Inductive Wireless Power Transfer System Research Articles

Investigation of 1.5 kW secondary side power controlled method in a inductive wireless power transfer system

The contemporary and utilitarianism of the existing consumer world is advancing towards the better world technical benefits in the electrical world such as wired phase to wireless phase utilizing its volatile features. This paper addresses the battery performance in constant current (CC), constant voltage (CV) through inductive wireless power transfer (IWPT) systems. To analyze this workable mode, the researcher has proposed the series-series (S-S) compensation topology which is load independent current output. While charging the battery through wireless, the coil resistance is found to be affected by the battery's current and power. To figure out a practical solution, the researcher has introduced novel closed loop bi-directional switches with duty cycle control. The existing theoretical and simulated results have been analyzed with 1.5 kW, 120 mm air-gap and 85 kHz frequency. In this connection, the researcher has self-developed a prototype to better understand the theoretical perceptions of the proposed WPT system.

Memristor Equivalent Model of an Inductive Wireless Power Transfer System Based on the Sigmoid Function

Memristor Equivalent Model of an Inductive Wireless Power Transfer System Based on the Sigmoid Function

Evaluation of Additive Manufacturing for Wireless Power Transfer Applications

Additive Manufacturing (AM) has emerged as an economical and feasible technology for creating industrial components. This paper evaluates the use of AM for inductive Wireless Power Transfer (WPT) systems. In particular, the innovative use of metal 3D printing is proposed as a manufacturing process for the coils. For this reason, the recent improvement of metal AM is proposed as a suitable solution to increase design opportunities, reduce costs and production time while improving transmission efficiency. In fact, the WPT coil current distribution can be preliminarily studied through Finite Element Analysis (FEA) to optimize its cross-section and geometry. In this work, a general design procedure for WPT coils using metal AM is presented and this technology is compared with traditional solutions (i.e. hollow and litz wire) through extensive experimental measurements. The analysis shows that AM allows to reduce the parasitic resistance, costs and weight while increasing the transmission efficiency. Thus, the obtained results confirm the potential of AM for producing WPT coils, nominating this technology as a flexible, sustainable, and rapid solution for custom WPT coils production.

A Wearable All-Printed Textile-Based 6.78 MHz 15 W-Output Wireless Power Transfer System and Its Screen-Printed Joule Heater Application

While research in passive flexible circuits for Wireless Power Transfer (WPT) such as coils and resonators continues to advance, limitations in their power handling and low efficiency have hindered the realization of efficient all-printed high-power wearable WPT receivers. Here, we propose a screen-printed textile-based 6.78 MHz resonant inductive WPT system using planar inductors with concealed metal-insulator-metal (MIM) tuning capacitors. A printed voltage doubler rectifier based on Silicon Carbide (SiC) diodes is designed and integrated with the coils, showing a power conversion efficiency of 80-90% for 2-40 W inputs over a wide load range. Compared to prior wearable WPT receivers, it offers an order of magnitude improvement in power handling along with higher efficiency (approaching 60%), while using all-printed passives and a compact rectifier. The coils exhibit a simulated Specific Absorption Rate (SAR) under 0.4 W/kg for 25 W received power, and under 21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C increase in the coils' temperature for a 15 W DC output. Additional fabric shielding is investigated, reducing harmonics emissions by up to 17 dB. We finally demonstrate a wirelessly-powered textile-based carbon-silver Joule heater, capable of reaching up to 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C at 2 cm separation from the transmitter, as a wearable application which can only be wireless-powered using the proposed system.

Design and Parameter Optimization of Double-Mosquito Combination Coils for Enhanced Anti-Misalignment Capability in Inductive Wireless Power Transfer Systems

This paper proposes a novel double-mosquito combination (DMC) coil for inductive wireless power transfer (IPT) systems to improve their anti-misalignment capability. The DMC coil consists of a mosquito coil with single-turn spacing and a tightly wound close-wound coil. By superimposing the magnetic fields generated by both coils, a relatively uniform magnetic field distribution is achieved on the receiving coil plane. This approach addresses the challenges of significant output voltage fluctuations and reduced transmission efficiencies caused by coupling coil misalignments in conventional IPT systems. To further optimize the DMC coil, an interaction law between its parameters and the mutual inductance is established, setting the coil mutual inductance fluctuation rate as the optimization objective, and using the coil turn spacing, number of turns, and outer diameter as constraint conditions. The beetle antennae search algorithm (BAS) is employed to enhance the whale optimization algorithm (WOA), facilitating the adaptive optimization of the coil parameters. An experimental IPT system platform with a 50 mm transmission distance is developed to validate the robust anti-misalignment capability of the proposed coil. The results demonstrate that within a horizontal misalignment range of 50 mm, the system’s output voltage fluctuation rate stays below 7.4%, and the transmission efficiency remains above 83%.

Increasing tolerable coupling coefficients range of series-series compensated inductive wireless power transfer systems operating in restricted sub-resonant frequency region with constant current output

Frequency control of series-series compensated inductive power transfer links (SS-IWPTL) operated in sub-resonant region while feeding variable voltage-type loads (e.g. batteries) with constant current under uncertain coupling conditions allows to minimize volt-ampere (VA) rating of transmitting-side converter. In such systems, variations of coupling coefficient and load voltage are counteracted by operational frequency adjustment so that primary current magnitude remains nearly unchanged throughout the complete operational range, as opposed to input voltage and phase shift control approaches. In practice, allowable operational frequency band is typically restricted by certain application and/or standard (e.g. SAE J2954). As a result, tolerable load voltage span and coupling coefficients range are also limited. Classical design guidelines impose the resonant frequency of SS-IWPTL to coincide with the upper bound of allowable operational frequency band for operation with the minimum expected coupling coefficient and the lower bound corresponding to operation with the maximum expected coupling coefficient. The paper demonstrates that generalizing this approach by releasing the former constraint adds a degree of freedom, allowing to expand tolerable coupling coefficients range for a given operational frequency band at the expense of slight efficiency deterioration. Analytical relations describing the above-mentioned behavior are established, clearly indicating the arising trade-offs. Simulation and experiments validate the proposed methodology.

A Single-Stage Universal Input Wireless Inductive Power Transfer System with V2G Capability

A Single-Stage Universal Input Wireless Inductive Power Transfer System with V2G Capability

Load Modulation Feedback in Adaptive Matching Networks for Low-Coupling Wireless Power Transfer Systems

This paper explores the use of load modulation feedback (LMF) in adaptive matching networks (MN) for low-coupling inductive wireless power transfer systems, with an emphasis on its use in implantable medical devices. After deriving the handy expressions of link efficiency and modulation depth in the case of LMF in the case of loose coupling, a brief overview of the most common capacitive resonance networks is presented. In particular, the MN employing two capacitors in Series–Parallel and in Parallel–Series configurations allow adaptivity with a wide range of load conditions. Then, the authors describe an effective design procedure of an adaptive matching network with LMF for an inductive wireless power transfer system, exploring the trade-off between power efficiency and modulation depth. Analytical and electrical simulations show that the proposed simple modulation strategy can successfully achieve high power transfer efficiency while maintaining steady back telemetry under varying loading conditions.

Joint Real-Time Identification for Mutual Inductance and Load Charging Parameters of IPT System

Accurate and fast identification for mutual inductance and load charging parameters of inductive wireless power transfer (IPT) system is essential for impedance matching, and the output control of communication-free IPT system. A joint real-time identification method for mutual inductance and load charging parameters of IPT system is proposed in this paper. Only via measuring the RMS value of fundamental voltage and current on primary side, the double equivalent impedance modulus equations about mutual inductance and equivalent load resistance are established. To obtain real-time identification results of mutual inductance and equivalent load resistance from the high-order implicit function equations, an improved adaptive filtering algorithm based on Least Mean Squares (LMS) is proposed. Then, the identification values of load charging parameters are obtained according to the identified mutual inductance and equivalent load resistance. Finally, a 3.6kW platform is built to verify the validity of the proposed method. And the experiment results show that, compared with other existing achievements, the proposed method can identify <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U_Bat</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_Bat</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_L</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> simultaneously in real-time without changing the system operation, and it has faster rate and higher accuracy of identification.

Observer-Based Control of Inductive Wireless Power Transfer System Using Genetic Algorithm

In this paper, we studied the feedback stabilization of an inductive power transfer system based on available output measurement. The proposed controller relies on a full-order state observer in order to estimate the unmeasured state. The control design problem is challenging due to the large dimension of the closed-loop system, which requires too many tuning parameters to be determined when conventional control methods are employed. To solve this issue, we propose an LQR methodology based on a genetic algorithm such that the weighing coefficients of the cost function matrices can be automatically computed in an optimized manner. The proposed approach combines the method of eigenstructure assignment and the LQR technique in order to design both the controller and the observer gain matrices. The design methodology provides a systematic way to compute the parameters of the LQR technique for a wireless power transfer system in an optimized manner, which can be a useful design tool for many other applications. The effectiveness of the approach was verified by numerical simulation on the dynamic model of the wireless power transfer system. The results show that the proposed design outperforms conventional design methods in terms of a better performance and reduced design iterations effort.

Implementation of an Accurate Measurement Method for the Spatial Distribution of the Electromagnetic Field in a WPT System

In an inductive wireless power transfer (WPT) system, the transferred power depends on the coupling between the transmitter coil and the receiver coil and, consequently, on their spatial positioning with respect to each other. Since this positioning needs to be as flexible as possible, one can design various construction shapes for the coils, in terms of both winding geometry and core geometry. The system efficiency for different positionings and configurations can be assessed if the structure and distribution of the electromagnetic field (EMF) in the space close to the system are determined. In this context, this paper proposes an investigation method based on measuring the intensity of the electromagnetic field generated by the emitting coil in the WPT space in terms of both modulus and direction. The measurements needed to be performed at a sufficient number of points, so that the entire field was determined. The EMF value was estimated by linear spatial interpolation between the measured points. Moreover, this paper presents the method and the results of investigations carried out only in the presence of the emitting coil. Calibration or correction solutions were also proposed to obtain sufficient accuracy, and the viability of the method was therefore demonstrated.

Integro-Differential Analysis of Resonant Magnetic Metasurfaces With Equivalent Medium Approximation

This paper proposes a strategy to consider the dielectric effects in the thin-wire integro-differential formulation and applies it to analyzing microstrip metasurfaces that support magnetic resonances. These structures comprise a periodic arrangement of subwavelength unit cells; therefore, the thin-wire approximation can be applied to analyze them. However, the substrate is usually disregarded. This work achieves more accurate results with a homogeneous equivalent medium approximation considering the dielectric properties. Moreover, an experimental methodology is presented to validate this implementation for each device as well as for the complete system. The proposed formulation is numerically solved with the Method of Moments, and the results show close agreement with experimental data. Besides, it leads to a significant reduction in the computation time compared to a full-wave analysis, which makes this approach also compelling for designing inductive wireless power transfer systems and magnetic resonators.

Inductive Wireless Power Transfer Systems for Low-Voltage and High-Current Electric Mobility Applications: Review and Design Example

Along with the technology boom regarding electric vehicles such as lithium-ion batteries, electric motors, and plug-in charging systems, inductive power transfer (IPT) systems have gained more attention from academia and industry in recent years. This article presents a review of the state-of-the-art development of IPT systems, with a focus on low-voltage and high-current electric mobility applications. The fundamental theory, compensation topologies, magnetic coupling structures, power electronic architectures, and control methods are discussed and further considered in terms of several aspects, including efficiency, coil misalignments, and output regulation capability. A 3D finite element software (Ansys Maxwell) is used to validate the magnetic coupler performance. In addition, a 2.5 kW 400/48 V IPT system is proposed to address the challenges of low-voltage and high-current wireless charging systems. In this design, an asymmetrical double-sided LCC compensation topology and a passive current balancing method are proposed to provide excellent current sharing capability in the dual-receiver structures under both resonant component mismatch and misalignment conditions. Finally, the performance of the proposed method is verified by MATLAB/PSIM simulation results.

A review of underwater inductive wireless power transfer system

AbstractThe IPT system has been studied for underwater applications such as autonomous underwater vehicles (AUVs) and subsea sensors. However, it rarely comparatively shows the performance of the IPT system in air, freshwater, and seawater. Based on the fore‐mentioned research background, this paper presents a survey of the properties of the IPT system in different mediums. Here, a 100 W power‐level experimental IPT prototype is built and tested. The resonant frequency is set at 300 kHz with a gap range from 10 to 190 mm. The comparison is focused on the efficiency, mutual inductance, coupling coefficient, coil resistance, and quality factor of the IPT system. The IPT system is placed in air, freshwater, and seawater with the same settings. What's more, the magnetic fields of coupling coils in air, freshwater, and seawater are presented in this paper. This paper could be acted as a reference to optimize the IPT system and facilitate future IPT research for underwater applications by analysing the performance of the IPT system in different mediums. The 3D Ansys Maxwell simulation of the IPT system is also given here to study the magnetic fields.

Comparison of Series/Series and Parallel/Series Resonance Circuit in 1.5 kW Inductive Wireless Power Transfer for EV Applications

Wireless power transfer system plays a key role in the present and future days, because of their upgraded comfort and safety and their merits of less green-house gas (GHG) emissions, cell phones, laptops and electric vehicle charging. In this paper, the basic two resonance circuits were analyzed using an inductive wireless power transfer (IWPT) system, at 1.5 kW, 120-mm, and 85 kHz resonance frequencies. It includes analyzing, designing, and comparing this resonance circuit to choose a suitable resonant circuit for the particular application of an IWPT system. The main analysis and comparison were: Mutual Inductance Effect (Misalignment), stresses on the components, Effect of mutual inductance on the efficiency, Effect of distance on the efficiency, Effect of frequency on the efficiency, Effect of the coupling coefficient (k) on the efficiency and transferred power, Effect of coupling coefficient (k) on the input impedance, Effect of distance on the coupling coefficient (k) and Mutual inductance, and both S/S and P/S circuits have same battery output dc power, current, voltage levels. Both resonance circuits designing formulas derived, electrical parameters are calculated for the given wireless power charger level reaches SAEJ2954 standards. In the end, both resonance circuits are verified through MATLAB simulation of the equivalent circuits.

Spatial filtering magnetic metasurface for misalignment robustness enhancement in wireless power transfer applications

In this paper, we present the design of spatial filtering magnetic metasurfaces to overcome the efficiency decay arising in misaligned resonant inductive Wireless Power Transfer systems. At first, we describe the analytical framework for the control of currents flowing on a finite-size metasurface, avoiding classical truncation effects on the periphery and opportunely manipulating, at the same time, the spatial magnetic field distribution produced by the closely placed RF driving coil. In order to validate the theoretical approach, we conceive a numerical test case consisting of a WPT system operating at 12 MHz. By performing accurate full-wave simulations, we prove that inducing a uniform current in the metasurface results in a more robust WPT system in terms of misalignment with respect to conventional configurations, also including standard metasurfaces. Therefore, while the use of metasurfaces in WPT systems has been already demonstrated to be beneficial in terms of efficiency enhancement, we confirmed that a proper control of the metasurfaces field filtering response can be advantageous also for the misalignment issue. Notably, the free space wavelength at the operating frequency (12 MHz) is 25 m, whereas the proposed metasurface dimensions are only 0.0024λ × 0.0024λ. Despite the extremely reduced dimensions, the spatial magnetic field distribution produced by the closely placed RF driving coil can be nevertheless opportunely manipulated. Finally, experimental measurements conducted on fabricated prototypes validated the numerical results, demonstrating the effectiveness of the proposed approach. These achievements can be particularly helpful in WPT applications where the position of driving and receiving coils frequently changes, as in consumer devices and biomedical implants.

A Fast Self-Positioning-Based Optimal Frequency Control for Inductive Wireless Power Transfer Systems Without Communication

A communication-free approach to achieve self-positioning optimal frequency control (SP-OFC) for a series–series-compensated wireless power transfer system is proposed in this article. Without any position sensor, the position of the receiver is located by only monitoring the winding current. The feasibility of optimal frequency control for achieving zero phase angle is elaborated based on the multiple transmitters charging condition. The proposed method involves no communication link with a small number of sensors, so the calculation effort in the controller is relieved. Hence, the control scheme can be fast, cost-efficient, and practically reliable. In addition, the technique allows random resonator parameters. Experimental results prove that the proposed SP-OFC process for high system efficiency at rated power level can be completed within 20 ms, and the phase difference can be controlled within 4.81° in the worst case. The system efficiency is proved to be improved by up to 14.3% by achieving optimal frequency. The interoperability of receivers with various coil shapes and positions is discussed in the form of the case study.

Rectifier Design for Highly Loaded Inductive Wireless Power Transfer Systems for Biomedical Applications

Power transfer efficiency (PTE) and harmonics are crucial performance parameters of the resonant rectifier design for low/medium coupling inductive wireless power transfer (WPT) systems used in wireless biomedical implants. The performance of a resonant rectifier degrades under higher loading and lower coupling conditions as the voltage available to the rectifier at the output of the receiver coil becomes low. As the diode turn-on impedance increases, diodes turn on incompletely, leading to non-linearities that reduce rectifier efficiency and output voltage. This work proposes a new rectifier design to increase efficiency and reduce harmonics by decreasing the diode turn-on impedance compared to traditional rectifier designs, such as resonant Half Wave Rectifier (HWR). The proposed rectifier design offers individual paths for RF and rectification signals, which reduces the non-linear loading on the receiver coil and improves diode turn-on performance. Measurement and SPICE simulation results show efficiency enhancement of 50% and reduction of harmonics by 6 dB for the proposed rectifier compared to HWR.

A Design Methodology for Irregularly Shaped Windings in Inductive Wireless Power Transfer Systems

Inductive wireless power transfer systems often incorporate unconventional, irregularly shaped transmitter windings for the purposes of covering a designated area, fitting into special enclosures and enhancing the tolerance of misalignment. To design and optimise the winding structures, the inductive parameters must be extracted and linked to the design objectives. Conventionally, these parameters can be extracted using three-dimensional finite element analysis, which often requires subjective manual tweaks and prolonged trial and error procedures. The efficacy is therefore greatly dependent on the experience of the designer. In this paper, a case study for modelling and optimising the spatial coverage by scuplturing the winding shape is demonstrated via a Christmas tree model, utilising the parametric formation equations and line-integral based numerical solvers. A cone-shaped winding with variable interturn pitches was used as the transmitter and a receiver winding was designed to be fit into a bubble that can be hung on the tree. A two-stage optimisation method with simplified degree-of-freedom parameters and brutal force search was used to find the optimal design candidate. Heatmaps of receiver output voltages were generated in a time-efficient way, intuitively helping the designers to make adjustments for the winding structures. A practical prototype was built to verify the open loop voltage distribution on the receiving winding at various positions and another demonstration was made to show the continuum of power coverage around the Christmas tree.

Design and modelling of a controlled saturable inductor for an LCC-S compensated WPT system

This paper analyses the design of a controlled variable inductor adopted as the series inductance of an LCC-S compensation network in an Inductive Wireless Power Transfer system. In this compensation topology, the power transfer to the load can be controlled by varying the differential inductance of the component through a DC bias. The analytical design process of a double E ferrite core variable inductor is presented, and the specifications for an experimental prototype are proposed. The design output is verified with FEM simulations to validate the obtained differential inductance profile and with circuit simulations to test the non-linear behaviour of the component under the typical current and voltage waveforms of the LCC-S compensated Wireless Power Transfer system. Finally, a prototype is realized, characterized and tested in an experimental Wireless Power Transfer system.