Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

Abstract

This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm3, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm3, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm3. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.

A Bidirectional Grid-Connected DC–AC Converter for Autonomous and Intelligent Electricity Storage in the Residential Sector

“…The electrical waveforms were evaluated based on the topology and control strategies detailed in the previous section. The approach to the sizing of the converter was classical because the two stages taken separately are now well-known and mastered [36][37][38][39][40]. Of course, this approach is adaptable according to the targeted application and design constraints.…”

“…As shown in Figure 8, the main components to be sized were the power MOSFETs of both stages [36][37][38], the inductor of the DC-DC stage [39,40] and the output voltage modulation of the DC-DC stage [26].…”

“…The power devices were turned on and off with zero crossing of the AC grid voltage to minimize losses. Concerning the optimization of the DC-DC stage inductance in terms of electromagnetic characteristics, compactness and mass, we took into account the geometry, toroidal or planar and the type of core, as well as the ferromagnetic material used, according to the frequency and the maximum induction [39,40]. Several technologies were studied in order to determine the most suitable inductance for the sized converter.…”

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“…Transformer's primary winding is helical winding. Centre tap winding construction is used for secondary due to high current requirement (12) . Close looped system is appropriate solution for better operation.…”

Estimation of Energy Losses in Nanocrystalline FINEMET Alloys Working at High Frequency

“…Nowadays, devices that work at high frequencies, e.g., such as thin film and/or planar transformers, also require high resistivity of the magnetic core to reduce losses [7,8]. Current technology in high frequency switching planar transformers involves the use of soft ferrites, for the core, with various chemical composition [9][10][11]. This class of ceramic materials fulfil the main requirements, such as high saturation flux density, high permeability (even for kHz frequencies), and low core losses.…”