Volt/Var Control on Distribution Systems with Lateral Branches Using Switched Capacitors and Voltage Regulators, Part I: The Overall Problem

In this paper (Part I) and two companion papers (Part II and Part III) the problem of volt/var control on general radial distribution systems is formulated, simplified and solved. The objective is to minimize the peak power and energy losses while keeping the voltage within specified limits under varying load conditions. The decision variables to be optimally determined are (i) the locations, sizes and the real-time control of the specified number of ON/OFF switched and fixed capacitors and (ii) the locations and real-time control of the minimum number of voltage regulators. It is shown in this paper (Part I) that the regulator (volt) and the capacitor (var) problem may be treated as two decoupled problems. Part II of this set of three papers, conjoined with part I, provides the analytical tools by which optimal solutions for both problems may be determined. Application of the theory to representative radial systems is shown in Part III which also illustrates the ecomonic benefits and numerical results achievable through both regulation and compensation schemes.