Modelling and Analysis of Transformer under Non-Sinusoidal Current Excitation

Abstract

The transformers are an integral part of the power system. Due to the non-linear loads, the transformers are much affected by the distorted currents and supply voltages which largely reduce its efficiency due to overheating. Thus analyzing this problem and reducing the losses of transformer has become a major area of research in today’s scenario. This report includes the effects of non-sinusoidal supply voltage on the transformer excitation current and the core losses which includes eddy current and hysteresis losses. The time domain waveform of excitation current and flux are observed. The equivalent circuit model of the transformer under no load was taken to observe the waveforms. The fast Fourier transform of the excitation current is performed to analyse the harmonics and the total harmonic distortion is shown for various harmonic components. The losses are calculated assuming the flux density to be sinusoidal. The modelling of the transformer is performed for linear core i.e without saturation and also for non-linear core i.e with saturation effects. The dynamic modelling equations of the transformer are derived and are solved to obtain the flux, magnetizing current and curve. The whole system is studied in the MATLAB-Simulink environment and the corresponding results are obtained with detailed analysis