Optimal Current Distribution Research Articles

Deep learning assisted anode porous transport layer inverse design for proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis cell (PEMEC) offers a clean and promising way for hydrogen production. The spatial internal current density and temperature distribution uniformity significantly determines its reliability and durability, as well as the hydrogen production performance. Here, a non-isothermal 3D computational fluid dynamics (CFD) model for PEMEC with parallel flow fields is employed to investigate the impacts of the heterogeneous porosity distribution within the anode porous transport layer (APTL) on the internal current density and temperature distribution uniformity and energy conversion performance. 800 heterogeneous APTL porosity distributions are applied for CFD calculation, providing dataset for deep learning. The deep operator network (DeepONet) is employed to mapping the heterogeneous APTL porosity distribution to the real physical fields such as temperature, oxygen molar fraction and current density distribution fields. Full-connected neural network is employed to construct the relationship between the heterogeneous APTL porosity distribution to the performance metrics. The gradient descent algorithm is applied to obtain APTL porosity distributions corresponding to the optimal internal current density and temperature distribution uniformity, respectively. Compared with the uniform porosity distribution, the current density and temperature uniformity are improved by 45.544 % and 26.680 %, respectively, at an average APTL porosity of 0.5.

Economic Evaluation of Using Ultracapacitors in Electric Vehicles

The main challenge of hybridizing ultracapacitors (UCs) with batteries in electric vehicles is their uncertain economic viability, besides their complexity and weight, which should be fully addressed. Therefore, this article determines the general condition for achieving a justified economic system, which is held when the average annual cost (AAC) of a battery‐UC system over a vehicle's useful life is lower than the annual cost of a sole‐battery for a specific system design, energy management strategy, vehicle type, and driving style. As such, the energy storage system is designed in a case study vehicle, and the optimal current distribution is found by dynamic programming (DP) under UDDS, HWFET, and US06 driving cycles. Then, by economic analysis, it is indicated that although adding an UC incurs additional costs, it saves the AAC by improving the battery health and prolonging its lifespan up to a maximum of 15‐year calendar life, which proves its economic justification. Investing in UCs is more economically viable for vehicles with severe driving cycles and high current stress. Finally, the DP optimal trajectory is implemented into an experimental setup under the US06 driving cycle to verify the evaluated strategy.

Design and Optimization of a Mid-Field Wireless Power Transfer System for Enhanced Energy Transfer Efficiency

Mid-field wireless power transfer (WPT) offers a compelling solution for delivering power to miniature implantable medical devices deep within the human body. Despite its potential, the current power delivery levels remain constrained, and the design of a compact source structure to focus the transmitter field on such implants presents significant challenges. In this paper, a novel miniaturized transmitter antenna operating at 1.71 GHz is proposed. Leveraging the antenna proximity-coupled feeding technique, we achieve optimal current distribution for efficient power transfer. Additionally, a receiver integrated within the human body is proposed, comprising a slotted ground and a meandering slotted radiating element. This receiver is excited via a coaxial feedline with a truncated ground. Our findings demonstrate wireless power transfer of −23 dB (0.501%) at a distance of 30 mm between the transmitter and receiver, alongside a peak gain of −20 dB with an impedance bandwidth of 39.61%. These results highlight promising advancements in enhancing energy transfer efficiency for deep-implant applications.

Power utilization efficiency improvement of distributed energy units in DC microgrids using primal‐dual subgradient method

AbstractTo improve the power utilization efficiency of distributed energy units (DEUs) in DC microgrids, a centralized current iteration regulation approach is presented in this paper. The power utilization efficiency is partially represented by the power losses of DEUs, which can be modelled as quadratic functions of the output currents of DEUs. The power efficiency is also dependent on the line losses on the resistances between the DEUs and DC buses, which can be formulated in the basis of the output currents as well. Thus, the total power losses of DEUs comprise line and converter losses, which are verified to be a constrained‐convex function of the current allocation coefficients. In this paper, a primal‐dual subgradient method (PDSM) using only explicit addition and subtraction iterations is adopted to obtain the optimal current distribution coefficients. On this basis, an adaptive droop regulation scheme is applied to further control the output voltage references of DEUs, and proportional‐integral (PI) controllers are applied to track the adaptive voltages based on the current sharing errors. Both simulation and empirical results demonstrate the effectiveness of the proposed control to improve the power utilization efficiency of DEUs regardless parameter and load variations in DC microgrids.

Lower Bounds to the Q Factor of Electrically Small Resonators Through Quasistatic Modal Expansion

The problem of finding the optimal current distribution supported by small radiators yielding the minimum quality (Q) factor is a fundamental problem in electromagnetism. Q factor bounds constrain the maximum operational bandwidth of devices including antennas, metamaterials, and nanoresonators, and have been featured in seminal papers in the past decades. Here, we determine the lower bounds of Q factors of small-size plasmonic and high-permittivity dielectric resonators, which are characterized by quasi-electrostatic and quasi-magnetostatic natural modes, respectively. We expand the induced current density field in the resonator in terms of these modes, leading to closed-form analytical expressions for the electric and magnetic polarizability tensors, whose largest eigenvalue is directly linked to the minimum Q factor. Our results allow also to determine in closed form the corresponding optimal current density field. In particular, when the resonator exhibits two orthogonal reflection symmetries the minimum Q factor can be simply obtained from the Q factors of the single current modes with non-vanishing dipole moments aligned along the major axis of the resonator. Overall, our results open exciting opportunities in the context of nano-optics and metamaterials, facilitating the analysis and design of optimally shaped resonators for enhanced and tailored light-matter interactions.

Second Harmonic Seamless Splicing Technique Based on Maximum Active-Voltage Vector for Online MTPA Tracking Control of SynRM

Maximum-torque-per-ampere (MTPA) control strategy is widely employed to achieve the optimal efficiency control of synchronous reluctance machines (SynRMs). However, the control efficiency of the conventional method that the optimal current distribution angle is directly calculated based on the knowledge of the machine parameters is seriously affected by the highly nonlinear and time-varying characteristics of SynRMs. Therefore, in order to effectively resolve this problem, a novel MTPA control scheme based on the second harmonic splicing technique is proposed in this article. Differing from the conventional method, the proposed solution utilizes the transient response current slopes of fundamental maximum active-voltage vector to splice a specific second harmonic signal that contains the optimal current distribution angle. After selecting two available and different splicing coefficients in each sector to guarantee the continuity of the spliced second harmonic signal, the optimal current distribution angle can be obtained accurately without any machine parameters through a simple signal demodulation, which significantly enhances the robustness to machine parameter variations. Furthermore, the influence of rotor position acquisition errors caused by the position sensor's limited accuracy and installation misalignment is analyzed in detail. Finally, the experimental results demonstrate the effectiveness and feasibility of the proposed MTPA control scheme.

Optimal distribution of heat exchanger area for maximum efficient power of thermoelectric generators

Based on the multi-element thermoelectric generator model established in the previous literature, finite-time thermodynamic theory is used to deduce the efficient power expression of the thermoelectric generator. For a fixed number of thermoelectric elements and total heat exchanger area, the maximum efficient power is obtained by optimizing heat exchangers area distribution and output current. The effects of the number of thermoelectric elements and the total heat exchanger area on the maximum efficient power are analyzed. The results show that there is an optimal heat exchangers area distribution and an optimal output current to maximize the efficient power of the thermoelectric generator. Thermal efficiency at maximum efficient power is always better than at maximum power output. The total heat exchanger area is increased from 0.03 m2 to 0.09 m2, the maximum efficient power is increased from 0.02 W to 0.26 W, and the corresponding optimal output current and optimal heat exchangers area distribution are increased by 138% and 6.7%, respectively. In the actual designing process of the thermoelectric generator, the influences of the number of thermoelectric elements, the total heat exchanger area, the output current and the heat exchangers area distribution on its performance should be considered.

Dual Ascent Algorithm-Based Improved Droop Control for Efficient Operation of AC Microgrid

In this work, the loss (including wire loss and converter loss) of island three-phase AC microgrid is modeled as a quadratic function of the current distribution coefficient, that is, a concave function with equality and inequality constraints. On the basis of the concave optimization principle, the optimal current distribution coefficient of the distributed energy unit (DEU) is calculated online by the double ascent optimization method (DAOM) to minimize the distribution loss. It is proven that the concave function with multi-variables can be optimized by the DAOM. Using the average reactive power distribution scheme, the optimal active power distribution coefficient with the minimum distribution loss of the AC microgrid can be obtained in real time. In addition, given the high R/X ratio in the short-distance AC microgrid, the active power–frequency (P-ω) droop control and reactive power–voltage amplitude (Q-E) droop control are not suitable for power distribution among DEUs. Thus, an advanced strategy comprising active power–voltage amplitude (P-E) droop control and reactive power-frequency (Q-ω) droop control is proposed to dispatch the output active powers and reactive powers of DEUs. Simulation examples are provided to verify the convexity of the proposed model and the effectiveness of the control strategy.

Genetic-Algorithm-Based Optimization of a 3D Transmitting Coil Design with a Homogeneous Magnetic Field Distribution in a WPT System

In magnetically coupled resonant wireless power transfer (MCR-WPT) systems, the nonhomogeneous magnetic field of the transmitting coil can lead to frequency splitting phenomena and lower efficiency. In this paper, a 3D transmitting coil (TX) with a homogeneous magnetic field distribution is proposed. The proposed coil structure consists of two layers with different numbers of turns per layer, i.e., with different current distributions. To achieve a homogeneous magnetic field distribution with a high magnetic field value and a low profile of the 3D coil structure, the optimal layer placement and current distribution were optimized using a genetic algorithm (GA). The prototype of the optimized coil was fabricated, and its magnetic field distribution was measured. The measurement results agreed more than 95% with the simulation results. The measured homogeneous area was at least 12.5% larger than reported in the literature. By using a different current distribution, the profile of the 3D coil structure was successfully reduced by 29% and the average magnetic field value was increased by 25% compared to our previous work.

Bipolar Spiral Midfield Wireless Power Transfer for Cardiac Implants Application

This letter proposes a midfield wireless power transfer system using a bipolar spiral-shape transmitter (BPSP-Tx) for cardiac implants application. Optimal current distribution is built on BPSP-Tx surface following spiral structure to generate a focused field inside human tissue and adapt the implantable receiver (Rx) misalignments. Source performance has been verified by implantable hooked-shape Rx (HKSD-Rx) that separated at a distance of 45 mm from Tx. Measurements are conducted in minced pork for validation. Experimental results show that the transmission coefficient can achieve -20.48 dB at a distance of 45 mm and -22.15 at 60 mm. Furthermore, the Rx misalignment is verified by output power level, which shows that the proposed system can maintain high performance on a rotation range of Rx from -90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> to 90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . Finally, the human safety regulations are verified to present a low specific absorption rate, which demonstrates the potential for cardiac implants.

Meta-heuristic optimization algorithms for synthesis of reconfigurable hexagonal array antenna in two principle vertical planes

AbstractThis study illustrates the dynamical reconfiguration of a concentric hexagonal antenna array radiation to generate a pencil beam and flat-top beam simultaneously by electronic control in two principle vertical planes under consideration. Both the beams share a common normalized optimal current excitation amplitude distribution while the optimal sets of phase excitation coefficients are varied radically across the hexagons to generate a flat-top beam. The proposed approach is able to solve the underlying multi-objective problem and flexible enough to the efficient implementation of additional design constraints in the considered φ-planes. In this paper, a set of simulation-based examples are presented in an integrated way. The outcomes validate the effectiveness of the stated optimization using meta-heuristic optimization algorithms (teaching–learning-based optimization, symbiotic organism search, multi-verse optimization) to reach the solution globally and prove actual relevance to the concerned applications.

Optimization and control of battery-flywheel compound energy storage system during an electric vehicle braking

Combining the advantages of battery’s high specific energy and flywheel system’s high specific power, synthetically considering the effects of non-linear time-varying factors such as battery’s state of charge (SOC), open circuit voltage (OCV) and heat loss as well as flywheel’s rotating speed and its motor characteristic, the mathematical models of a battery-flywheel compound energy storage system are established. Taking the recovered braking energy of the system as an objective, an energy optimization method based on GA is proposed to obtain the optimal electric braking torque and current distribution factor under different working conditions, which realizes the current distribution between the battery and the flywheel as well as the allocation between the mechanical braking torque and the electric braking torque. Simultaneously, a double neural networks-based adaptive PI vector control method is proposed to regulate the rotating speed of the flywheel motor. Research results demonstrate that using the proposed methods the overall recovered energy increases by 1.17times and the maximum charging current of the battery decreases by 42.27% compared with a single battery system, and the stability and robustness of the flywheel system are significantly improved, which provides theoretical and technical references for making the energy management plan of electric vehicles.

Optimal control allocation for the parallel interconnection of buck converters

This paper presents a control algorithm for the parallel interconnection of heterogeneous power converters. A single resistive load is assumed to be fed by an arbitrary number of buck converters via a common DC bus. The approach is based on control allocation theory and a constrained quadratic optimization algorithm. The strategy achieves a fast voltage response with an optimal current distribution among the converters, while taking into account the current limits, the dynamic response, and the efficiency of the individual converters. An interesting by-product of the approach is the ability to put converters in and out of service through trivial adjustments of the code. The benefits of the approach are assessed through simulations and an experimental evaluation.

Analysis and Optimization of Current Dynamic Control in Induction Motor Field-Weakening Region

The maximum-torque-output (MTO) trajectory can achieve optimal current distribution for induction motor (IM) field-weakening (FW) control. To provide the dynamic model for MTO, this letter proposes quantitative analysis of the current dynamic character in FW control. As the current vector moves along MTO trajectory, the current changing rate and voltage margin requirement are calculated to study the dynamic control objective and the realization condition of FW control. According to the summarized changing law of voltage margin requirement, the d -axis voltage margin priority approach is applied to the IM FW system for current dynamic optimization. The effectiveness of the studied method is verified through comparison experiments on an advanced RISC machine (ARM)-based 3.7-kW IM platform.

Realizing Optimal Current Distributions for Radiation Efficiency in Practical Antennas

Modern antenna design is facing increasing issues with the radiation efficiency, since the space available for antennas is scarce and antennas are fitted into lossy environments. This letter presents a multiport antenna design method with a computationally efficient way to realize the port currents providing the highest radiation efficiency. In this method, an antenna is described with multiple excitation ports in electromagnetic simulations. The measurement results of an example design demonstrate the achieved benefit compared to traditional antenna design.

Efficiency Bound of Radiative Wireless Power Transmission Using Practical Antennas

In this communication, we provide the efficiency bound of radiative wireless power transmission (WPT) for several types of practical receiving antennas. The optimal current distribution of the transmitting surface is analytically derived. In addition, the maximum bound of the power transfer efficiency (PTE) and the optimal shape of the base station current are found in terms of the transmitting area and the transfer distance. Examples applying the proposed theory to three types of practical mobile antennas are shown and the results are compared with those of previous reports, demonstrating significant differences. The results indicate that the optimum current distribution on the transmitting surface and the maximum efficiency of radiative WPT depend on the radiating field pattern of the mobile antenna. The results further show that microwave power transmission using a compact patch antenna can achieve high power transmission efficiency, especially in the Fresnel region.

Optimal Three-Dimensional Current Computation Flux Weakening Control Strategy for DC-Biased Vernier Reluctance Machines Considering Inductance Nonlinearity

An optimal three-dimensional current computation flux weakening control strategy for dc-biased Vernier reluctance machines (VRMs) is proposed in this paper. Compared with permanent magnet synchronous machines, dc-biased VRMs have an additional degree of freedom to regulate the rotor flux through variable dc-biased armature current. The conventional flux weakening control strategy does not utilize the adjustable dc field current, and the output capacity in the flux weakening region is limited. In this paper, the optimal three-dimensional current distribution is calculated at the intersection of current and voltage constraint. Meanwhile, in order to maintain the armature voltage within the voltage constraint, the inductance nonlinearity is reflected by constructing the inductance table. The algorithm provides maximum output capability and high efficiency for dc-biased VRMs despite the changes in inductance parameters in the whole flux weakening region. Finally, the effectiveness of the proposed control strategy is validated by experimental results for a prototype machine.

Calculation of Printed Circuit Board Power-Loop Stray Inductance in GaN or High &lt;italic&gt;di/dt&lt;/italic&gt; Applications

This paper is concerned with the determination of parasitic inductance values in very fast switching power devices. To keep improving today's power converters, new technologies are studied, which exhibit very low switching times. The wide-bandgap semiconductors are among the key aspects of these improvements. Thanks to their internal properties, they allow very fast di/dt and dv/dt with very small footprint. Stray loop inductance needs to be kept low, as it creates high peak voltage upon switching of a transistor with fast di/dt . In particular, the stray inductance value with respect to the loop size and geometry needs to be calculated accurately at the design stage of the power converters. This paper analyzes three loop geometries and studies one with minimized stray inductance and optimal current distribution. An analytical method is proposed, which uses the Biot–Savart law for an accurate analytical estimation of the magnetic field intensity in the selected geometry, leading to inductance calculation. A comparison between the classical two-plate inductance estimation formula and the proposed stray inductance estimation is presented, proving more accurate value with the method proposed in this paper. Finally, an experiment has validated the new inductance estimation formula.

СURRENT FILTERING IN A THREE-PHASE THREE-WIRE POWER SYSTEM AT ASYMMETRIC SINUSOIDAL VOLTAGES

Purpose. Investigation of the optimal current distribution between source, shunt active filter and reactive compensator of a three-phase three-wire system that provides consumption of a sinusoidal symmetric current under asymmetric source voltages with minimal power losses was provided. Methodology. The tasks were solved by conducting theoretical and experimental studies. The main provisions of the theory of electrical circuits, the apparatus of mathematical analysis, methods for solving linear differential and algebraic equations, elements of matrix and complex calculus and vector algebra are used. During the development, modern methods and software of computer simulation of electrical engineering complexes and dynamic systems were applied: Matlab-Simulink, MATHCAD. Originality. The principle of compensating current distribution between PAF and reactive compensator of a three-phase three-wire power system with asymmetric sinusoidal voltage was proposed at which the input current is equal to the positive-sequence active current and rms value of PAF current is minimal. The feasibility to compensate the inactive sinusoidal Fryze current by reactive elements under arbitrary combination of load and source parameters was proved and expression for direct calculation of the reactive compensator parameters for generation of inactive Fryze current in the source unbalanced mode was obtained. Practical value. The simulative example for transmission line load showed that combined application of PAF and reactive compensator with the specified distribution of compensating currents ensured a reduction of power losses in 3.273 times and rms value of the SAF current is 12.9 % of rms value total compensation current.

Reduction of leakage inductance and AC resistance of planar transformers by optimising the current distribution

Planar transformers (PTs) are becoming increasingly popular in high-power density, high-frequency SMPS in recent years due to their unique advantages including low profile structures and excellent thermal properties. This study focuses on detailed investigation of the effects of coil current distribution within each winding layer on leakage inductance and AC resistance of a PT, and an analytical derivation based on variational method is given. Then the optimal current distribution is proposed and verified through 3D finite element analysis simulation and physical experiments. The results show that the leakage inductance and AC resistance can be reduced further by optimising the current distribution. Accordingly, a practical implementation method is proposed to control the current distribution within a winding layer by adjusting the widths of conductors.