Optimal Power Transfer Research Articles

Design and implementation of a dual band bioinspired leaf rectenna for RF energy harvesting applications

In this article, both design and implementation of a novel Omni-directional bioinspired Linden leaf-shaped rectenna are reported. The antenna is designed for the energy harvesting purposes under the operation frequency range between 1.6 and 2.65 GHz with a second harmonic rejection property. At the rectifier stage, voltage doubler circuit is designed and implemented with the help of microstrip transmission lines, which are used for impedance matching procedure between the antenna and the rectifier for the optimum power transfer from the antenna to the load for the operation dual bands of universal mobile telecommunication service and WIFI. In the design, SMS7630Schottky diodes, high frequency capacitors and inductors are used as the main surface mount devices. The FR4 epoxy material is selected as a substrate material for both the antenna and the rectifier circuit due to its low cost and easy—production scheme. The maximum efficiency value realized at the dual band operation is 42% at the 0 dBm input power level. The output voltage value and the harvested power at this point are nearly 960 mV and 0.42 mW with an optimum load RL = 2.2 KOhm. The implemented system can be used efficiently for the RF energy harvesting applications for the proposed frequency bands.

Optimum power transfer in RF front end systems using adaptive impedance matching technique

Matching the antenna’s impedance to the RF-front-end of a wireless communications system is challenging as the impedance varies with its surround environment. Autonomously matching the antenna to the RF-front-end is therefore essential to optimize power transfer and thereby maintain the antenna’s radiation efficiency. This paper presents a theoretical technique for automatically tuning an LC impedance matching network that compensates antenna mismatch presented to the RF-front-end. The proposed technique converges to a matching point without the need of complex mathematical modelling of the system comprising of non-linear control elements. Digital circuitry is used to implement the required matching circuit. Reliable convergence is achieved within the tuning range of the LC-network using control-loops that can independently control the LC impedance. An algorithm based on the proposed technique was used to verify its effectiveness with various antenna loads. Mismatch error of the technique is less than 0.2%. The technique enables speedy convergence (< 5 µs) and is highly accurate for autonomous adaptive antenna matching networks.

Effect of Coil Parameters on Layered DD Coil for Efficient Wireless Power Transfer

Inductive wireless power transfer technology (WPT) is gaining momentum recently for wide range of applications. This ranges from charging of portable electronic devices to static and dynamic charging of electric vehicles. It is enabled by the use of magnetic coils wound in certain shapes and dimensions. In order to gain optimal wireless power transfer, coil parameters such as the wire spacing and the core area, are critical. A less optimal selection of values for these parameters can lead to destructive or constructive interaction between the generated fields. In this letter, some coil parameters such as the inter-layer and turn spacing of the Layered DD (LDD) coil are investigated to determine how they influence the inductance which influences the WPT efficiency. It was deduced that the start radius of the LDD coil is directly proportional to the inductance. The inter-layer distance and change in radius exhibit an inversely proportional relationship.

A neuro-fuzzy approach for tracking maximum power point of photovoltaic solar system

This work presents a hybrid soft-computing methodology approach for intelligent maximum power point tracking (MPPT) techniques of a photovoltaic (PV) system under any expected operating conditions using artificial neural network-fuzzy (neuro-fuzzy). The proposed technique predicts the calculation of the duty cycle ensuring optimal power transfer between the PV generator and the load. The neuro-fuzzy hybrid method combines artificial neural network (ANN) to direct the controller to the region where the MPP is located with its reference voltage estimator and its block of neural order. After that, the fuzzy logic controller (FLC) with rule inference begins to establish the photovoltaic solar system at the MPP. The obtained simulation results using MATLAB/simulink software for the proposed approach compared to ANN and the perturb and observe (P&amp;amp;O), proved that neuro-fuzzy approach fulfilled to extract the optimum power with pertinence, efficiency and precision

Minimum Power Input Control for Class-E Amplifier Using Depletion-Mode Gallium Nitride High Electron Mobility Transistor

In this study, we implemented a depletion (D)-mode gallium nitride high electron mobility transistor (GaN HEMT, which has the advantage of having no body diode) in a class-E amplifier. Instead of applying a zero voltage switching control, which requires high frequency sampling at a high voltage (&gt;600 V), we developed an innovative control method called the minimum power input control. The output of this minimum power input control can be presented in simple empirical equations allowing the optimal power transfer efficiency for 6.78 MHz resonant wireless power transfer (WPT). In order to reduce the switching loss, a gate drive design for the D-mode GaN HEMT, which is highly influential for the reliability of the resonant WPT, was also produced and described here for circuit designers.

Vocalization with semi-occluded airways is favorable for optimizing sound production.

Vocalization in mammals, birds, reptiles, and amphibians occurs with airways that have wide openings to free-space for efficient sound radiation, but sound is also produced with occluded or semi-occluded airways that have small openings to free-space. It is hypothesized that pressures produced inside the airway with semi-occluded vocalizations have an overall widening effect on the airway. This overall widening then provides more opportunity to produce wide-narrow contrasts along the airway for variation in sound quality and loudness. For human vocalization described here, special emphasis is placed on the epilaryngeal airway, which can be adjusted for optimal aerodynamic power transfer and for optimal acoustic source-airway interaction. The methodology is three-fold, (1) geometric measurement of airway dimensions from CT scans, (2) aerodynamic and acoustic impedance calculation of the airways, and (3) simulation of acoustic signals with a self-oscillating computational model of the sound source and wave propagation.

Acute Comparative Effect of Foam Rolling and Static Stretching on Range of Motion in Rowers

Rowers’ anthropometric characteristics and flexibility are fundamental to increase stroke amplitude and optimize power transfer. The aim of the present study was to analyze the effect of foam rolling and static stretching on the range of motion over time. Eight university rowers (24.8 ± 3.4 yrs., height 182.3 ± 6.5 cm, body mass 79.3 ± 4.6 kg) participated in an alternating treatment design study with two-way repeated measures ANOVA. The sit and reach test was used to measure the range of motion. Both in the foam rolling and in the static stretching method, a pre-test (T0), a post-test (T1), and a post-15-min test (T2) were performed. A significant effect was observed on the range of motion over time (p &lt; 0.001), but not for time x method interaction (p = 0.680). Significant differences were found between T0 and T1 with foam rolling and static stretching (p &lt; 0.001, d = 0.4); p &lt; 0.001, d = 0.6). The differences between T0 and T2 were also significant with both methods (p = 0.001, d = 0.4; p &lt; 0.001, d = 0.4). However, no significant difference was observed between T1 and T2 (p = 1.000, d = 0.1; p = 0.089, d = 0.2). Foam roller and static stretching seem to be effective methods to improve the range of motion but there seems to be no differences between them.

Maximizing Transfer Efficiency with an Adaptive Wireless Power Transfer System for Variable Load Applications

Electronic devices usually operate in a variable loading condition and the power transfer efficiency of the accompanying wireless power transfer (WPT) method should be optimizable to a variable load. In this paper, a reconfigurable WPT technique is introduced to maximize power transfer efficiency in a weakly coupled, variable load wireless power transfer application. A series-series two-coil wireless power network with resonators at a frequency of 150 kHz is presented and, under a variable loading condition, a shunt capacitor element is added to compensate for a maximum efficiency state. The series capacitance element of the secondary resonator is tuned to form a resonance at 150 kHz for maximum power transfer. All the capacitive elements for the secondary resonators are equipped with reconfigurability. Regardless of the load resistance, this proposed approach is able to achieve maximum efficiency with constant power delivery and the power present at the load is only dependent on the input voltage at a fixed operating frequency. A comprehensive circuit model, calculation and experiment is presented to show that optimized power transfer efficiency can be met. A 50 W WPT demonstration is established to verify the effectiveness of this proposed approach.

Theoretical analysis of the optimization of power transfer from half loop source in a simple cavity

A model that illustrate the optimal placement of coupler inside an RF cavity is proposed. The chosen geometry of the cavity are rectangular and cylindrical cavity. A small half loop of localized current source which acts as a coupler is placed on the side of the cavity. The half loop is then rotated along an axis perpendicular to the side of the cavity. An angle which gives maximum transferred power for both cavities is then sought. The result is then compared between cavities, which is then used to estimate the optimized configuration of a half loop coupler inside an RF cavity.

Impedance Bandwidth Improvement of a Planar Antenna Based on Metamaterial-Inspired T-Matching Network

In this paper a metamaterial-inspired T-matching network is directly imbedded inside the feedline of a microstrip antenna to realize optimum power transfer between the front-end of an RF wireless transceiver and the antenna. The proposed T-matching network, which is composed of an arrangement of series capacitor, shunt inductor, series capacitor, exhibits left-handed metamaterial characteristics. The matching network is first theoretically modelled to gain insight of its limitations. It was then implemented directly in the 50- $\Omega $ feedline to a standard circular patch antenna, which is an unconventional methodology. The antenna’s performance was verified through measurements. With the proposed technique there is 2.7 dBi improvement in the antenna’s radiation gain and 12% increase in the efficiency at the center frequency, and this is achieved over a significantly wider frequency range by a factor of approximately twenty. Moreover, there is good correlation between the theoretical model, method of moments simulation, and the measurement results.

Simultaneous wireless information and power transfer optimization via alternating convex-concave procedure with imperfect channel state information

Simultaneous Wireless Information and Power Transfer (SWIPT) systems are viable models to implement wireless charging in Broadcast Channel (BC) systems. With the emergence of Internet of Things (IOT) and the 5th generation of telecommunication systems (5G), to make lifelong powered devices, wireless charging gets wider attention in scientific and industrial community. To optimally design such a system, we optimize a multi-user multi-antenna BC by simultaneously maximizing the sum of harvested energy and minimizing the sum Mean Square Error (MSE) for symbol detection at each receiver node. To have a tractable design problem, we recast this multi-objective problem as a Difference of Convex (DC) bilinear problem. The derived design problem is solved using the Alternating Convex Search (ACS) method and the Penalty Convex-Concave Program (PCCP) procedure. We solve this problem under two conditions: the perfect and the imperfect Channel State Information (CSI). Simulation results prove that the proposed algorithm outperforms reported recent research studies in this field.

A High-Q Resonant Inductive Link Transmit Driver With Adaptive-Predictive Phase-Continuous Tuning and Deviation Frequency Calibration for Enhanced FSK/PSK Modulation and Power Transfer

Inductively coupled power transfer systems often use high- $Q$ antenna circuits to reduce losses and increase transmission range. However, the narrow bandwidth due to the high $Q$ -factor conventionally constrains the modulation rate on the carrier, creating a tradeoff between power transfer efficiency and data rate. In this article, we show how instantaneous tuning of the antenna can permit frequency and phase modulation data rates beyond the $Q$ -factor limitations, provided that the drive and antenna resonance frequencies are kept the same at all times. It is also necessary to ensure that the modulation symbol boundaries are precisely aligned with the tracking of the resonance tuning to ensure phase continuity and optimum power transfer. With instantaneous tuning, phase modulation can be implemented by defined numbers of cycles at an offset frequency, provided the offset is precisely controlled. We describe how the required instantaneous resonance tuning can be achieved using a switched fractional capacitor technique and present a system architecture that can follow abrupt frequency changes due to the modulation while tracking changes to the resonant condition due to environmental detuning effects at each modulation frequency. An integrated mixed-signal driver/modulator/tuner demonstrator system is presented, operating from 10 kHz–2 MHz using a 0.18- $\mu$ m 1.8–50-V CMOS/laterally-diffused metal-oxide semiconductor (LDMOS) process. The system maintains phase continuity in the antenna current throughout frequency shift keying (FSK) and phase-shift keying (PSK) modulation and employs self-calibration of the PSK modulation frequencies to achieve precise angles of phase rotation for QPSK. The antenna tuning, modulation, and frequency calibration are verified with experimental results.

Optimization of Multi-energy Transfer Considering Internal Interaction and External Collaboration in Micro-Energy Network Group

Micro-energy network realizes the complementary of distributed energy production according to the characteristics of users’ energy demand and local resource conditions. In order to realize the efficient operation of micro-energy network group, this paper proposed an optimal power transfer model based on Mutual Energy Supporting Pattern in micro-energy network group. The concept of micro-energy network is given and the basic structure of micro-energy network group based on the interconnection of external energy hubs is first established. Then, the micro-energy network model of internal energy hub and optimal power transfer model is established. The optimal power transfer model of micro-energy network group is subdivided into two kinds of operation modes, the internal cooperation mode and the synergy cooperation mode. The internal cooperation mode is to address the problem of energy shortage at the micro-energy network, while the synergy cooperation mode is to solve the problem through the coordination of multiple energy hubs in the micro-energy network group. Finally, the model is validated by a system including electricity, gas, heat/cooling load and external energy hub.

Design and Implementation of Hybrid Active Power Filter (Hapf) for UPS System

Hybrid Active Power Filter (HAPF) is designed and applied for Uninterrupted Power Supply (UPS) System to mitigate harmonic currents in UPS during the power conversion from rectifiers to inverters (AC-DC-AC Converters). Various UPS types and topologies are used for continuous power supply without delay and protection to connected loads. In spite of the fact that UPS is one of the power quality apparatus but it has also drawback of disturbing the power system quality of system by current harmonics and voltage distortion during conversion of power. Passive and EMI Filters could not eliminate harmonics effectively from UPS system therefore it requires modern, rapid filtering method as well combination of Active and Passive Filters. Proposed model of HAPF for UPS System could mitigate current harmonics for optimal power transfer and minimize losses, increase overall efficiency, reliability and life span of equipment. Higher harmonic current and higher voltage distortion leads to greater power loss. In this paper the (d-q) theorem is applied for the identification of harmonic currents. The d-q theorem and calculation creates the signal of reference compensation current and this produced signal of current is tracked by the yield current of the voltage source converter.. Hysteresis based controller for HAPF is applied to create the switching signals to regulate and maintain the voltage source converter output currents. Harmonics and efficiencies are analyzed at different loads and on charging and discharging of batteries of various UPS System in different industries and sectors on the basis of experimental investigation then HAPF is designed and implemented. In simulation results, it is observed that THD reduced from 46 to 10%, the harmonic currents were compensated and eliminated effectively which improved power quality of UPS System. Furthermore, addition of proposed HAPF could save the power up to 15 % which lost due to poor power quality of UPS System.

Adaptability evaluation and active power regulation of FID in active distribution network

In this study, a two-layer model is established for evaluating the adaptability and regulating the active power to improve the economy and stability of a distribution network. A flexible interconnection device (FID) is used to provide flexible, fast, and accurate power conversion control in the active distribution network. It solves the power reverse problem due to photovoltaics (PV). The adaptability model is established in the planning layer to evaluate the revenue of the distribution network after access to FIDs in different numbers and positions with respect to the economy. The adaptive step-size search algorithm and FID active power transfer interval (which can be advantageous to the distribution network) are considered as the operation regions. Subsequently, the operation regions are transferred to the active power regulation model in the optimization layer via the sequential scan method to adjust the PV permeability and load ratio of the distribution network for stability. The elitist non-dominated sorting genetic algorithm is used to select the optimal position, number, and active power transfer values of the FID corresponding to the optimal PV permeability and load rate in the operation regions. Finally, the results of a realistic case study are provided and indicate that the proposed approach improves the economy and stability of the distribution network. The simulation results verify the effectiveness and feasibility of the proposed method.

The Relationship Between Mountain Bike Seat Tube Angle, Knee-pedal Alignment, And Knee Range Of Motion

PURPOSE: Newer bicycles have increasingly steep seat tube angles. Seat tube angle (STA) is consistent within each bike model, but changes with seat height and post positioning. Traditionally, a bike fit will vertically align the knee with the pedal at the midpoint of the downstroke. This positioning has an effect on a rider’s knee range-of- motion (ROM) potentially affecting fatigue rates. Additionally, the ROM may affect the knee-pedal spindle alignment position thereby affecting power capacity. Therefore, the purpose of this study was to determine if effective seat tube angle affects knee-pedal alignment and knee ROM. METHODS: Participants included 17 male and female (176.9 ±3.9 cm, 66.6 ±25.4 kg), amateur and elite, cross-country mountain bike racers. Reflective markers were placed by the same researcher at locations on the participants dominant side: greater trochanter of femur, lateral condyle of femur, and lateral malleolus of fibula. Photographs were taken of the bike alone and with the participant in their typical riding position, with leg at full extension, full flexion, and halfway through the downstroke. Photographs were analyzed to determine knee-to-spindle horizontal distance (KTS), peak knee flexion angle (KFA), and STA using digital measurement software (Dartfish USA, Alpharetta, GA). Linear regression was used to statistically analyze the data (alpha=0.05). RESULTS: For every 1 degree increase in STA, knee position moved forward 1.42 cm closer to the handlebars (p=0.050, R2= 0.23). After accounting for STA, KFA explained an additional 44% of the variance in KTS (p<0.001) where every 1 degree increase in KFA resulted in knee position moving 0.58 cm further away from the handlebars. When combined, STA and KFA explain 67% of the variance in KTS. CONCLUSIONS: It is generally accepted that KTS should be 0 to have optimal power transfer to the pedals and limit sagittal forces on the knee joint. Changing STA in order to decrease KTS may be effective to increase performance. Further research should examine how individualized STA could affect rider positioning and performance during endurance efforts.

Experimental study of resistive load for impedance matching of triboelectric energy harvester fabricated with patterned polydimethylsiloxane polymer layer

Impedance matching of the power source with the external load is one of the imperative parameters of any electronic system for the optimized power transfer from the power source to the load. Mismatch in impedance of power source and the external load may cause a drastic reduction in the power transfer due to reflections. In this paper, a systematic experimental study of load matching between energy harvester and load resistance has been presented. The experimental results showed output voltage without external load condition is 68.46 V with the output current of 14.59 µA, consequently instantaneous power of 0.937 mW. Under the optimum load of 4 MΩ, the output power reduced to 0.248 mW. A rigorous experimental study has been carried out under the frequency and force of 4.5 Hz and 2.8 N, respectively. The triboelectric energy harvester device has also been demonstrated for the potential applications of the self-sustained system.

Analysis of Fundamental Differences between Capacitive and Inductive Impedance Matching for Inductive Wireless Power Transfer

Inductive and capacitive impedance matching are two different techniques optimizing power transfer in magnetic resonance inductive wireless power transfer. Under ideal conditions, i.e., unrestricted parameter ranges and no loss, both approaches can provide the perfect match. Comparing these two techniques under non-ideal conditions, to explore fundamental differences in their performance, is a challenging task as the two techniques are fundamentally different in operation. In this paper, we accomplish such a comparison by determining matchable impedances achievable by these networks and visualizing them as regions of a Smith chart. The analysis is performed over realistic constraints on parameters of three different application cases both with and without loss accounted for. While the analysis confirms that it is possible to achieve unit power transfer efficiency with both approaches in the lossless case, we find that the impedance regions where this is possible, as visualized in the Smith chart, differ between the two approaches and between the applications. Furthermore, an analysis of the lossy case shows that the degradation of the power transfer efficiencies upon introduction of parasitic losses is similar for the two methods.

Free-Positioning Wireless Power Transfer System Based on One-to-Multiple Topology

The wireless power transfer (WPT) system is an interesting alternative for charging electric vehicles and has a broad prospect in public transport applications. In order to obtain optimal power transfer, the existing WPT systems often require perfect alignment between the primary and secondary coils, which can hardly be met in real applications. To relieve this problem and achieve the goal of free positioning, a one-to-multiple WPT topology being able to improve the misalignment tolerance at the secondary side is proposed in this letter. Based on circuit analysis and MATLAB simulation, a mixed mode is proposed to obtain a steady power transfer with horizontal misalignment. To verify the proposed topology, a one-to-two WPT system with a three winding transformer is developed in this letter, showing that proposed topology with the mixed mode can significantly increase the positioning adaptability.

Development of Maximum Power Point Tracking Solar Charge Controller for 120 Volt Battery System at Pandansimo Hybrid Power Plant

Pandansimo Hybrid Power Plant (HPW) is located at Pandansimo Beach, Bantul, Yogyakarta. It has a maximum capacity of 57.5 kW, combining solar and wind energy technologies. Currently a part of it (4 kWp solar panel system) is used for ice maker machine with an efficiency merely of 60% in average. To increase efficiency of system and safety of battery charging, a special Maximum Power Point Tracking (MPPT) Solar Charge Controller is developed. This system is developed to optimize power transfer from solar panel array to battery, which is shown as solar panel characteristic in a I-V curve. The purpose of this research is to develop the MPPT Solar Charge Controller with PID algorithm for 120 volt battery system and 4 kWp solar panel. The Solar Charge Controller (SCC) design uses microcontroller system that is easy to repair and improve. The SCC component can be found easily in local electronic components stores around Yogyakarta. The SCC design involves several main parameter: PWM switching frequency 50 kHz, mosfet IRFP260 power switching device, 120 Volt battery, rated current charge of 40 ampere, and three state battery charge sequential. The result of this research are the MPPT SCC with average efficiency of more than 90%, real charge current of 30 Ampere, and PV voltage optimum of 165 Volt.