Comparison between static models of commercial/residential loads and their effects on Conservation Voltage Reduction

International Standards ANSI C84.1-2006 and IEEE std 1250-1995 specify the range of supply voltage to electronics equipment from 0.9 to 1.05 per-unit (pu) of nominal voltage. From this information, it is possible to feed electronics equipment with a voltage level below of nominal voltage without failures. The Conservation Voltage Reduction (CVR) is a technique that aims to achieve the reduction of power consumption by reducing the level of supply voltage, giving at the customer location a lowest possible level of voltage compatible with both nominal values of equipment and the levels stipulated by the regulatory agency. It is essential obtaining a good model that describes the behavior of the loads connected to grid to evaluate the effectiveness of the CVR application. This paper presents an evaluation of three static load model techniques, being two ZIP load models and an exponential model. The model parameters were estimated for samples obtained from measurements performed on residential/commercial loads, through the variation of supply voltage within the operational acceptable range. The data collection was performed at three different periods of times to mitigate the grid's influence on the results. The load models are obtained through an optimization algorithm based on the collected data. The ellipsoidal optimization algorithm was applied to estimate the parameters of each model, searching for the best feasible solution. Some papers in the literature exhibit mathematical solutions for load models without physical meaning. Unlike that, this algorithm is not limited only to find a mathematical solution but also a physical one.