Inductive Power Transfer Charging System Research Articles

A brief review: basic coil designs for inductive power transfer

The inductive power transfer (IPT) has contributed to the fast growth of the electric vehicle (EV) market. The technology to recharge the EV battery has attracted the attention of many researchers and car manufacturers in developing green transportation. In IPT charging system, the coil design is indispensable in enhancing the EV battery charging process performance. This paper starts by describing the two charging techniques; static charging and dynamic charging before further presents the IPT system descriptions. Afterwards, this paper describes a brief review of coil designs which discusses the critical factors that affect the power transmission efficiency (PTE) including their basic designs, design concepts and features merits. The discussions on the basic coil designs for IPT are of the circular spiral coil (CSC), square coil (SC), rectangular coil (RC), and double-D coil (DDC). Furthermore, the significant advantages and limitations of each research on different geometries are analyzed and discussed in this paper. Finally, this paper evaluates some essential aspects that influence the coil geometry designs in practical.

Design and optimization of 3‐kW inductive power transfer charging system with compact asymmetric loosely coupled transformer for special applications

SummaryInductive power transfer (IPT) technology has become popular in wireless charging applications. Compared with the traditional 3‐kW wireless charging application, the diameter for the primary coil and the secondary coil in this special design are required to be smaller than 260 and 110 mm, respectively. In order to achieve this target, an approach to design and optimize the loosely coupled transformer (LCT) is proposed to match the strict geometry limitation, while achieving the high conversion efficiency. Different from the traditional design method, the low resonant current and voltage stress are considered as the input of the design flowchart, especially the LCT. Thus, the overall conversion efficiency can be improved. Based on series–series (S–S) compensation topology, the parameter range of the LCT is determined by analyzing transformer‐based equivalent model. To achieve the desired coil size, an asymmetric LCT with single‐layer primary coil and three‐layer secondary coil is designed and optimized by the proposed approach. Furthermore, the closed‐loop controller with narrow frequency variation range is design to realize constant current (CC) charge and constant voltage (CV) charge. A 3‐kW IPT charging prototype is built to demonstrate the validity of the proposed method. Experimental results show that the peak efficiency from input to battery load is 95.69% at 3‐kW output power in the transition point from CC mode to CV mode.

Variable parameter and variable frequency‐based IPT charging system with configurable charge current and charge voltage

Variable parameter (VP) or variable frequency (VF) methods for load-independent output current or output voltage in inductive power transfer (IPT) systems have been widely studied. This study proposes an IPT system based on series-series compensation topology with VP and VF methods to achieve constant-current–constant-voltage (CC–CV) charging for electric bicycles (EBs). The proposed IPT system can operate in CC and CV modes regardless of load conditions at two different operating frequencies with corresponding values of compensation capacitors. The rating current/voltage of the proposed method is configurable by altering the compensation capacitor and operational frequency. Therefore, one charging stand can be shared by various EBs to save the space and to cut the overall cost. Only one capacitor is needed for one EB specification. The proposed IPT system can achieve zero-voltage switching under all load conditions. An experimental prototype with two ratings of 48 V/3A and 60 V/4A is built to verify the feasibility of the proposed method. The experimental results demonstrate the feasibility of the proposed method.

Development of a Cross-Type Magnetic Coupler for Unmanned Aerial Vehicle IPT Charging Systems

Inductive power transfer (IPT) is an optimal way for the unmanned aerial vehicle (UAV) wireless charging. The magnetic coupler is the key component in the IPT system, which determines the power transmission capacity and efficiency in IPT system. Due to the particularity of UAV application, the magnetic field height should be strictly limited to avoid the damage caused by high frequency magnetic field heat the UAV's metal equipment. A cross-type magnetic coupler with receiving coil placed on UAV's one landing gear was proposed to solve this problem, but it has the possibility of making UAV fuselage imbalance. Therefore, a novel cross-type magnetic coupler is proposed to overcome its difficulties in this paper, and most of magnetic fields are restrained to be lower than UAV's landing gear height h 1 = 145mm, which will not cause damage to the UAV's equipment. And a simple and practical iterative method for designing the magnetic coupler geometry parameters is proposed, with simplification of the complex design process for the finite element analysis, improves the design efficiency. The experimental results show that the system can charge the 260W UAV normally with the system efficiency of 91.577% within the misalignment range of X-axis direction 25mm, Y-axis direction 40mm and rotation 25.

Decoupling Circuit for Automated Guided Vehicles IPT Charging Systems With Dual Receivers

It is more efficient to employ inductive power transfer (IPT) systems to charge automated guided vehicles (AGVs) than traditional plug-in systems. In order to provide independent and different charging power for the driven system and the control system of AGVs simultaneously, this letter proposes a coaxial dual-receiver structure and a decoupling circuit, which utilizes a passive component connected with two receiving coils to cancel out the mutual inductance between each other. By using this decoupling method, the two receiving coils could be treated as independent receivers without precise placement or additional transformers. First, the decoupling model is analyzed in detail, and the value of the decoupling component is given without any restriction of the ratio of their current. Then, the structure of the dual receiver is designed. Finally, an IPT system with one transmitter and dual receivers is built to verify the feasibility of the proposed method. Experimental results show that when one of the loads varies from 20 to 80 Ω, the voltage fluctuation of the other load is as small as 1.36% with decoupling, whereas 54.46% of voltage fluctuation without decoupling. The results validate that the proposed method is suitable for the application requiring dual independent outputs in the same equipment.

Variable-Parameter T-Circuit-Based IPT System Charging Battery With Constant Current or Constant Voltage Output

Load-independent output characteristics of inductive power transfer (IPT) systems are increasingly popular in battery charging. This paper proposes a novel variable-parameter T-circuit (VT) for an IPT system charging a battery with constant current (CC) or constant voltage (CV) output. The VT can transfer a CC/CV input to a CC or CV output by using an ac switch and a passive component (inductor or capacitor). An IPT system with a VT for CC–CV charging can reduce the number of passive components and ac switches. Besides, the proposed VT merits more design freedom of charge current/voltage with the constraints imposed by the loosely coupled transformer parameters compared to that of the traditional one. In addition, there are three kinds of VTs for various IPT charging systems with different requirements. A 400 W laboratory-scale prototype with a 150 mm air gap was built to verify the theoretical analyses. Both electronic load and lead-acid battery are utilized to verify the charging profile of the proposed method. The experimental results of the IPT system indicate that the fluctuation of the charging current in CC mode is less than 2%, and the change rate of charging voltage in CV mode is within 2.9%. The maximum overall efficiency 93.93% of the charging system is achieved from a dc 110 V input to a dc 100 V output.

Cost‐effective inductive power transfer charging system for electric bicycles with variable charging current using primary‐side detuned series‐series topology

Due to the convenience and long travelling distance, electric bicycles (EBs) are becoming more and more popular. Charging EBs with inductive power transfer (IPT) technology can free people from wearisome plugging actions and avoid electric shock hazards. However, the cost, including component cost and control cost, is a big challenge for the extensive promotion of the IPT charging systems (IPTCSs) for EBs. This article proposes an IPTCS using primary-side detuned series-series (SS) compensation topology, cancelling control scheme and reducing the component cost. With the proposed parametric design method, the IPTCS can operate with variable charging current according to the variable equivalent resistance of a battery. Besides, the inductive input impedance is guaranteed to achieve soft switching for the high-frequency inverter. An experimental setup is constructed to validate the proposed method. The performance shows that the charging current decreases from 1.8 to 0.1 A, and charging voltage increase from 42.23 to 54.01 V during the whole charging process, where the maximum efficiency of the IPTCS can reach up to 92.8%. The results demonstrate the proposed IPTCS is a cost-effective and potential solution for charging EBs.

A Misalignment-Tolerant Series-Hybrid Wireless EV Charging System With Integrated Magnetics

Electric vehicles (EVs) are becoming increasingly popular as a mean of mitigating issues associated with fossil fuel consumption in transportation systems. A wireless inductive power transfer (IPT) interface between EV and the utility grid has several key advantages, such as safety, convenience, and isolation. However, physical misalignments between the pads of IPT charging systems used in EVs are unavoidable and cause variations in key system parameters, significantly increasing losses and affecting power throughput. This paper presents a novel series-hybrid topology in which the series inductors of the primary and pick-up inductor–capacitor–inductor ( LCL ) networks are integrated into polarized magnetic couplers to improve the system performance under pad misalignment. A mathematical model is developed to investigate the behavior of the proposed system under misalignment. To demonstrate the viability of the proposed method, the results of a 3.3-kW prototype series-hybrid IPT system are presented, benchmarked against a conventional IPT system. Experimental results clearly indicate that the proposed system maintains the output power within ±5% of its rated power despite the pad misalignment. The proposed system is efficient, reliable, and cost effective in comparison to conventional LCL- and CL -compensated IPT systems.

Comparison of Tripolar and Circular Pads for IPT Charging Systems

Recently, a magnetic pad called the tripolar pad (TPP) has been introduced for inductive power transfer (IPT) systems. This paper evaluates the effective coupling factor and leakage magnetic field of a 20-kW IPT system that uses a combination of TPP and circular pad (CP) topologies over a range of lateral displacements. The results show that the effective coupling factor and the leakage magnetic field of the TPP–TPP system are substantially better when the secondary is displaced away from ideal alignment. Leakage magnetic field is reduced up to 43% compared to the CP–CP system at the worst-case misalignment, which is due to the ability of the TPP–TPP system to generate and capture different types of magnetic field shapes. Simulation methods for both the TPP and CP are validated in the laboratory using a 2-kW system operating at 85 kHz.

Self-Tuning Variable Frequency Controller for Inductive Electric Vehicle Charging With Multiple Power Levels

A self-tuning controller for contactless electric vehicle (EV) charging systems based on inductive power transfer (IPT) with multiple power levels is proposed. The multiple charging levels (consisting of ten charging levels) are achieved by controlling the energy injection frequency of the transmitter coil of the IPT system. The proposed controller is capable of self-tuning the switching operations to the natural resonance frequency of the IPT system, and it benefits from soft-switching operations (zero-current switching), which ensures the maximum performance of the IPT system. The proposed controller has such a simple design, which can be implemented based on a simplified control circuit. The simulation of the proposed controller for an inductive charging system at different charging levels is carried out in MATLAB/Simulink. Also the proposed controller with an ac/dc/ac converter is implemented experimentally on an IPT charging system to verify the effectiveness of the controller at different charging levels. The experimental test results conform with the simulation results and verify that the proposed controller effectively enables self-tuning capability and soft-switching operations at different charging levels for IPT-based contactless EV charging systems.