Optimal Allocation of Capacitor Bank in Radial Distribution System for Loss Minimization and Voltage Profile Improvement

Abstract

Distribution system links the consumer with the power system. Distribution system in Nepal is mainly radial in nature because of its simple design and low capital cost. In radial distribution system, voltage decreases along the feeder due to which voltage of the terminal nodes attains lower values which is below statutory voltage limit. Load of distribution system is mostly inductive in nature so reactive power compensation is required. Power is generated at generating stations and is transported to the load centers. However, reactive power is generally locally produced near to the load centers. Capacitor banks in distribution system helps to improve power factor of the system thereby minimize the system loss, increase the power transfer capacity and improve the voltage profile. This study presents MATLAB based particle swarm optimization (PSO) technique to determine the optimal location and size of the capacitor bank in distribution system. First of all, load flow was carried out using backward forward sweep algorithm. The voltage profile, current flowing through the line and system losses was calculated from the load flow. Using Loss sensitivity index (LSI), the candidate nodes for the location of capacitor bank was determined. The buses with high value of LSI was sorted in descending order and top fifty percentage of bus with high LSI value has been considered as the variable for the location of capacitor bank. Two types of variables have been considered for the optimization problem. One is the location and another is the size of capacitor bank. LSI was used to determine the candidate node for capacitor bank installation while particle swarm optimization was used to optimize the size and location of the capacitor bank. The location and size of capacitor bank which gives in minimum annual loss has been considered the optimum solution. The proposed procedure was applied to IEEE 34 and 69 bus system and on a real distribution system, i.e. Parsa feeder, Chitwan. The result of IEEE 34 and 69 bus system was compared with previous publications. After compensation using capacitor bank, the peak power loss of IEEE 34 bus, IEEE 69 bus and Parsa feeder decreased by 29.9%,42.48% and 45.41% respectively. Simulation results showed improved voltage profile and remarkable savings can be obtained after installation of capacitor bank in radial distribution system.