Capacitor bank step state optimization under load alteration in smart distribution networks

Abstract

Distribution network's high resistance and current results in high distribution losses, contributing to large voltage drops, low voltage stability, increased power losses and decreased reliability to sustain disturbance. As the distribution systems generally have composed of industrial, commercial, residential and lighting loads and the peak load on the substation transformers and feeders occur at different times of the day, the systems may have heavy load or overload at some times during the day and may have light load in other times. This research focuses on the reactive power compensation on medium voltage radial distribution network using placement and step optimization of multi-step capacitor bank to achieve power loss reduction, system capacity release and acceptable voltage profile. It is essential to be mentioned that the paper does not consider renewable energy generation (REG) units in the network. In smart network it can be achieved real time under variable load pattern. It is clear that reactive power compensation considering load variation needs a time consuming computation and capacitor bank depreciation due to hourly step switching. Therefore, in this work, annual loads are categorized in three levels (heavy, normal, and light loads) that each level of loads, are categorized in three smaller coefficients during a year: 0.15, 0.3 and 0.45 for light loads, 0.6, 0.75 and 0.9 for medium loads and 1.05, 1.2 and 1.35 for heavy loads. This paper achieves multi-step capacitor bank placement and their state optimization during load alteration to reduce power losses at each load level considering voltage and current constraints using Cuckoo Search Algorithm (CSA).