1,720,968 research outputs found
An improved bridgeless PFC boost-doubler rectifier with high-efficiency
No full textAn improved bridgeless boost-doubler rectifier is proposed for high-efficiency power-factor correction (PFC). In the proposed rectifier, the conduction losses are reduced by essentially eliminating the full-bridge diode rectifier. A bidirectional switch is used for the power switches, simplifying the overall power circuit structure. The reverse-recovery problems of the rectifying diodes are also reduced by using a simple passive snubber circuit. Zero-current turn-off of the rectifying diodes can be achieved, which removes the reverse-recovery losses of the rectifying diodes in the continuous conduction mode operation. The proposed rectifier provides high power-factor and improves power efficiency for low line voltage applications. The performance of the proposed rectifier is evaluated on an 800W (400V/2A) experimental prototype at 110V rms line voltage.1126sciescopu
Multi-mode MPPT control for improved efficiency
No full textA multi-mode maximum power point tracking (MPPT) control for wide photovoltaic (PV) voltage range and improved efficiency is proposed in this paper. This MPPT control is fitted for the two-stage PV power system which is composed of a step-up converter and a step-down inverter. In the low PV voltage, the step-up converter performs the MPPT. On the other hand, in the high PV voltage, the inverter performs the MPPT control. The proposed MPPT control makes the dc link voltage low as soon as possible and improves the power efficiency under the wide PV voltage range.113sciescopu
High-Efficiency Soft-Switching AC-DC Converter With Single-Power-Conversion Method
No full textThis paper presents a high-efficiency isolated ac-dc converter topology. The proposed converter consists of a full-bridge diode rectifier, an isolated resonant dc-dc converter, and only one controller. The proposed converter provides the soft-switching technique for all components operating at high frequency, allowing for an improvement in power density without a cost of power-conversion efficiency. Furthermore, by using a novel control algorithm that controls both power factor and output power, the converter performs ac-dc power conversion in only a single-power-processing step. These characteristics enable the proposed converter to provide high efficiency, high power density, and a high power factor. A 2-kW prototype was implemented, and its performance and validity were evaluated based on experimental results. ? 2017 IEEE.11sciescopu
Single Power-Conversion LED Backlight Driving System With High Power Factor Control
No full textA single power-conversion LED backlight driving system with high power factor control is proposed. The proposed converter is composed of a full-bridge diode rectifier and a quasi-resonant flyback converter. The proposed converter provides a simple structure, a low cost, and high power factor of 0.988 by using the novel control algorithm without the PFC circuit. To achieve good controllability, the novel control algorithm is transformed by adding a nominal value predetermined to relax its control burden. Detailed analysis and experimental results for a 90-W prototype are discussed.X1144sciescopu
Single power-conversion DAB microinverter with safe commutation and high efficiency for PV power applications
No full textThis paper presents a single power-conversion dual-active-bridge (DAB) microinverter with safe commutation and high efficiency for PV power applications. In DAB microinverters, the commutation problem is a crucial issue which must be solved in order to achieve a higher power capability. Owing to its novel circuit structure, the proposed microinverter can provide the commutation path in any switching case, so that it avoids the high voltage spikes from the commutation problem and provides high reliability. Moreover, the proposed microinverter has a circuit structure that is simpler and requires fewer auxiliary circuits compared to conventional DAB microinverters. In addition, the proposed microinverter achieves simple closed-loop current control and zero-voltage-switching turn-on of all switches owing to its control algorithm. Because these advantages are obtained with only a single power-conversion, the proposed microinverter has high efficiency and simple structure with high reliability. The operation principle and commutation issue of the proposed microinverter are theoretically analyzed in detail, and experimentally validated on a 400-W prototype.11Nsciescopu
A Soft-Switching Single-Stage Converter with High Efficiency for a 3.3-kW On-Board Charger
No full textThis paper presents a highly efficient 3.3-kW single-stage on-board charger (OBC). The proposed OBC consists of two interleaved cells sharing a full-bridge diode rectifier. Each cell is composed of an active clamp circuit and a series resonant circuit. The proposed OBC provides zero-voltage switching of all switches and reduces the reverse-recovery problem by zero-current switching of the output diodes. The interleaved technique maintains the proper power level with high efficiency. The proposed control algorithm enables power factor correction by the OBC without any auxiliary circuit and balances the input current between the two cells. In addition, the proposed converter requires no electrolytic dc-link capacitor, ensuring compact size and a long lifetime. Owing to these features, the proposed OBC efficiently outputs a high power factor over a wide power range and achieves reliability with a simply structured, single-power processing step. Therefore, the proposed OBC is potentially feasible for automotive applications. Finally, the theoretical analysis is confirmed in a 3.3-kW prototype and validated in experimental results. © 1982-2012 IEEE.11Nsciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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