Power Losses Calculation for Medium Voltage DC/DC Current-Fed Solid State Transformer for Battery Grid-Connected

Abstract

Current fed solid-state transformers (CF-SSTs) offer substantial weight and size reduction advantages over 50/60Hz traditional transformers. CF-SSTs have low source current ripple which makes it suitable for the connection of large batteries in the medium voltage grid. However, power losses are high compare to the traditional one due to the high operating frequency range. Therefore, power losses calculations are the main key to select the main design parameters. Unlike most of the published work dealing one aspect of power losses or a specific element and only consider voltage fed Solid State Transformers topology (VF-SSTs), this paper presents a power losses calculation method for CF-SSTs considering all the power losses, the shape of the voltage waveforms, cores dimensions and manufacturer datasheets are main paper pros. ANSYS and Matlab Simulink are employed to validate the analytical equations. Due to simplicity, this method can be used for optimization.

Design Optimisation of a Current-Fed Solid-State Transformer for MV Grid-Connected Applications

“…The inductance of the choke coil is assumed high enough to maintain a constant current through it. The switching events, currents and voltage waveforms are shown in Figure 3 [16,37] which will be used in the power loss calculations in the next sections. D1 and D2 are the duty ratios to generate the gate signals for H-bridge 1 and of Hbridge 2, respectively.…”

“…Based on the switching frequency, power electronics switches datasheets, average and RMS values of the current and voltage of the power electronics switches, the power electronics losses can be calculated as in [37]. The total power electronics losses can be calculated as in [37].…”

“…Based on the switching frequency, power electronics switches datasheets, average and RMS values of the current and voltage of the power electronics switches, the power electronics losses can be calculated as in [37]. The total power electronics losses can be calculated as in [37]. R th can be calculated as [46]: R th = T j − T A P PE (40) The optimisation constraints for both objective functions are voltage per turn (E t < σ), clearance between two coils (l > ξ), transformer core flux (B min < B < B max ) and the operating frequency ( f min < f < f max ).…”