Generation of Non‐Stationary Parameters for Electric Arc Furnace Modelling Using the Avdonin Equation

ABSTRACT

An electric arc furnace (EAF) plays a fundamental role in steel production in the industry. As one of the largest loads in power systems, EAF is time‐varying, and its voltage‐current relationship is nonlinear. The time‐varying characteristic causes voltage flicker, and the nonlinearity causes voltage and current harmonics. Therefore, EAF modelling becomes important for studying the negative effects of EAF on the network and for developing compensation methods. This paper investigates the mathematical modelling of EAF. Mathematical models play a vital role in understanding and optimising the complex processes related to the operation of EAFs. In this paper, the nonlinear and dynamic equations of the Avdonin model are used to generate time‐varying and non‐stationary parameters for voltage and current modelling. For this purpose, many real instantaneous voltage and current signals from EAFs at Mobarakeh Steel Company have been recorded. The outcomes of this research include several parts: (a) the Avdonin model is investigated, and two modified models are proposed in which the parameters and orders of the models are considered time varying. (b) The time‐varying parameters of the proposed models are calculated using the least‐squares method. (c) The time‐varying parameters are treated as time series and modelled with the ARMA model, and a database of the extracted model parameters is obtained in the form of the enclosed MATLAB codes. The MATLAB code at every run generates a parameters time series based on different ARMA models, which results in a non‐stationary time‐varying process. (d) The time‐varying characteristics of the proposed models are evaluated using power spectral density, instantaneous measures, and short‐term flicker criteria in accordance with the IEC 61000‐4‐15 standard.