Volt/VAr control in distribution systems by fuzzy multiobjective and particle swarm

This paper presents the optimal dispatch for the under load tap changer (ULTC) of a substation transformer, substation capacitors, and feeder capacitors for volt/VAr control in a distribution system. Three objectives of interest in the problem consist of energy loss, total capacitor kVAr to be switched on, and total number of daily switching operations of the ULTC and all capacitors. The optimization problem is subjected to power flow equations, voltage limits, and maximum switching operations for the ULTC and the capacitors. All the objectives are fuzzified using a trapezoidal membership function and are integrated to represent the fuzzy decision value. Fuzzy multiobjective and particle swarm optimization are employed to determine the optimal dispatch schedule that provides the best compromise among all the objectives. The methodology is demonstrated by a 29-bus distribution system of Provincial Electricity Authority (PEA), Thailand.