Low Power Loss Research Articles

Microwave heating of thin rubbers based on single-ridged waveguide

Microwave heating has been gradually applied to rubber vulcanization. However, it is difficult to process thin rubber using microwaves because of low electromagnetic power loss and rapid heat dissipation. Therefore, in this study, a single-ridged waveguide was designed to efficiently heat thin rubber. First, a single-ridged waveguide was designed and optimized to ensure good wave transmission and a strong electric field, and its energy efficiency was approximately 331.9 times greater than that of multi-mode cavity and 77.9 times greater than that of WR340. Then, a multiphysics model coupling the electromagnetic field and heat transfer in a solid was built to investigate the heating performance. The results of additional experiments showed that the experimental and simulated temperature distributions were consistent. Finally, the effects of the working state, offset of the short-circuited surface, the rubber's thickness and permittivity on the heating performance were investigated, and the vulcanization analyses were discussed.

Improved GaN-based Current Aperture Vertical Electron Transistor (CAVET)

The objectives of this research are to improve and optimize a vertically structure HEMT device based on AlGaN/GaN heterojunctions. This novel proposed structure with double gate command would allow for a better dispersion of the electric field, with peaks lower and farther from the surface than a lateral structure. The research focuses on estimating the performance of a GaN-based vertical structure called a "Current Aperture Vertical Electron Transistor (CAVET)" that combines a two-dimensional electron gas (2DEG) and a vertical structure with technology, operation, settings, and performance that can be seen in power applications. Performance operating at high frequencies and low power loss consumer, a device that will, therefore, lead function to best in electrical power and higher system efficiency with IDss equal 0.95 A, -6 V for pinch-off, fT/fMax are 110/250 GHz and 14 % for Drain-lag.

Design optimization of a stepped HTS magnet for electrodynamic suspension train

High-temperature superconducting (HTS) magnets are promising candidates for transportation and power systems, such as the electrodynamic suspension (EDS) train, ultra-high field magnet and magnetic resonance imaging, because of their large current-carrying capacity and low power loss. The critical current depending on magnetic flux density is an essential factor in assessing the application performance of HTS magnets. As usual, the existing HTS magnet is wound with rectangular cross-section, which results in magnetic field concentration inside winding. In this paper, we propose a novel HTS magnet structure with stepped cross-section to alleviate the magnetic field concentration, and resultantly improve the critical current. From this point, this paper aims to design and optimize a stepped HTS magnet with the critical current maximized. Firstly, the structure design of the stepped HTS magnet is performed with a consideration of the application scenario of EDS train. Then, the critical current of the HTS magnet is estimated with a homogenized self-consistent model. Afterwards, an HTS magnet with stepped cross-section is optimized, fabricated and finally tested. The critical current was experimentally measured to verify the simulation results, followed by the electromagnetic investigations of the stepped HTS magnet in the EDS train.

Analysis of component current stresses of grid-forming converters for two-phase three-wire isolated AC power grids

Isolated ac grids are feasible solutions to energize remote communities usually based on renewables and batteries, interfaced by power electronics converters that require high reliability. The key element of such a system is the grid-forming converter witch provides voltage magnitude and frequency. This paper compares the current stresses of grid-forming converters under an isolated grid mission profile, considering three different grid configurations in terms of line voltage displacement angles: 90° (αβn-system); 120° (abn-system) and 180° (xyn-system). Besides, analytical expressions for the current stress through the semiconductors and the dc-link capacitor are proposed for each system. The lifetime analysis of the grid-forming converter indicates that the xyn-system has the lowest wear-out. Furthermore, this work highlights the influence of high-frequency components on the rms dc-link capacitor current. The xyn-system demonstrates a lower probability of capacitor failure compared to the other system, even presenting higher low-frequency. components. Finally, a sensitivity analysis shows that the grid-forming converter in xyn-system can increase its output power in 12% or reduce its heatsink volume in 25% to achieve the same wear-out B10 lifetime as the abn-system (i.e., benchmark) under nominal conditions. An experiment is conducted using a full-bridge converter to measure the power losses in the semiconductors and the case temperature of the IGBTs. The xyn converter shows 44% lower power losses, and the abn converter shows 18% lower power losses, both compared with the αβn converter.

Impact of parasitic elements on the power dissipation of Si superjunction MOSFETs, SiC MOSFETs, and GaN HEMTs

In power conversion systems, where higher switching frequencies are required for miniaturization, the selection of power switches with lower power loss becomes essential for achieving better efficiency. At higher switching frequencies, the parasitic elements of the power switch largely dictate the efficiency of the power electronic system. Hence, it becomes critical to investigate the impact of parasitic losses on overall efficiency. The parasitic components of the power transistor vary with the semiconductor technology and thus effects the power converter system differently. This paper compares three power switch technologies: Silicon (Si) based Superjunction (SJ) power MOSFET, Silicon Carbide (SiC) based power MOSFET, and Gallium Nitride (GaN) based HEMT, for three different voltage ratings: 650 V, 900 V, and 1200 V. The effect of the parasitic components on the converter efficiency has been demonstrated using an inductive clamped loading circuit implemented in LTSPICE. The results demonstrate that at a frequency of 200 kHz, the total power loss for 650 V power switches was 44 W, 108 W, and 127 W for GaN, SiC, and SJ, respectively. At 500 kHz, the total power loss for 1200 V power switches was 622 W and 720 W for GaN and SiC, respectively. Overall, the GaN technology provides lower power losses than SiC and SJ due to lower parasitic capacitance and on-resistance, indicating the potential of GaN power devices for higher voltage applications. This comparison enables a power engineer to select an appropriate power switch that ensures the best possible efficiency for a specific application.

Very-High-Frequency Resonant Boost Converter With Wide Output Power Range and Synchronous Drive

This paper presents a new resonant boost dc-dc converter suitable for operation at very high frequency (VHF). It consists of a series-parallel Class E inverter and a conventional Class E rectifier. The series-parallel Class E inverter operated alternately in series and parallel manner can achieve higher ac voltage, while the rectifier is responsible for forming a dc voltage to supply to the load. Whilst improving the voltage boosting capability and output power range, the proposed converter also has simpler drive structure with synchronous drive method. Compared with the existing VHF converters, the boost factor of the proposed inverter stage is increased to 2.06, which results in lower switching current stress and power losses for its converter. This is beneficial to select switching components and improve the power density. The analysis, simulation and experiment indicate that the proposed converter is suitable for wide output power range applications, such as wireless power transmission and renewable energy source. Finally, its feasibility and performance are also experimentally evaluated by a 30MHz prototype with rated power of 20W, and its measured efficiency as well as voltage gain are up to 80.1% and 2.81, respectively.

Dual Converter Operating With Floating Capacitors Connecting Open-End Winding Doubly-Fed Induction Generator to the DC Microgrid

This paper presents a novel configuration to connect a three-phase doubly-fed induction generator (DFIG) to the dc microgrid. The proposed topology connects an uncontrolled con- verter and a full-controlled converter in series with the generator stator windings in an open-end winding (OEW) configuration. The full-controlled converter is connected to an independent dc link based on floating capacitors. The paper discusses the converter operating principles, pulse-width modulation (PWM), DFIG power control, and the floating capacitors' voltage reg- ulation. The work compares the proposed and conventional systems regarding current harmonic distortions, torque ripple, and semiconductor losses. Simulations and experiments show steady-state and transient results for a 0.56-kW DFIG operating at the rated power. Finally, it was verified that the proposed topology presents lower power losses and low-distorted voltages and currents over the DFIG stator windings.

Efficient Wireless Power Transfer Topology for Phone Charging Application

Abstract: Wireless power transfer scheme used on phone chargers are expected to have high efficiency, and reliability. However, existing AC-DC converter schemes were shown to be susceptible to leakage inductance and have lower regulation or excessive power losses. Output voltage regulation is a concern for wireless power converter topologies due to the need for additional shunt devices at DC output. In this paper, literature survey on various wireless power transfer scheme is performed with specific focus on phone charging applications. A modified topology using impedance matching transformer is presented with circuit analysis and LT spice simulation results. It is shown that the proposed topology can deliver better output voltage regulation at various coupling coefficients indicating a superior circuit performance for various separation distances between transmitting and receiving coil.

Impact of Distributed Generation on the Effectiveness of Electric Distribution System Reconfiguration

Distribution system reconfiguration (DSR) is an essential activity in the operation of distribution utilities, usually carried out to lower active power losses and improve reliability metrics. The insertion of distributed generation (DG) units in electric power distribution systems (EPDS) causes the rearrangement of power flows through the conductors and changes the real power losses and voltage profile; therefore, up to a certain point, the insertion of certain quantities of DG may potentially delay or change the reconfiguration strategy of EPDS. This article presents an analysis of the impact of DG, for different locations of the units and different levels of active power supplied by them, on real power losses and on the effectiveness of DSR. The article presents tests with different distribution systems with varying sizes and topologies, showing that the allocation of DG units in buses far from the substation provided the best cost–benefit results. The DSR impact changes depending on the installment location and the generation level of the DG units, corroborating that DSR must be considered and performed using certain criteria, to maximize its efficiency.

Polycrystalline silicon 2 × 2 Mach-Zehnder interferometer optical switch.

In this paper, we demonstrate a broadband Mach-Zehnder interferometer optical switch based on polycrystalline silicon (poly-Si), which enables the development of multilayer photonics integrated circuits. The poly-Si is deposited under a low temperature of 620 °C to avoid unexpected thermal stress and influence on optoelectronic performance. By introducing a π/2 phase shifter and a push-pull configuration, the switch achieved low power consumption and loss caused by carrier plasma absorption (CPA). The switch operates effectively in both "Bar" and "Cross" states at voltages of -3.35 V and 3.85 V. The power consumptions are 7.98 mW and 9.39 mW, respectively. The on-chip loss is 5.9 ± 0.4 dB at 1550 nm, and the crosstalk is below -20 dB within the C-band. The switch exhibits a 10%-90% rise time of 7.7 µs and a 90%-10% fall time of 3.4 µs at 1550 nm. As far as we know, it is the first demonstration of a poly-Si switch on an 8-inch wafer pilot-line. The low-temperature deposited poly-Si switch is promising for multilayer active photonic devices and photonic-electronic applications.

Smart home charging of electric vehicles using a digital platform

As the penetration of electric vehicles (EVs) grows, it is important to understand the implications of home charging technologies for grid operations and for the budget of users. We conduct an empirical study analyzing data on 438 EVs over a period of 3,687 consecutive hours, collected by an energy aggregator which operates a digital platform. We first develop an optimization model to compute an optimal schedule of charging for all EVs in the dataset at minimum cost. Then, we compare the realizations against this optimal solution, distinguishing householders who use a smart charging functionality of the digital platform from those who do not use it. Our findings indicate that the smart charging behaviour conduces to better results, and close to the optimal solution. The non-users tend to start charging as soon as they plug-in their EVs, often at peak consumption times. In contrast, the smart charging strategy usually shifts the charging schedules towards times where the consumption is cheaper and the grid is less congested, facilitating a higher load factor and lower power losses. These results highlight the positive role of energy aggregators and digital platforms in coordinating users to lower the cost and enhance efficiency of energy consumption.

Innovative Methodologies for Higher Global MPP of Photovoltaic Arrays under PSCs: Experimental Validation

Partial shading conditions (PSCs) are responsible for the root causes of photovoltaic (PV) system performance deprivation such as hotspots (damaged PV cells), mismatch power losses and multiple power maxima. Recently, PV array reconfiguration strategies have proven to be beneficial in improving PV system performance and achieving improved shade dispersion properties. This research analyzes the improved Su-Do-Ku (I-SDK) PV array configuration in order to counteract the shading effect. This approach implements a 6 × 6 size PV array configuration and performance evaluation under different realistic shading scenarios. The performance of the I-SDK configuration is assessed and compared to that of the total-cross-tied (TCT) and Su-Do-Ku (SDK) arrangements. The performance indices such as power loss (PL), power at global maximum power point (GMPP), fill-factor (FF), performance ratio (PR), power enhancement (PE) and execution ratio (ER) are analyzed to show comprehensive comparison. An experimental analysis confirms the MATLAB/Simulink findings, demonstrating that the I-SDK configuration outperforms both the TCT and SDK array setups. The GMPP values of 143.5 W, 141.7 W, 138.1 W and 129.3 W also show the superiority of I-SDK during four shading instances compared to conventional SP, TCT, SDK and SM arrangements. Moreover, under similar PSCs, higher %FF (74.61%, 76.10%, 77.1%, 75.92%) and lower PL (36.7 W, 38.5 W, 42.1 W, 50.9 W) support the adoptability of I-SDK for experimental validation/commercial viability.

Multi-Objective Location Method for Small Capacity Distributed Generation under Timing Characteristics

The conventional multi-objective location method of distributed generation mainly uses the static stability index to determine the load of distributed generation, which is vulnerable to the impact of load timing characteristics, resulting in a high active power loss of different nodes. Therefore, it is necessary to design the multi-objective location method of small-capacity distributed power sources based on the timing characteristics. That is, the multi-objective location algorithm of small capacity distributed generation is designed based on the multi-objective function, and the multi-objective location model of small capacity distributed generation is constructed according to the timing characteristics to achieve the multi-objective location of small capacity distributed generation. The experimental results show that the designed multi-objective location method has low active power loss, which proves that the designed location method has good location effect, energy saving and certain application value, and has made a certain contribution to saving the comprehensive operation cost of distributed power generation.

Microstructure, magnetic, and power loss characteristics of low‐sintered NiCuZn ferrites with La2O3‐Bi2O3 additives

AbstractLow‐temperature‐sintered Ni0.5Cu0.125Zn0.375Fe1.98O4 ferrites co‐added with x wt% (x = 0.00‐0.25 wt%) La2O3 and 0.25 wt% Bi2O3 were successfully prepared via conventional solid‐phase reaction method. The phase composition, microstructure, magnetic properties, and especially power loss variation of the samples were systematically studied. The results showed that all samples possessed a single spinel phase structure at a sintering temperature of 900°C, exhibiting high degree of densification and uniform grains. The appropriate amount of La2O3 additive improved the saturation flux density and permeability of NiCuZn ferrites, simultaneously reducing the coercivity and power loss. The maximum permeability and the lowest power loss were achieved at x = 0.15 wt%. The corresponding sample had the homogeneous microstructure and excellent magnetic properties, being a promising low‐temperature co‐fired ferrite candidate for magnetic power components.

Multi‐input multi‐output converter for simultaneous buck and boost voltage conversion

SummaryInternet of Things (IoT) devices, portable electronics, and electric vehicle (EV) accessories have increased the need for DC power distribution with various outputs. Multiport converters (MPCs) handle numerous inputs and loads with fewer components, low power losses, and less cost. Most multi‐input converters are time‐shared and restrict the duty cycle's working range, limiting energy sources and output voltage. Single‐input multi‐output (SIMO) converters have inductor current and duty cycle limits. In this study, a dual‐input dual‐output (DIDO) converter is proposed to overcome the limitations mentioned above. It can operate multiple loads without restrictions on charging inductor currents and cross‐regulation problems. Any variations will not influence the proposed converter's output voltage VO1 (VO2) by the load current iO2 (iO1). To verify the feasibility of the proposed configuration, a 250 W laboratory prototype has been developed, and experimental results are validated.

Design and analysis of normally-off GaN-HEMT using β-Ga2O3 buffer for low-loss power converter applications

An enhancement mode HETM with β-Ga2O3 buffer is proposed, and its electrical characteristics are analyzed using the physics-based numerical simulator ATLAS TCAD. HEMT with p-GaN/AlGaN/GaN/β-Ga2O3 utilized for normally-off mode operation of HEMT. The proposed β-Ga2O3 buffer based HEMT in this work reveals low on-resistance (Ron), high drain current density (IDS,max), high transconductance (gm,max), excellent breakdown voltage (VBR) and low gate switching delay. The ultra-wide bandgap β-Ga2O3 (EG ∼ 4.7 eV) buffer on silicon carbide (SiC) substrate HEMT mitigates the interface-related traps due to nearly lattice match with GaN and suppressing buffer leakage current by serving as a natural back-barrier. This β-Ga2O3 back-barrier structure increases the 2DEG (two-dimensional electron gas) and mitigates buffer leakage currents. Numerical simulation shows IDS,max of 0.95 A/mm, Ron of 4.26 Ω mm, and VBR of 835 V. for LG = 0.8 μm HEMT. The excellent device characteristics indicate the merits of β-Ga2O3 buffer-based normally-off HEMT for medium voltage range (<800 V) low resistive loss power converters applications.

A 28-GHz 26.8-dBm Doherty Power Amplifier With Four-Way Differential Hybrid Load- Modulated Combiner in 55-nm CMOS

This letter presents a 28-GHz high-power four-way differential Doherty power amplifier (PA) in 55-nm bulk CMOS technology. A transformer-based hybrid load-modulated combiner (HLMC) (i.e., a parallel combined series-load-modulated Doherty output network) is proposed to simultaneously achieve high output power, low-loss power combining, and a true-Doherty load modulation. Meanwhile, the closed-form expressions of the proposed combiner are derived. The measured results of the proposed Doherty PA demonstrate a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm{sat}}$</tex-math> </inline-formula> of 26.8 dBm, an output 1-dB compression point (OP1dB) of 25.2 dBm, a peak power added efficiency (PAE) of 26.7%, and 19.2% PAE at 6-dB power back-off (PBO) at 28 GHz. The PA is also tested with 400-MSym/s 64-quadrature amplitude modulation (QAM) signals, and it achieves 17.9-dBm average output power with 14.1% average PAE at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 26.2-dB error vector magnitude (EVM).

Developing High-Power-Density Electromagnetic Devices with Nanocrystalline and Amorphous Magnetic Materials

With the increasing demand for smaller, lighter, and more affordable electromagnetic devices, there is a growing trend toward developing high-power-density transformers and electrical machines. While increasing the operating frequency is a straightforward approach to achieving high power density, it can lead to significant power loss within a limited volume, resulting in excessive temperature rise and device degradation. Therefore, it is crucial to design high-power-density electromagnetic devices that exhibit low power loss and efficient thermal dissipation to address these challenges. Advanced techniques, such as the utilization of novel and advanced electromagnetic materials, hold great promise for overcoming these issues. Specifically, nanocrystalline and amorphous magnetic materials have emerged as highly effective solutions for reducing power loss and increasing efficiency in electromagnetic devices. This paper aims to provide an overview of the application of nanocrystalline and amorphous magnetic materials in transformers and electrical machines, along with key technologies and the major challenges involved.

A New Efficient Cuckoo Search MPPT Algorithm Based on a Super-Twisting Sliding Mode Controller for Partially Shaded Standalone Photovoltaic System

The impact of Partial Shading Conditions (PSCs) significantly influences the output of Photovoltaic Systems (PVSs). Under PSCs, the Power-Voltage (P-V) characteristic of the PVS unveils numerous power peaks, inclusive of local maxima and a global maximum. The latter represents the optimum power point. Traditional Maximum Power Point Tracking (MPPT) algorithms struggle to track the Global Maximum Power Point (GMPP). To address this, our study emphasizes the creation of a novel algorithm capable of identifying the GMPP. This approach combines the Cuckoo Search (CS) MPPT algorithm with an Integral Super-Twisting Sliding Mode Controller (STSMC) using their benefits to enhance the PVS performance under PSCs in terms of high efficiency, low power losses, and high-speed convergence towards the GMPP. The STSMC is a second-order Sliding Mode Control strategy that employs a continuous control action that attenuates the “chattering” phenomenon, caused when the first-order SMC technique is employed. Indeed, the proposed CS-STSMC-MPPT algorithm consists of two parts. The first one is based on the CS algorithm used for scanning the power-voltage curve to identify the GMPP, and subsequently generating the associated optimal voltage reference. The second part aims to track the voltage reference by manipulating the duty cycle of the boost converter. The proposed CS-STSMC-MPPT algorithm is featured by its strength against uncertainties and modeling errors. The obtained simulation results underline a high convergence speed and an excellent precision of the proposed method in identifying and tracking the GMPP with high efficiency under varying shading scenarios. For comparative purposes, this method is set against the hybrid CS-Proportional Integral Derivative, the conventional CS, the Particle Swarm Optimization, and the Perturb and Observe algorithms under different PSCs, including zero, weak, and severe shading. Simulation conducted in the Matlab/Simulink environment confirms the superior performance of the proposed CS-STSMC-MPPT algorithm in terms of precision, convergence speed, efficiency, and resilience.

High-performance FeSiAl soft magnetic composites achieved by confined solid-state reaction

Soft magnetic composites (SMCs) consisting of insulated metallic magnetic particles are critical materials in modern electronics. However, the simultaneous optimization of power loss and permeability for SMCs remains challenging due to the vulnerable insulation layer inside. Here, we succeed in fabricating FeSiAl SMC by confined solid-state reaction between TiO2 and FeSiAl matrix, which leads to the formation of homogeneous and lattice-matched Al2O3 layer and brings about effective electrical insulation of FeSiAl particles. TiO2 can progressively release O atoms and confine the solid-state reaction strictly within the interfacial region. Meanwhile, itself becomes ferromagnetic with deficient oxygen, resulting in alleviated magnetic dilution. Fast domain wall displacement and small hysteresis loss are directly observed by in-situ Lorenz transmission electron microscopy. The obtained FeSiAl SMC exhibits low power loss of 130 mW·cm−3 (50 mT, 100 kHz) and high effective permeability of 143, which is desired in energy-saving and high-efficiency devices. This work relates the interfacial behavior with magnetic properties and highlights a new strategy for fabricating high-performance SMCs.