Comparison of the ZIP load model and the exponential load model for CVR factor evaluation

Abstract

Evaluating the effectiveness of Conservation Voltage Reduction (CVR) is a key challenge for utilities to determine the target feeder for voltage reduction deployment. In this paper, a time varying ZIP (TZIP) load model is developed to estimate the constant impedance, the constant current, and the constant power coefficients to calculate the CVR factor by applying a two-stage recursive least squares (RLS) algorithm. The objective of this study is to determine the accuracy of the CVR factor calculation using the TZIP coefficients and to compare with the CVR factor dependent on the exponent of time varying exponential load model (TEXP). In addition, a probabilistic method is also introduced to analyze the nature of voltage uncertainty during CVR deployment period in comparison to the case when CVR is not deployed in the same interval. Actual data from Duke Energy Progress is used for validation. Finally, time series simulation is conducted in OpenDSS to validate the results.