This paper presents a discrete sliding mode control (DSMC) scheme for a series-series compensated wireless power transfer (WPT) system to achieve fast maximum energy efficiency (MEE) tracking and ...output voltage regulation. The power transmitter of the adopted WPT system comprises a dc/ac converter, which incorporates the hill-climbing-search-based phase angle control in achieving minimum input current injection from its dc source, thereby attaining minimum input power operation. The power receiver comprises a buck-boost converter that emulates an optimal load value, following the MEE point determined by the DSMC scheme. With this WPT system, no direct communication means is required between the transmitter and the receiver. Therefore, the implementation cost of this system is potentially lower and annoying communication delays, which deteriorate control performance, are absent. Both the simulation and experiment results show that this WPT system displays better dynamic regulation of the output voltage during MEE tracking when it is controlled by DSMC, as compared to that controlled by the conventional discrete proportional-integral (PI) control. Such an improvement prevents the load from sustaining undesirable overshoot/undershoot during transient states.
Due to limitations of low power density, high cost, heavy weight, etc., the development and application of battery-powered devices are facing with unprecedented technical challenges. As a novel ...pattern of energization, the wireless power transfer (WPT) offers a band new way to the energy acquisition for electric-driven devices, thus alleviating the over-dependence on the battery. This paper presents an overview of WPT techniques with emphasis on working mechanisms, technical challenges, metamaterials, and classical applications. Focusing on WPT systems, this paper elaborates on current major research topics and discusses about future development trends. This novel energy transmission mechanism shows significant meanings on the pervasive application of renewable energies in our daily life.
Inductive power transfer (IPT) and capacitive power transfer (CPT) are mainly two effective ways to achieve wireless power transfer (WPT). IPT system needs capacitor to compensate the system, while ...the CPT system requires inductor to tune the system. Therefore, IPT coupler can be used to compensate the CPT coupler and vice versa. In this article, an inductive and capacitive hybrid wireless power transfer (HWPT) system is proposed to improve the system coupler antimisalignment ability. The couplers of IPT and CPT are employed together to compensate each other and transfer power together. Superposition theory is used to analyze the system working principle in detail. With the analysis results, a scaled-down system is built to validate the performance of the proposed approach. Experimental results show that the proposed HWPT system can achieve 653 W output power with 87.7% dc-dc efficiency at the well-aligned condition, and the maximum variation of the output power is 8.3% with the coupler misalignment from 0 to 270 mm (halfwidth of the coupler), which agree well with the analysis results.
The mass and volume of wireless power transfer (WPT) systems for charging electric vehicles are directly related to the rated power of the system. The difficulties of high-power wireless charging are ...exacerbated by the need to meet the same practical constraints associated with vehicle integration as lower power systems. Therefore, more advanced techniques are necessary to improve power density and specific power of wireless charging systems for high-power applications. This article presents theory and analysis of three-phase inductive WPT systems with bipolar phase windings. Magnetic coupler topologies and the theoretical and practical aspects of series three-phase resonant compensation networks are discussed. The systems under consideration are designed to utilize rotating magnetic fields to achieve a power transfer characteristic that is temporally smoother than single-phase systems. Other benefits associated with rotating magnetic field based WPT, including reduced ferrite mass, filter component requirements, and electromagnetic field emissions, are discussed. Experimental results of a prototype system are presented in both aligned and misaligned configurations. The system is demonstrated transferring 50 kW with 95% dc-to-dc efficiency over a 150-mm airgap in the aligned case. Onaper-pad basis, the magnetic couplers achieve a power density of 195 kW/m 2 and a specific power of 3.65 kW/kg. This article is accompanied by a video of the rotating magnetic field produced by a simulated three-phase WPT system.
Expandable and flexible wireless power transfer (WPT) systems have been in demand in numerous industry applications, especially for dynamic chargers in electric vehicles. Those systems, however, ...bring about certain technical issues such as modulation technique and topology of the transmitter side, and transferred power profile of the transmitters. In this article, a new converter topology to drive closely spaced segmented dynamic wireless power transfer (DWPT) systems is proposed. The proposed converter can be expanded to cater for different number of transmitters, and it can provide a uniform transferred power profile throughout the path of transmitter coils, known as track. Furthermore, this article focuses on analyzing the operation of the converter and the effect of closely spaced transmitters over its operation. To show the effectiveness of the proposed topology and its modulation technique, the converter is simulated and experimentally tested using a laboratory prototype. The results are compared and analyzed, and their close agreement shows the validity of the proposed technique.
In this paper, a novel long-distance wireless power transfer (WPT) system using repeater coils is proposed to provide power supplies for the driver circuits in high-voltage applications, such as ...flexible alternative current transmission systems. Different from most of the existing wireless repeater systems where the load is only connected to the last coil and the repeater coils function solely as power relays, in the proposed system, multiple loads are powered by the repeaters. The repeater coils transfer power not only to the subsequent coils but also to the loads connected to them. Dual coil design is proposed for the repeaters with which load-independent characteristics are obtained with a suitable design of coupling coefficients. As a result, the load power can be easily adjusted without affecting each other. Load current characteristics and system efficiency have been analyzed in detail. The power transfer capability of the proposed system is illustrated for different coil quality factors and coupling coefficients. An experimental setup with 10 loads has been built to validate the effectiveness of the proposed long-distance WPT system. The maximum reachable system efficiency is about 84%.
This letter proposes a rotation-free wireless power transfer system based on a new coil structure to achieve stable output power and efficiency against rotational misalignments for charging ...autonomous underwater vehicles. The new coil structure has two decoupled receivers composed of two reversely wound receiver coils and the magnetic flux directions of the two receivers are perpendicular to each other, guaranteeing a relatively constant total mutual inductance and a decoupled characteristic under rotational misalignments. The proposed coil structure is verified via finite element analysis based on ANSYS Maxwell. A rotation-free LCC-LCC compensated WPT prototype is built and the experimental results verify the theoretical analysis and simulations. The system can deliver 664 W with a dc-dc efficiency of 92.26% under the best case and 485 W with a 92.10% dc-dc efficiency under the worst case.
This paper presents a new design of near-field focused metasurface for high-efficiency wireless power transfer with multifocus characteristics. A general synthesis procedure is outlined to design ...metasurfaces with desired multiple foci in the near-field zone. The unit cell of printed tridipole is used to realize the focused metasurface which has a large range of phase shift and is adapted to near-field focusing applications. Different feeding and focusing designs of the printed tridipole metasurfaces are proposed and analyzed. Two kinds of metasurfaces with 20×20 elements are designed, fabricated, and measured at 5.8 GHz. One is the single-feed and single-focus case, and the other is single-feed and two-focus case. Two-dimensional planar near-field scanning technique is implemented to measure the E -field focusing characteristics. Full-wave simulations and experiments demonstrate that the proposed focusing metasurfaces have a high wireless power transfer efficiency of 70%. The relative bandwidth with 50% power focusing efficiency is about 16%. The measured results are in good agreement with the theoretical designs and simulated results, which verify the feasibility and correctness of the proposed approach in this paper.
Wireless power transfer network (WPTN) is composed of nodes and power transfer routes, which can supply power for group devices. In the application of WPTN, the number and position of load nodes are ...usually random. The random variation and the adjustment of output characteristics of some load nodes will affect the electrical performance of the other nodes due to the complex cross-coupling. This paper constructs an array WPTN that can maintain the independence of the node output current with the load change by designing a special topology structure. Combined with the topology structure switching strategy of nodes, the power transfer direction can be flexibly adjusted according to the position of load nodes. On this basis, the power transfer routes are optimized for the goal of maximum efficiency. And the breadth-first search algorithm is adopted to optimize the power transfer routes based on its fast search speed. Finally, the experimental results verify the effectiveness of the proposed method.
Wireless power transfer (WPT) is a key technique for many existing and emerging applications in biomedical devices. This paper presents a novel implantable magnetic coupling resonate WPT system by ...integrating with metasurface for biological applications. The receiver element is implanted under the skin surface 3 mm and has the dual-band property for transferring power and data telemetry simultaneously. A conformal strongly coupled magnetic resonator coil is used as the transmitting coil to construct the wireless power link. In addition, we integrate the proposed WPT system with negative permeability (MNG) metasurface over the human skin surface as a miniaturized wearable device to improve the WPT efficiency. The property of the MNG and its effect on the WPT efficiency are analyzed. Considering the special implantable environment, various misalignment tolerances between the metasurface and the receiver are discussed to evaluate the coupling response of the proposed WPT system. Finally, the efficient WPT system integrating with MNG has been verified by the experimental measurements, and the measured result shows that 15.7 dB coupling enhancement can be obtained by integrating with the MNG metasurface.
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