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  • 1
    Language: English
    In: IEEE transactions on power electronics, 2013-02, Vol.28 (2), p.625-636
    Description: Application of multilevel inverters for higher power purposes in industries has become more popular. This is partly because of high-quality output waveform of multilevel inverters in comparison with two-level inverters. In this paper, initially a new topology for submultilevel inverter is proposed and then series connection of the submultilevel inverters is proposed as a generalized multilevel inverter. The proposed multilevel inverter uses reduced number of switching devices. Special attention has been paid to obtain optimal structures regarding different criteria such as number of switches, standing voltage on the switches, number of dc voltage sources, etc. The proposed multilevel inverter has been analyzed in both symmetric and asymmetric conditions. The validity of the proposed multilevel inverter is verified with both computer simulations using PSCAD/EMTDC software and laboratory prototype implementation.
    Subject(s): Algebraic topology ; Applied sciences ; Capacitors ; Circuit properties ; Design and construction ; Electric inverters ; Electric, optical and optoelectronic circuits ; Electrical engineering. Electrical power engineering ; Electronic circuits ; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics ; Electronics ; Engineering design ; Equations ; Exact sciences and technology ; Generalized topology ; Insulated gate bipolar transistors ; Inverters ; Logic gates ; Methods ; multilevel inverter ; optimal structure ; Power electronics, power supplies ; Research ; Signal convertors ; submultilevel inverter ; Switches ; Switching, multiplexing, switched capacity circuits ; Topology
    ISSN: 0885-8993
    E-ISSN: 1941-0107
    Source: IEEE Electronic Library (IEL)
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  • 2
    Language: English
    In: IET power electronics, 2013-04, Vol.6 (4), p.642-651
    Description: Multilevel inverters have attractive features which make them one of the most popular fields of investigations. They can operate in high power and high voltage conditions. Multilevel inverters generate output voltage with high quality and low harmonic contents. As the number of output voltage levels increases, the quality of the output voltage is improved leading to reduction of the filtering requirements. However, multilevel inverters have the disadvantage of increased power electronic switches. This leads to higher cost, size and complication. Some advanced topologies have been introduced to reduce the number of power electronic switches, unfortunately, most of these topologies need high voltage switches on their structure making them unsuitable for high voltage conditions. In this study, an innovative topology for multilevel inverter is proposed which reduces the number of switches considerably without using high voltage switches. The proposed topology is a general topology which can be extended for any number of voltage levels. The authors call this topology as cross-switched multilevel inverter. The simulation results obtained in PSCAD/EMTDC as well as the experimental results verify the proposed topology.
    Subject(s): cross‐switched multilevel inverter ; filtering requirements ; high power conditions ; high voltage conditions ; innovative topology ; invertors ; power electronic switches ; power electronics ; PSCAD/EMTDC
    ISSN: 1755-4535
    E-ISSN: 1755-4543
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 3
    Article
    Article
    2015
    ISSN: 0036-8075 
    Language: English
    In: Science (American Association for the Advancement of Science), 2015-09-04, Vol.349 (6252), p.1029-1029
    ISSN: 0036-8075
    E-ISSN: 1095-9203
    Source: JSTOR Life Sciences
    Source: Single Journals
    Source: Academic Search Ultimate
    Source: Alma/SFX Local Collection
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  • 4
    Language: English
    In: IEEE transactions on power delivery, 2010-10, Vol.25 (4), p.2676-2683
    Description: In this paper, two new topologies are proposed for three-phase dynamic voltage restorers (DVRs). These topologies are based on direct converters. The proposed topologies do not require dc-link energy storage elements. As a result, they have less volume, weight, and cost. They can also compensate long-time voltage sags and swells. The proposed DVRs can compensate several types of disturbances, such as voltage sags, swells, unbalances, harmonics, and flickers. Moreover, due to the fact that the compensation voltage for each phase is taken from all three phases, the proposed topologies can compensate one-phase outages. In the proposed topologies, three independent three-phase to single-phase direct converters are used. Each converter operates independently and, as a result, the proposed DVRs properly compensate unbalanced voltage sags and swells. The used converters can be constructed by four or six power switches. Depending on the structure of the used converters, the compensation ranges will be different. A new control method is also proposed for using direct ac/ac converters. The experimental and simulation results verify the capabilities of the proposed topologies in compensation of voltage distortions.
    Subject(s): Applied sciences ; Converters ; Convertors ; Direct current networks ; Direct energy conversion and energy accumulation ; Direct three-phase to single-phase converter ; Disturbances. Regulation. Protection ; dynamic voltage restorer (DVR) ; Electric current regulators ; Electrical engineering. Electrical power engineering ; Electrical machines ; Electrical power engineering ; Energy accumulation ; Exact sciences and technology ; flicker ; Harmonic analysis ; harmonics elimination ; Innovations ; Power networks and lines ; Power quality ; Power system simulation ; Research ; Topology ; Voltage regulators ; voltage sag ; voltage swell
    ISSN: 0885-8977
    E-ISSN: 1937-4208
    Source: IEEE Electronic Library (IEL)
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  • 5
    Language: English
    In: IET power electronics, 2013-07, Vol.6 (6), p.1041-1050
    Description: This study proposes and analyses a new cascaded multilevel inverter in both symmetric and asymmetric conditions. Firstly, the topology is presented in general form and then it is optimised. For any given number of voltage levels, the proposed topology reduces the number of switches. In the symmetric condition, the proposed topology offers capability of charge balance control method while reducing the number of switches. Also, unlike the other reduced switch topologies, the proposed topology does not increase the total standing voltage of the switches in comparison with the conventional cascaded H-bridge (CHB) multilevel inverter. In the asymmetric condition, the proposed topology has highest output voltage resolution while keeping the total standing voltage equal to the CHB topology. In other words, in both symmetric and asymmetric conditions the number of switches in the proposed topology is lower than that of the CHB topology. However, both the proposed topology and also the CHB topology have the same total standing voltage on the switches. Other asymmetric topologies use higher number of switches and have higher total standing voltage in comparison with the proposed asymmetric topology. A modified phase-shifted-pulse width modulation is also presented for the proposed symmetric topology. The proposed topology is verified with simulation and experimental results.
    Subject(s): asymmetric conditions ; cascaded cross‐switched multilevel inverter ; charge balance control method ; CHB topology ; H‐bridge multilevel inverter ; modified phase‐shifted‐pulse width modulation ; PWM invertors ; symmetric conditions ; total standing voltage ; voltage levels ; voltage resolution
    ISSN: 1755-4535
    E-ISSN: 1755-4543
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 6
    Language: English
    In: IET power electronics, 2021-04-08, Vol.14 (5), p.936-945
    Description: A new non‐isolated single‐input dual‐output boost DC–DC converter is introduced in this paper. The motivation of the work is that in various applications such as some multilevel converters, it is required to provide multiple dc sources that are not required to be isolated. In the proposed structure, the output ports of the converter can provide different values of power and still balance the output voltage. Even, if required, the output voltages can be set to different values. From practical point of view, the proposed topology uses minimum number of power‐electronic switches (two switches for two outputs) which have common ground making their drive circuit simple and easy to implement. The state‐space modelling of the proposed converter is presented, then, the model is used to design the passive elements. Moreover, the proposed converter is compared with the relevant converters. In order to verify the performance of the proposed DC–DC converter, a prototype of the converter has been implemented and the results are presented.
    ISSN: 1755-4535
    E-ISSN: 1755-4543
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
    Source: Nexis Uni
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  • 7
    Language: English
    In: Journal of cellular physiology, 2019-09, Vol.234 (9), p.15357-15368
    Description: Regeneration and functional recovery after peripheral nerve damage still remain a significant clinical problem. In this study, alginate/chitosan (alg/chit) hydrogel was used for the transplantation of olfactory ectomesenchymal stem cells (OE‐MSCs) to promote peripheral nerve regeneration. The OE‐MSCs were isolated from olfactory mucosa biopsies and evaluated by different cell surface markers and differentiation capacity. After creating sciatic nerve injury in a rat model, OE‐MSCs were transplanted to the injured area with alg/chit hydrogel which was prepared and well‐characterized. The prepared hydrogel had the porosity of 91.3 ± 1.27%, the swelling ratio of 379% after 240 min, weight loss percentages of 80 ± 5.56% after 14 days, and good blood compatibility. The 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay, 4′,6‐diamidino‐2‐phenylindole, and LIVE/DEAD staining were done to assay the behavior of OE‐MSCs on alg/chit hydrogel and the results confirmed that the hydrogel can provide a suitable substrate for cell survival. For functional analysis, alg/chit hydrogel with and without OE‐ MSCs was injected into a 3‐mm sciatic nerve defect of Wistar rats. The results of the sciatic functional index, hot plate latency, electrophysiological assessment, weight‐loss percentage of wet gastrocnemius muscle, and histopathological examination using hematoxylin–eosin and Luxol fast blue staining showed that utilizing alg/chit hydrogel with OE‐MSCs to the sciatic nerve defect enhance regeneration compared to the control group and hydrogel without cells. Figure 10 using alginate/chitosan hydrogel to transplantation olfactory ectomesenchymal stem cells to improve the effectiveness of peripheral nerve regeneration.
    Subject(s): alginate/chitosan ; Analysis ; Cell Biology ; Cell differentiation ; hydrogel ; Life Sciences & Biomedicine ; olfactory ectomesenchymal stem cells ; Physiology ; Porosity ; sciatic nerve ; Science & Technology ; Stem cells ; Tissue engineering ; Transplantation
    ISSN: 0021-9541
    E-ISSN: 1097-4652
    Source: Web of Science - Science Citation Index Expanded - 2019〈img src="http://exlibris-pub.s3.amazonaws.com/fromwos-v2.jpg" /〉
    Source: Alma/SFX Local Collection
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  • 8
    Language: English
    In: IET power electronics, 2014-03, Vol.7 (3), p.576-590
    Description: Dynamic voltage restorer (DVR) is a power electronic converter-based custom power device used to compensate for voltage variations. The inverter used in the DVR structure can have different topologies. Multilevel inverters are a good candidate to be used in the DVR structure especially in higher voltage level. This study proposes a new scheme for DVR based on a multilevel inverter. In the proposed DVR, a dc–dc converter is attached to the multilevel inverter. The dc-link voltage is regulated by the dc–dc converter considering the voltage sag magnitude. In this way, the output voltage of the multilevel inverter has always its maximum possible number of levels. This results in better quality of output voltage in both deep and shallow voltage sags. It is important to emphasise that the existing inverter-based DVR topologies do not have this capability. Also, in the proposed DVR, there is no need for an output filter. Moreover, the fundamental frequency control method for the multilevel inverter can be used instead of pulse width modulation-based methods. This can result in lower switching losses and lower switching stresses. The mathematical analysis of the operation range of the proposed DVR is given in detail. The simulation results using Power System Computer Aided Design/Electromagnetic Transient including DC (PSCAD/EMTDC) as well as the experimental results from a laboratory prototype verify the proposed DVR scheme.
    Subject(s): adjustable DC‐link voltage ; DC‐DC converter ; deep voltage sags ; DVR structure ; dynamic voltage restorer ; frequency control ; fundamental frequency control method ; inverter‐based DVR topology ; invertors ; losses ; multilevel inverter ; output voltage quality ; power electronic converter‐based custom power device ; power supply quality ; power system restoration ; PSCAD‐EMTDC ; pulse width modulation‐based method ; PWM power convertors ; shallow voltage sags ; switching losses ; switching stresses ; voltage sag magnitude ; voltage variation
    ISSN: 1755-4535
    E-ISSN: 1755-4543
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 9
    Language: English
    In: IET power electronics, 2013-07, Vol.6 (6), p.1188-1196
    Description: In this study, firstly a new basic unit is proposed for multilevel converters. The proposed basic units are used as building blocks to form a cascaded multilevel converter. In other words, the proposed topology consists of cascaded basic units. The proposed basic unit and the proposed multilevel converter use lower number of switching devices and gate driver circuits. In the proposed topology, two design parameters are available: the number of cascaded basic units and the number of dc voltage sources in each basic unit. These two parameters can be used to design the desired multilevel converter based on the operational conditions. Therefore the proposed topology offers good flexibility in designing. An algorithm for determining the values of the dc voltage sources is given in order to generate maximum number of voltage levels. The comparison results with some recently introduced topologies show that the proposed topology effectively reduces the components count. The simulation results obtained in PSCAD/EMTDC as well as the experimental results of a 51-level inverter based on the proposed topology are presented to verify its performance.
    Subject(s): 51‐level inverter ; asymmetrical multilevel converter topology ; cascade networks ; cascaded basic units ; cascaded multilevel converter ; dc voltage source value determination ; design parameters ; driver circuits ; gate driver circuits ; invertors ; operational conditions ; PSCAD/EMTDC simulation ; switching convertors ; switching devices
    ISSN: 1755-4535
    E-ISSN: 1755-4543
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 10
    Language: English
    In: International journal of circuit theory and applications, 2019-11, Vol.47 (11), p.1812-1836
    Description: Summary In this paper, the concept of converter design, using the least number of elements and achieving high voltage gain at the low duty cycle, is proposed for the microgrids. One of the important issues in the microgrids is boosting the low voltage output of sources to the utility voltage level. Therefore, the step‐up DC‐DC converters are widely used in these systems to attain the utility voltage. The benchmarking of the converters mainly in terms of the voltage gain, efficiency, the number of active and passive components, stresses on semiconductors, and simplicity is considered. In this paper, a new extendable non‐isolated boost DC‐DC converter is presented. Comparing the conventional boost converter, the basic structure of the proposed converter has a high voltage gain and reduced stress on the switch. To increase the voltage gain, the basic structure of the proposed converter can be easily extended. The modulation technique employed is high‐frequency pulse‐width modulation (PWM). The detailed analysis of the proposed converter in continuous current mode (CCM) and discontinuous current mode (DCM) is presented. The relations between currents and voltages and the voltage gain in CCM and DCM are obtained. Experimental results are carried out to verify theoretical concepts by using the hardware prototype. A new converter design using the least number of elements and achieving high voltage gain at the low duty cycle is proposed for the microgrids. The benchmarking of the converters mainly in terms of the voltage gain, efficiency, the number of active and passive components, stresses on semiconductors, and simplicity is considered. The basic structure of the proposed converter has the high voltage gain and reduced stress on the switch.
    Subject(s): continues current mode (CCM) ; discontinuous current mode (DCM) ; Engineering ; Engineering, Electrical & Electronic ; microgrids ; non‐isolated step‐up DC‐DC converter ; Science & Technology ; Technology ; voltage gain
    ISSN: 0098-9886
    E-ISSN: 1097-007X
    Source: Web of Science - Science Citation Index Expanded - 2019〈img src="http://exlibris-pub.s3.amazonaws.com/fromwos-v2.jpg" /〉
    Source: Alma/SFX Local Collection
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