Wireless Power Transfer System Research Articles

An I/Q Phase Detection-Based Harmonic- Insensitive Phase Synchronization Method for Bidirectional Wireless Power Transfer System

An I/Q Phase Detection-Based Harmonic- Insensitive Phase Synchronization Method for Bidirectional Wireless Power Transfer System

Synthesis and Control of a Three-Port LCL Resonant Wireless Power Transfer System for DC Energy Conversion Applications

Synthesis and Control of a Three-Port <i>LCL</i> Resonant Wireless Power Transfer System for DC Energy Conversion Applications

Fast Start-Up Control of Both-Side Current Without Overshoot Focusing on Rectification Timing for Dynamic Wireless Power Transfer Systems

The paper proposes a method to improve the tran- sient characteristics of current overshoot and oscillation at the start of power transmission for a dynamic wireless power transfer system. The system is important to reduce the settling time as short as possible without current overshoots for a stable power supply. However, conventional methods to suppress current overshoot have a slow response on the secondary side. This paper proposes the superposition of primary and secondary responses. The proposed method controls the secondary voltage by comparing the steady-state current with the current value on the secondary side. The method can effectively suppress the oscillations in the transient response by applying the secondary voltage at the appropriate timing. This paper also studied the ro- bustness of constraints based on model analysis and experimental verification. In the experiments, the proposed method reduces the current overshoot and the settling time of the secondary current, and maximizes the receiving energy.

A Novel Rotating Wireless Power Transfer System for Slipring with Redundancy Enhancement Characteristics

This study investigates the dynamics of wireless power supply technology under rotation and its system redundancy, aiming to design a redundant, rotating wireless power supply system. In order to satisfy specifications of redundancy and fault tolerance, the circuit design of the wireless power transmission system was developed, and a planar three-sector coil coupling mechanism was designed; finally, the stability and power output characteristics of the system were assessed under static and dynamic working conditions, and the results show that the maximum output power of the system can reach 3 kW and the efficiency is more than 91% under both static and dynamic working conditions. The study improved the rotating wireless charging system’s efficiency, which improves the energy utilization efficiency.

Multi-Objective Optimization Study on the Coupling Mechanism of Underwater Wireless Power Transfer Systems

Magnetically coupled resonant wireless power transfer (MCR-WPT) technology offers longer effective transmission distances and higher efficiency compared to traditional charging methods, making it better suited to the prolonged and efficient operation of autonomous underwater vehicles. This paper first establishes a traditional mathematical model and then refines it while analyzing the variations in the self-inductance and mutual inductance of underwater coils. To further enhance the system’s performance, a multi-objective optimization of the coupling mechanism is conducted. An orthogonal experiment is employed to determine the effects of various influencing factors on the coils’ self-inductance and mutual inductance. Subsequently, an RBF neural network is used to create a regression prediction model based on the results of the orthogonal experiment. The NSGA-II algorithm is then applied for the multi-objective optimization of the coupling mechanism, resulting in a Pareto front solution set. The optimized efficiency is 93.35%, representing an approximately 6% improvement over the original system, with the power density increasing from 1.267×106 W/m3 before optimization to 4.782×106 W/m3 after optimization. Significant enhancement in system performance is achieved.

Decoupled dual‐channel loosely coupled transformer with hybrid nanocrystalline and ferrite core for current sharing of modular wireless power transfer system

AbstractCross‐coupling and current sharing are the main problems faced by modular wireless power transfer (WPT) systems for electric vehicle (EV) applications. In this study, a decoupled dual‐channel wireless power transfer loosely coupled transformer (LCT) with a hybrid core composed of nanocrystalline and ferrite is proposed for modular WPT systems, as well as WPT systems with specific hybrid topology or detuned compensation. Firstly, the requirements of the LCT for modular parallel dual‐channel WPT system and detuned compensation are discussed. For these requirements, the structure and corresponding optimization design method of the decoupled dual‐channel LCT with a hybrid core is then proposed, and an LCT is designed with this method for the case study. Furthermore, the LCT is analysed by the finite element method (FEM). It is revealed that the mutual inductances of the proposed LCT between transmitting and receiving coils can be symmetrical under misalignment in multiple directions, while the cross‐coupling is eliminated. Finally, the designed LCT is manufactured and verified in a modular parallel dual‐channel WPT system. The experimental results show that the current and power sharing is realized under misalignment in multiple directions.

Enhanced efficiency of magnetic resonant wireless power transfer system using rollable and foldable metasurface based on polyimide substrate

Enhanced efficiency of magnetic resonant wireless power transfer system using rollable and foldable metasurface based on polyimide substrate

Waveform Design for the Integrated Sensing, Communication, and Simultaneous Wireless Information and Power Transfer System.

Next-generation communication systems demand the integration of sensing, communication, and power transfer (PT) capabilities, requiring high spectral efficiency, energy efficiency, and low cost while also necessitating robustness in high-speed scenarios. Integrated sensing and communication systems (ISACSs) exhibit the ability to simultaneously perform communication and sensing tasks using a single RF signal, while simultaneous wireless information and power transfer (SWIPT) systems can handle simultaneous information and energy transmission, and orthogonal time frequency space (OTFS) signals are adept at handling high Doppler scenarios. Combining the advantages of these three technologies, a novel cyclic prefix (CP) OTFS-based integrated simultaneous wireless sensing, communication, and power transfer system (ISWSCPTS) framework is proposed in this work. Within the ISWSCPTS, the CP-OTFS matched filter (MF)-based target detection and parameter estimation (MF-TDaPE) algorithm is proposed to endow the system with sensing capabilities. To enhance the system's sensing capability, a waveform design algorithm based on CP-OTFS ambiguity function shaping (AFS) is proposed, which is solved by an iterative method. Furthermore, to maximize the system's sensing performance under communication and PT quality of service (QoS) constraints, a semidefinite relaxation (SDR) beamforming design (SDR-BD) algorithm is proposed, which is solved using through the SDR technique. The simulation results demonstrate that the ISWSCPTS exhibits stronger parameter estimation performance in high-speed scenarios compared to orthogonal frequency division multiplexing (OFDM), the waveform designed by CP-OTFS AFS demonstrates superior interference resilience, and the beamforming designed by SDR-BD strikes a balance in the overall performance of the ISWSCPTS.

Analysis and design of high‐frequency multiple‐output wireless power transfer system with load‐independent class‐E/F inverter

AbstractThis paper proposes a high‐frequency multiple‐receiver wireless power transfer (WPT) system with a load‐independent class‐E/F inverter. Each receiver has a post‐regulator, which changes the equivalent resistance seen from the inverter to obtain the necessary power for output voltage regulation. Because the load‐independent class‐E/F inverter generates constant AC current ( ), the transmitter supplies the minimum required power to the receivers by the change of the equivalent resistances. Besides, the load‐independent inverter consistently achieves zero‐voltage switching (ZVS) without any control. As a result, no information feedback by wireless communication is necessary for output regulation and ZVS achievement, simplifying the system configuration and improving the transient response of the control. This paper presents analytical expressions of the proposed system. Besides, the experiment was carried out with a two‐receiver WPT system. The implemented system worked well by individual and independent output regulation of the post regulator at each receiver. The implemented WPT system achieved the power‐delivery efficiency of 83.4% at the 6.78 MHz transmission frequency and the total output power of 40 W.

Power boundaries in resonant electrodynamic wireless power transfer systems

This article focuses on deriving the maximum power that can be transmitted using recent wireless power transfer technology based on an electrodynamic receiver. Analytical derivations reveal two main constraints that can limit transmitted power: the magnetic field safety limit and the maximum stress before breaking the receiver. From these limits, expressions of maximum magnetic forces and power are derived, providing physical insights on how to optimize the transmitted power. Interestingly, the optimal electrical condition and the optimal electromechanical efficiency differ when maximizing the transmitted power under each constraint. In the final section of the paper, the proposed theoretical boundaries are applied to two types of receivers, based on either electromagnetic or piezoelectric transducers. The results demonstrate that the maximum power density achievable with both receivers is inherently limited (&lt;10 mW/cm3) under realistic assumptions regarding electromechanical coupling and electrical circuitry. This value is smaller than some previously reported results involving rotating or magnetoelectric solutions, indicating that clamped-free beams are not the optimal solution for electrodynamic wireless power transfer. This analysis can be extended to other types of receivers and will be useful for optimizing, sizing, and assessing any technological solution for wireless power transfer.

A reconfigurable wireless power transfer system with constant exciting current for charging multiple batteries

At present, wireless power transfer (WPT) systems with constant current (CC) or constant voltage (CV) characteristics are typically achieved using a single transmitter and single pickup (STSP) configuration, which cannot transfer power to multiple battery loads simultaneously. In this paper, the LCC-LCC/S reconfigurable topology is proposed to realize the CC-to-CV transition for multiple battery loads. An LCC topology is designed on the primary side to achieve a constant current (0.362A) flowing through the transmitting coil to enable independent operation of power pickups. A reconfigurable LCC/S topology is designed on the secondary side to achieve the CC-to-CV transition of the battery loads. The received power from the pickups remains unaffected when pickups are moved in or out or are in different operating modes (CC or CV). The circuit can maintain zero phase angle (ZPA) operation, which greatly enhances the overall power density of the system. Additionally, detailed design process for the compensation parameters on both the primary and secondary sides are provided. Theoretical analysis proves that good system stability and robustness can be obtained in the case of variable quantity of pickups and quality factors of coils. The experimental prototype was built, with the CC value for the battery load designed at 0.7A and the CV value designed at 8 V. Experimental results demonstrate the smooth CC-to-CV transition of the proposed WPT system (with 3 pickups) at a power output of 15.4 W, and the system’s maximum efficiency can reach 75.5 %.

Rotating wireless power transfer: A new concept for wireless charging systems

Fast and safe charging are current concerns in relation to wireless charging of autonomous guided vehicles (AGVs). Wireless Power Transfer (WPT) is a capable solution and a replacement for conventional contact-based methods. However, resonant inductive and capacitive WPT topologies demand more power as the gap between transmitter and receiver pads increases. These structures, initially developed for electric vehicle applications, do not adequately optimize power transfer and power quality for the smaller surface areas of AGVs. In this paper, a novel topology for wireless charging concept is described and validated. This methodology has been named rotating WPT, with a primary side spinning neodymium magnet disc. The receiver pad is composed of a circular coil with ferrite U-cores. Calculations of the induced voltage over the rotating magnetic field resulted in 1.95 V at an operating frequency of 2.7 kHz. FEM simulation results show approximately 3 V, while laboratory experiments outputted 33 mV at 3.8 kHz. A sinusoidal waveform was observed from prototype, and power was successfully transferred to the receiver end, validating this proposed topology. This novel WPT system has no inverter, rectifier, nor compensation, decreasing reactive power, assembly costs and complexity while transferring power and enhancing power quality.© 2017 Elsevier Inc. All rights reserved.

A CV‐type WPT system based on CLC‐N compensation with compact receiver

AbstractThe demand for wireless power transfer (WPT) systems that can maintain a constant voltage (CV) output characteristic is gradually increasing in some practical application areas of WPT, such as industrial power supplies. However, existing CV‐type systems are often limited by the parameter design of the loosely coupled transformer (LCT), and the configuration of the receiver side is not compact enough. Therefore, this paper proposes a strongly coupled system with a CV output function composed of capacitor‐inductor‐capacitor‐none (CLC‐N) topology. The system's transmitter uses a CLC compensation, while the receiver conforms to a minimalist design without the need for compensation components such as capacitors and inductors. The initial segment of the paper pertains to the discussion of the conditions required to satisfy both the zero‐phase‐angle (ZPA) and CV output functionality of the suggested system. Subsequently, an in‐depth approach to parameter design is outlined, accentuating that the output voltage remains unrestricted by the LCT's parameters. Additionally, this paper examines the realization of zero‐voltage switching (ZVS) within the suggested system as well as the influence that variations in compensation components have on the CV output function. To underscore the benefits of the suggested CV‐type WPT system that employs CLC‐N compensation, the paper presents a comparison with a range of other CV‐type WPT systems. Ultimately, an experimental prototype is fabricated to test the theoretical framework, and the results from these experiments confirm the feasibility of the suggested CV‐type WPT system based on CLC‐N compensation.

Dynamic Resonant-Inductive Wireless Power Transfer System for Automated Guided Vehicles with Reduced Number of Position Sensors

This paper deals with the position detection of automated guided vehicles (AGVs) in dynamic resonant-inductive wireless power transfer (WPT) systems. A position detection is necessary to activate the correct transmitting coil. One of the simplest and most effective approaches for a position detection method is to use optical or magnetic position sensors for each coil. However, due to needing a high number of sensors, this technique is relatively expensive. Therefore, an AGV position detection technique based on a reduced number of optical or magnetic sensors (by a factor of two) is proposed. The proposed detection technique was verified experimentally by using a scaled-down prototype of the dynamic WPT system. The proposed approach can be easily implemented by uploading a specific program code to a microcontroller. The microcontroller with the code developed by us was used for processing data from AGV position detection sensors, activating a suitable transmitting coil and controlling an inverter of the dynamic WPT system. As shown by the experiments, due to the proposed approach for the position detection of AGVs and activation of transmitting coils, the number of the position detection sensors is reduced by a factor of two, leading to reductions in the overall cost and level of complexity of the dynamic WPT system without degrading its performance.

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.

Reconfigurable Intelligent Surface-Assisted RF Wireless Power Transfer for Internet of Things System

In this work, we study the utilization of reconfigurable intelligent surface (RIS) for assisting the radiofrequency (RF) based wireless power transfer (WPT) in the Internet of Things (IoT) system. The RIS device in this system is utilized to provide the line of sight (LOS) path when an obstacle blocks the direct power transmission from the transmitter to the receiver. In this work, we present a comprehensive modeling of the RIS-assisted RF WPT for IoT systems, which includes the spatial model, RIS-assisted RF WPT model, and total receiver power model. The performance of RIS-assisted RF WPT is evaluated by simulation matched to the IoT system. By simulation, we have verified that the RIS device can assist the RF WPT in the IoT system, especially when the obstacle completely blocks the power transmission directly from the transmitter to the receiver. The receiver can achieve 0,4714% end-to-end power transfer efficiency at a 1 meter distance from the RIS device. Meanwhile, 0,0290% end-to-end power transfer efficiency is achieved within a 15 meters distance from the RIS device. In this work, we have investigated the performance of RIS-assisted RF WPT with various numbers of unit cells in the RF WPT system. We found that increasing the number of unit cells in RF WPT after a certain number is ineffective for the RF WPT in an IoT system.

Thin Film Magnetic Sensor for Magnetic Near‐Field Measurement in Wireless Power Transfer System

In this study, we employed a high‐frequency‐driven thin‐film magnetic sensor to precisely measure the magnetic near field with enhanced spatial resolution, a challenge often faced by conventional loop antennas. Our study introduced an innovative approach utilizing this magnetic sensor to assess the magnetic near field in wireless power transfer systems, comparing its performance against that of a loop antenna. Our findings demonstrate that the magnetic sensor achieves its peak signal‐to‐noise ratio at a DC bias field of 4.7 Oe and carrier frequency of 0.5 GHz, boasting a detection limit for magnetic fields of ~0.4 A/m. Moreover, the magnetic field trend measured by the magnetic sensor closely aligns with simulation results, exhibiting sharper changes around the center compared to the loop antenna. These results highlight the superior sensitivity and spatial resolution of the magnetic sensor over conventional loop antennas. By enhancing the reliability of electronic systems across diverse applications, these sensors pave the way for advanced EMI/EMC evaluation techniques. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Design and implementation of a high misalignment-tolerance wireless charger for an electric vehicle with control of the constant current/voltage charging

Wireless charging of Electric Vehicles (EVs) has been extensively researched in the realm of electric cars, offering a convenient method. Nonetheless, there has been a scarcity of experiments conducted on low-power electric vehicles. To establish a wireless power transfer system for an electric vehicle, optimal power and transmission efficiency necessitate arranging the coils coaxially. In wireless charging systems, coils often experience angular and lateral misalignments. In this paper, a new alignment strategy is introduced to tackle the misalignment problem between the transmitter and receiver coils in the wireless charging of Electric Vehicles (EVs). The study involves the design and analysis of a coil, considering factors such as mutual inductance and efficiency. Wireless coils with angular misalignment are modelled in Ansys Maxwell simulation software. The proposed practical EV system aims to align the coils using angular motion, effectively reducing misalignment during the parking of two-wheelers. This is achieved by tilting the transmitter coil in the desired direction. Furthermore, micro sensing coils are employed to identify misalignment and facilitate automatic alignment. Additionally, adopting a power control technique becomes essential to achieve both constant current (CC) and constant voltage (CV) modes during battery charging. Integrating CC and CV modes is crucial for efficiently charging lithium-ion batteries, ensuring prolonged lifespan and optimal capacity utilization. The developed system can improve the efficiency of the wireless charging system to 90.3% with a 24 V, 16 Ah Lithium Ion Phosphate (LiFePO4) battery at a 160 mm distance between the coils.

Design and validation of a DC–DC converter-based inductive power transfer system with increased efficiency and reduced voltage stress across switches

Research in wireless power transfer(WPT) focuses on improving efficiency, reducing energy consumption, improving safety, and increasing sustainability. It prioritises developing more efficient transmission technologies, such as high-frequency switching and resonant coupling, to enhance the system’s overall performance. However, high voltage stress across the semiconductor devices during switching operations at high frequencies can result in increased switching loss, leading to decreased overall efficiency of the WPT system. The switching loss can be minimised by reducing voltage stress, resulting in higher efficiency and improved energy transfer performance. This leads to more cost-effective WPT solutions without compromising performance or reliability by using lower-rated components and reducing the need for elaborate voltage clamping and protection circuits. Lowering voltage stress across switches can also help WPT systems comply with industry standards and regulations related to electrical safety, electromagnetic compatibility (EMC), and energy efficiency. Meeting these standards is essential for ensuring the widespread adoption and commercial success of WPT technology. In this article, a class ø2 inverter and a modified class-E rectifier is integrated and applied in a WPT system. The benefits of a Resonant class ø2 inverter are zero voltage switching(ZVS) and lower switch voltage stress as compared to its predecessors. Also, a resonant class E/F3 rectifier inductively coupled in the receiving stage reduces the peak voltage stress across the diode. The system shown here is tuned to achieve maximum overall transfer efficiency. The proposed class ø2-E/F3 combined WPT system operating at 50 kHz simulated in PSIM software yielded a dc-dc efficiency of 94.56 percent, and the peak voltage stress across switches is found to reduced (2.4–2.7 times the input voltage as compared to the existing topologies where it surges upto 3.6–4 times the input voltage). These are also validated in Typhoon HIL’s Real-Time Emulator HIL402. In addition to that, a machine learning algorithm based on an Artificial Neural Network is used to generate a model to predict the switching frequency for a specified output voltage and efficiency.

Toward efficient very low frequency wireless power transfer for EVs: From grid to battery

This paper aims to improve the efficiency, affordability, and safety of Wireless Power Transfer (WPT) devices. While wireless inductive charging is common in devices like smartphones, charging electric vehicles presents significant challenges due to high frequency electromagnetic fields that can be dangerous for users and those nearby. Current systems are expensive due to the use of specialized materials and components. By developing WPT systems with drastically reduced frequency levels, this research has the potential to significantly impact the widespread adoption of affordable, safe, and efficient WPT devices for high-power applications like electric vehicle charging. In fact, using lower frequencies allows us to build WPT systems with far less expensive materials, e.g. no need of Litz wires and ferrites that can be replaced by single core copper wires and classical magnetic steels. The effectiveness of the method is demonstrated through simulation using MATLAB Simulink® and experimental tests. The results indicate that it is possible to maintain good performance, reduce limitations and costs, and improve user acceptance of WPT systems by considerably lowering the frequency of electromagnetic fields that are classically used in such systems.