Modeling of loads dependent on harmonic voltages

Abstract

Electrical system models are important to allow the accomplishment of several studies aiming at reducing losses, and improving power quality, among others. In the current context, carrying out harmonic analysis becomes necessary due to the increasing insertion of nonlinear loads in the system. Since the networks voltage and current profiles are strongly affected by the load behavior, their modeling is essential to perform such analyses. Different from the other harmonic models found in the literature, this paper presents a new proposal of load modeling, combining the ZIP model and a cross admittance matrix. This combination brings together the benefits of load characterization with the traditional ZIP model, which provides some physical knowledge about the load, as well as the frequency crossing given by an admittance matrix. In this way, it is possible to accurately determine the harmonic power injection in the load bus, by knowing its harmonic voltage. The present proposal still considers a limitation for the ZIP coefficients, in order to identify the power ratio in terms of constant impedance, constant current and constant power. In addition to discussing the method for determining the load model parameters, using exhaustive search and multiple linear regression, a real case study with data obtained with a power quality meter exemplifies the model application in an electronic load. The results show that the proposed harmonic model was able to represent the load with high accuracy, and the parameters found provide information about the type of the modeled load.