Accurate copper loss analysis of a multi-winding high-frequency transformer for a magnetically-coupled residential micro-grid

© 2017 IEEE. Improvements in characteristics of magnetic materials and switching devices have provided the feasibility of replacing the electrical buses with high frequency magnetic links in micro-grids. This effectively reduces the number of voltage conversion stages, and the size and cost of the renewable energy system. It also isolates the converter ports, which increases the system safety and facilitates bidirectional power flow and energy management. To design the magnetic link optimally, an accurate evaluation of copper loss of the windings considering both current waveforms and parasitic effects is required. This paper studies the accurate copper loss analysis of a three-winding high-frequency magnetic link for residential micro-grid applications. Due to the non-sinusoidal nature of the voltage and currents, the loss analysis is carried out on a harmonic basis taking into account variations of phase shift, duty ratio and amplitude of waveforms. The high frequency skin and proximity effects have are taken into account. The maximum and minimum copper loss operating points of the converter and their dependency on the phase shift and duty ratio of the waveforms are studied and simulation results are presented

Copper loss analysis of a multiwinding high-frequency transformer for a magnetically-coupled residential microgrid

© 2018 IEEE. Improvements in characteristics of magnetic materials and switching devices have provided the feasibility of replacing the electrical buses with high-frequency magnetic links in small-scale microgrids. This can effectively reduce the number of voltage conversion stages, size, and cost of the microgrid, and isolate the sources and loads. To optimally design the magnetic link, an accurate evaluation of copper loss of the windings considering both the current waveforms and parasitic effects are required. This paper studies the copper loss analysis of a three-winding high-frequency magnetic link for residential microgrid applications. Due to the nonsinusoidal nature of the voltages and currents, the loss analysis is carried out on a harmonic basis taking into account the variations of phase shift, duty ratio, and amplitude of the waveforms. The high-frequency parasitic phenomena including the skin and proximity effects are taken into account. The maximum and minimum copper loss operating conditions of the magnetic link and their dependency on the phase shift angle and the duty ratio of the connected waveforms are studied. A prototype of the microgrid including the magnetic link is developed to validate the theoretical analysis, evaluate the microgrid efficiency, and perform the loss breakdown

Pd-Doped SnO 2

Methane (CH4), ethane (C2H6), ethylene (C2H4), and acetylene (C2C2) are important fault characteristic hydrocarbon gases dissolved in power transformer oil. Online monitoring these gaseous components and their generation rates can present the operational state of power transformer timely and effectively. Gas sensing technology is the most sticky and tricky point in online monitoring system. In this paper, pure and Pd-doped SnO2 nanoparticles were synthesized by hydrothermal method and characterized by X-ray powder diffraction, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy, respectively. The gas sensors were fabricated by side-heated preparation, and their gas sensing properties against CH4, C2H6, C2H4, and C2H2 were measured. Pd doping increases the electric conductance of the prepared SnO2 sensors and improves their gas sensing performances to hydrocarbon gases. In addition based on the frontier molecular orbital theory, the highest occupied molecular orbital energy and the lowest unoccupied molecular orbital energy were calculated. Calculation results demonstrate that C2H4 has the highest occupied molecular orbital energy among CH4, C2H6, C2H4, and C2H2, which promotes charge transfer in gas sensing process, and SnO2 surfaces capture a relatively larger amount of electric charge from adsorbed C2H4

Evaluation of core loss calculation methods for highly non-sinusoidal inputs

A modular, hybrid HVDC transformer, located in the turbine nacelle has been proposed for the offshore wind industry to improve efficiency and redundancy while reducing costs. The injection of harmonics by the transformer power electronics however, complicates the core loss calculations of such a transformer. The standard Steinmetz Equation is no longer valid and the alternative loss equations proposed in the literature are significantly more complicated. Therefore, many in the industry still use the Steinmetz Equation with the signal's Fourier Transform. However, the literature suggests this to be inaccurate without quantifying it. This paper will therefore compare the accuracy of this approach to a prominent alternative presented in the literature, the improved Generalised Steinmetz Equation

High Frequency LTCC based Planar Transformer

As we move towards high power and higher frequency related technology, conventional wire-wound magnetics have their own limitations which has led path to the development of planar based magnetic materials. Nowadays more planar magnetic technology has been employed because it is easier to fabricate them. The planar magnetic is a transformer or an inductor that replaces the wire-wound transformer or inductors which generally uses copper wires. One of the main reasons why we move to planar magnetic technology is its operation at higher frequency which provides higher power density. This study explains in detail about the design and fabrication of planar transformer for power electronics applications. The most important part of the transformer is its core. The cores in the planar transformer have different shapes and are available in different sizes. A planar core that is optimized, when compared with the conventional core with similar properties, exhibit better properties. In planar winding, we have different configurations available and with the optimum configuration, the losses of the transformer can be efficiently reduced. In this work, we have considered all the design specifications and came up with an optimum design procedure in order to design a good power planar transformer. This also deals with the case where the temperature rise is higher than what the PCB can withstand and try to come up with a solution for that. The next step for the planar transformer is to move from printed circuit board (PCB) to low temperature co-fired ceramic (LTCC) substrate which is attempted in this work. The main emphasis in this work is the design and fabrication procedure of LTCC based planar transformer. Ceramic can withstand higher temperature and has a better coefficient of thermal expansion (CTE) but has its own disadvantages which are also discussed here