Power Quality Index of a Radial Distribution System with Photovoltaic Sources and Nonlinear Loads

The current penetration of distributed generation and nonlinear loads to the radial distribution systems challenges their operation. For that reason, this paper presents a new power quality index applied to distribution networks. The index is composed by three elements, the first one is a four-digit number for each node, where each digit evaluates a specific characteristic of voltage. The second one is the average number of the four digits, with two decimals, allowing comparison of the PQ of the nodes, and the third element is a color palette associated with the number or second element, which is placed over the single-line diagram of the distribution system. The index is formulated from a sensitivity analysis of voltages facing the variations of four parameters: the feeder resistances, electric loads, the location and penetration of photovoltaic sources, and the location and penetration of nonlinear loads. To calculate the voltage in the distribution system, a method based on the impedances of feeders and electric loads is proposed and used. To validate the power quality index, multiple scenarios are carried out on the IEEE 33-node test system. The scenarios include the variation of load resistances and feeder resistances, also the variation in the level of penetration of photovoltaic sources and nonlinear loads. Results demonstrate that the new index allows the classification of the nodes according to the effect of the parameters over the variables of a radial distribution system.