Mathematical Representation of Voltage Regulation Impact on Distribution Feeder Voltages

Abstract

Accurate representation of the impact of voltage regulation equipment (VRE) on distribution feeders is fundamental for assessing photovoltaic (PV) impacts and for many other applications in distribution planning and operations. VRE are frequently controlled based on the voltage observed at the VRE terminals. Conventionally, the operation of VRE is assessed by solving three-phase unbalanced power flows. Using conventional modeling approaches for applications such as PV hosting capacity can require solving prohibitively large number of power flows in order to capture the impact that VRE have on the network. In this paper, we explore the applicability of sensitivitybased modelling to estimate the controller voltages of tap changing transformers, line voltage regulators and capacitor banks on large-scale, complex three-phase unbalanced, radial distribution systems. The sensitivity-based model can estimate the VRE controller voltage based on the load and current state of discrete controllable elements in the circuit. The proposed model is shown to accurately estimate VRE controller voltages on both a modified IEEE-123 bus test feeder with 3 voltage regulating devices and on a realistic large-scale utility feeder with 12 voltage regulating devices. The proposed mathematical representation can be leveraged for fast determination of voltage in distribution application such as PV hosting capacity.