Search results for "Capacitor"
showing 10 items of 164 documents
Introduction: Periodic Filters and Filter Banks
2014
In this chapter filtering of periodic signals is outlined. Periodic filters and periodic filter banks are defined. Perfect reconstruction filter banks are characterized via their polyphase matrices.
An improved Flyback converter
2009
This paper presents a modified Flyback converter able to operate with higher efficiency and smaller size, overcoming most of the conventional flyback converter drawbacks, and also keeping its low cost and simplicity. In particular, the proposed converter allows the mosfet off voltage to be reduced and clamped to the input, thus recovering the transformer leakage energy. As a consequence, the duty cycle can be extended to unity, thus reducing the voltage stress across the output rectifier, and lowering both the magnetizing inductance and the transformer bias current values. In addition, due to the auxiliary mosfet, the magnetizing current can become negative, eliminating the discontinuous co…
A demagnetization circuit for forward converters
2009
This paper presents a demagnetization circuit able to operate the forward converter with an higher efficiency and with a wider input range. In particular, by the means of few added components, the magnetizing energy and the leakage one are continuously recovered, and the transformer reset and the primary mosfet OFF voltage clamp to the input, both under steady state and transient operations, are provided. The reduced voltage stress allows the converter to operate with a duty extended to unity over the typical 70% limit of the Active Clamp topology, with smaller output inductance, better converter dynamics and wider input range. Furthermore, thanks to this technique, by employing a duty appr…
Improving the energy efficiency of an islanded distribution network using classical and innovative computation methods
2016
The paper presents the analysis of some potentially suitable actions for reducing the energy losses of an islanded Medium Voltage distribution network, with the aim of improving electricity distribution efficiency. For this purpose, four actions are considered: 1) increasing the network's rated voltage; 2) reactive power compensation through static capacitor banks; 3) reactive power compensation through switchable capacitor banks; 4) installation of distributed photovoltaic (PV) generation. The first two measures are typically taken into account by the distribution system operators and can be examined by means of classical design methods, whereas the latter two more innovative actions are t…
Four-Level Three-Phase Inverter With Reduced Component Count for Low and Medium Voltage Applications
2021
This paper proposes a novel three-phase topology with a reduced component count for low- and medium-voltage systems. It requires three bidirectional switches and twelve unidirectional switches for producing four-level voltages without using flying capacitors or clamping diodes, reducing the size, cost, and losses. Removing flying capacitors and clamping diodes allows it to simplify control algorithms and increase the reliability, efficiency, and lifetime. A modified low-frequency modulation (LFM) scheme is developed and implemented on the proposed topology to produce a staircase voltage with four steps. Further, a level-shifted pulse width modulation (LSPWM) is used to reduce the filter siz…
Direct experimental observation of mesoscopic fluorous domains in fluorinated room temperature ionic liquids
2017
Fluorinated room temperature ionic liquids (FRTILs) represent a class of solvent media that are attracting great attention due to their IL-specific properties as well as features stemming from their fluorous nature. Medium-to-long fluorous tails constitute a well-defined apolar moiety in the otherwise polar environment. Similarly to the case of alkyl tails, such chains are expected to result in the formation of self-assembled fluorous domains. So far, however, no direct experimental observation has been made of the existence of such structural heterogeneities on the nm scale. We report here the first experimental evidence of the existence of mesoscopic spatial segregation of fluorinated dom…
Oxygen-deficient Co3O4 submicron porous sphere films as highly active supsercapacitor electrodes
2021
Abstract Herein, we report Co3O4 films with different content of oxygen vacancies and shapes of particles for supercapacitor electrodes. Under the similar area ratio of OII peak in the XPS spectrum of oxygen elements, the specific capacitance of electrode films with hollow spongy-like particles (963 F/g under a scan rate of 5 mV/s) is 1.6 times higher than that of the electrodes with solid irregular particles (596 F/g), indicating the effect of particle shapes on electrochemical properties. The films composed of submicron porous spheres and containing highest content of oxygen vacancies exhibited the specific capacitances as high as 1700 F/g under the scan rate of 5 mV/s. By contrast, after…
A Feasibility Analysis of an Electric KERS for Internal Combustion Engine Vehicles
2019
In this work, the authors evaluate the energetic and economic advantages connected to the implementation of an electric Kinetic Energy Recovery System (e-KERS) on an internal combustion engine vehicle (ICEV). The e-KERS proposed is based on the use of a supercapacitor (SC) as energy storage element, a brushless motor generator unit (MGU) for the conversion of the vehicle kinetic energy into electric energy (and vice versa), and a power converter properly designed to manage the power transfer between SC and MGU. The low complexity of the system proposed, the moderate volume and weight of the components selected for its assembly, together with their immediate availability on the market, make …
Influence of irradiation on the switching behavior in PZT thin films
2005
Spatially nonuniform imprint behavior induced by X-ray synchrotron, electron and neutron irradiation has been investigated in sol–gel Pb(Zr,Ti)O3 thin films. The analysis of the switching current data reveals the strong influence of irradiation on the switching current shape. The obtained effects have been explained as a result of acceleration of the bulk screening process induced by irradiation. It was shown that the spatial distribution of the internal bias field is determined by the domain structure existing during irradiation. The changes in the structural characteristics during fatigue cycling have been reveled by high resolution synchrotron X-ray diffraction experiments on (1 1 1)-ori…
A six legs buck-boost interleaved converter for KERS application
2020
This paper addresses the design of a bi-directional DC/DC power converter to interface a supercapacitor bank and a motor-generator unit. The design is based on an interleaved six legs topology in which the current is shared among six inductors to minimize their weight and cost, allowing, besides, a low switching frequency to lessen switching losses. The converter is conceived to be employed in an electric Kinetic Energy Recovery System for Internal Combustion Engine Vehicles. The system makes use of a supercapacitor as a storage system, and a motorgenerator unit connected to the drive shaft for vehicle acceleration and braking. The system uses available commercial devices, thus obtaining a …