ZVS Auxiliary Circuit for a 10 kW Unregulated LLC Full-Bridge Operating at Resonant Frequency for Aircraft Application

In modern aircraft designs, following the More Electrical Aircraft (MEA) philosophy, there is a growing need for new high-power converters. In this context, innovative solutions to provide high efficiency and power density are required. This paper proposes an unregulated LLC full-bridge operating at resonant frequency to obtain a constant gain at all loads. The first harmonic approximation (FHA) model is not accurate enough to estimate the voltage gain in converters with high parasitic resistance. A modified FHA model is proposed for voltage gain analysis, and time-based models are used to calculate the instantaneous current required for the ZVS transition analysis. A method using charge instead of current is proposed and used for this ZVS analysis. Using this method, an auxiliary circuit is proposed to achieve complete ZVS within the whole load range, avoiding a gapped transformer design and increasing the efficiency and power density. A 28 Vdc output voltage prototype, with 10 kW peak output power, has been developed to validate the theoretical analysis and the proposed auxiliary circuit. The maximum efficiency (96.3%) is achieved at the nominal power of 5 kW.

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Dual-Side Phase-Shift Control for Strongly Coupled Series–Series Compensated Electric Vehicle Wireless Charging Systems

World Electric Vehicle Journal ◽

10.3390/wevj13010006 ◽

2021 ◽

Vol 13 (1) ◽

pp. 6

Author(s):

Yiming Zhang ◽

Zhiwei Shen ◽

Yuanchao Wu ◽

Hui Wang ◽

Wenbin Pan

Keyword(s):

Phase Shift ◽

Power Density ◽

High Efficiency ◽

Harmonic Approximation ◽

Future Trend ◽

Soft Switching ◽

Power Transfer ◽

Strongly Coupled ◽

Loosely Coupled ◽

Shift Control

Wireless power transfer (WPT) for electric vehicles is an emerging technology and a future trend. To increase power density, the coupling coefficient of coils can be designed to be large, forming a strongly coupled WPT system, different from the conventional loosely coupled WPT system. In this way, the power density and efficiency of the WPT system can be improved. This paper investigates the dual-side phase-shift control of the strongly coupled series–series compensated WPT systems. The mathematical models based on the conventional first harmonic approximation and differential equations for the dual-side phase-shift control are built and compared. The dual-side phase-shift angle and its impact on the power transfer direction and soft switching are investigated. It is found that synchronous rectification at strong couplings can lead to hard switching because the dual-side phase shift in this case is over 90°. In comparison, a relatively high efficiency and soft switching can be realized when the dual-side phase shift is below 90°. The experimental results have validated the analysis.

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A High Efficiency, Extended Load Range Boost Regulator Optimized Forenergy Harvesting Applications

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.534.206 ◽

2013 ◽

Vol 534 ◽

pp. 206-219

Author(s):

Zachary Nosker ◽

Yasunori Kobori ◽

Haruo Kobayashi ◽

Kiichi Niitsu ◽

Nobukazu Takai ◽

...

Keyword(s):

High Efficiency ◽

Input Voltage ◽

Maximum Efficiency ◽

Load Range ◽

Pulse Width Modulated ◽

Steady State Operation ◽

Start Up ◽

Control Scheme ◽

Separate Control ◽

Boost Regulator

A small, low power bootstrapped boost regulator is introduced that can start upwith an input voltage of 240mV and achieve a maximum efficiency of 96%. The proposed circuituses two separate control schemes for startup and steady-state operation. A xed-frequencyoscillator is used to initially start up the circuit and raise the output voltage. Once the outputvoltage has reached a level adequate to bias the internal circuitry, a constant-on-time stylehysteretic control scheme is used, which helps increase system efficiency compared to using aconventional Pulse-Width-Modulated control scheme. While maintaining a high efficiency, theproposed circuit only requires 3 external components|2 capacitors (input and output) and aninductor. The e ectiveness of this approach is shown through Spectre simulation results.

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Modelling and analysis of vienna rectifier for more electric aircraft applications using wide band-gap materials

Journal of Physics Conference Series ◽

10.1088/1742-6596/2120/1/012027 ◽

2021 ◽

Vol 2120 (1) ◽

pp. 012027

Author(s):

Ling Jin Loong ◽

Chockalingam Aravind Vaithilingam ◽

Gowthamraj Rajendran ◽

Venkatkumar Muneeswaran

Keyword(s):

Power Density ◽

High Power ◽

High Efficiency ◽

Wide Band ◽

Wide Bandgap ◽

High Power Density ◽

Vienna Rectifier ◽

Electric Aircraft ◽

Aircraft Application ◽

More Electric Aircraft

Abstract This paper presents a comprehensive study on the switching effects of wide bandgap devices and the importance of power electronics in an aircraft application. Silicon (Si), silicon carbide (SiC), and gallium nitride (GaN) are wide bandgap devices that act as a power electronic switch in the AC-DC converter for More Electric Aircraft (MEA) applications. Therefore, it is important to observe their converting efficiency to identify the most suitable wide bandgap device among three devices for AC-DC converters in aircraft applications to provide high efficiency and high-power density. In this study, the characteristics of Si, SIC, and GaN devices are simulated using PSIM software. Also, this paper presents the performance of the Vienna rectifier for aircraft application. The Vienna rectifier using Si, SiC, and GaN devices are simulated using PSIM software for aircraft application. GaN with Vienna rectifier provides better performance than Si and SiC devices for aircraft applications among the three devices. It gives high efficiency, high power density, low input current THD to meet IEEE-519 standard, and high-power factor at mains.

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Optimization and Analysis of a High Power Density and Fault Tolerant Starter–Generator for Aircraft Application

Energies ◽

10.3390/en14010113 ◽

2020 ◽

Vol 14 (1) ◽

pp. 113

Author(s):

Bo Wang ◽

Gaurang Vakil ◽

Ye Liu ◽

Tao Yang ◽

Zhuoran Zhang ◽

...

Keyword(s):

Fault Tolerance ◽

Permanent Magnet ◽

Power Density ◽

High Power ◽

High Efficiency ◽

Great Effort ◽

High Power Density ◽

Element Analysis ◽

Starter Generator ◽

Aircraft Application

Permanent magnet synchronous machines provide many dramatic electromagnetic performances such as high efficiency and high power density, which make them more competitive in aircraft electrification, whereas, designing a permanent magnet starter–generator (PMSG), with given consideration to fault tolerance (FT), is a significant challenge and requires great effort. In this paper, a comprehensive FT PMSG design process is proposed which is applied to power systems of turboprops. Firstly, potential slot/pole combinations were selected based on winding factor, harmonic losses and manufacture issues. Then, pursuing high power density, a multiple objective optimization process was carried out to comprehensively rank performances. To meet a fault tolerance target, electrical, magnetic and thermal isolation topologies were investigated and compared, among which 18 slot/12 pole with dual three-phase was selected as the optimal one, with a power density of 7.9 kW/kg. Finally, a finite element analysis verified the performance in normal and post-fault scenarios. The candidate machine has merits concerning high power density and post-fault performance.

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Analysis of LC-LC2 Compensated Inductive Power Transfer for High Efficiency and Load Independent Voltage Gain

10.20944/preprints201807.0031.v1 ◽

2018 ◽

Author(s):

Md Morshed Alam ◽

Saad Mekhilef

Keyword(s):

Output Power ◽

High Efficiency ◽

Domain Analysis ◽

Air Gap ◽

Maximum Efficiency ◽

Voltage Gain ◽

Resonant Converter ◽

Power Transfer ◽

Inductive Power Transfer ◽

Inductive Power

This paper presents a novel LC-LC2 compensated resonant converter topology to achieve both high efficiency and good voltage gain controllability. An additional receiving side inductor working together with the receiving coil has the contribution to work with a large range of air gap distance. Due to this property, proposed compensation technique is effective for IPT based EV charging application. The frequency domain analysis of the proposed resonant converter provides the load independent voltage gain and ZPA of the input impedance. On the other hand, time domain analysis gives the circuit operation. A 500 W LC-LC2 compensated resonant converter prototype is built to testify the theoretical analysis. To perform the efficiency-comparison under different air gap, an S-SP compensated resonant converter with a similar amount of output power is also presented. In order to obtain the effectiveness, the proposed compensation method is verified by the experimental results. The maximum efficiency of the proposed compensated resonant converter is 93% at an output power of 500 W with a 140-mm air gap between the two sides of the IPT (inductive power transfer) transformer.

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Analysis and Pareto Frontier Based Tradeoff Design of an Integrated Magnetic Structure for a CLLC Resonant Converter

Energies ◽

10.3390/en14061756 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1756

Author(s):

Gang Wang ◽

Qiyu Hu ◽

Chunyu Xu ◽

Bin Zhao ◽

Xiaobao Su

Keyword(s):

Magnetic Structure ◽

Power Density ◽

High Efficiency ◽

Pareto Frontier ◽

Optimization Procedure ◽

Magnetic Core ◽

Pareto Optimization ◽

High Power Density ◽

Resonant Converter ◽

Conduction Loss

This paper proposes an integrated magnetic structure for a CLLC resonant converter. With the proposed integrated magnetic structure, two resonant inductances and the transformer are integrated into one magnetic core, which improves the power density of the CLLC resonant converter. In the proposed integrated magnetic structure, two resonant inductances are decoupled with the transformer and can be adjusted by the number of turns in each inductance. Furthermore, two resonant inductances are coupled to reduce the number of turns in each inductance. As a result, the conduction loss can be reduced. The trade-off design of the integrated magnetic structure is carried out based on the Pareto optimization procedure. With the Pareto optimization procedure, both high efficiency and high-power density can be achieved. The proposed integrated magnetic structure is validated by theoretical analysis, simulations, and experiments.

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Design of Grating Al2O3 Passivation Structure Optimized for High-Efficiency Cu(In,Ga)Se2 Solar Cells

Sensors ◽

10.3390/s21144849 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4849

Author(s):

Chan Hyeon Park ◽

Jun Yong Kim ◽

Shi-Joon Sung ◽

Dae-Hwan Kim ◽

Yun Seon Do

Keyword(s):

Solar Cells ◽

High Efficiency ◽

Surface Passivation ◽

Rear Surface ◽

Maximum Efficiency ◽

Structural Factors ◽

Carrier Recombination ◽

Cigs Solar Cells ◽

Effective Carrier ◽

Opening Width

In this paper, we propose an optimized structure of thin Cu(In,Ga)Se2 (CIGS) solar cells with a grating aluminum oxide (Al2O3) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al2O3 is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL. Compared with an unpassivated thin CIGS solar cell, the efficiency was improved up to 20.38% when the pitch of the GAPL was 7.5–12.5 μm. Furthermore, the efficiency was improved as the COW of the GAPL was decreased. The maximum efficiency value occurred when the COW was 100 nm because of the effective carrier recombination inhibition and high reflectivity of the Al2O3 insulator passivation with local contacts. These results indicate that the designed structure has optimized structural points for high-efficiency thin CIGS solar cells. Therefore, the photovoltaic (PV) generator and sensor designers can achieve the higher performance of photosensitive thin CIGS solar cells by considering these results.

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Near-field thermophotovoltaics for efficient heat to electricity conversion at high power density

Nature Communications ◽

10.1038/s41467-021-24587-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Rohith Mittapally ◽

Byungjun Lee ◽

Linxiao Zhu ◽

Amin Reihani ◽

Ju Won Lim ◽

...

Keyword(s):

Power Density ◽

High Power ◽

High Efficiency ◽

Near Field ◽

Electrical Power ◽

Photovoltaic Cells ◽

High Power Density ◽

Pv Cell ◽

Electrical Power Output ◽

Power Densities

AbstractThermophotovoltaic approaches that take advantage of near-field evanescent modes are being actively explored due to their potential for high-power density and high-efficiency energy conversion. However, progress towards functional near-field thermophotovoltaic devices has been limited by challenges in creating thermally robust planar emitters and photovoltaic cells designed for near-field thermal radiation. Here, we demonstrate record power densities of ~5 kW/m2 at an efficiency of 6.8%, where the efficiency of the system is defined as the ratio of the electrical power output of the PV cell to the radiative heat transfer from the emitter to the PV cell. This was accomplished by developing novel emitter devices that can sustain temperatures as high as 1270 K and positioning them into the near-field (<100 nm) of custom-fabricated InGaAs-based thin film photovoltaic cells. In addition to demonstrating efficient heat-to-electricity conversion at high power density, we report the performance of thermophotovoltaic devices across a range of emitter temperatures (~800 K–1270 K) and gap sizes (70 nm–7 µm). The methods and insights achieved in this work represent a critical step towards understanding the fundamental principles of harvesting thermal energy in the near-field.

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Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Energies ◽

10.3390/en14082234 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2234

Author(s):

Hongye Zhang ◽

Zezhao Wen ◽

Francesco Grilli ◽

Konstantinos Gyftakis ◽

Markus Mueller

Keyword(s):

Quantitative Analysis ◽

Power Density ◽

High Efficiency ◽

Alternating Current ◽

Coated Conductors ◽

Ac Loss ◽

Electrical Machines ◽

Qualitative And Quantitative Analysis ◽

Qualitative And Quantitative ◽

Reduction Techniques

Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especially for those operating at high speeds for future aviation. Given that a critical review on the research advancement regarding the AC loss of superconductors has not been reported during the last dozen years, especially combined with electrical machines, this paper aims to clarify its research status and provide a useful reference for researchers working on superconducting machines. The adopted superconducting materials, analytical formulae, modelling methods, measurement approaches, as well as reduction techniques for AC loss of low-temperature superconductors (LTSs) and high-temperature superconductors (HTSs) in both low- and high-frequency fields have been systematically analyzed and summarized. Based on the authors’ previous research on the AC loss characteristics of HTS coated conductors (CCs), stacks, and coils at high frequencies, the challenges for the existing AC loss quantification methods have been elucidated, and multiple suggestions with respect to the AC loss reduction in superconducting machines have been put forward. This article systematically reviews the qualitative and quantitative analysis methods of AC loss as well as its reduction techniques in superconductors applied to electrical machines for the first time. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for the future development of superconducting machines and applied superconductivity.

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Double-Deck Metal Solenoids 3D Integrated in Silicon Wafer for Kinetic Energy Harvester

Micromachines ◽

10.3390/mi12010074 ◽

2021 ◽

Vol 12 (1) ◽

pp. 74

Author(s):

Nianying Wang ◽

Ruofeng Han ◽

Changnan Chen ◽

Jiebin Gu ◽

Xinxin Li

Keyword(s):

Kinetic Energy ◽

Power Density ◽

Energy Harvester ◽

High Efficiency ◽

Vibrational Energy ◽

Average Power ◽

Wafer Level ◽

Peak Voltage ◽

Silicon Mold ◽

Casting Technique

A silicon-chip based double-deck three-dimensional (3D) solenoidal electromagnetic (EM) kinetic energy harvester is developed to convert low-frequency (<100 Hz) vibrational energy into electricity with high efficiency. With wafer-level micro electro mechanical systems (MEMS) fabrication to form a metal casting mold and the following casting technique to rapidly (within minutes) fill molten ZnAl alloy into the pre-micromachined silicon mold, the 300-turn solenoid coils (150 turns for either inner solenoid or outer solenoid) are fabricated in silicon wafers for saw dicing into chips. A cylindrical permanent magnet is inserted into a pre-etched channel for sliding upon external vibration, which is surrounded by the solenoids. The size of the harvester chip is as small as 10.58 mm × 2.06 mm × 2.55 mm. The internal resistance of the solenoids is about 17.9 Ω. The maximum peak-to-peak voltage and average power output are measured as 120.4 mV and 43.7 μW. The EM energy harvester shows great improvement in power density, which is 786 μW/cm3 and the normalized power density is 98.3 μW/cm3/g. The EM energy harvester is verified by experiment to be able to generate electricity through various human body movements of walking, running and jumping. The wafer-level fabricated chip-style solenoidal EM harvesters are advantageous in uniform performance, small size and volume applications.

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