Electromagnetic Power Research Articles

Bulk Motions in the Black Hole Jet Sheath as a Candidate for the Comptonizing Corona

Abstract Using two-dimensional general relativistic resistive magnetohydrodynamic simulations, we investigate the properties of the sheath separating the black hole jet from the surrounding medium. We find that the electromagnetic power flowing through the jet sheath is comparable to the overall accretion power of the black hole. The sheath is an important site of energy dissipation as revealed by the copious appearance of reconnection layers and plasmoid chains. About 20% of the sheath power is dissipated between 2 and 10 gravitational radii. The plasma in the dissipative sheath moves along a nearly paraboloidal surface with transrelativistic bulk motions dominated by the radial component, whose dimensionless 4-velocity is ∼1.2 ± 0.5. In the frame moving with the mean (radially dependent) velocity, the distribution of stochastic bulk motions resembles a Maxwellian with an “effective bulk temperature” of ∼100 keV. Scaling the global simulation to Cygnus X-1 parameters gives a rough estimate of the Thomson optical depth across the jet sheath, ∼0.01–0.1, and it may increase in future magnetohydrodynamic simulations with self-consistent radiative losses. These properties suggest that the dissipative jet sheath may be a viable “coronal” region, capable of upscattering seed soft photons into a hard, nonthermal tail, as seen during the hard states of X-ray binaries and active galactic nuclei.

High-efficiency analysis of electromagnetic-thermal effects for absorbing honeycomb based on transformation optics.

Wave-absorbing honeycombs have garnered widespread attention due to their high-efficiency absorption, ultra-wideband absorption, lightweight nature, and high load-carrying capacity. However, as electromagnetic radiation power increases, the temperature of the absorbing honeycomb increases rapidly, even leading to burning. Therefore, it is significant to possess an efficient and accurate assessment of the thermal effects of absorbing honeycombs under electromagnetic radiation. However, the complex thin-walled structure of the honeycomb increases computational complexity, resulting in time-consuming, resource-intensive, and occasionally unsolvable actions. To address this issue, we implement transformation optics to expand the thin-walled structure and reconstruct the transformed electromagnetic and thermal property parameters. The transformed electromagnetic-thermal coupling simulation results were highly consistent with the actual model. Specially, the mesh count dropped from 272,717 to 17,621, the simulation time decreased from 15,792s to 242s, and the efficiency was improved by 65 times. The proposed methodology overcomes analysis difficulties on multi-scale complex structures, making it possible to analyze the honeycomb structures that traditional methods cannot handle.

INFLUENCE OF MICROWAVE ACTIVATION OF COAL ON ITS PETROGRAPH-IC PROPERTIES

Despite the development of renewable sources, coal occupies an important place in the energy balance of many countries, especially those with large reserves. One of the ways to influence the characteristics of coal and add specified properties to it is its preliminary microwave activation. As a result of the studies, it was found that with microwave activation with an electromagnetic field power of 750 W for 240 s, an ambiguous effect on the characteristics of coal samples is observed, namely, coal with R0 greater than 1.16 before activation, microwave activation occurs faster, while the vitrinite reflectivity increases to 1.58 %, the yield of volatile substances and the thickness of the plastic layer decrease. Coals of a high stage of metamorphism are activated faster due to a denser structure. The presence of a more ordered structure than less metamorphosed coals, during the activation process, the condensed carbon layers come closer together, which ultimately increases their metamorphism stage. On the contrary, for coal with R0 less than 1.03 before activation, microwave activation is slower, while the vitrinite reflectance index decreases to 0.75 %, the yield of volatile substances and the thickness of the plastic layer increase. Obviously, this is due to the fact that coal of a low metamorphism stage is characterized by a less dense structure and more time is needed for its activation. Also, to increase the metamorphism stage, it is necessary to apply more energy so that the formed radicals and structural units connect with each other and form an ordered aromatic structure. Therefore, for coals of a low metamorphism stage, the activation time should be longer. The research results indicate the possibility of changing the coal metamorphism stage, which will increase the efficiency of coal processing processes, reduce energy costs and minimize harmful emissions due to the use of microwave technologies. In addition, the use of microwave activation can expand the raw material base for various coal technologies, especially in conditions of fuel shortage.

An Advanced High Power Electromagnetic Pulse Generator with High Repetition Frequency

Abstract In this paper, an electromechanical pulse power source with repetitive frequency based on piezoelectric ceramic array and miniature plasma diode is introduced, which drives the piezoelectric ceramic array with an electromechanical system to generate a high-voltage pulse, which can generate strong electromagnetic radiation power after interacting with the gaseous medium plasma in the miniature plasma diode. This pulse power source can produce high output energy gain by using low-power DC power supply, and the pulse repetition frequency can be electronically adjusted by adjusting the motor speed. This pulse power source also has the advantages of compact structure and low cost, with a wide range of application prospects.

Dynamics and control of marine mechatronic oscillators using electromagnetic coupling and switching power electronics

Dynamics and control of marine mechatronic oscillators using electromagnetic coupling and switching power electronics

A Rotating Tidal Current Controller and Energy Router Siting and Capacitation Method Considering Spatio-Temporal Distribution

As the proportion of new energy access increases year by year, the resulting energy imbalance and voltage/trend distribution complexity of the distribution network system in the spatio-temporal dimension become more and more prominent. The joint introduction of electromagnetic rotary power flow controller (RPFC) and energy router (ER) can improve the high proportion of new active distribution network (ADN) consumption and power supply reliability from both spatial and temporal dimensions. To this end, the paper proposes an ADN expansion planning method considering RPFC and ER access. A two-layer planning model for RPFC and ER based on spatio-temporal characteristics is established, with the upper model being the siting and capacity-setting layer, which takes the investment and construction cost of RPFC and ER as the optimization objective, and the lower model being the optimal operation layer, which takes the lowest operating cost of the distribution network as the objective. The planning model is solved by a hybrid optimization algorithm with improved particle swarm and second-order cone planning. The proposed planning model and solving algorithm are validated with the IEEE33 node example, and the results show that the joint access of RPFC and ER can effectively improve the spatial-temporal distribution of voltage in the distribution network and has the lowest equivalent annual value investment and operation cost.

Modeling of Liquefied Natural Gas Cold Power Generation for Access to the Distribution Grid

Cold energy generation is an important part of liquefied natural gas (LNG) cold energy cascade utilization, and existing studies lack a specific descriptive model for LNG cold energy transmission to the AC subgrid. Therefore, this paper proposes a descriptive model for the grid-connected process of cold energy generation at LNG stations. First, the expansion kinetic energy transfer of the intermediate work mass is derived and analyzed in the LNG unipolar Rankine cycle structure, the mathematical relationship between the turbine output mechanical power and the variation in the work mass flow rate and pressure is established, and the variations in the LNG heat exchanger temperature difference, seawater flow rate, and the turbine temperature difference in the cycle system are investigated. Secondly, based on the fifth-order equation of state of the synchronous generator, the expressions of its electromagnetic power, output AC frequency, and voltage were analyzed. Finally, the average equivalent models of the machine-side and grid-side converters are established using a direct-fed grid-connected structure, thus forming a descriptive model of the overall drive process. The ORC model is built in Aspen HYSIS to obtain the time series expression of the torque output of the turbine; based on the ORC output torque, the permanent magnet synchronous generator (PMGSG) as well as the direct-fed grid-connected structure are built in MATLAB/Simulink, and the active power and current outputs of the grid-following-type voltage vector control method and the grid-forming-type power-angle synchronous control method are also verified.

A 2.4 GHz High-Efficiency Rectifier Circuit for Ambient Low Electromagnetic Power Harvesting.

A novel 2.4 GHz high-efficiency rectifier circuit suitable for working under very-low-input electromagnetic (EM) power conditions (-20 to -10 dBm) is proposed for typical indoor power harvesting. The circuit features a SMS7630 Schottky diode in a series with a voltage booster circuit at the front end and a direct-current (DC)-pass filter at the back end. The voltage booster circuit consists of an asymmetric coupled transmission line (CTL) and a high-impedance microstrip line (of 100 Ω instead of 50 Ω) to significantly increase the potential at the diode's input, thereby enabling the diode to operate effectively even in very-low-power environments. The experimental measurements show that the microwave direct-current (MW-DC) conversion efficiency of the rectifier circuit reaches 31.1% at a -20 dBm input power and 62.4% at a -10 dBm input power, representing a 7.4% improvement compared to that of the state of the art. Furthermore, the rectifier circuit successfully shifts the input power level corresponding to the peak rectification efficiency from 0 dBm down to -10 dBm. This design is a promising candidate for powering low-energy wireless sensors in typical indoor environments (e.g., the home or office) with low EM energy density.

Self-powered human movement measurement with a unidirectional ratchet driven wearable energy harvester

A large amount of energy is generated during human movement which is mostly not effectively utilized. To collect human movement energy and utilize it rationally, a wearable piezoelectric-electromagnetic energy harvester (WPEEH) driven by a unidirectional ratchet is proposed, which adopts the principle of up-conversion to convert mechanical energy into electrical energy. The electromagnetic power generator unit is used to obtain energy to power the sensing circuit, while piezoelectric generator unit can be used for both energy generation and self-powered sensing. A spring push rod and a ratchet structure are used to convert the swinging of the human limb into the unidirectional rotation of the device to enhance its energy harvesting efficiency. The theoretical model of the WPEEH is established, and the experimental test platform is built. The results show that the WPEEH is able to generate a maximum power of 17.2 mW at an oscillation frequency of 1.5 Hz. In the actual wearable test, the proposed energy harvester is able to supply the harvested energy to the low-power electronic devices through capacitors, and it enables to light up 42 LEDs as well as to drive the digital thermo-hygrometer to work continuously and stably. Apart from having excellent properties of a high output power and low drive frequency, the proposed energy harvester also exhibits a high energy density (7.1 × 10–5 W/cm3). What’s more, the speed of human movement can be predicted and calculated for different individuals by testing the results of the swing frequency with a maximum error of 2.71 %. The investigation proves that the proposed WPEEH can measure human movement and has great potential in the field of power supply for low-power electronic devices.

Research on Decoupling Duty Cycle Optimization Control Method of a Multiport Converter for Dual-Port Direct Drive Wave Power Generation System

Dual-port direct drive wave energy power generation systems (DP-DDWEPGS) have received widespread attention due to their smooth and zero-free output power, compared to single-port direct drive wave energy power generation systems (SP-DDWEPGS) which have the disadvantage of large out-put power fluctuations. To further enhance the performance of the DP-DDWEPGS, optimal power capture control is proposed to achieve maximum power point tracking. Meanwhile, a multiport converter is applied to the DP-DDWEPGS to solve the problem caused by an excessive number of switching devices in the overall system converter. The multiport converter fulfills all the functional requirements of the DP-DDWEPGS while reducing the number of switching devices. However, switch multiplexing of the multiport converter also introduces coupling relationships between each port and the wave force exhibits time-varying characteristics, necessitating advanced control methods with superior fast-tracking capability. Therefore, in this paper, a decoupling duty cycle optimization model predictive control for DP-DDWEPGS is proposed. Based on the characteristics of switching multiplexing, NSC finite control set model predictive control (FCS-MPC) decouples the current prediction and the cost function, reduces the number of candidate voltage vectors in each operation, and shortens the operation time by 70%. To address the issues of high ripple value and increased error due to decoupling in FCS-MPC, duty cycle optimization control is added, greatly reducing the fluctuations in electromagnetic force and power of the permanent magnet linear generator (PMLG). Based on the established simulation model, the feasibility and superiority of the multiport converter and decoupling duty cycle optimization model predictive current control method are verified.

Approach to Validate ISPM-15 Compliance for Commercial Treatment Certification of Dielectric Standard Heating of Bulk Solid Wood Packing Materials using Radio Frequency

Abstract To substantially reduce the risk of alien invasive species moving to new geographic areas, phytosanitary treatment of wood packaging materials (WPM) in compliance with the International Standard of Phytosanitary Measures No. 15 (ISPM-15) is required by trading partners. Approved treatments include conventional heating, methyl bromide and sulfuryl fluoride fumigation, and dielectric heating (DH). The DH standard was officially adopted in 2013 but has not been practiced commercially due primarily to insufficient operational validation at commercial scale. In 2022, we converted our 50-kW radio frequency (RF) unit with a 1,200-board foot capacity from an oscillator electromagnetic field power generator to a solid-state power supply, which allows for selective power input adjustments during treatment; we also switched from a five-plate to a three-plate winged electrode system to improve heating uniformity. Each loading cycle can treat sufficient material to build ∼94 standard Grocery Manufacturers Association pallets. Our research team characterized the dielectric heating pattern and options for monitoring wood temperatures over a wide-ranging test matrix of WPM that varied by wood species, dimension, moisture content, and loading configuration. We found that this upgraded RF system markedly reduced treatment times and improved heating uniformity, allowing us to develop methods that can be used to verify compliance with ISPM-15 for improved technology transfer to industry. We also discuss the operational cost of RF treatment and make general cost comparisons to conventional heat treatment for WPM.

Attenuation of Sommerfeld effect in a four DOF vibration system driven by a non-ideal induction motor

The Sommerfeld effect is a phenomenon in which a non-ideal prime mover fails to provide enough energy around the resonance speed in a vibration system, resulting in resonance capture and a nonlinear jump. This study discusses the successful techniques for attenuating the Sommerfeld effect in a vibration system with four degrees of freedom (DOFs) driven by a non-ideal induction motor. The kinetic equations of the system are derived using the Lagrange function. Additionally, the mean rotational speed and stability of a non-ideal motor are studied by energy balance and perturbation analysis method. Then, the relationship between electromagnetic torque and motor speed in the Sommerfeld effect is analyzed. The Sommerfeld effect exists near the natural frequencies (NFs) with electrical frequency increased or decreased. The main reason is that the gradually increasing mechanical load power of the vibrating system near the NFs contradicts the finite electromagnetic output power of the non-ideal induction motor. Moreover, the validity of the proposed methods is demonstrated through numerical analysis and simulation. The Sommerfeld effect can be effectively mitigated by appropriately increasing the damping coefficient, reducing the installation distance, and minimizing both the eccentric mass and eccentricity radius of the rotor.

A Transient Damping Improvement Strategy for Enhancing Grid-Connected Active Power Response Performance of VSG

The given power and grid frequency disturbances can cause transient oscillations and steady-state deviations in the output power of a virtual synchronous generator (VSG), which can be effectively addressed by adding transient damping. However, this approach may result in significant power overshoot. This article proposes an improved VSG control strategy based on transient electromagnetic power feedback compensation and a small-signal model reduction scheme. Firstly, the grid-connected active closed-loop small-signal models of typical VSG control and transient damping VSG control are established, respectively. The transient oscillation suppression mechanism of active power is revealed through root locus and frequency response analyses, and the power overshoot characteristics of the two control strategies are analysed by combining them with the system of zero points. Secondly, the active transient feedback compensation method and the small-signal model reduction design method are introduced in detail. Finally, comparative analysis experiments are conducted using the Matlab/Simulink and hardware-in-the-loop experimental platform. It is verified that the proposed control strategy can suppress transient oscillations in active power, prevent steady-state deviations, and effectively mitigate the power overshoot problem of the system.

Transformable 3D curved high-density liquid metal coils – an integrated unit for general soft actuation, sensing and communication

Rigid solenoid coils have long been indispensable in modern intelligent devices. However, their sparse structure and challenging preparation of flexible coils for soft robots impose limitations. Here, a transformable 3D curved high-density liquid metal coil (HD-LMC) is introduced that surpasses the structural density level of enameled wire. The fabrication technique employed for high-density channels in elastomers is universally applicable. Such HD-LMCs demonstrated excellent performance in pressure, temperature, non-contact distance sensors, and near-field communication. Soft electromagnetic actuators thus achieved significantly improved the electromagnetic force and power density. Moreover, precise control of swinging tail motion enables a bionic pufferfish to swim. Finally, HD-LMC is further utilized to successfully implement a soft rotary robot with integrated sensing and actuation capabilities. This groundbreaking research provides a theoretical and experimental basis for expanding the applications of liquid metal-based multi-dimensional complex flexible electronics and is expected to be widely used in liquid metal-integrated robotic systems.

Design and experimental validation of a compact dual-band metamaterial perfect absorber for electromagnetic energy harvesting applications

This article introduces, characterizes, and experimentally validates an innovative design for a compact-sized metamaterial (MM) perfect absorber (PA) for electromagnetic (EM) energy harvesting (EH) applications. The absorber design, comprised of three octagonal ring resonators made of annealed copper, incorporates split gaps at 45-degree inclinations within the uppermost and middle resonators. A split strip line connects the inner octagonal ring resonators, while the split gaps of the outermost and inner rings are filled with a 50 Ω resistive load. This structure is made on a Rogers RT5880 substrate, and the back side of the proposed design is entirely coated with annealed copper. The proposed absorber achieves precise impedance matching with free space, facilitating efficient absorption and redirecting EM power toward the resistive loads. The absorber demonstrates absorption peaks of 99.98 % at 2.4 GHz and 99.99 % at 4.9 GHz. In addition, the efficiency of absorption is assessed for different incident (θ) and polarization angles (ϕ) in both the Transverse Electric (TE) and Transverse Magnetic (TM) modes. Simulated harvesting efficiencies of 95.33 % at 2.4 GHz and 95.99 % at 4.9 GHz are recorded. An experimental validation is performed using a 3 × 3 array that measures 30 × 30 mm. The tests are carried out in an anechoic chamber. The measured harvesting efficiencies strongly correlate with the simulated results, indicating the reliability of the proposed design. This absorber's efficiency and compact size make it an excellent option for EH systems in wireless sensor networks (WSNs).

Satellite Onboard Transmitter Design With Spread Spectrum MIMO Antenna for 5G Wireless Networks

AbstractThe 5G new era implements standalone satellite communications that support wireless networking systems for future mobile communications by locating multiple satellites in low Earth orbit to provide global coverage of the entire Earth's surface. In this research, a newly found model of a satellite onboard transmitter using a uniform circular array multiple‐input multiple‐output antenna was designed to operate at a carrier frequency of 12 GHz and derived theoretical equations compared to the real‐time scenario. The integration of spread spectrum with multiple‐input multiple‐output antenna provides an advantage for higher capacity. It has a higher percentage of gain amplification on improving the transmission of electromagnetic power to meet the bandwidth requirement of center operating frequency, and this can transmit over a bandwidth of 1.28 GHz. The proposed satellite onboard transmitter model design aims to minimize the components, increase the speed of operations for higher bandwidth, and transmit large amounts of information to a large group of users. The transmitter can operate for the speed of 1.28 Gbps using pseudo‐random code, direct‐sequence spread spectrum, quadrature phase shift keying modulation, bandwidth separated in bands for 64 symbols using 128 Chebyshev‐type bandpass filter for transmission using 128‐element uniform circular array multiple‐input multiple‐output antenna. The satellite transmitter antenna produces a maximum gain of 14.526 dBi, and a maximum directivity of 17.986 dBi, and the efficiency at 12 GHz is 45.1% for the radiated power at 0.93 mW. This satellite transmitter will interconnect 5G wireless networks for the application of mobile communications complement terrestrial‐dependent networks.

Sub-GHz Broadband Multi-channel Waveguiding Based on Subwavelength Wire Media

The paper involves the development of a new type of image transfer. With this aim the multi-channel waveguide was considered in a novel representation – it was based on a wire media structure where each space between each four the closest wires is a single subchannel. The utilized wire media (WM) structure has 10-by-10 wires dimensions and 150 mm of the length, thus the first Fabry-Perot resonance appears around 0.9-1 GHz. The goal is to show the broadband multi-channel imaging at frequencies lower than the first Fabry-Perot resonance that means the considered structure tends to electrically short size that has not been studied previously. Taking into account the multi-channel principle of the wire media, the imaging can be performed as a binary one. For this reason, each single channel is fed by individual electromagnetic (EM) source that is a dipole antenna in the non-resonant mode. The reason is to use a weak source and match it with a single channel because in the other case the dipole is perfectly matched at the defined resonance frequency. It was found in the paper that the broadband transfer is possible in the frequency range-under-study and impossible at the region of the first Fabry-Perot resonance due to the perfect complex interaction between all wires of structure. As evidence, a simultaneous transfer of EM power from several independent EM sources shaped as R-letter was performed in the frequency range from 0.3 to 0.75 GHz by simulations and experimental investigations. The clear recovery of the transferred letter is possible in the case when it performs not at the frequency of Fabry-Perot and for the enough value of signal-to-noise ratio (SNR). The binary recovery of the transferred image became possible in the paper with an additional post-image processing with a threshold method involvement.

Analysis and improvement of power quality in the onboard electrical power systems within a self-propelled floating crane

This research addresses electromagnetic compatibility and power quality (EMC and PQ) challenges in shipboard electric power systems (SEPS) with dynamic positioning (DP) capabilities, focusing on the self-propelled floating crane (SPFC) “EXPERT 3.” Our goal is to enhance methodologies for evaluating power quality indicators (PQI) related to voltage and current waveform distortions, specifically in converter-based propulsion complexes (CBPCs) featuring variable-frequency regulated asynchronous drives (VFDs). We investigate harmonic current and voltage distortions, reactive power generation, and power factor (PF) in SEPS “EXPERT 3″ during the operation of VFDs with conventional semiconductor power converters (SPCs). A refined MATLAB model considers equipment and cable network parameters, validating distortion indicators at ship synchronous generators (SGs). PQI compliance with international maritime standards is verified at the point of common coupling (PCC) for various VFD configurations with pulse width modulated (PWM) SPCs and filter-compensating devices (FCDs). We propose an improved controlled FCD (CFCD) incorporating a resonance filter (RF) and a controllable reactor compensator (CRC). CFCD efficiency in various VFD configurations is experimentally validated. We analyze harmonic distortions of voltage and current, including high-frequency (HF) commutations in VFDs with input thyristor-based rectifiers (TBRs), considering parasitic ”phase-hull“ capacitances of cable line segments (CLS). Our study examines harmonics in CBPC-based SEPS in two sub-frequency ranges: low-frequency (LF) − 0 to 2 kHz and high-frequency (HF) − 2 kHz to 500 kHz.© 2017 Elsevier Inc. All rights reserved.

Noncontact magnetically coupled piezo-electromagnetic rotary energy harvester

Aiming at the problems of high environmental vibration frequency, low output power and short life of the energy harvesters, a noncontact magnetically coupled piezo-electromagnetic rotary energy harvester is proposed in this paper. It consists of a base, a top cover, a rotating body, a cantilever beam, a permanent magnet, a coil, a hollow tube and a clamp. The novel hybrid harvester can produce both piezoelectric and electromagnetic energy at the same time, and in addition, it can efficiently generate electricity at low ambient vibration. Moreover, the piezoelectric material is protected from direct collision by noncontact magnetic coupling excitation. In order to conduct a comprehensive study on the performance of the piezoelectric-electromagnetic rotary energy harvester, we set up a rotating test platform to carry out systematic test verification, and to determine the distance between the permanent magnet and the rotating body and the number of permanent magnets on the rotating body. The test results show that when four permanent magnets are uniformly pasted on the rotating body and the rotating speed is 775 r/min, the piezoelectric and electromagnetic output power are 3.4 mW and 2.69 mW, respectively, and the total hybrid output power is 6.09 mW.

Design and development of a compact, wide-angle metamaterial electromagnetic energy harvester with multiband functionality and polarization-insensitive features

This article presents a compact, wide-angle, polarization-insensitive metamaterial harvester that can efficiently harvest electromagnetic (EM) energy in the S, C, X, and Ku bands. The harvester's unit cell consists of a split ring resonator, two strip lines, and two split strip lines, giving it a total size of (10 × 10) mm2. Each split gap is filled with a 50 Ω resistive load. The input impedance of the harvester is precisely designed to match that of free space, allowing for efficient absorption of EM power and appropriate redirection towards the resistive loads. The harvester's performance is also evaluated for various polarization and incident angles, considering the Transverse Electric and Transverse Magnetic modes. The simulation results reveal that the proposed harvester exhibits a notably greater conversion efficiency of around > 95%. The simulation outcomes were carefully validated through experimental tests conducted in an anechoic chamber using a 3 × 3 cell array of the proposed design. This ensured the accuracy and reliability of the results. The strong correlation between the experimental data and the full-wave simulations strongly supports the effectiveness of the proposed harvester. Therefore, the demonstrated efficiency and compact size make it a perfect fit for energy harvesting systems in wireless sensor networks.