High-performance Single-phase Research Articles

Electrochemical investigation of synthesized (Mg0.21Cr0.21Mn0.21Fe0.21Cu0.16)3O4 high entropy oxide for supercapacitor electrode material

Electrochemical investigation of synthesized (Mg0.21Cr0.21Mn0.21Fe0.21Cu0.16)3O4 high entropy oxide for supercapacitor electrode material

Large-Scale Synthesis of High Energy Thermal Battery Cathode Ni0.5Co0.5S2 by a Simple Sintering Technique.

With the synergies of multiple elements, bimetallic sulfides exhibit excellent performance as splendid electrode materials and effective catalysts. However, large-scale synthesis of high-performance single-phase multicomponent sulfides has always been a challenge. Based on thermodynamic calculations, the intermediate phases NiS2 and Co3S4 are devoted to the synthesis of single-phase Ni0.5Co0.5S2. Because the reaction from NiS2 and Co3S4 to Ni0.5Co0.5S2 goes through a lower energy, it thermodynamically contributes to achieving a single-phase structure. Thus, single-phase Ni0.5Co0.5S2 can be simply and quickly prepared by two-step sintering and successfully scalable for mass production. This technique can extend to the whole ingredients Ni1-xCoxS2. Ni0.5Co0.5S2 demonstrates excellent thermal stability and good conductivity. It delivers a specific capacity of 671 mAh·g-1 and a specific energy of 1173 Wh·kg-1 when applied to a thermal battery cathode, which are increased by 18.6% and 25.0%, respectively, compared to pristine NiS2 (566 mAh·g-1) and CoS2 (537 mAh·g-1). This work proposes an innovative sintering method, which is applicable for cost-efficient and large-scale synthesis of single-phase multicomponent sulfides.

Strength and oxidation resistance of Laves phase-containing refractory Nb-Ti-Zr-Cr alloys: Effect of chemical complexity

Strength and oxidation resistance of Laves phase-containing refractory Nb-Ti-Zr-Cr alloys: Effect of chemical complexity

Preparation and Microstructure of Multi-Component High Entropy Alloy Powders Fabricated by Gas Atomization Method

As an attractive high-entropy alloy, AlCrCoNiCu high-entropy alloy has excellent corrosion resistance, wear resistance, and anti-bacterial capabilities, and is considered to be a potential substitute material for marine and nuclear industry materials with great potential. One key to further optimizing the performance of high entropy alloy was to prepare high entropy alloy powder materials with uniform composition, good flow-ability, and stable performance. In this work, the AlCrCoNiCu high entropy alloy powder was prepared by the gas atomization method. The results indicated that the powder was spherical in shape, homogeneous in composition, and composed of a face-center cubic (FCC) phase. After adding Fe and Mn elements, FCC and body-center cubic (BCC) phases appeared and the particle size of the powder was mainly located at 10–50 μm. Furthermore, the larger the particle size was, the more obvious the surface roughness was. With the decreasing powder size, its shape became relatively regular, and the surface roughness decreased. This work provided an experimental and theoretical reference for preparing high-performance single-phase and multi-phase high entropy alloy spherical powders.

Processing of high-performance Co doped Y2O3 as a single-phase electrolyte for low temperature solid oxide fuel cell (LT-SOFC)

The high-performance single-phase semiconductor materials with higher ionic conductivity have drawn substantial attention in fuel cell applications. Semiconductor materials play a key role to enhance ionic conductivity subsequently promoting low temperature solid oxide fuel cell (LT-SOFC) research. Herein, we proposed a semiconductor Co doped Y2O3 (YCO) with different molar ratios, which may easily access the ionic conductivity and electrochemical performances at low operating temperatures. The resulting fabricated fuel cell 10% Co doped Y2O3 (YCO-10) device exhibits high conductivity ∼0.16 S.cm−1 and a higher power density of 856 mW.cm−2 along with 1.10 OCV at 530 °C. The electrochemical impedance spectroscopy (EIS) reveals that YCO-10 electrolyte based SOFC delivers the least ohmic resistance 0.11–0.16 Ω.cm2 at 530-450 °C. Electrode polarization resistance of the constructed fuel cell device reduces from 0.28 Ω.cm2 to 0.59 Ω.cm2 in H2/air environment with the increase of temperature from 450 °C to 530 °C. This work suggests that YCO-10 can be a promising alternative electrolyte, owing to its high performance and enhanced ionic conductivity for LT-SOFC.

Review of Soft-Switching Topologies for Single-Phase Photovoltaic Inverters

Soft switching is one of the effective techniques to improve the efficiency and power density of power electronics converters. This article presents a comprehensive review of the soft-switching topologies used in single-phase photovoltaic (PV) inverters for residential applications. The topologies of single-phase PV inverters are investigated and divided into two types of power conversion stages: the PV interface stage for boosting PV voltage and the grid interface stage for feeding ac power to the grid. The soft-switching topologies for each type of power conversion stage are reviewed and compared, respectively, including the soft-switching mechanisms, efficiency, device ratings, and design challenges. Discussions and recommendations of soft-switching topologies for each stage are also provided. This article is an attempt to provide a helpful reference for engineers working on high-performance single-phase PV inverters.

High Performance Single-Phase Single-Stage Grid-Tied PV Current Source Inverter Using Cascaded Harmonic Compensators

In this paper, a single-phase single-stage photovoltaic (PV) grid-tied system is investigated. The conventional pulse width modulated (PWM) voltage source inverter (VSI) is replaced by a PWM current source inverter (CSI) for its voltage boosting capabilities, inherent short-circuit proof and higher reliability features. Modeling, design, and analysis of the considered CSI are presented altogether with enhanced proposed control loops aided with a modified PWM technique. DC-link even current harmonics are commonly reflected as low-order odd harmonics in the grid resulting in a poor quality grid current. In order to overcome the latter, a high performance proportional resonant controller, applied in the inverter inner grid current loop, is proposed using cascaded resonant control units tuned at low-order frequencies to eliminate injected grid current harmonics. Hence, with a less-bulky smoothing inductor at the CSI DC-side, grid power quality and system efficiency are simultaneously improved. Simulation and experimental results verify the proposed controller effectiveness.

The energy-saving single-phase full-bridge resonant-pole inverter with a single auxiliary switch

ABSTRACTThe topology of the energy-saving single-phase full-bridge resonant-pole soft-switching inverter is proposed to improve the power conversion efficiency of the single-phase full-bridge inverter. The auxiliary circuit is connected with the bridge arm of the inverter and contains only one auxiliary switch and a few passive devices, which is conducive to reducing the hardware cost of the auxiliary circuit and simplifying the control of the auxiliary circuit, so as to improve the reliability and practicability of the inverter. During the operating process of the inverter, the main switch and the auxiliary switch can achieve soft-switching by using the auxiliary circuit, and the energy-saving operation of the inverter can be realised by reducing the switching loss. In this paper, the operating process of the circuit and the realisation condition of the soft-switching are analysed. The experimental results on a single-phase prototype with the rated power of 3 kW show that the switching device can achieve soft-switching, and the efficiency of the prototype at the rated power reaches 98.6%, which lays a theoretical and technical foundation for the further research and development of a new practical high-performance single-phase full-bridge soft-switching inverter.

Superior room-temperature magnetic field-dependent magnetoelectric effect in BiFeO3-based multiferroic

Abstract Multiferroics that exhibit simultaneous electric and magnetic orders have attracted a great deal of interests both in fundamental science and practical applications. In general, high-performance single-phase multiferroics are extremely rare, owing to the incompatibility between ferroelectricity and magnetism. The most interesting property that makes multiferroics useful in device applications is the direct and significant magnetoelectric coupling at room temperature, resulting in a hysteretic magnetoelectric response. However, it still remains a great challenge to realize such a cross-coupling hysteresis loop between the ferroelectric and magnetic orders, i.e. an effective magnetic command of polarization, or an electric-field command of magnetization in a single-phase bulk material. Here we report the multiferroic behavior of chemically modified bismuth ferrite, Bi0.88Dy0.12Fe0.97Ti0.03O3+δ, which exhibits simultaneous (weak) ferromagnetism and ferroelectricity. More interestingly, this solid solution shows an evident magnetoelectric effect at a low magnetic field by demonstrating a hysteretic loop that characterizes the electric voltage signal as a function of bias magnetic field. Moreover, the room-temperature magnetoelectric effect with the saturated magnetoelectric coefficient up to ±0.23 mV/cm•Oe at ±250 Oe is obtained. The observed properties are attributed to the combination of linear magnetoelectric effect and domain wall motion. This result points to potential new applications of single-phase multiferroic materials in spintronic devices in which electric dipoles can be effectively tuned by a magnetic field.

Modified Bridgeless SEPIC Rectifier for Power Factor Correction with Reduced Switch Stress Operating in Continuous Conduction Mode

In this paper, a high performance single-phase modified bridgeless AC–DC converter with reduced switch voltage stress for power factor correction (PFC) is introduced. The proposed converter is based on a single-ended primary-inductance converter (SEPIC) to meet the demands of PFC to unity and output voltage regulation. To reduce the number of components, the input bridge is combined with the SEPIC converter since the conventional SEPIC PFC is suffering with high conduction losses. It offers many advantages, such as fewer semiconductor devices in current flowing path which lead to improve the thermal management, low stress on each component, improved efficiency, high power factor compared to classical converter. Detailed analysis and design equations of the converter are presented. Simulation and experimental results are discussed for a 300[Formula: see text]W prototypeunder the universal input voltage (85–235[Formula: see text]V) to validate the performance of the converter.

A Novel Single-Phase Reactive Current Detection Algorithm Based on Fast Orthogonal Signal Generator and Enhanced Moving Average Filter

This paper developed a novel single-phase reactive current detection algorithm based on fast orthogonal signal generator (OSG) and enhanced moving average filter (MAF), overcoming the limitation of conventional schemes in detection speed, computation burden and noise/harmonic immunity. A fast and accurate OSG scheme is introduced first, which can remarkably improve the precision and response speed of the developed detection scheme. In d-q frame, the enhanced MAF is developed and its optimal design principle is also presented, which can sufficiently eliminate the noise and harmonics while achieve the possible shortest response time, particularly in the case of selective harmonics cancellation. Finally, high-performance single-phase STATCOM control is realized utilizing the proposed method. Experiments reveal that the proposed detection scheme exhibits fast speed, high precision as well as noise/harmonics immunity, providing satisfactory control performances.

Resonant level-induced high thermoelectric response in indium-doped GeTe

Resonant levels are promising for high-performance single-phase thermoelectric materials. Recently, phase-change materials have attracted much attention for energy conversion applications. As the energetic position of resonant levels could be temperature dependent, searching for dopants in phase-change materials, which can introduce resonant levels in both low and high temperature phases, remains challenging. In this study, possible distortions of the electronic density of states due to group IIIA elements (Ga, In, Tl) in GeTe are theoretically investigated. Resonant levels induced by indium dopants in both rhombohedral and cubic phase GeTe have been demonstrated. The experimental Seebeck coefficients of InxGe1−xTe exhibit a large enhancement compared with those observed for other prior dopants. Indium dopants reduce the defect concentrations in GeTe, and thus, they lower the carrier concentrations and suppress the electronic component of the total thermal conductivity. The enhanced Seebeck coefficient, together with the suppressed thermal conductivity, leads to a reasonably high ZT of 1.3 at a temperature near 355 °C in In0.02Ge0.98Te. The corresponding average ZT is enhanced by ~70% across the entire temperature range of the rhombohedral and cubic phases. These observations indicate that indium-doped GeTe is a promising base material for achieving an even higher thermoelectric performance.

Nonstoichiometric (La0.95Sr0.05)xGa0.9Mg0.1O3−δ electrolytes and Ce0.8Nd0.2O1.9–(La0.95Sr0.05)xGa0.9Mg0.1O3−δ composite electrolytes for solid oxide fuel cells

Abstract A-site nonstoichiometric electrolytes (La0.95Sr0.05)xGa0.9Mg0.1O3−δ (LSGM, x = 0.97, 1.00, 1.03), and their composites Ce0.8Nd0.2O1.9 (NDC)–LSGM, were synthesized and investigated. The nonstoichiometry efficiently enhanced the total conductivity of LSGM electrolyte, and the A-site deficient composition showed the highest total conductivity above 550 °C (σt,LSGM(x=0.97) = 0.880 S m−1 > σt,LSGM(x=1.03) = 0.808 S m−1 > σt,LSGM(x=1.00) = 0.582 S m−1 at 600 °C). The cubic fluorite and perovskite structures were adopted by all the composites. The LSGM additive significantly promoted the grain growth of the composite electrolyte. The grain boundary conductivities of the composite electrolytes were more or less 5–10 times higher than that of NDC electrolyte at 500 °C. The optimum A-site nonstoichiometry was found to be x = 0.97 in composite electrolytes. This study provides a possible route to design high performance single phase or composite electrolytes for SOFCs.

High Reliability and Performance PWM Inverter for Standalone Microgrids

In this paper a high reliability and performance single-phase PWM inverter for standalone microgrids is presented. To obtain the before mentioned characteristics this work propose, two different controller structures and a straightforward design methodology for these controllers, based on the internal model principle. In order to validate the proposed design methodology, digital controllers and to demonstrate the steady state and transient performance, experimental results are presented from a 5kVA PWM modulated single phase inverter, fully controlled by a DSP TMS320F2407.

Direct AC-AC Step-Down Single-Phase Converter with Improved Performances

The paper presents two high-performance single-phase AC chopper circuits which perform AC-AC bidirectional direct conversion;one of them contains resistive loads and the other one is for inductive loads. It includes useful equations for chopper design. The correctfunctioning is tested by simulation.DOI: http://dx.doi.org/10.5755/j01.eee.18.10.1305

비선형 부하에서 커패시터 전류 궤환을 통한 고성능 UPS 설계

This paper presents a digital control solution to process capacitor current feedback of high performance single-phase UPS for non-linear loads. In all UPS the goal is to maintain the desired output voltage waveform and RMS value over all unknown load conditions and transient response. The proposed UPS uses instantaneous load voltage and filter capacitor current feedback, which is based on the double regulation loop such as the outer voltage control loop and inner current control loop. The proposed DSP-based digital-controlled PWM inverter system has fast dynamic response and low total harmonic distortion (THD) for nonlinear load. The control system was implemented on a 32-bit Floating-point DSP controller TMS320C32 and tested on a 5[KVA] IGBT based inverter switching at 11[Khz]. The validity of the proposed scheme is investigated through simulation and experimental results.

A High-Performance Single-Phase Bridgeless Interleaved PFC Converter for Plug-in Hybrid Electric Vehicle Battery Chargers

In this paper, a new front end ac-dc bridgeless interleaved power factor correction topology is proposed for level II plug-in hybrid electric vehicle (PHEV) battery charging. The topology can achieve high efficiency, which is critical for minimizing the charger size, PHEV charging time and the amount and cost of electricity drawn from the utility. In addition, a detailed analytical model for this topology is presented, enabling the calculation of the converter power losses and efficiency. Experimental and simulation results are included for a prototype boost converter converting universal ac input voltage (85-265 V) to 400 V dc output at up to 3.4 kW load. The experimental results demonstrate a power factor greater than 0.99 from 750 W to 3.4 kW, THD less than 5% from half load to full load and a peak efficiency of 98.9% at 70 kHz switching frequency, 265 V input and 1.2 kW load.

New method for preparation of luminescent lanthanide materials BaMoO4:Eu3+

<title/>A new solid state synthesis method, called the high temperature ball milling (HTBM) method, was developed for the production of high performance single phase BaMoO4:Eu3+ phosphor powders. In this work, X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques and emission spectra test were used to characterise the obtained phosphor powders. Compared with chemical precipitation method often employed for the synthesis of phosphors interested, the HTBM method not only decreased the solid synthesis temperature from 1000 to 600°C, but also enhanced the emission intensity of yielded phosphors in the red light region by 48%. Additionally, BaMoO4:Eu3+ red phosphor powders produced by the HTBM method have relatively small and more uniform particle sizes. The HTBM method thus opens a new path to solid state synthesis, especially for the materials difficult to obtain at low temperature.

A research to high-performance multi-level single-phase AC/DC power factor correct switching converter

This letter studies and analyzes the working features of main circuit of tri-level boost Power Factor Correct (PFC) converter and the advantages of tri-level switch converter in aspects of bearing high-voltage of power components, overall system loss and magnetic component selection based upon the single-level boost PFC switch converter. Besides, relying on the application of microprocessor in power converter technology and DSP (Digital Signal Processing) chip’s strong calculating capacity, the letter presents the adoption of modified scheme of tri-level boost PFC converter under the control of predictive control algorithm. Moreover, the operating principle and control method are specified, the results of circuit test and analysis are provided and the advantages of predictive control technology-based multi-level boost PFC converter is verified.

High-Performance Transformerless Online UPS

In this paper, a high-performance single-phase transformerless online uninterruptible power supply (UPS) is proposed. The proposed UPS is composed of a four-leg-type converter, which operates as a rectifier, a battery charger/discharger, and an inverter. The rectifier has the capability of power-factor collection and regulates a constant dc-link voltage. The battery charger/discharger eliminates the need for the transformer and the increase of the number of battery and supplies the power demanded by the load to the dc-link capacitor in the event of the input-power failure or abrupt decrease of the input voltage. The inverter provides a regulated sinusoidal output voltage to the load and limits the output current under an impulsive load. The control of the dc-link voltage enhances the transient response of the output voltage and the utilization of the input power. By utilizing the battery charger/discharger, the overall efficiency of the system is improved, and the size, weight, and cost of the system are significantly reduced. Experimental results obtained with a 3-kVA prototype show a normal efficiency of over 95.6% and an input power factor of over 99.7%.