Omnidirectional Wireless Power Transfer Research Articles

Free-Positioning and Omnidirectional Wireless Power Transfer Using Self-Decoupled Planar Transmitter Coils

Free-Positioning and Omnidirectional Wireless Power Transfer Using Self-Decoupled Planar Transmitter Coils

Research on Maximum Power Point Tracking Control in Omnidirectional Wireless Power Transfer System

Research on Maximum Power Point Tracking Control in Omnidirectional Wireless Power Transfer System

A multi‐receiver adaptive design of variable magnetic coupled structure for omnidirectional WPT system

SummaryOmnidirectional Wireless Power Transfer (OWPT) system can provide power to multiple loads in space. The different loads have different requirements for current and power levels under various operating conditions. This paper proposes a Variable Receiving Coil (VRC) structure and its control strategy. Active regulation of the output current is achieved by adjusting the geometric size of the receiving coil. Meets the power supply needs of equipment in different scenarios. This design allows the effective value of the VRC current to remain stable within the range of 1.01–1.62A (transmission distance of 22–27 cm). By adjusting the geometric transformation state of the VRC, different output currents can be obtained under fixed positions, loads, and input voltages. The designed receiver can meet the differential current requirements of multiple spatial loads, and is insensitive to factors such as load, transmission distance, and rotation angle. This system can reduce the design complexity of charging and power supply systems and effectively promote the application of Wireless Power Transfer (WPT) in the field of Internet of Things devices.

Design and Optimization of a Planar Omnidirectional Wireless Power Transfer System for Consumer Electronics

Design and Optimization of a Planar Omnidirectional Wireless Power Transfer System for Consumer Electronics

Output Power Control Strategy for Omnidirectional Wireless Power Transfer System Based on Maximum Mutual Inductance Information Estimation

Output Power Control Strategy for Omnidirectional Wireless Power Transfer System Based on Maximum Mutual Inductance Information Estimation

Axial magnetic quadrupole mode of dielectric resonator for omnidirectional wireless power transfer

To achieve omnidirectional wireless power transfer (WPT) with high efficiency, a high Q-factor transmitter generating homogeneous magnetic field is crucial. Traditionally, orthogonal coils of different shapes are used to realize transmitters. In this paper, we develop an omnidirectional magnetic resonant WPT system based on a dielectric disk resonator with colossal permittivity and low loss operating at the axial magnetic quadrupole mode. The constant power transfer efficiency of 88% at the frequency of 157 MHz over the transfer distance of 3 cm for all azimuth angles of a receiver is experimentally demonstrated. The possibility of multi-receivers charging is also studied demonstrating a total efficiency of 90% regardless of azimuth angle between two receivers with respect to the transmitting disk resonator. The minimized exposure of biological tissues to the electric and magnetic fields as well as a low specific absorption rate is observed that makes the WPT system safer for charging with higher input power.

Enhancement Method of Weak Transmission Area for Omnidirectional Wireless Power Transfer System

Enhancement Method of Weak Transmission Area for Omnidirectional Wireless Power Transfer System

Square Polyhedron Transmitter for Three-Dimensional Omnidirectional Wireless Power Transfer

Square Polyhedron Transmitter for Three-Dimensional Omnidirectional Wireless Power Transfer

Efficiency Optimization and Power Allocation of Omnidirectional Wireless Power Transfer for Multiple Receivers

Omnidirectional wireless power transfer to multiple devices has become a research hotspot due to its high spatial freedom and flexible design. However, this power supply method often faces the problems of high leakage flux and different receiver power requirements. This article studied the effects of currents of transmitting coils on transmission efficiency mathematically. A method of maximum efficiency tracking and power allocation for omnidirectional wireless power transfer to multiple receivers was proposed, and a mutual inductance identification method based on primary feedback is presented. Through the parameters identified by the primary side feedback, the current amplitudes and phases of the Tx coils were adjusted to achieve maximum efficiency, and the flexible power requirements of multiple devices can be realized. Finally, the above methods are experimentally verified. The two receivers can be charged with 58.8% efficiency and the power ratio can be precisely controlled from 0 to 100 percent, which is difficult for conventional method.

Omnidirectional Wireless Power Transfer System Using Modified Saddle-Shaped Coil Pair for Implantable Capsule Robots

Omnidirectional Wireless Power Transfer System Using Modified Saddle-Shaped Coil Pair for Implantable Capsule Robots

A Novel Three-Phase Omnidirectional Wireless Power Transfer System With Zero-Switching-Loss Inverter and Cylindrical Transmitter Coil

Aiming at the problems of large switching loss and large output power fluctuation in the existing omnidirectional wireless power transfer (OWPT) system, a novel OWPT system with zero-switching-loss inverter and cylindrical transmitter coil is proposed. By introducing an auxiliary resonant network with simple structure and low-loss on each phase arm of the three-phase inverter, zero-voltage switching (ZVS) turn-ON and zero-current switching (ZCS) turn-OFF within the full power range can be acquired. The switching loss in the main circuit of inverter is reliably eliminated. The transmitter coil is a cylindrical coil composed of the three curved rectangular coils, whose excitation current amplitude is equal and the phase difference is 120°. It can arise a spatial rotating magnetic field around the transmitter coil and provide an omnidirectional energy transmission channel. The operating principle of soft-switching is analyzed in detail, and the design rules of soft-switching in full power range and the parameter design method of coupler to reduce the fluctuation of output power are given. Ultimately, an experimental prototype is used to verify the feasibility of the proposed OWPT system. The experimental results indicate that the system output power is retained at 93.4W∼104.7W and transfer efficiency is retained at 71.2%∼78.1% under arbitrary angular misalignment of receiver.

Design and Implementation of an Underwater Spatial Omnidirectional Wireless Power Transfer System

Design and Implementation of an Underwater Spatial Omnidirectional Wireless Power Transfer System

Maximum Power Tracking for Magnetic Field Editing-Based Omnidirectional Wireless Power Transfer

This paper proposes and implements an optimized omnidirectional wireless power transfer (WPT) system using distributed transmitter coils is proposed. Under the consideration of practical WPT applications which involve human safety concerns, such as daily home apparatus or wireless rechargeable medical implants, the proposed system can achieve the shortest charging time within the safe limits of human exposure to radiofrequency electromagnetic energy. Based on the calculation of the magnetic intensity generated by multi-coupling WPT systems, a more processable magnetic threshold model is presented and analyzed based on the common standard. A newly developed optimization model of the transmitter currents and accordant control strategy is designed and presented to realize both maximum power tracking and flux suppression at target positions. The double-resonant circuit topology with LCC compensation is adopted to reach the stable and synchronized transmitter currents. The cross-coupling problem in multi-input WPT systems will be solved as well. Full-range magnitude control is realized with a single controller and direct current power source. The hybrid frequency pacing technique is adopted for lower switching frequency and higher system efficiency under weak coupling operations. Taking practical wireless rechargeable medical implant as the research object, both simulation and experimental results validate the feasibility and the prospect of the proposed system.

Cylindrical Transmitting Coil for Two-Dimensional Omnidirectional Wireless Power Transfer

Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This article proposes a cylindrical-shaped coil, which can produce the homogeneous magnetic field in a plane. The coil consists of two helical windings, which are wound to guide the current in opposite directions. A single power source is used to excite the transmitter without any current amplitude or phase control circuits. Furthermore, since the parasitic capacitance of the coil is not negligible due to the complexity of the coil shape, we develop a general equivalent model with parasitic capacitance for the analysis of complex coils. The system efficiency of the proposed omnidirectional wireless power transfer device is validated by a practical experiment. The measured dc-to-dc efficiency of approximately 72.4% and the load power of 13 W are demonstrated for the proposed wireless charging system at 6.78-MHz operating frequency. Finally, we verify that the electromagnetic exposure satisfies the safety regulations.

Modified tri-axial square Helmholtz coil for omnidirectional wireless power transfer

Modified tri-axial square Helmholtz coil for omnidirectional wireless power transfer

Output-Voltage Adaptive of Omnidirectional Wireless Power Transfer Based on Receivers With Digital Coils

Omnidirectional wireless power transfer (WPT) can provide power for multiple loads at any position in space. The voltage required for different loads is unavoidably various, and the characteristics of load may also change at different stages of power replenishment (e.g., battery impedance). WPT needs to adjust the supply voltage and power in real time to meet the needs of different loads and diverse working conditions. This article presents a receiver composed of digital receiving coil (DRC) with voltage adaptive regulation. The layers of DRC are changed to adjust the coupling state of magnetic coupling mechanism (MCM). The voltage of DRC is actively adjusted to maintain continuous stability of power supply, or to meet the specific requirements for different stages. The proposed design can achieve the peak-to-peak voltage of DRC stabilized in the range of 8.5–14 V with the transmitting distance varying from 28 to 47 cm, 18–26 V with the load of 3–100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> , and 8–13.5 V with the input dc voltage changing from 11.5 to 46 V. When the layers of DRC are adjusted, different voltages can be obtained with fixed distance, load, and input DC voltage. The designed receiver with DRC is less sensitive to load, transmission distance, rotation angle, and other factors, and meet the differential voltage requirements of space multiload. The proposed system can reduce the design difficulty and requirements of the converter, and will promote the application of WPT in the field of power supply for Internet of Things (IoT) equipment.

Compact and Free-Positioning Omnidirectional Wireless Power Transfer System for Unmanned Aerial Vehicle Charging Applications

Compact design in receiver and misalignment tolerance are two basic considerations for practical applications of wireless power transfer (WPT) in unmanned aerial vehicles (UAVs). To balance these two requirements, a novel magnetic design with the composite interval-acted parallel- & vertical-flux throw, orthogonal two-dimensional flux pick-up, and power-flow summed output is proposed in this letter. The resulting magnetic structure includes a target-shaped transmitter and two quadrature receivers, and the transmitter consists of four annular-type coils which are magnetized in a bipolar mode, making it possible to form a magnetic field with a parallel- and vertical-flux complementary distribution. Moreover, by integrating two orthogonal receiving coils into one receiver, a stable summed output current can supply the UAV onboard load with only a small size receiver. A UAV WPT prototype is established based on the proposal. The results show that the prototype can deliver 325 W with a system efficiency of 86%, and especially the variation of the output current is within ±0.76 A for different landing positions and directions. The overall system efficiency is from 87.3% down to 83.1%.

A Reticulated Planar Transmitter Using a Three-Dimensional Rotating Magnetic Field for Free-Positioning Omnidirectional Wireless Power Transfer

This article proposes a free-positioning omnidirectional wireless power transfer (WPT) system with a reticulated planar transmitter, which enables multiple receivers to be powered simultaneously in arbitrary positions and orientations. The reticulated planar transmitter is equipped with four interleaved and overlapped meander coils, thus, a three-dimensional (3-D) rotating magnetic field is generated with the designed excitation current. Therefore, only a planar single-coil (such as a loop-type coil) is required to realize free-positioning omnidirectional WPT. According to the theoretical modeling of the magnetic field, the excitation current that can generate a 3-D rotating magnetic field is given. To obtain a uniform and strong magnetic field distribution, the transmitter grid width is optimized. Furthermore, an excitation current modulation strategy based on phase-shift control is presented to regulate the amplitude of the excitation current. The experimental results show that the output power is greater than 13.1 W no matter how the center of the receiver moves or rotates freely within 400 × 400 mm. When five receivers are powered simultaneously in different positions and orientations, 82.5 W total output power and 55.6% efficiency can be achieved. The experimental results demonstrate that free-positioning omnidirectional WPT can be realized with only planar single-coil receivers by using the proposed reticulated planar transmitter and its excitation current modulation strategy.

High-Efficiency Omnidirectional Wireless Power Transfer System

To achieve omnidirectional wireless power transfer (WPT), it is crucial to tune the direction of the total magnetic field from the transmitter (Tx) coils toward the receiver coil (Rx) that can be placed at different positions with respect to Tx. Several methods, such as amplitude modulation, phase-shifting, and frequency modulation, have been proposed to vary the Tx currents, depending on the angular position of Rx, but complex sensing and feedback control systems are required. In this article, we propose an efficient omnidirectional WPT system that is capable of self-tuning the power flow without any feedback from the Rx-side. It only requires a simple Tx current switching rather than complex feedback control system for detecting the Rx position. The proposed system consists of three orthogonal transmitter–repeater (Tx-Rp) channels that deliver power to Rx. In this configuration, the Tx currents are proportional to the mutual coupling between the Rp and Rx in the same channel, which ensures the self-tuning of the optimal power flow through channels. Both theoretical and experimental studies are performed to validate the proposed method. The prototype of the proposed approach enables the Rx to harvest power with almost uniform high efficiency (about 90%) regardless of its angular position.

Self-Tuning Omnidirectional Wireless Power Transfer Using Double-Toroidal Helix Coils

In this article, we suggest and study a novel omnidirectional wireless power transfer (WPT) system based on unusual double-toroidal helix coils. The suggested antenna is a double-helix coil wounded around a torus. It creates two mutually orthogonal magnetic fields. One is toroidal and confined inside the torus, and another one is poloidal and is distributed outside it. The intensities of these two fields can be independently tuned via the geometry of the turns. The coupling coefficients are tailored to ensure high efficiency regardless of the receiver position and orientation, without active circuitry for tuning or control. This topology provides self-tuning functionality which is achieved when the coupling between the transmitter and receiver is minimized while the coupling in the pairs transmitter–repeater and repeater–receiver is strong. The system consists of three transmitter–repeater pairs orthogonal to each other, ensuring omnidirectional functionality. Experimental results confirm self-tunability and high efficiency for any position and orientation of receivers. The proposed double-helix antenna is applicable to different WPT applications where the coupling/decoupling between coils can be freely controlled.