High performance, highly efficient DC-DC converters play a key role in improving the penetration of renewable energy sources in the context of smart grids in applications such as solid-state transformers, built-in power drives in electric vehicles and interfacing photovoltaic and wind-power systems. Advanced medium-frequency transformers (MFTs) are fundamental to enhance DC-DC converters and determining its behavior, therefore MFT design procedures have become increasingly important in this context. This paper investigates which type of core material, between nanocrystalline and silicon steel, has the best properties for designing MFTs for distinct applications. Unlike to other proposals, in this work, two 1 kVA-120 V/240 V-1 kHz lab MFT prototypes, with a different type of core material, are developed for the purpose of comparing its physical characteristics, behavior, and performance under real-life conditions. A final section, the experimental results show that the nanocrystalline MFT has greater power density and efficiency. The results of this work introduce nanocrystalline MFTs as an option in a wider range of applications in niches in which other materials are currently used.

The medium frequency transformer (MFT) with nanocrystalline alloys is quintessential in new DC–DC converters involved in various front-end applications. The center piece to achieve high-performance, efficient MFTs is the core. There are various options of core materials; however, no deep information is available about which material characteristics and design procedure combo are best to get high performance MFTs while operating at maximal power density. To provide new insights about interrelation between the selection of the core material with the compliance technical specifications, differently to other proposals, this research work aims to design and build, with the same methodology, two MFT prototypes at 20 kHz, with nanocrystalline and ferrite cores, to highlight power density, and overall performance and cost, as matching design criteria. As the experimental results show, a nanocrystalline core has the highest power density (36.91 kW/L), designed at 0.8 T to obtain low losses at 20 kHz, achieving an efficiency of 99.7%. The power density in the ferrite MFT is 56.4% lower than in the nanocrystalline MFT. However, regarding construction cost, the ferrite MFT is 46% lower, providing this a trend towards low-cost DC–DC converters. Finally, high power density in MFTs increases the power density of power DC–DC converters, which have relevant applications in fuel cell-supplied systems, renewable energies, electric vehicles, and solid-state transformers.

DC-DC converters are essential in the interconnection of photovoltaic (PV) systems and systems that operate at different voltages, frequencies, and powers, such as smart grids. Due to the energy transition, and therefore the need for high efficiency in PV systems and smart grids, there is a great challenge to develop DC-DC converters with the highest possible efficiency. Therefore, in this paper an isolated DC-DC converter with high efficiency and easy implementation is developed, in comparison with other similar structures. In isolated converters it is necessary to address the analysis and design of the transformer. Poor performance of this element can contribute to high losses and low efficiency of the converter topology. This study proposes an isolated DC-DC converter (FBDC) that operates at different levels of harmonic content in its supply. The design is subjected to two levels (2L) and three levels (3L), which affects the THD value. The proposed converter model is simulated in MATLAB-Simulink and validated in a laboratory prototype. Finally, the prototype is incorporated into the multilevel FBDC topology, obtaining an efficiency of 96.6% for 2L and 97.0% for 3L in the laboratory, showing the high performance of the proposed design.

This paper presents an isolated DC-DC converter with high voltage gain that features an advanced inter-built nanocrystalline-core medium-frequency transformer (NC-MFT). The isolated DC-DC converter with an NC-MFT is specifically designed for applications such as interconnect photovoltaic (PV) systems, DC microgrids, DC loads, and DC buses, where voltage gain is one of the essential issues to consider. The NC-MFT inside the DC-DC converter is designed with a new approach that not only provides isolation but also contributes to achieving high efficiency and a higher step-up ratio. The high efficiency of the converters contributes to the integration of PV systems into DC microgrids. The converter yields a high voltage conversion ratio of 16.17. The experimental results obtained at 41.8 V/676 V and 275 W for the prototype revealed high efficiency (95.63% at full load). The experimental results validate the theoretical analysis and simulation, confirming that the converter achieves the main objective of high voltage conversion and high efficiency. These results will contribute to the interest in the use of this type of energy and its impact on the reduction in CO₂ emissions.

One of the main elements for the development and implementation of bidirectional converters applied to smart grids and micro CD grids is the medium frequency transformer (MFT). This element integrates a high efficiency together with a high power density due to the increase in the design frequency of the transformer, compared to conventional transformers at 60 Hz. This change requires the analysis and development of new methodologies and materials in the design to support the needs of these new transformers applied to DC-DC converters in photovoltaic systems, wind systems, solid-state transformers, and electric vehicles. This article describes the design and construction of an MFT, it’s computer simulation and experimental validation by building a prototype in the laboratory. The MFT has an efficiency of 98.71 % which was obtained for a laboratory prototype with 2.5 kVA, 250 V / 670 V and a frequency of 5 kHz.

In recent years, the increase in energy demand has been an incentive to search for new ways to generate energy. An alternative is producing this energy from daily human activities. To do this, piezoelectric devices have been used in different human activities to collect energy. Some of these potential activities are transportation, biomedicine, and electronic devices. Harvesting energy from the mechanical force applied by a pianist during their performance is one of these activities that can be used. The implementation of piezoelectric devices under the keys of an electric organ was carried out. A theoretical model was developed to estimate the amount of energy we could recover. The system was characterized by controlled forces. The volume generated by the forces was measured via a Musical Instrument Digital Interface (MIDI) using the open-source music production software “LMMS (Linux MultiMedia Studio) 1.2.2 version”. The electric potential difference was measured as a function of the volume generated by the pianist. The voltages generated for different frequencies of the pianist’s rhythm were studied. The efficiency calculated in the mathematical model agreed with that obtained in the implemented system. The study results indicate that the batteries were recharged, which resulted in 53 s of organ operation.