Power Loss-Optimized Control for Multi-Inverter, Multi-Rectifier Wireless Power Transfer Systems in Charging Stations

Many researches have been carried out by previous researchers to get better performance of a wireless power transfer (WPT) system. This research uses a partitioned shielding made of metallic material to protect WPT system from electromagnetic interference (EMI). Also, a shielding material is connected to ground, so that it can reduce occurrence of stray/parasitic capacitance between electrodes of electronic components. Both the electromagnetic interference and the stray/parasitic capacitance can deteriorate performance of WPT system. In this research, the WPT system works at voltage 14.7V, frequency 56,298 Hz, distance coil to coil is 0 till 5 cm. The efficiency of WPT system is achieved until 14.9 % (without shielding) and until 17.9% (with partitioned shielding).

The power transfer efficiency of magnetic-resonance coupled wireless power transfer (WPT) systems is sensitive to the alignment of coils. In this paper, a novel multi-coil WPT system is proposed to enhance power transfer efficiency. It can overcome the misalignment problem and maintain high power transfer efficiency. The proposed coil loop structure can provide a strong magnetic resonance coupling between the Tx and Rx coils. There are four induvial resonators applied in the system and it demonstrates that at least a pair of coupled resonators in several misaligned conditions could realize high power transfer efficiency over a misaligned distance. The experimental results show that the proposed multi-loop WPT system can achieve 90.2% peak efficiency when the coils are well aligned. Mean-while, this WPT system maintains over 70% efficiency over a misalignment distance from 0 to 55 mm, which is about 66% of the length of the Rx board. The proposed WPT system could be used either in implant devices for biomedical healthcare and treatment or for electric vehicles charging systems.

This paper presents a novel design concept for near-field wireless power transfer (WPT) systems that leverages the seamless integration of metamaterials (MTMs) into slotted resonators. This approach enhances magnetic field ( $$\textbf{B}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> </mml:math> ) distribution, strengthens evanescent wave coupling, and hence improves overall WPT performance. An MTM structure exhibiting negative permeability at the operating frequency of 433 MHz was designed and incorporated into a square-slot-based resonator. Electromagnetic (EM) analysis revealed increased current density and subsequently enlarged $$\textbf{B}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> </mml:math> around the resonator. Additionally, impedance matching, key parameter extraction, and equivalent circuit (EC) modeling were performed using the effective J-inverter method. The developed WPT system, with compact dimensions of 30 $$\times$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>×</mml:mo> </mml:math> 30 $$^{\text {2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mtext>2</mml:mtext> </mml:mmultiscripts> </mml:math> , achieved a power transfer efficiency of 82% at 33 mm. The design was experimentally validated, showing excellent agreement among EM simulations, EC modeling, and measurement results. Finally, performance comparison with other reported systems confirmed the superiority and practical effectiveness of the proposed design in enabling compact and highly efficient WPT systems.

A highly efficient wireless power transfer (WPT) system is required in many applications to replace the conventional wired system. The high temperature superconducting (HTS) wires are examined in a WPT system to increase the power-transfer efficiency (PTE) as compared with the conventional copper/Litz conductor. The HTS conductors are naturally can produce higher amount of magnetic field with high induced voltage to the receiving coil. Moreover, the WPT systems are prone to misalignment, which can cause sudden variation in the induced voltage and lead to rapid damage of the resonant capacitors connected in the circuit. Hence, the protection or elimination of resonant capacitor is required to increase the longevity of WPT system, but both the adoptions will operate the system in nonresonance mode. The absence of resonance phenomena in the WPT system will drastically reduce the PTE and correspondingly the future commercialization. This paper proposes an open bifilar spiral coils based self-resonant WPT method without using resonant capacitors at both the sides. The mathematical modeling and circuit simulation of the proposed system is performed by designing the transmitter coil using HTS wire and the receiver with copper coil. The three-dimensional modeling and finite element simulation of the proposed system is performed to analyze the current density at different coupling distances between the coil. Furthermore, the experimental results show the PTE of 49.8% under critical coupling with the resonant frequency of 25 kHz.

The magnetic coupler plays an important role in wireless power transfer (WPT) system and concerns the transmission efficiency and output characteristic of system. The effects of asymmetric two-coil and three-coil magnetic couplers with a large intermediate coil on lateral misalignment tolerance for WPT system are studied. First, circuit models of two-coil and three-coil magnetic couplers are analyzed and the key parameters affecting the efficiency of two-coil and three-coil coupler are deduced. Then, a 3-D finite element model of the two-coil coupler is established, and the efficiency of WPT systems with two different structures is investigated while misaligning. Finally, the applicable conditions of two coil structures are discussed. The results show that when the maximum misalignment distance is reached, the misalignment tolerance effect of two-coil structures is weakened, and the system efficiency can be higher by using the three coils structure with a large intermediate coil.

Exploring Dielectric Resonator Antennas (DRAs) in Electric Vehicles (EVs) Wireless Power Transfer (WPT) systems is the focus of this study. DRA technology has gained prominence for its unique advantages, offering high efficiency and compact form factors in comparison to conventional antennas. In the context of EVs, the integration of DRAs in WPT systems has shown promising results in addressing challenges related to charging efficiency and spatial constraints. The resonant properties of DRAs enhance power transfer efficiency by mitigating impedance mismatches and reducing energy losses during transmission. Furthermore, the dielectric material properties of DRAs contribute to minimizing electromagnetic interference and enhancing the reliability of WPT in EV applications. This highlights the potential benefits of employing DRAs in achieving robust and efficient wireless charging solutions for electric vehicles. The study encompasses theoretical analysis, simulation studies, and practical implementations to validate the performance of DRAs in WPT systems. The findings suggest that DRA-based WPT systems present a compelling avenue for advancing the state-of-the-art in EV charging technology with efficiency of 84%, providing a more streamlined and effective approach to meet the growing demands of electric mobility in scooters.

A Wireless Power Transfer (WPT) system, known for its contactless power delivery, is extensively used for power supply in spacecraft applications. Achieving efficient and stable power transfer necessitates the integration of DC/DC converters on both the primary and secondary sides of WPT systems for power conversion and control. Traditional efficiency optimization methods primarily focus on impedance matching within the wireless power resonance network, often neglecting the overall efficiency optimization of multi-stage DC-DC and WPT systems. This oversight results in suboptimal overall system efficiency despite optimal efficiency in the wireless transmission segment. Additionally, the time-varying nature of mutual inductance and load parameters during power transmission in WPT systems presents challenges for maximum efficiency tracking and power control. This paper introduces a multi-level coordinated control efficiency optimization method for WPT systems utilizing the particle swarm optimization (PSO) algorithm. This method takes into account the transmission losses across all power conversion units within the WPT system, establishing a mathematical model for the joint optimization of overall system transmission efficiency and power. The PSO algorithm is then employed to solve this optimization model using estimated mutual inductance and load values. By adjusting the DC/DC converters on both sides, the method ensures optimal overall system efficiency and consistent power transmission. Experimental results indicate that under varying load and mutual inductance conditions, a Series–Series (SS) compensated WPT system using this method achieves a 200 W power output with maximum efficiency tracking, a power output error of 0.63%, and an average transmission efficiency of 86.2%. This demonstrates superior power transmission stability and higher efficiency compared to traditional impedance matching methods.

It is well known that the power transfer efficiency (PTE) of a two-coil wireless power transfer (WPT) system is maximized at critical coupling under fixed system parameters. However, the two-coil WPT system is critical-coupled with a relatively short distance between the coils. To overcome the problem, a multicoil WPT system has been studied. In this paper, we review the impedance characteristics of the critical-coupled two-coil WPT system and reveal that the conventional three-coil WPT system cannot have the same impedance characteristics as critical coupling. Based on the impedance matching conditions with critical coupling of the two-coil WPT system, we propose a design method of a three-coil WPT system in which the free resonant frequencies of all resonators are changed. The proposed design method is successfully implemented at the operating frequency of 6.78 MHz. The experimental results are in good agreement with the simulated PTEs and show that by changing the free resonant frequencies, a higher PTE can be effectively achieved in comparison to the conventional two-coil and thee-coil WPT systems.

The magnetic fields (MF) generated in close proximity to high power wireless power transfer (WPT) systems generally exceed exposure limits and might also violate basic restrictions (BR). However, there are as yet no available standards describing methods to measure the MF generated by WPT systems. In this study, a new method for demonstration of compliance with the BR in the close proximity to sources at frequencies from 3 kHz to 10 MHz is proposed. This approach mitigates overestimation by incident field assessment in strong field gradients close to WPT systems. The spatial peak MF amplitude and gradient generated by WPT systems are measured with a field gradient probe at the closest location to the source. The induced fields and absorbed power are then calculated on the basis of specific transformation functions for testing of compliance with the BR of all international safety guidelines.

In previous researches, an operator-based sliding mode control design to achieve high power transfer efficiency of a wireless power transfer (WPT) system via magnetic resonance coupling were shown. However, it is difficult to reduce the steady-state error by using SMC-based tracking controller. In this paper, an operator-based integral sliding mode control method is adopted to reduce the steady-state error in the WPT system. Moreover, high power efficiency should be achieved in the WPT system by using an impedance matching control. The effectiveness of the proposed method is verified by simulation results.

The wireless power transfer (WPT) system based on parity-time (PT) symmetry has the advantages of robustness, stable, and efficient power transmission. However, the region of PT symmetry is limited, which cannot satisfy some practical requirements. Multiple transmitting coils have been shown to improve the misalignment tolerance of WPT systems. Towards this end, a parity-time-symmetric-based WPT (PT-based WPT) system with double-transmitting coil is presented in this article. First, an approximate equivalent circuit model of this PT-based WPT system was developed. Second, compared with the conventional single transmitting coil PT-based WPT system, the proposed system expands the PT symmetry region and provides higher output power and transmission efficiency. Furthermore, the mutual inductance between two transmitting coils can be designed to meet the requirements of different scenarios, which improves the freedom of system design. Finally, a 30 W prototype is designed to evaluate the proposed WPT system. Experimental results show that the critical coupling coefficient is reduced by about 12.5% at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> = 0.51, which implies a longer transmission distance. Moreover, the maximum output voltage fluctuation in the strongly coupled region is only 3.5%, while the transfer efficiency is approximately constant, which implies stable and efficient power transfer.

Dual-band coil modules facilitate efficient access to distinct-band, high-power, or rapid-charging wireless power transfer (WPT) systems. However, they do not function efficiently when the frequency ratio between two operating frequencies is large. To overcome this problem, we propose enhanced dual-band coil modules that adopt repeaters in the WPT system. We present a circuit-based analysis of repeaters in various dual-band coil modules compared with those in a single-band WPT system. The analytical results provide a design methodology applicable to diverse types of dual-band coil modules with a repeater in the WPT system. Our experimental results are consistent with the circuit-based analysis: coil power transfer efficiencies of 55% at 200 kHz and 74% at 6.78 MHz were obtained concurrently in the dual-band WPT system with a dual-band repeater. This paper reduced the application constraint of dual-band coil modules and facilitated the realization and application of multiband WPT systems.

A wireless power transfer (WPT) system via magnetic resonance coupling method is attracting attention to high convenience. A WPT system has problems such as power transmitting loss and output voltage fluctuation due to the change in the coupling coefficient and the load state. In previous method, sliding mode control system as a tracking controller considering nonlinearity and uncertainty has been proposed, but the output of this control system had bias and chattering. This paper proposes operator-based nonlinear sliding mode control system to reduce chattering and bias simultaneously for a WPT system using buck converter. First, the model of the WPT system using rectifier and buck converter is explained and dynamics formulas are derived. Next, the proposed operator-based nonlinear sliding mode control system design for the WPT system is described and tracking performance is confirmed. Finally, the result of simulation of constant voltage control and comparison with the previous method is shown.

The defected ground structure (DGS) technique enables miniaturization of the resonator which leads to the development of the compact near-field wireless power transfer (WPT) systems. In general, numerous challenges are inherent in the design of the DGS-based WPT systems and, hence, appropriate trade-offs for achieving optimal performance are required. Furthermore, the design advancements have led to the development of the DGS-based multi-band WPT systems to fulfill the needs of simultaneous data and power transfer. The innovations in the DGS-based WPT systems have also resulted in the definition of more commonly used figures-of-merit for the benchmarking of various performance metrics. The literature is replete with the design schemes to address one or more associated design challenges and successful WPT system realizations with enhanced performance. With this in mind, this paper touches upon the DGS-based WPTs developments and presents a concise report on the current state-of-the-art and future directions.

This paper presents the design of a bidirectional wireless power and information transfer system. The wireless information transfer is based on near-field technology, utilizing communication coils integrated into power transfer coils. Compared with conventional far-field-based communication methods (e.g., Bluetooth and WLAN), the proposed near-field-based communication method provides a peer-to-peer feature, as well as lower latency, which enables the simple paring of a transmitter and a receiver for power transfer and the real-time updating of control parameters. Using the established communication, control parameters are transmitted from one side of the system to another side, and the co-control of the inverter and the active rectifier is realized. In addition, this work innovatively presents the communication-signal-based synchronization of an inverter and a rectifier, which requires no AC current sensing in the power path and no complex algorithm for stabilization, unlike conventional current-based synchronization methods. The proposed information and power transfer system was measured under different operating conditions, including aligned and misaligned positions, operating points with different charging powers, and forward and reverse power transfer. The results show that the presented prototype allows a bidirectional power transfer of up to 1.2 kW, and efficiency above 90% for the power ranges from 0.6 kW to 1.2 kW was obtained. Furthermore, the integrated communication is robust to the crosstalk from the power transfer and misalignment, and a zero BER (bit error rate) and ultra-low latency of 15.36 µs are achieved. The presented work thus provides a novel solution to the synchronization and real-time co-control of an active rectifier and an inverter in a wireless power transfer system, utilizing integrated near-field-based communication.