Wireless Power Transfer Converter Research Articles

Segmented-Vector Pulse Frequency Modulated Three-Level Converter for Wireless Power Transfer

Segmented-Vector Pulse Frequency Modulated Three-Level Converter for Wireless Power Transfer

An Integrated Three-Phase AC–DC Wireless-Power-Transfer Converter With Active Power Factor Correction Using Three Transmitter Coils

Three-phase AC-DC converters are more commonly used for high-power applications compared to single-phase converters. For high-power wireless power transfer (WPT) applications, such as wireless electric vehicle chargers, usually a two-stage topology is applied, which consists of a three-phase AC-DC rectifier with power factor correction and a DC-DC converter for WPT. Recently, there are several studies on three-phase single-stage WPT solutions being proposed to reduce power conversion stages, and furtherly increase overall efficiency and reduce system cost. In this paper, an integrated three-phase AC-DC WPT converter topology with active power factor correction is proposed. The count of power semiconductor devices is significantly reduced compared to state-of-the-art three-phase single-stage topologies. Moreover, three transmitter coils are used to enhance the system power capacity. Topology description, operation analysis, control method, power loss analysis, and reference design guideline of the proposed topology are presented in detail. Finally, a laboratory prototype is built and evaluated. The functionalities, performances, and advantages are demonstrated by the corresponding experimental results.

A Hybrid LCC-SP Compensation Network With Adjustable Impedance Angle Used for Single-Stage Wireless Power Transfer

In order to realize constant current output (CCO) and constant voltage output (CVO) in single-stage wireless power transfer (WPT), this paper proposes a hybrid LCC-SP compensation network with adjustable impedance angle. The switching between CCO and CVO could be realized by changing the parameters of the circuit rather than changing the structure of the circuit, which cause fewer influence on the circuit when the operation mode switches. Due to the structure of the proposed compensation network, the hybrid LCC-SP compensation network could isolate the DC component in single-stage WPT converter which is caused by asymmetric modulation strategy to ensure the loosely coupled transformer works normally. Zero voltage switching (ZVS) can be realized by adjusting the impedance angle. Moreover, the current of primary coil could keep constant which can be used to protect the primary converter when the secondary coil is moved accidentally. And the transfer gain of the proposed compensation network does not rely on the transformer parameters, more parameters design freedom can be realized. The few passive devices are used in this circuit for higher efficiency and lower cost. Finally, the superiorities of the proposed circuit are verified by experiments.

Bidirectional inductive underwater wireless power transfer converter with variable structure

The undersea sensor networks have an important function in marine resource exploration. To prolong the lifetime of the sensor networks, a bidirectional inductive underwater wireless power transfer (BI-UWPT) system with variable structure is proposed. With the proposed system, the autonomous underwater vehicle (AUV) could receive energy from the undersea docking station and transmit energy to the undersea sensor networks. The two full bridge topologies and the SS compensation networks are adopted in the system to achieve the bidirectional power transfer. To achieve bidirectional energy transmission of different power levels, two different operating frequencies and variable compensation capacitors are employed by the AUV. The system mathematical model is also presented. To verify the theoretical analysis, a 432 W simulation model when the AUV receiving electric energy and a 96 W simulation model when the AUV transmitting electric energy are constructed, respectively. The theoretical analysis is verified by the simulation results. Simulation results show that the variable compensation networks can obtain high transfer efficiency of the BI-UWPT system.

Software-Reconfigurable Multistage Constant Current Wireless Battery Charging Based on Multiharmonic Power Transmission

Wireless power transfer (WPT) technology has been widely applied in electric vehicle battery chargers because of its convenience, reliability, and safety. A typical battery charging profile consists of a constant current (CC) charging process followed by a constant voltage charging process. Recently, a multistage constant current (MSCC) charging profile is proposed to increase the charging speed, flexibility, and other performances. MSCC charging profile consists of multiple CC charging processes, which are applied to the battery in turn. This article proposes a low-cost software-reconfigurable MSCC charging technique for a typical single-stage dc–dc series–series compensated WPT converter using multiple high-order harmonics power transmission approach. Such a technique does not require any additional component and it can achieve inherent load-independent CC output and zero phase angle input characteristics. Moreover, it provides a precharge process for deeply discharged batteries to increase their lifetime. A scaled-down design example and the corresponding laboratory prototype are implemented to verify the proposed method.

Constant-Current and Constant-Voltage Output Using Hybrid Compensated Single-Stage Resonant Converter for Wireless Power Transfer

At present, single-stage wireless power transfer (WPT) resonant converter with boost bridgeless power-factor-correction (PFC) rectifier has not been promoted due to the rising voltage of dc-link and unstable output voltage of the converter. The compensation network with load-independent constant current output (CCO) and constant voltage output (CVO) characteristics cannot be analyzed in this converter due to the above problems. In order to solve these problems, a new asymmetric modulation method and the corresponding compensation network design method for single-stage WPT converter are proposed in this article. The proposed modulation method makes the voltage of dc link and the output voltage of single-stage WPT converter constant. Based on the new modulation method, the design method of the compensation network and the implementation of zero-voltage switching (ZVS) in single-stage WPT converter are proposed and analyzed in this article. Compared with the other WPT converters, the proposed scheme has advantages in efficiency and cost. Finally, the superiorities of the proposed circuit are verified by experiments.

A Single-Stage Wireless Power Transfer Converter With Hybrid Compensation Topology in AC Input

Miniaturization and low cost contribute to the development and popularization of wireless power transfer (WPT). Reducing the number of power conversion stages can reduce the volume and cost of the WPT converter, and even make it possible to improve the efficiency. A single-stage WPT converter with constant current (CC) and constant voltage (CV) output and its asymmetric modulation method are proposed in this paper. A direct AC-AC converter is applied to the primary side of the WPT converter to directly convert line-frequency AC to high-frequency AC. The applied direct AC-AC converter that can replace the commonly used multi-stage primary converter reduces the number of circuit devices, thereby reducing the volume and cost of primary converter. The proposed WPT converter can realize zero voltage switching (ZVS) and power factor correction (PFC). In order to achieve CC and CV output, a switchable hybrid compensation topology is applied to the proposed WPT converter. A 720-W experimental prototype was manufactured to verify the rationality of the proposed WPT converter and the correctness of the theoretical analysis.

Design and Multiobjective Optimization of an Auxiliary Wireless Power Transfer Converter in Medium-Voltage Modular Conversion Systems

This article proposes an optimized design for a wireless power transfer converter serving as an auxiliary power supply in a medium-voltage, high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathrm{d}v/\mathrm{d}t$</tex-math></inline-formula> modular conversion system. A <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC-CL</i> circuit topology is implemented to generate a load-independent output voltage with a coupling-coefficient-independent resonant frequency. The output voltage of the circuit can be tuned by changing one pair of resonant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> parameters, which decouples the circuit gain from the coil design. Essential parameters of coil and magnet are extracted analytically or numerically to avoid time-consuming 3-D finite element analysis simulations for the subsequent optimization. After the design of the circuit and coil, a multiobjective optimization is carried out with objectives being efficiency, isolation capacitance, and insulation rating of the converter. Finally, experiments demonstrate a 48- to 48-V dc–dc converter with 100 W output power, 92.78% efficiency, 2.78 pF isolation capacitance, and 27 kV insulation rating to validate the optimization result.

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.

Single-phase bidirectional AC-AC converter with H-bridge energy buffer for wireless power transfer applications

This paper introduces a single-phase bidirectional AC-AC Matrix type converter for wireless power transfer (WPT) applications. The proposed converter converts mains 50 Hz alternating current (AC) directly to high frequency 85 kHz AC without an intermediate direct current (DC) conversion stage. A minimum cost realization of only two bidirectional AC switches comprised each of two semiconductor device and one gate drive signal is employed. The converter operation modes are quantum energy injection and circulating self-oscillation. Elimination of the DC link introduces a sag in the power transfer during the zero crossing of input AC mains, which is well documented in literature. A novel H-bridge buffer structure is introduced which eliminates the power sag by storing energy during mains peak and delivering energy during the zero-crossing period. The converter operates with inherent zero current switching, thus achieving a low switching loss and electro-magnetic interference. The control feature ensures that the converter can be used for both static and dynamic wireless charging applications. The bidirectional power transfer capability ensures that the system can operate in both grid to vehicle (G2V) and vehicle to grid (V2G) power transfer modes. The proposed converter design is analyzed analytically and verified through thorough simulation study.

Constant voltage control of a secondary side controlled wireless power transfer converter using LC/S compensation

Constant voltage control of a secondary side controlled wireless power transfer converter using LC/S compensation

High efficiency constant voltage control of LC/S compensated wireless power transfer converter based on pulse density modulation control

ABSTRACT In this work, the secondary side controlled wireless power transfer (WPT) converter using a LC/S compensation topology is proposed. The constant voltage charging control mode of the proposed converter is evaluated based on high efficiency. In the secondary side, a semi-bridgeless active rectifier (SBAR) is used for the output voltage regulation. In order to improve the efficiency performance of the converter, the pulse density modulation (PDM) control method is applied to the switches of the SBAR. The primary switches operate at the constant operation frequency as independent of the secondary side. There is no communication needed between primary and secondary sides of the proposed converter. Besides, the switches of the SBAR operate with soft switching. The basic principles of the LC/S compensation network and SBAR topology are presented with steady state analysis. The PDM control strategy applied to the switches of the SBAR is discussed. In order to validate the performance of the proposed converter, a prototype is built with 8 cm air gap coreless coupling coils. The input voltage of the converter is 30 V, and its maximum output power is 60 W. The maximum efficiency is achieved as 85.26% at full load condition during CV regulation.

High‐efficiency LC‐S compensated wireless power transfer charging converter for implantable pacemakers

AbstractThis paper deals with wireless power transfer (WPT) based on magnetic coupling resonance in order to delivery power to a cardiac pacemaker from the outside of the body. The high‐efficiency power delivery, implantation, and safety are key parameters for a WPT system, designed for active implantable medical devices. Therefore, this paper is focused on high‐efficiency power transfer, implantation, and safety issues. For the wireless charging of the pacemaker, the LC‐S compensation topology is presented and designed based on high‐efficiency power delivery. The resonant components of the LC‐S compensation topology were extracted in order to ensure that WPT converter operates at resonance frequency. The operation of the presented WPT charging converter is validated by a prototype operating at 300‐kHz operation frequency. At 4.2 V output voltage and 0.45 A output current, the WPT efficiency of the prototype is measured as 82.39%. Finally, the safety evaluation of the proposed WPT converter is also discussed based on reference values presented in the literature.

Design of A Wireless Power Transfer Converter with LC/S Compensation for Electrical Vehicle Battery Charge Applications

Wireless power transfer (WPT) has drawn a lot of attention due to its significant advantages such as safety, reliability, weather proof, etc. This paper presents the design methodology of a WPT converter with LC/S compensation topology for electrical vehicle (EV) battery charge applications. The power loss analysis is employed for each component in the WPT converter. The components in the converter are determined based on low power loss and high-power efficiency. The Lithium- ion battery is also preferred in the design due to it’s high power density advantage. Since the designed WPT system does not use a dc-dc converter to regulate the output current and voltage, the size and the weight of the overall system can be reduced. Finally, according to given design procedure, a field-electric common simulation of WPT converter is performed with 2 kW output power while the output voltage is changing between 250 V-400 V. The simulated peak efficiency of the converter is obtained around 96.70% with 0.3 coupling coefficient.

Inductive Power Transfer Converter With Center-Tapped Pickup Winding

A step-down wireless power transfer converter with center-tapped pickup windings is proposed in this article. The pickup winding is split into two sections and only one is connected to the load. This topology is more suitable for low-voltage level applications, such as consumer electronic products. Like the conventional series-parallel compensation technique, the circuit does not induce high circulation current at the transmitter coil under light load operation. The loosely coupled coils are analyzed with mutual inductance model; in addition, the input impedance and voltage gain are derived. The input impedance is proportional to the load impedance, and the voltage gain is less sensitive to the load variation. The proposed topology performs better than the conventional one at higher load conditions, especially when the coupling is poor. The efficiency of a laboratory circuit reaches 88.8% at best condition and it is higher than 63% ranging from 10- to 100-W load at 10- or 60-mm coil separation.

A CMOS Adaptive 433/900 MHz Differential RF Power Harvester with Wide-Dynamic Range for Wireless Powering

A wide-dynamic range high-efficiency differential RF-to-DC power converter for wireless power transfer (WPT) applications is presented. The architecture offers high power conversion efficiency (PCE) over a wide range of input powers by employing cross-coupled high-threshold rectifying devices with stacking diodes. The proposed rectifier uses the adaptive biasing technique to control the rectifying devices’ conduction and minimizes the leakage current of the feedback diodes by utilizing the dynamic body biasing. Compared to the conventional cross-coupled rectifier, the proposed rectifier has a [Formula: see text] dynamic range. A prototype of the proposed rectifier is implemented in 65-nm CMOS technology and occupies an area of 0.0148[Formula: see text]mm2. The rectifier achieves [Formula: see text][Formula: see text]dBm sensitivity for 1[Formula: see text]V output and a 79.4% peak PCE. A dynamic range of 17.3[Formula: see text]dB is achieved at the 433[Formula: see text]MHz in the Industrial Scientific Medical band (ISM band) with a 100-K[Formula: see text] load. Furthermore, the proposed design offers a peak PCE of 62.6% and a wide dynamic range of 16.1[Formula: see text]dB at the UHF 900[Formula: see text]MHz band with a load resistance of 100-K[Formula: see text].

Single stage AC–DC converter for wireless power transfer operating within wide voltage control range

In the field of e-mobility and automated guided vehicles, studies on a wireless power transfer (WPT) charging system have been conducted recently owing to its convenience, reliability, and positive environmental impact due to the elimination of cords. In this paper, a wireless power transfer charging system using a single-stage AC–DC converter is proposed that can be reduced in size and weight to ensure convenience. The proposed single-stage AC–DC converter can control a wide output voltage (36–54 VDC) within the coupling ranges due to the variable link voltage applied to a WPT resonant circuit through phase-shifted modulation at a fixed switching frequency. In addition, the input power factor (PF) and the total harmonic distortion (THDi) can be improved through the use of the proposed converter. A 1-kW prototype with a 50-mm air gap was fabricated and its effectiveness was validated based on analysis and experimental results.

An Investigation of Class E VSI based DC-DC Converter for Wireless Charging Application

A class E voltage source inverter (VSI) based DC-DC step down converter is used for Inductive Power Transfer (IPT) which is generally used for the application of wireless power transfer (WPT). It has less number of switches, and can be turned ON with zero voltage zero current switching (ZVZCS), and turned OFF with zero voltage switching (ZVS). Significant progress has been achieved in the field of IPT, there are many obstacles and design challenges are still present. Low power transfer efficiencies and short power transfer range. Higher efficiencies are possible for very short transmission distances. Large amounts of power can be transferred for large distances but at reduced efficiencies. This paper addresses the limitations of IPT systems. A complete study and analysis of the converter have been given, FEM simulation tool has been used to study the shape or structure of coil has been presented. The change in coupling coefficient of two magnetically coupled coils is evaluated at different air gap and misaligned positions. The outcome of this work results in the selection of suitable shape of coil and efficient converter for wireless power transfer.

PERFORMANCE EVALUATION OF A WIRELESS CHARGING CONVERTER FOR ACTIVE IMPLANTABLE MEDICAL DEVICES

This paper evaluates the performance of a wireless power transfer (WPT) converter for active implantable medical devices (AIMDs). The efficiency is the key parameter in the design of a WPT converter for charging of AIMDs. The compensation topology of a WPT system has an important role for high efficiency power transfer. Thus, this work analyses a WPT converter using LC/S hybrid compensation topology, for wireless charging of AIMDs, in terms of high efficiency power transfer. In the efficiency analyses, the WPT converter is tested by 3D electromagnetic simulation software. The maximum efficiency is obtained as 72.33% while the output voltage is 4.2 V and the current is 0.45 A. Finally, safety performance of proposed WPT converter is also evaluated based on specific absorption rate (SAR) analysis. The average peak spatial head/torso SAR produced by WPT converter is obtained as 0.0254 W/kg, which is lower than recommended restrictions.

Theoretical Analysis of Prospects of Organic Photovoltaics as a Multi-Functional Solar Cell and Laser Power Converter for Wireless Power Transfer.

Few reports have researched on utilization of laser power conversion systems for wireless power transfer in aeronautical applications. III-V compound semiconductors are commonly used as photovoltaic (PV) power converters in the previous studies. We propose the prospects of using organic absorbers as PV power converters. For laser power conversion to be applied for portable devices, the PV module should be easily processable, thin, low-weight, and printable on flexible substrates. Organic PVs provide all the above advantages, and thus, could serve as a potential candidate for laser power harvesting applications. Moreover, they can also be made transparent, which could be utilized in power harvesting lamination coatings and windows. We had simulated the possibility of using single-junction and tandem photovoltaic structures for 670 nm and 850 nm laser power harvesting. FDTD simulations were conducted to optimize the PV structure in order to maximize the absorption at the laser wavelengths. A maximum PCE of 16.17% for single-junction PV and 24.85% for tandem PV was theoretically obtained.