus 13: 93.01% violates the statutory limit condition of 0.95-1.0 5p. u for Bus Voltage. Also, the total real and reactive power losses in the line are 47.298 MW+j 212.143 Mvar.  The power loss index was calculated using loss sensitivity and normalized in the range of [0, 1]. The voltage performance index and loss sensitivity index are fed as inputs to the Fuzzy Inference System to obtain Capacitor Suitability Index (CSI) used in determining the most suitable bus for capacitor installation. Experimentally, CSI with a value greater than 0.6 are chosen for capacitor installation. The result obtained after fuzzifications of both inputs and outputs using the associated membership functions shows that the CSI values for Bus 12 and 13 are 0.604 and 0.635 and are chosen as the optimal location for capacitor bank placement. The size of the capacitor bank was determined index vector-based method. When a capacitor bank of 75Mvar was installed at Bus 12 and 13 respectively, it was noticed that the total real and reactive power loss was reduced by 28.626MW+j90.53Mvar and the voltage profile of buses 12 and 13 improved by 7.23% and 7.19% respectively. Hence, the installation of capacitors impacted positively on power loss reduction and voltage profile improvement.