Power Transmission Efficiency Research Articles

Research on non-contact wet mateable connector for optical communication and power transmission

At present, contact watertight connectors are commonly utilized for the connection between underwater electromechanical equipment and the seabed observation network. Such traditional watertight connectors are easy to be irreversibly worn when plugging and unplugging, however, they have complicated sealing structures and limited service life. This paper designs a Non-contact Wet Mateable connector for Optical Communication and Power Transmission (OCPT-NWMC), which is based on technology of Contactless Power Transmission (CLPT) and optical communication. Docking structure of the sockets and plugs are designed, facilitating Remotely Operated Vehicle (ROV) to operate. A prototype of the OCPT-NWMC was established. The experimental results show that the connector designed can achieve 200W power transmission, with a maximum power transmission efficiency of 94%. The communication bandwidth reaches 18MHz. The OCPT-NWMC can assist the rapid and safe deployment and operation of seabed observation network.

High power transmission efficiency of wireless power transfer system using high-quality factor superconducting bulk coil

We developed a high-quality-factor high-temperature superconducting (HTS) bulk coil to increase the power transfer efficiency (PTE) of wireless power transfer (WPT) systems. We proposed the resonant frequency tuning by using the two sapphire substrates thickness of coil support. The configuration of a 65 mm diameter HTS bulk coil was optimized to a resonant frequency of 64 MHz. The measured quality factor of the HTS bulk coil was 9,431, which is 12 times that of the copper coil. At the transfer distance of 20 cm, the measured PTE of the WPT system using HTS bulk coils and one using copper coils were 74.8% and 20.6%, respectively.

Iterative multi-target detection for PA-FDA dual-mode radar

In this paper, the multi-target detection for joint phased array (PA) and frequency diverse array (FDA) radars, referred to as PA-FDA dual-mode radar, is investigated by exploiting the high transmit power efficiency of PA as well as wide spatial coverage of FDA. The PA-FDA dual-mode radar is formulated in a signal-level fusion manner by combining the PA and the FDA, which enables us to exploit the joint information in the PA-FDA dual-mode radar. In the sequel, an iterative multi-target detection method is devised with two main steps: i) the generalized likelihood ratio test (GLRT) is performed, which provides the knowledge of target parameters, and ii) the conditional-cancelation-before-detection GLRT (CCBD-GLRT) detector is carried out, which detects other targets based on the previous detection knowledge. At the analysis stage, the optimal detector is provided for the signal-level fusion of PA and FDA radars. Moreover, the corresponding analytical expressions of the probabilities of detection as well as the probabilities of false alarm with respect to both the developed GLRT and CCBD-GLRT detectors are derived for multi-target detection. Simulation results demonstrate that the proposed multi-target detection method is effective and the PA-FDA dual-mode radar outperforms the PA and the FDA radars.

W-Band Beam-Tilted H-Plane Horn Array Antenna with Wideband Integrated Waveguide Feed Network Based on MMPTE

A W-band H-plane horn array antenna with tilted radiation beam based on waveguide structure is proposed in this paper. The designed antenna array consists of four H-plane antenna elements and a broadband feed network. The distribution of excitations is determined by the theory of maximum power transmission efficiency (MMPTE). A multiple branch coupler, two T-junctions and three fixed phase shifters are employed to construct the feed network, which can generate the required amplitude and phase in broadband frequency range from 80 GHz to 100 GHz. The computer numerical control (CNC) milling machines technology is employed to machine the feed network and antenna. All measured and simulated results are in good agreement, which verify the feasibility of the theory of MMPTE to generate a radiation beam directed to any angle from -35° to 35° with suitable excitation provided by the proposed feed network in this paper.

The altitude correction term of the corona loss on alternating-current transmission lines

The increase in mobility of charged particles causes high-voltage alternating-current (AC) transmission lines in high-altitude areas to be more likely to undergo severe corona discharge and associated losses, to the detriment of the economic efficiency of power transmission. Evaluating the corona loss on transmission-line conductors in high-altitude areas is conducive to conductor selection, parameter optimization, transmission-line tower arrangement, and optimization of the phase sequence arrangement. The altitude correction factor K of 3.33 dB/km recommended by the Bonneville Power Administration (BPA) in the United States is commonly used in engineering design, however, measured data indicate that the correction method may be subject to significant error, so the altitude correction factor is discussed under different weather conditions. K is suggested to be 4.5 and 1.5 dB/km separately under dry and rainy conditions, the better to evaluate the coronal loss.

A Single-Layer Circularly Polarized Reflectarray Antenna with High Aperture Efficiency for Microwave Power Transmission

In this article, a single-layer circularly polarized reflectarray antenna (RA) with a linearly polarized feed is proposed for microwave power transmission. The unit cell of the reflectarray is composed of a rectangular patch surrounded by four groups of E-shaped structures, which feature a very low level of cross-polarization. Simulation results demonstrate that the phase of its reflection coefficient can be tuned continuously in a range of 500° by adjusting the lengths of the E-shaped structures. In response to a normally incident plane wave, the phase values of the reflection coefficient associated with two orthogonal linear polarization directions of the reflected wave can be tuned independently, which makes it possible to convert a linearly polarized incident wave to a circularly polarized beam. A reflectarray with 15 × 15 unit cells is fabricated and tested. The measurement results demonstrate a 3-dB axial ratio bandwidth of more than 2 GHz around the center frequency of 5.8 GHz. The measured gain value of the fabricated reflectarray is 25.4 dBi, corresponding to an aperture efficiency of 52.5%.

Computational approaches for improving machining precision in five-axis flank milling of spiral bevel gears

Spiral bevel gears are a critical component in mechanical systems that offers high power transmission efficiency between nonparallel axes. The current gear manufacturing, which normally requires specialized machines and cutting tools specific to one gear type, offers limited production flexibility. An effective alternative is to utilize 5-axis computer numerical control milling on general-purpose machine tools. This paper aims to improve the machining precision in the flank milling of spiral bevel gears, particularly the tooth surfaces, using computational approaches. First, a geometric method was developed to approximate the contact path of a gear pair without solving the complex equations in tooth contact analysis. A quantitative measure was introduced to evaluate the contact path deviation from the center curve of the tooth surface. Second, we proposed an optimization scheme for generating tool paths that induce minimal geometrical errors on the finished surface. It employs a metaheuristics-based search algorithm with the errors as an objective in tool path planning. Test results on real gears verified the effectiveness of the proposed scheme. Three measures of the meshing performance, namely the average sampling error, the contact path deviation, and the transmission error, were cross-compared on different gear pairs to examine whether they consistently distinguish the performance rank. This work provides feasible solutions for controlling machining errors in 5-axis flank milling of complex gears.

3 × 1 fiber signal combiner with high beam quality Gaussian-like beam for a 10kW-level fiber laser.

We present the design and fabrication of a 3 × 1 signal combiner with high beam quality based on supermode theory. For improving beam quality, the fiber with core diameter of 34 µm and numerical aperture of 0.11 is first chosen as the output fiber. An 8.89 kW output laser with a power transmission efficiency of 97.2% and a low temperature rise coefficient of 3.5 °C/ kW at >8 kW is obtained when the combiner launched by three Yb-doped fiber lasers. In addition, the energy density distribution of the output beam is Gaussian-like and M2 factor is 2.32, which is the best beam quality compared with the presented signal combiners for high power laser to the best of our knowledge.

Switchable compliant actuator with fast stiffness modulation and energy efficient power transmission

This article presents the design of a switchable compliant actuator (Swi-CA), capable of fast stiffness modulation over a wide range and energy-efficient equilibrium position control. Compliant actuators are designed to have a variable stiffness to generate a restoring force upon displacement. In previous studies, such actuators provided compliance by changing both output stiffness and equilibrium position using a clutch to switch between two modes. We implemented a bifurcation-based switching mechanism to shift between stiffness modulation and equilibrium position control modes via mechanical integration of a variable stiffness spring with a parallel elastic unit without the use of an additional clutch. The distinctive features of the proposed Swi-CA are threefold. First, the central bending of a leaf spring widens the range of modulated stiffness and increases the average stiffness modulation speed. Second, the developed slider-crank mechanism has high power transmission efficiency and fast stiffness modulation. Lastly, an optimized elliptical cam generated negative stiffness during output and enabled switching between the two modes without the use of a controllable clutch. Analytical models and experimental validation of the proposed design clearly demonstrated its advantages for applications requiring fast stiffness modulation and energy-efficient operation, such as some robotics applications.

Research on Transfer Mechanism and Power Improvement Technology of the SCC-WPT System

Single capacitive coupled wireless power transfer (SCC-WPT) technology only needs one pair of metal plates for energy transmission. This provides a unique advantage in two-dimensional plane dynamic wireless power transfer. However, in practical application, this technology has a clear challenge in improving the transmission power ratings and efficiency. This article studies the power transfer mechanism of the SCC-WPT system based on stray capacitance and self-capacitance. A universal system model has been investigated, where the equivalent circuit model of the system is proposed. The two-port network of the coupler critical factors that limit the transmission power of the system has been analyzed. A new <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC–CL</i> compensation topology is proposed to achieve a phase difference of voltage between the primary side and secondary side to 90°, which improves the transmission power of the SCC-WPT system. In addition, the resonant operating condition of the system together with the efficiency is analyzed. Finally, an experimental prototype is built under the guidance of the analysis. Both simulation and experimental results verify the validity of the proposed model and the topology. The experimental results show that the prototype achieves 266 W output power with 62% dc–dc efficiency.

Research on Fractional Order Modeling and PIλ Control Strategy of V2G Two-Stage Bidirectional Converter

With regard to the insufficiency of independent modeling accuracy in V2G two-stage bi-directional converter in the two-stage system of integer order, it is impossible to accurately describe the actual situation of the poor dynamic performance of the classical PI control strategy as well as the lower power transmission efficiency. Based on the fractional calculus theory, the modeling methods based on the fractional, namely, the state space averaging method and the extended description function method are proposed. The integer inductance and capacitance in the system are extended to fractional inductance and capacitance, and the Fourier decomposition in the extended description function method is extended from integer order to fractional order. The joint mathematical model and small signal model of fractional order for V2G two-stage bidirectional converter are constructed, and the fractional order transfer function of the whole system is obtained. Therefore, a fractional PI <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</sup> control strategy for V2G two-stage converter is designed. Finally, a 3kW prototype is built in the laboratory, which verifies the correctness and feasibility of fractional modeling and fractional PI <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</sup> control strategy.

A Load-Independent Fission-Type Inductive Power Transfer System for 3D Reconfigurable IoT Array

In recent years, the number of electronic devices and appliances that support wireless charging has rapidly increased, owing to the research and development breakthroughs in inductive power transfer (IPT) technology. The existing wireless charging protocols, such as Qi and AirFuel, support only a few devices to be charged simultaneously. They cannot be directly utilized to construct a complex IPT network. This article introduces a reconfigurable three-dimensional (3D) IPT system based on series-parallel (SP) compensation for wirelessly powering multiple adjacent cubic Internet of Things (IoT) devices. These cubes can be configured into different 3D array combinations according to the application demands. After the 3D cube array is formed, a self-detection mechanism runs to turn off the uncoupled coils, such that to maximize the power transmission efficiency of the entire system. These cubes serve as not only IoT loads but also wireless power relays. In this way, the number of loads is not limited by the size of a single transmission coil. In addition, it maintains a constant drive voltage to each load device, regardless of the load variations in local or adjacent cubes. The constant voltage design eases local power management. A prototyped IPT cube array is manufactured and tested to validate the proposed idea. This fission-type IPT system makes a valuable exploration of the 3D IPT technology toward future ubiquitous and reconfigurable IoT arrays.

Beam Shaping of Base Station Antenna Array by Using MMPTE

In this paper, a beam shaping scheme is presented for the optimal design of base station antenna array. The antenna array consists of four linearly arranged dual-band dual-polarized antenna elements, and it is designed to cover the LTE frequency band (2.3-2.69 GHz) and 5G frequency band (3.3-3.6 GHz). The shaped beams with possible maximum gain, suppressed sidelobe level smaller than -16 dB, front-to-back ratio larger than 18dB, and filled-up null point larger than -23 dB are accomplished through two steps by using the unconstrained methods of maximum power transmission efficiency (MMPET) and constrained MMPTE, respectively. In the proposed beam shaping scheme, all the realistic factors of the antenna array have been taken into account, such as the difference of element radiation patterns, complexity and tolerance of the element structure and spacing.

Voltage stability and power loss minimization with UPFC using heuristic and hybrid heuristic methods

Present-day power systems have highly complex and stressed operating conditions owing to insufficient reactive power to meet the required power demand. This leads to increased real power and reactive power losses, as well as voltage instability within a power system. To achieve the flexible operation of the power system, Flexible Alternating Current Transmission System (FACTS) devices have been employed. The optimal location of FACTS devices influences the system's performance and significantly affects line/bus reactive power flows. Consequently, the line or bus voltage profiles have been improved, leading to a reduction in power losses. Particle Swarm Optimization (PSO) heuristic methods and HFPSO Hybrid heuristic methods have been used to identify the weakest bus/branch for the suitable placement of UPFC devices, improving voltage stability. This paper discusses a more significant reduction in power losses in a MATLAB environment. Flexible Alternating Current Transmission System (FACTS) devices address reactive power challenges in power systems and enhance operational flexibility. Strategic placement using Particle Swarm Optimization (PSO) and HFPSO Hybrid methods identifies weak points, optimizing Unified Power Flow Controller (UPFC) placement for improved voltage stability. UPFC integration strategically reduces real and reactive power losses, improving power transmission efficiency. This enhances line and bus voltage profiles, addressing instability and significantly reducing overall power losses. The paper offers a detailed analysis of the power system, highlighting the synergy between FACTS devices, heuristic optimization, and power loss reduction. Simulations in MATLAB validate the proposed methodology, demonstrating a noteworthy improvement in power system performance.

500kV급 HVDC 폴리머 애자의 전계 완화에 관한 연구

An HVDC(high voltage direct current) is economical owing to its excellent power transmission efficiency and a low insulation class compared with HVAC(high voltage alternative current). In addition, HVDC is known as a high efficiency green technology because power systems with different frequencies can be connected asynchronously. Therefore, research on the HVDC is being actively conducted. In order to develop HVDC transmission lines, it is necessary to secure insulation design technology for DC insulators. DC has different properties from AC due to the presence of space charge and the temperature dependence of conductivity. However, until now, there is no standard for the insulation design of DC insulators. In this study, the difference in insulation design was verified through AC electric field and DC electric field analysis, and a corona ring design was derived to improve the electrical stability of the 500kV DC insulator.

A 70%-power transmission efficiency, 3.39 Mbps power and data telemetry over a single 13.56 MHz inductive link for biomedical implants

A 70%-power transmission efficiency, 3.39 Mbps power and data telemetry over a single 13.56 MHz inductive link for biomedical implants

Fast Multinull Steering of Antenna Array

In this letter, a fast multinull steering technique is demonstrated by a linearly polarized linear antenna array. The new technique is based on the electric fields generated by each antenna element on a far-field arc of the antenna array, which are extracted in advance by simulation or measurement. The power transmission efficiency is used as the performance index to control the pattern nulls. By solving a matrix eigenvalue equation, in which the matrix is made up by selecting the corresponding electric fields on different positions on the arc standing for the null directions, the eigenvector corresponding to the zero eigenvalue is identified and used as the optimized distribution of excitations (ODEs) for the antenna array. Single-null and multinull patterns are tested from the ODEs and the results indicate that the number and directions of the multiple nulls can be controlled in the elevation space. The simulated and measured 2-D null patterns are shown in good agreement.

Designing and analyzing multi-coil multi-layers for wireless power transmission in stent restenosis coronary artery

Wireless power transfer technology features shorter power transmission distances in biomedical applications. This is a result of the small size of the implanted coils, biocompatible material conductivity, and the large distances between the receiving and transmitting coils. There have been numerous attempts to improve the power transfer efficiency across longer distances. Multiple coils, including 2-, 3-, 4-, and multi-layered coils, were previously considered. This study proposes a novel approach to achieve higher power transmission efficiency by integrating a single coil on the receiving side and three asymmetric coils on the transmitter side. As such, it delivers power to the sensor implanted within the coronary artery that monitors the blood pressure while introducing a uniquely shaped stent. The efficiency of power transmitted to the stent in its dual implanted forms, helical and zigzag helical, was examined as well, with the wireless power transmission system thereby analyzed at the 27 MHz Industrial Scientific Medical band operating frequency. For the four-coil technique, the power transmission efficiency at a distance of 25 mm between the receiver and transmitter sides by using biological human tissue as a medium between the transmission coils and the receiver stent can reach 56.42%, whereas other approaches show lower efficiencies: the three-coil method’s efficiency is 32.88%, the double-layer parallel method’s efficiency is 27.75%, the two-coil method’s efficiency is 24.76%, the triple-layer parallel method’s efficiency is 17.31%, the double-layer series method’s efficiency is 0.501%, and the triple-layer series method’s transmission efficiency is 0.092%. In addition, the suggested approach is demonstrated to be more efficient than prior designs with regard to the size of the implanted coils, which represent stents.

Resource allocation for UAV-assisted 5G mMTC slicing networks using deep reinforcement learning

The Internet of Things (IoT) application scenarios is becoming extensive due to the quick evolution of smart devices with fifth-generation (5G) network slicing technologies. Hence, IoTs are becoming significantly important in 5G/6G networks. However, communication with IoT devices is more sensitive in disasters because the network depends on the main power supply and devices are fragile. In this paper, we consider Unmanned Aerial Vehicles (UAV) as a flying base station (BS) for the emergency communication system with 5G mMTC Network Slicing to improve the quality of user experience. The UAV-assisted mMTC creates a base station selection method to maximize the system energy efficiency. Then, the system model is reduced to the stochastic optimization-based problem using Markov Decision Process (MDP) theory. We propose a reinforcement learning-based dueling-deep-Q-networks (DDQN) technique to maximise energy efficiency and resource allocation. We compare the proposed model with DQN and Q-Learning models and found that the proposed DDQN-based model performs better for resource allocation in terms of low transmission power and maximum energy efficiency.

Theoretical transmission analysis to optimize Gearbox for a 2.6 kW automatic pepper transplanter

A gearbox is an essential component of an automatic transplanter to transmit engine power to the transplanter components. It is necessary to find the appropriate gearbox dimensions and materials for the pepper transplanter to minimize transmission losses. Therefore, the objectives of this research were to simulate the power transmission efficiency of the gearbox, and to determine a suitable number of stages, and materials and the dimensions of the spur gears. A 2.6 kW gasoline engine was considered as the prime source to power the entire transplanter. The available maximum length between the engine and transplanter subsystem was 422 mm. By considering design issues, a simulation model was created to determine the efficiency of the pepper transplanter gearbox, including various types of mechanical losses in the gearing system. Three different modules (1, 2, and 3 mm) and two materials were used to evaluate the effects on transmission. The analysis results indicated that the gearbox transmission efficiency levels of seven to twelve stages were in the range of 93.0–98.7%, whereas the eight-stage gearbox yielded the maximum efficiency of 98.7%, greater than our target efficiency of 98.0%. Therefore, an eight-stage gearbox was selected for power transmission to the components. The power transmission simulation results showed that the overall efficiency from engine to transplanting mechanism shaft varied in range of 95.2–95.9% owing to contact of the gear meshes. The analysis results also indicated that the 25CrMo4 carbon steel material with a 2-mm module gear was appropriate for the pepper transplanter. The analysis in this paper can be used as reference in the design of pepper transplanter gears and gearboxes with suitable material properties to provide the desired efficiency.