Optimal unbalanced capacitor placement in distribution systems for voltage control and energy losses minimization

This paper describes an allocation methodology for capacitor placement in unbalanced distribution systems to achieve loss minimization with an adequate voltage profile. Switched capacitor banks and/or fixed banks can be allocated on a per-phase or multi-phase, discrete basis, and this allows consideration of the actual unbalanced characteristics of distribution systems. While most methods available in the literature address some specific network loading conditions, e.g. average, light-load or heavy-load, the proposed algorithm is based on the daily load variation curve. The method consists of two main steps: (i) reactive power demand calculation to achieve loss minimization; (ii) discrete capacitor placement. The method is applied on the IEEE 4-bus, IEEE 123-bus and IEEE NEV Test Feeders as well as on an 85-bus feeder. Several alternative allocations are calculated and comparisons with results available in the literature are presented.