Inductive Power Transfer System Research Articles

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.

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

A robust parity‐time‐symmetric hybrid wireless power transfer system with extended coupling range

SummaryInductive power transmission (IPT) and capacitive power transmission (CPT) are currently the two main wireless power transfer technologies. Hybrid power transmission (HPT) systems that combine IPT and CPT can improve transmission performance and are more attractive for some charging applications such as electric bicycles (e‐bikes). However, HPT systems are more sensitive to parameter variations, and the coupling mechanism is prone to misalignment during wireless charging. Therefore, achieving stable output power and constant transfer efficiency over a wide range of coupling coefficient variations is still a major challenge for HPT systems. In this work, the parity–time (PT) symmetry theory is applied to an SS‐type HPT system, and a circuit model of the PT‐based HPT system is developed by using coupling capacitance and coupling inductance. The effect of connecting the plates to the homonymous end or heteronymous end of the coupling coils on the PT symmetry range of the HPT system is discussed. It is found that the heteronymous end connection of the coils can effectively increase the range of constant output power and stable transfer efficiency. Finally, a prototype is built to verify the feasibility and effectiveness of the proposed PT‐based HPT system. The transfer power and efficiency remain constant in the PT‐symmetric range, and the inductive and capacitive coupling coefficients are smaller compared to IPT and CPT systems with the same parameters.

Assessment of heat transfer mechanisms of a novel high-frequency inductive power transfer system and coupled simulation using FEA

The calculation of the temperature fields in solid state transformers is a critical step of the design process in order to ensure the stable and efficient operation of the device. Transformers operating in high frequencies can develop increased temperatures that potentially may result in the failure of the components due to the associated thermal stresses. This paper investigates the heat transfer mechanisms of a novel inductive power transfer (IPT) system submerged in a dielectric oil and operating at 50 kHz, in the context of SSTAR, a Horizon Europe project. The commercial software ANSYS is employed to implement a one-way coupled electromagnetic-thermal finite element simulation model in order to calculate the temperature field of the IPT components based on the electromagnetic losses. To cross-validate the model, the results obtained from ANSYS are benchmarked against the COMSOL software, revealing accepted temperature deviations between the two software. A comprehensive parametric analysis explores the impact of rated power, operating frequency, and dielectric gap on generated heat, highlighting their direct correlation with temperature increase. The findings underscore increased temperature levels, approximately reaching 224 °C under nominal operating conditions, with the temperature distribution concentrated around the transformer's windings.

Constant-Voltage and Constant-Current Controls of the Inductive Power Transfer System for Electric Vehicles Based on Full-Bridge Synchronous Rectification

When an inductive power transfer (IPT) system conducts wireless charging for electric cars, the coupling coefficient between the coils is easily affected by fluctuations in the external environment. With frequent changes in the battery load impedance, it is difficult for the IPT system to achieve constant-voltage and constant-current (CVCC) controls. A CVCC control method is proposed for the IPT system that has a double-sided LCC compensation structure based on full-bridge synchronous rectification. The proposed method achieved good dynamic stability and was able to effectively switch between the output current and voltage of the system by adjusting only the duty cycle of the switch on the secondary side of the rectification bridge. As a result, the system efficiency was improved. The output characteristics of the double-sided LCC compensation structure was derived and the conduction condition with zero voltage was analyzed by using four switches through two conduction time series of the rectifier circuit. Then, the output voltage of the synchronized rectifier was derived. The hardware implementation of the full-bridge controllable rectifier was described in detail. Finally, a MATLAB/Simulink 2018a simulation model was developed and applied to an 11 kW prototype to analyze and validate the design. The results showed that the designed system had good CVCC output characteristics and could maintain constant output under certain coupling offsets. Compared with semi synchronous rectification methods, the proposed method had a higher efficiency, which was 95.6% at the rated load.

Self-Oscillating Converter Based on Phase Tracking Closed Loop for a Dynamic IPT System

The coupling of converters with resonant networks poses significant challenges for frequency tracking and power control in inductive power transfer (IPT) systems. This paper presents an implementation method that addresses these issues by dividing the system’s operation into two distinct states: self-oscillating and power-injecting. Based on these states, a phase-closed loop is constructed. Within this closed loop, the phase tracking unit detects and tracks frequency drift, while the power regulating unit incorporates an integrator and adopts a control variable to adjust the output power by modifying the duration of the power injecting state. Meanwhile, the oscillating unit operates in the self-oscillating state. Operating in this manner, the system achieves self-oscillation and demonstrates the capability to effectively track and compensate for system variations within a single cycle. A verification prototype has been constructed, and it demonstrates that the converter within it completely decoupled from the resonant network. Experimental results validate that altering the control variable solely affects the duration of the power-injecting state, allowing for independent control of the output power. When the control variable changes from 2.0 V to 3.5 V, the output power changes from 178 W to 519 W while the self-oscillating state remains unchanged. Furthermore, the system accurately tracks frequency changes, even under significant variations in the coupling coefficient or load, without compromising the power injection state. When the air gap changes from 3 cm to 12 cm, the duration of the self-oscillating state changes from 22.1 μs to 26.3 μs, while the power injecting state remains unchanged. This approach exhibits a robust performance, particularly suitable for dynamic IPT systems sensitive to parameter variations.

A Control Strategy for Achieving Constant Voltage Output with an Extensive ZVS Operating Range in Bidirectional Wireless EV Charging Systems

Variations in the coupling coefficient of loosely coupled transformers and dynamic loads have a significant impact on the overall performance of bidirectional inductive power transfer (BIPT) systems. However, a wide range of load and coupling coefficient variations are common in the actual charging process, which may cause the converter on both sides to operate in a hard switching state, resulting in switching noise, reduced efficiency, and potential safety concerns. In this paper, a triple-phase-shift control (TPSC) strategy is proposed to study the zero-voltage switching (ZVS) operating range and constant-voltage output (CVO) characteristics of the double-side-LCC (DS-LCC) topology. To ensure a CVO over the wide range of coupling coefficient variations, a dual-phase-shift control is introduced for AC voltage matching. Based on this, the third phase-shift angle control between the converters on both sides is introduced to ensure the ZVS realization. Meanwhile, the time-domain model is developed to analyze the rationality of the proposed third phase-shift angle and the ZVS operating range. Finally, the effectiveness of the proposed TPSC strategy is validated through a 1.5 kW experimental prototype with an air gap of 100–150 mm.

An LC Squared-Compensated Inductive Power Transfer System With Misalignment Tolerance and Constant-Current Output

An <i>LC</i> Squared-Compensated Inductive Power Transfer System With Misalignment Tolerance and Constant-Current Output

Inner Resonance and Outer Current Based Control Strategy for Inductive Power Transfer System Used in Wireless Charging for Electric Vehicles

The wireless charging for electric vehicle is getting popular due to the absence of sophisticated cable connection and associated issues with the actuators in field for connected charging. The major challenges in inductive power transfer (IPT) systems are the control of the resonance converter and synchronisation in communications with the vehicle and power supply. In IPT system, the dynamic nature of load as well as system demands extra care for the existing charging architectures. This work proposes a unique control algorithm to charge the Li-ion battery under coupling coefficient and load variations. The developed control algorithm is validated in MATLAB simscape platform. Further, the control logic is validated using the Texas C2000 Delfino controller in 1 kW IPT system. The developed control logic would ensure proper frequency of operation as well as the constant voltage and constant current control.

Comparative Evaluation of Different Cables for Magnetic Couplers in Inductive Power Transfer Systems

Comparative Evaluation of Different Cables for Magnetic Couplers in Inductive Power Transfer Systems

Design of Compensation Topology for IPT System Considering Coils’ Parameters and Load Variations for CC or CV Output

The inductive power transfer (IPT) technology is drawing increasing attention. Variations in the height of the secondary coil are inevitable due to the fluctuations in the height of the electrical equipment or the pressure of the tires, which leads to variations in the coils’ parameters (self-inductances and mutual inductance). The coils’ parameters and load variations can dramatically affect the performance of the IPT system. In this paper, a unified mathematical model which can describe multiple compensation topologies is established. A design method is proposed to obtain suitable topology and component parameters based on the unified mathematical model and the non-dominated sorting genetic algorithm II. In addition, not only the stable output voltage/current is achieved, but the efficiency and cost are also improved. Finally, two experimental prototypes were built to verify the effectiveness, which has the output characteristics of constant current (3.5A/600W) and constant voltage (72V/100W), respectively. The results show that the output fluctuations are less than 5.63%, and the maximum efficiency is above 94.69% when the coils’ parameters (the primary self-inductance change from 85.76μH to 102.2μH, the secondary self-inductance change from 86.26μH to 102.35μH, and the mutual inductance change from 38.2μH to 72.1μH) and load (double change) vary.

Dynamic Improvement of Sub-Resonant Frequency Control for Inductive Power Transfer Systems by Coupling Estimation and Sending-Side Gain-Scheduled Control

Dynamic Improvement of Sub-Resonant Frequency Control for Inductive Power Transfer Systems by Coupling Estimation and Sending-Side Gain-Scheduled Control

Performance Investigation of HFR Full-bridge Inverter in Resonant Inductive Coupled Power Transfer System for an Electric Vehicle

Inductive WPT of the resonant category is generally employed for medium and high-power transmission applications like electric vehicle charging due to it contributes excellent efficiency. The high-frequency resonant full-bridge inverter using series-series resonant topology is proposed. The design of the high-frequency resonant inverter is simulated and verified by MATLAB/SIMULINK software. The charging scheme which is available in the AC-DC as well as in the DC-DC converter should operate with the two steps to achieve a duty cycle-based voltage control and hysteresis current control. The resonant frequency of the proposed system has a frequency range of 65 kHz with a DC voltage of 12V. The simulation has been carried out successfully and transmitted a 5KW power load of constant current and voltage control. The Performance chart of with the existing method is carried out in terms of parameters and the efficiency can be achieved by 95%.

Rectifier load modeling and zero voltage switching design of inductive power transfer system with S‐type topology on the secondary side

SummaryRectifier load in inductive power transfer system has nonlinear characteristics. However, the traditional analysis method equates it to a pure resistor, which leads to a certain deviation between the theoretical analysis and the actual circuit. This will reduce the accuracy of the inductive power transfer (IPT) system model and affect the soft switching operation of the inverter. In this paper, the IPT system with S‐type topology on the secondary side is studied. Firstly, the resistance–inductance characteristics of the rectifier load are analyzed by simulation, and then a second‐order circuit response model is established to solve the time‐domain expression of voltage and current. Then, the fundamental component of voltage and current is extracted by Fourier transform to calculate the impedance value of the rectifier load, and the mathematical calculation model of the rectifier load is established. On this basis, the influence of the inductive component of the rectifier load on the input impedance of the IPT system is analyzed. Then, a parameter design method for zero voltage switching is proposed for S‐S and LCC‐S topologies. Finally, an experimental platform of S‐S and LCC‐S IPT system is built. The correctness and effectiveness of the theoretical analysis and the proposed parameter design method are verified by experiments.

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%.

Development of Wireless Charging System Using Square-Circular Coupled Coils with Different Misalignments

Now a days, inductive power transfer (IPT) has gained a lot of attention from researchers as it has ease of use and realiability for electric vehicle (EV) battery charging systems. This paper examines the increasing attention from researchers towards inductive power transfer (IPT) as a means of charging electric vehicle (EV) batteries. This interest originates from the user-friendly characteristics and notable reliability associated with IPT. The evaluation of mutual inductance (MI) holds importance within the domain of Inductive Power Transfer (IPT) systems, as it serves a critical function in enabling effective power transfer. Therefore, it is essential to perform a comprehensive analysis of the mutual inductance between the two coils that are connected through inductive coupling. This study provides an examination of mutual inductance (MI) and efficiency within the context of interoperability conditions of interconnected coils. The transmitter coil is represented as a square structure, denoted as TxS, whereas the receiving coil is represented as a circular structure, denoted as RxC. Furthermore, the application of ferrite cores and steel chassis inclosures, in combination with coils, is utilised for the objective of electric vehicle (EV) battery charging. The magnetic induction (MI) analysis is performed by the utilisation of finite element method (FEM) simulation. The finite element method (FEM) simulation outcomes of the interconnected coils with misalignments, encompassing both non-core and steel chassis configurations, are juxtaposed with the corresponding empirical observations.

Soft ferrite 3D printing of magnetic couplers of inductive power transfer systems

AbstractTraditional soft ferrite manufacturing is limited to simple geometries and materials, while 3D printing offers greater flexibility for complex designs. Notably, soft ferrites are crucial for magnetic couplers (pads) in inductive power transfer (IPT) systems to achieve efficient wireless power transmission. The adoption of soft ferrite 3D printing in IPT systems could lead to significantly improved magnetic coupler design, yet research in this area is limited. Hence, the paper first makes a comprehensive comparison of the existing soft ferrite 3D printing methods to ascertain their suitability for magnetic couplers in IPT systems, and then proposes the binder jetting (BJT) as a potential 3D printing approach that could be appropriate for IPT magnetic coupler implementation being versatile, cost‐effective, and suitable for large‐scale manufacturing with high precision. This paper explores the suitability of BJT by 3D printing toroid cores with Mn–Zn ferrite powder under different sintering temperature profiles. Experimental results are presented to show that toroid cores can be 3D printed with high printing precision, mechanical strength, and a relative permeability of 10. This paper also highlights the impact of sintering temperature on 3D‐printed cores, the challenges, limitations, and future research directions of soft ferrite 3D printing for IPT magnetic couplers by the BJT method.

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.

Modularized Inductive Power Transfer Systems With Inherent Impedance Decoupling for High-Power Applications

Due to the capacity and costs of single power electronic devices, the modularized inductive power transfer systems (MIPT) are widely used in high-power electronic applications. To achieve safe and efficient operation of high-power IPT technology, this paper proposes a modularized topology design method with inherent impedance decoupling feature. When the module number changes, the current and voltage stresses of the devices in the proposed system remain unchanged inside modules at the rated power. Moreover, the impedance of any module will not be affected by neighboring modules, especially in cases where the module number may change abruptly. Such a desired feature significantly improves the reliability of high power IPT systems. A 15 kW MIPT prototype with 3 modules connected in parallel is implemented to verify the validity of the proposed method. The result clearly shows that both the impedance and device stress are decoupled with the module number. The system exhibits peak efficiency of 95.1% and over 92.4% when the power is between 2kW and 15kW.

A Frequency-Switching Inductive Power Transfer System for Wireless, Miniaturised and Large-Scale Neural Interfaces.

Three-coil inductive power transfer is the state-of-the-art solution to power multiple miniaturised neural implants. However, the maximum delivered power is limited by the efficiency of the powering link and safety constrains. Here we propose a frequency-switching inductive link, where the passive resonator normally used in a three-coil link is replaced by an active resonator. It receives power from the external transmitter via a two-coil inductive link at the low frequency of 13.56 MHz. Then, it switches the operating frequency to the higher frequency of 433.92 MHz through a dedicated circuitry. Last, it transmits power to 1024 miniaturised implants via a three-coil inductive link using an array of 37 focusing resonators for a brain coverage of 163.84 mm 2. Our simulations reported a power transfer efficiency of 0.013% and a maximum power delivered to the load of 1970 μ W under safety-constrains, which are respectively two orders of magnitude and more than six decades higher compared to an equivalent passive three-coil link. The frequency-switching inductive system is a scalable and highly versatile solution for wireless, miniaturised and large-scale neural interfaces.