Different approaches to short-term optimal voltage scheduling based on voltage control zones concept

Optimal voltage scheduling procedure is usually a part of a day-ahead or hour-ahead planning phase, done by Transmission System Operator (TSO). It provides an implementation of a voltage control ancillary service that consists of a planning phase based on optimal power flow algorithm, realtime operation and accounting and settlement. Voltage control ancillary service model described in the paper is based on a division of power system into a voltage control zones. In every zone a reactive power market is formed. Reactive energy prices and voltage scheduling plan are determined through a two-step optimal power flow algorithm. Three algorithms are presented in the paper, differing in the design of optimization steps. Proposed algorithms are tested on IEEE 39-bus test system. Test results are compared and discussed. Article is concluded with the possible directions for continuation of the presented research.