Improving the accuracy and time of calculating steady-state modes of increased frequency electrical systems

Abstract

The authors of modern Russian and foreign works suggest using the method of frequency analysis with Fourier transforms for modeling alternating current systems with a non-sinusoidal supply voltage. By applying the above-mentioned method to calculating steady-state modes of increased frequency power electrical systems (IFPES), we have found that there are significant differences between the calculated and experimental results, and the model calculation time is long. These problems can be solved by obtaining generalized formula expressions for the internal resistance value of IGBT transistors and the amplitudes of the acting EMF (voltage) in the IFPES applying Fourier decomposition. The generalized expressions for determining the internal resistance of IGBT transistors were obtained by analyzing physical processes of charge diffusion. The amplitude of the acting EMF (voltage) was determined by numerical integration. Simplified analytical expressions suitable for determining the frequency dependence of the resistance of IGBT transistors in the open state in electrical devices have been obtained. The IFPES calculation rate model has been optimized by frequency analysis. The obtained generalized analytical expressions allow making more accurate calculations of the transistor internal resistance value (with a difference of 70 % compared to the previously used value). By optimizing the calculation method we were able to reduce the model calculation from 8 hours to 3 minutes with Nk = 3000 harmonics. The modernized method can be used not only for calculating the IFPES but also for analyzing any electrical circuits with power electronics components exposed to non-periodic and non-sinusoidal currents and voltages.