Wireless Power Transfer Topology Research Articles

Gyrator-Gain Variable WPT Topology for MC-Unconstrained CC Output Customization Using Simplified Capacitance Tuning

Load-independent constant current (CC) outputs are desirable in many applications of wireless power transfer (WPT). Yet the WPT gain of a conventional system is normally dependent on the magnetic components (MCs) such as coils or inductors, making it difficult to customize the output for interoperability. This paper presents a gain variable WPT topology for CC output customization, which only employs capacitance tuning to provide sufficient freedom in gain regulation. To break the gain limitation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-S</i> compensation, which is the simplest with gyrator characteristics for CC output, a capacitive or inductive component is paralleled to the coil as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SP-S</i> or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-PS</i> compensation. A thorough analysis based on the Y-Δ transform indicates that the gain is restrictively variable with the parallel component. An <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S-CLC</i> -compensated topology without an independent inductor is further proposed to avoid those restrictions with as few additional components as possible. The inductor in the topology, coupled with the transmitter coil and integrated into the receiver coil, extends the gain variable range. A complete design process of the topology is presented to realize efficient WPT and CC output customization with a wide variable-gain range and misalignment tolerance. Analytical and simulation results confirm the effectiveness of the gyrator-gain variation by capacitance tuning. Finally, the performance of the WPT topology is evaluated by experimental results on a scaled-down prototype.

Efficient Wireless Power Transfer Topology for Phone Charging Application

Abstract: Wireless power transfer scheme used on phone chargers are expected to have high efficiency, and reliability. However, existing AC-DC converter schemes were shown to be susceptible to leakage inductance and have lower regulation or excessive power losses. Output voltage regulation is a concern for wireless power converter topologies due to the need for additional shunt devices at DC output. In this paper, literature survey on various wireless power transfer scheme is performed with specific focus on phone charging applications. A modified topology using impedance matching transformer is presented with circuit analysis and LT spice simulation results. It is shown that the proposed topology can deliver better output voltage regulation at various coupling coefficients indicating a superior circuit performance for various separation distances between transmitting and receiving coil.

A Soft-Switched Power-Factor-Corrected Single-Phase Bidirectional AC–DC Wireless Power Transfer Converter With an Integrated Power Stage

Bidirectional ac–dc wireless power transfer (WPT) converters are widely used in grid-connected electric vehicle systems for grid-to-vehicle and vehicle-to-grid applications. They usually apply a two-stage topology with a bidirectional ac–dc power factor correction converter and a bidirectional dc–dc WPT converter. Such a two-stage topology cannot achieve high efficiency and low cost. Recently, single-stage matrix bidirectional ac–dc WPT converters have been proposed. However, the matrix-converter-based topologies do not utilize remarkably lower count of power switches and generate large double-line frequency ripple in the dc-side voltage or current. This article proposes a new single-phase bidirectional ac–dc WPT topology with an integrated power stage to overcome the drawbacks of the matrix-converter-based topologies and retain the advantages of single-stage topologies. Description of the proposed topology with the modulation and control methods, theoretical analysis, and reference design procedure are presented in detail. Finally, a scaled-down laboratory prototype with 500-W output power is implemented with experimental results presented to validate the principle, analysis, and design.

Wireless power transfer topology analysis for inkjet-printed coil

Abstract The fabricated inkjet-printed coils (IPCs) are a suitable candidate for near-field wireless power transmission (WPT) to the next generation of high-performance implantable medical devices with extreme size constraints that will target intraocular and intracranial spaces. It is a challenging task for anyone to design an efficient inductive link for power transmission as, the secondary coil (receiver element) is placed 3 mm under the skin surface. This paper focuses on an analytical comparison among the basic four topologies of the WPT system in terms of compensation requirement and power efficiency. Hence, designers can choose the best possible topology depending on the coupling coefficient, coil design, and load impedance. In this work, the printed coil is designed with 10 layers of 10 μm thickness, respectively, in both cases. The effect of IPCs on the secondary side is briefly analyzed by considering the parasite resistance of the coil for compensation; the behavior of the system is not significantly affected by using the printed coils for compensation on the primary side. As the compensating capacitance does not depend on the parasite resistance, the series–series topology is preferable for the WPT system. The efficiency decreases due to the presence of parasite resistance in the printed coils. Moreover, it is required to choose an efficient topology as the efficiency varies from 56% to only 38%.

A Wireless Power Transfer System With Inverse Coupled Current Doubler Rectifier for High-Output Current Applications

In this paper, a series-series wireless power transfer (WPT) system combined with an inverse coupled current-doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high current low voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with diode rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10kW 400V/48V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 Vdc and 55 Vdc, and the rated output current is 200A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220W energy saving with respect to the traditional diode-rectifier system, when 9.5kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high power WPT applications.

A New Bidirectional Wireless Power Transfer Topology

There is a growing demand in the marketplace for wirelessly powered consumer applications. Some of these low-power applications require wireless power transfer with bi-directional power flow. For such consumer applications, this paper proposes a new bi-directional wireless power transfer (BD-WPT) topology that facilitates wireless power transfers in both directions using fewer components. The paper describes the operating principles of the topology in detail and presents a mathematical model to predict and investigate its performance. Besides, the the control method is proposed for this topology including the power transfer control and synchronization. Simulations and theoretical results are presented in comparison to the measured results of a 60W prototype BD-WPT to demonstrate the viability of the proposed converter topology. Results are convincing and indicate that the proposed converter is suitable for low power applications being low cost, reliable, and efficient.

A Wireless Power Transfer System for Spinal Cord Stimulation Based on Generalized Parity–Time Symmetry Condition

In recent years, the parity&#x2013;time (PT) symmetry principle has been introduced into wireless power transfer (WPT) systems, which can improve the stability of WPT within a certain range. In this article, we analyze the generalized PT-symmetry conditions of four basic WPT topologies based on circuit theory (CT) and coupled mode theory (CMT). The results show that the series&#x2013;parallel (SP) topology meets the PT-symmetry condition based on the CMT, although it does not meet the condition obtained by the CT. The symmetry between the energy of the two-resonance system is established in the SP topology. According to this unique characteristic, a constant-voltage WPT system for spinal cord stimulation is designed, which is independent of the transfer distance and load in a wide range.

Low-Frequency-Switching High-Frequency-Resonating Wireless Power Transfer

This article proposes and implements a multi-topological low-frequency-switching (LFS) high-frequency-resonating (HFR) wireless power transfer (WPT) system, which can significantly improve the system efficiency and fluctuations for specific HFR-WPT applications at equal power level. To adjust the HFR wireless power, high-frequency-switching phase-shift control (PSC) will increase the switching loss and operating temperature, thus inevitably degrading the system efficiency and stability. With the system optimization for suppressing current fluctuations, an LFS-PSC technology is deeply investigated to control wireless power while reducing the switching and conduction losses. Also, it can effectively mitigate the adverse impacts of dead zones on the power and efficiency losses. The system efficiencies using two exemplified WPT topologies can reach 89.53% and 91.62%, while they can be improved by 2.75% and 2.13% during power control. The theoretical analysis, simulation, and experimentation are given to verify the feasibility of the proposed systems using LFS-PSC.

Free-Positioning Wireless Power Transfer System Based on One-to-Multiple Topology

The wireless power transfer (WPT) system is an interesting alternative for charging electric vehicles and has a broad prospect in public transport applications. In order to obtain optimal power transfer, the existing WPT systems often require perfect alignment between the primary and secondary coils, which can hardly be met in real applications. To relieve this problem and achieve the goal of free positioning, a one-to-multiple WPT topology being able to improve the misalignment tolerance at the secondary side is proposed in this letter. Based on circuit analysis and MATLAB simulation, a mixed mode is proposed to obtain a steady power transfer with horizontal misalignment. To verify the proposed topology, a one-to-two WPT system with a three winding transformer is developed in this letter, showing that proposed topology with the mixed mode can significantly increase the positioning adaptability.

Wireless Power Transfer Topologies used for Static and Dynamic Charging of EV Battery: A Review

AbstractElectric vehicles (EV) are found to be a good alternative for the conventional internal combustion (IC) engine vehicles in transportation sector due to its various advantages. Now-a-days, wireless charging of EV battery is preferred among the various methods used for charging EV battery. In this paper, extensive review is carried out on various methods used for wireless charging of an EV battery. Different techniques used for transferring power in wireless mode to charge the EV battery are static EV charging technique and dynamic EV charging technique. Static wireless EV battery charging technique adopts inductive and capacitive method for transferring power whereas, dynamic wireless EV battery charging technique adopts only inductive method for transferring power. These techniques are discussed thoroughly in this paper and broad review is carried out with a focus on the compensation circuit topologies, types of core for magnetic coupled inductors, different converters and controllers used for wireless power transfer (WPT) system. Also, design aspects of an static wireless EV battery charging system along with its equivalent circuit analysis is presented in this paper. Challenges and future development in wireless charging of EV battery is also explained in this paper.

A Wireless EV Charging Topology With Integrated Energy Storage

This article presents a wireless power transfer topology based on inductive power transfer (IPT) with integrated supercapacitor (SC) energy storage. The proposed topology is suitable for dynamic charging of electric vehicles (EVs), where pulses of energy must be processed without placing excessive strain on the utility grid or the EV battery. This topology extends the functionality of a typical LCL- tuned bidirectional IPT system by adding the ability to store energy in an SC in a controlled manner. Operation of the system is described in terms of the switching patterns and control variables required to transfer energy between the input, output, and the SCs. A mathematical model that predicts the overall transfer of power between the input, output, and SCs is presented along with experimental results at a nominal power level of 3.8 kW to validate the model and the topology under a variety of typical operating conditions.

Sampled-Data Modeling for Wireless Power Transfer Systems

In this paper, a dynamic model based on the sampled-data method is presented for a wireless power transfer (WPT) system. The orders of the derived model are equal to the orders of a system. The modeling is different from the existing dynamic modeling for WPT systems, which almost double the model's order. Furthermore, the systematic analysis process is suitable for any WPT topologies and without the higher harmonics neglected and low-frequency approximation. Meanwhile, the state variables are allowed to vary up to twice the switching frequency, since the half-period symmetry property is exploited. In this paper, the series–series (SS) compensated WPT system is chosen as an example and the large-signal model and the steady-state operation point are determined. The small-signal responses perturbed by the phase-shift angle, switching frequency, and input voltage are obtained. The derived model is more adequate with simulation and experimental validation.

A Novel Single-switch Phase Controlled Wireless Power Transfer System

Battery charging is a fundamental application of Wireless Power Transfer (WPT) systems that requires effective implementation of Constant Current (CC) and Constant Voltage (CV) power conduction modes. DC-DC converters used in WPT systems utilize large inductors and capacitors that increase the size and volume of the system in addition to causing higher DC losses. This work proposes a novel single-switch active rectifier for phase controlled WPT systems that is smaller in volume and weight as compared to conventional WPT topologies. The proposed method simplifies the control scheme using improved Digital Phase Control (DPC) and Analog Phase Control (APC) to realize the CC and CV power transfer modes. Furthermore, it prevents forward voltage losses in Silicon Carbide (SiC) switches and shoot through states with improved switching patterns. Simulation studies and experimental results are added to verify the effectiveness of the proposed methodology.

Dual-Phase-Shift Control Scheme With Current-Stress and Efficiency Optimization for Wireless Power Transfer Systems

Traditional wireless power transfer (WPT) systems usually adopt the single-phase-shift (SPS) control method to maintain a constant output current or a constant output voltage for various applications. However, the current-stress on one side is much higher than that of the other side especially under operating conditions with high voltage conversion ratio and light-load. This phenomenon actually can be proven by the established mathematical model of the current-stress of WPT systems using SPS control. This large current-stress will damage power devices and lower the efficiency of WPT systems. In addition, it will result in an increase of system total cost because of the need for the devices with the higher volt-ampere rating. A control strategy based on dual-phase-shift control is developed for WPT systems with an active rectifier to reduce the maximum value of current-stresses on both sides as well as to maintain a constant output voltage or current. Consequently, the system efficiency can be improved compared to traditional WPT systems with SPS control. A scaled-down experimental prototype is constructed to verify the effectiveness of the proposed WPT topology and the control method. Experimental results show that the proposed method can reduce the maximum current-stress significantly and improve the system efficiency compared to traditional WPT systems under SPS control.

Bidirectional Current-Fed Half-Bridge (C) (LC)–(LC ) Configuration for Inductive Wireless Power Transfer System

This paper contributes to the analysis and development of a new power electronics system for bidirectional wireless power transfer (WPT). The major focus is the analysis and implementation of a new current-fed resonant topology with current-sharing and voltage-doubling features. A new bidirectional WPT system with current-fed half-bridge voltage-doubler circuit is proposed and analyzed with series–parallel and series resonant networks. Traditionally used parallel L–C resonant tank in transmitter circuit with current-fed WPT topology causes higher voltage stress across the inverter devices to compensate the reactive power consumed by the loosely coupled coil. In the proposed topology, this is mitigated by adding a suitably designed capacitor in series with the transmitter coil; thus, developing a series–parallel CLC tank. Detailed analysis and design is reported for both grid-to-vehicle and vehicle-to-grid operations. The power flow is controlled through variable frequency modulation. Soft switching of the devices is obtained irrespective of the load current. A proof-of-concept experimental hardware prototype rated at 1.2 kW is developed and tested. Experimental results are presented to verify the analysis and demonstrate the performance of the system with bidirectional power flow.

A bidirectional wireless power transfer system for an electric vehicle with a relay circuit

In order to extend the transfer distance, enhance the tolerance for coil misalignment, and improve the capability of energy feedback and power transfer efficiency of conventional wireless power transfer (WPT) systems for electric vehicles, this paper presents a bidirectional WPT topology with a relay circuit. In the proposed topology, the primary and pickup circuits are implemented with virtually identical structures, which can operate in both magnetic field excitation and magnetic field receiving modes to facilitate bidirectional power flow between the primary side and the pickup side. A relay circuit is introduced to achieve high transfer efficiency under special conditions such as long distance or coil misalignment. The mathematical model of the system is established to describe its working mechanism in detail. Both the direction and amount of power flow can be regulated by controlling the shift phase voltages generated by primary and pickup switches. At the same time, the power and efficiency of system are analyzed, which provides a reference to optimize the parameters. The viability of the proposed system is verified by experiments, and the results suggest that the relay bidirectional WPT system is a reliable and efficient system for electric vehicle charging systems.

A New Current-Fed CLC Transmitter and LC Receiver Topology for Inductive Wireless Power Transfer Application: Analysis, Design, and Experimental Results

This paper presents a new wireless power transfer topology for electric vehicle (EV) charging application. The main emphasis is given on high-frequency dc–ac and ac–dc wireless power transfer stage where the inversion stage is current-fed topology. The required resonance in transmitter side is (C) (LC) type and in the receiver-side series (LC) type. The proposed resonance tank network reduces the inverter switch stress to half of the conventional (L) (C) parallel resonance tank network. Inductor in dc-link provides natural short-circuit protection during inverter fault. The required high-transmitter coil (TC) current for air core coupled inductor circulates through parallel resonating capacitor which reduces inverter switch current stress. Resonant converter provides soft switching at device turn on which reduces switching loss. Also, soft recovery at bridge rectifier eliminates diode reverse recovery loss. The converter is analyzed and simulated using PSIM 9.3. A proof-of-concept 420-W lab-prototype is designed and developed, and hardware results are added to validate the analysis and simulation results.

Compact and Efficient Bipolar Coupler for Wireless Power Chargers: Design and Analysis

Compactness and efficiency are the two basic considerations of the wireless battery chargers for electric vehicles (EVs) and plug-in hybrid EVs. The double-sided LCC compensation topology for wireless power transfer (WPT) has been proved to be one of the efficient solutions lately. However, with the increase of the numbers of compensation components, the volume of the system may become larger, which makes it less attractive. To improve the compactness, a bipolar coupler structure with a compensation-integrated feature is proposed. The inductors of the LCC compensation networks are designed as planar-type and attached to the power-transferring main coils. Extra space and magnetic cores for the compensated inductors outside of the coupler are saved. The cost is that extra couplings between the compensated coils (inductors) and the main coils are induced. To validate the feasibility, the proposed coupler is modeled and investigated by 3-D finite-element analysis tool first. The positioning of the compensated coils, the range of the extra couplings, and the tolerance to misalignment are studied. This is followed by the circuit modeling and characteristic analysis of the proposed WPT topology based on the fundamental harmonic approximation. At last, a 600 mm × 600 mm with a nominal 150-mm-gap wireless charger prototype, operated at a resonant frequency of 95 kHz and a rated power of 5.6 kW has been built and tested. A peak efficiency of 95.36% from a dc power source to the battery load is achieved at rated operation condition.