There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

/pdf/light-emitting-diodes-ubzde6g9qc.pdf

Light-emitting diodes

Physics-informed machine learning (PIML) has been emerging as a promising tool for applications with domain knowledge and physical models. To uncover its potentials in power electronics, this article proposes a PIML-based parameter estimation method demonstrated by a case study of dc–dc Buck converter. A deep neural network and the dynamic models of the converter are seamlessly coupled. It overcomes the challenges related to training data, accuracy, and robustness which a typical data-driven approach has. This exemplary application envisions to provide a new perspective for tailoring existing machine learning tools for power electronics.

Parameter Estimation of Power Electronic Converters With Physics-Informed Machine Learning

A multiphase converter suitable for a very high input voltage is proposed. It is formed by n switch pairs in the primary-side, an n-phase isolation transformer, whose primary windings are connected with dc blocking capacitors, and an n-phase rectifier. The switching patterns applied to the switch pairs have a phase difference of 360° / n. It features V i / n voltage stress on the primary-side switches, which commute under a ZVS condition, and a high output current capacity. The current stress of the inductors and diodes in the rectifier is reduced to one-nth of the load current. Compared with the input-series connected modular converters, the proposed converter feature a half of the switches number, for the same voltage stress across them. The reduced conduction losses and soft-switching give a high efficiency: 88.3% measured for a 1500V/48V, 2 kW prototype.

A class of single-step high-voltage DC-DC converters with low voltage stress and high output current capacity

Thermal stress reduction of quasi-Z source inverter drive by model predictive control

Wide-Scale Adoption of Photovoltaic Energy

In single-phase inverters, DC-link capacitors are installed at the DC-link to buffer the ripple power between the AC side and DC side. Active decoupling methods introduce additional circuits at the DC side or AC side to partially or fully supply the ripple power. So that the demanded DC-link capacitor capacitance can be decreased. However, few research is about the effect of DC side and AC side decoupling on the DC-link capacitor reliability considering its electro-thermal stresses. This paper presents a quantitative analysis on the lifetime of capacitors with power decoupling circuits at the DC side and AC side, respectively. The ripple current spectrum of the capacitors is obtained by double Fourier analysis of a H-bridge inverter with natural sampling PWM modulation. A study case is demonstrated by a 2,000 W H-bridge inverter with 400 V DC-link voltage.

Huai Wang

Papers

Parameter Estimation of Power Electronic Converters With Physics-Informed Machine Learning

A class of single-step high-voltage DC-DC converters with low voltage stress and high output current capacity

Thermal stress reduction of quasi-Z source inverter drive by model predictive control

Wide-Scale Adoption of Photovoltaic Energy

Lifetime estimation of DC-link capacitors in a single-phase converter with an integrated active power decoupling module