Improved Design of Wireless Electrical Energy Transfer System for Various Power Applications

This thesis introduces a state-of-the-art review of existing wireless power transfer (WPT) technologies with a detailed comparison and presents the limitations of the inductive power transfer system through simulation and practical analyses. This thesis also presents the expanded use of the high-frequency analysis tool, known as FEKO, and the novel application of frequency response analyser (FRA) with various simulations and practical demonstrations for enhancing the design and maintenance of WPT systems

Capacitive power transfer for maritime electrical charging applications

Wireless power transfer can provide the convenience of automatic charging while the ships or maritime vehicles are docking, mooring, or in a sailing maneuver. It can address the challenges facing conventional wired charging technologies, including long charging and queuing time, wear and tear of the physical contacts, handling cables and wires, and electric shock hazards. Capacitive power transfer (CPT) is one of the wireless charging technologies that has received attention in on-road electric vehicle charging applications. By the main of electric fields, CPT offers an inexpensive and light charging solution with good misalignment performance. Thus, this study investigates the CPT system in which air and water are the separation medium for the electrical wireless charging of small ships and unmanned maritime vehicles. Unlike on-road charging applications, air or water can be utilized as charging mediums to charge small ships and unmanned maritime vehicles. Because of the low permittivity of the air, the air-gapped capacitive coupling in the Pico Farad range requires a mega-hertz operating frequency to transfer power over a few hundred millimeters. This study examines an air-gapped CPT system to transfer about 135 W at a separation distance of 50 mm, a total efficiency of approximately 83.9%, and a 1 MHz operating efficiency. At 13.56 MHz, the study tested a shielded air-gapped CPT system that transfers about 100 W at a separation distance of 30 mm and a total efficiency of about 87%. The study also examines the underwater CPT system by submerging the couplers in water to increase the capacitive coupling. The system can transfer about 129 W at a separation distance of 300 mm, a total efficiency of aboutapproximately%, and a 1.1 MHz operating efficiency. These CPT systems can upscale to provide a few kW for small ships and unmanned maritime vehicles. But they are still facing several challenges that need further investigations

A Secondary-Side Controlled Electric Vehicle Wireless Charger

In this paper, the design procedure of an electric vehicle (EV) wireless charger is presented. Unlike most of the systems available in the literature, the proposed charging system is regulated from the vehicle side. The on-board electrical circuit automatically adapts the resonant compensation to guarantee compatibility with the primary inverter characteristics and achieve high transmission efficiency without communication between sides. Moreover, the proposed control strategy, used to regulate the secondary full active rectifier (FAR), allows the supply of the the EV battery, maximizing the efficiency during the whole charging process

High Power Capacitive Power Transfer for Electric Vehicle Charging Applications

Capacitive power transfer (CPT) technology is an effective way to charge electric vehicles, in which electric fields between metal plates are used to transfer power. Compared to the conventional inductive power transfer (IPT) system, a CPT system has three advantages: it does not generate eddy-current loss in nearby metal objects; it can reduce the system weight and cost; it has better misalignment performance. However, the coupling capacitance in a CPT system is usually in the pF range, which limits the CPT system power and efficiency. Through overcoming the limitation of small capacitance in a CPT system, this dissertation has achieved three breakthroughs in CPT technology: the system power is increased from several tens of watts to several kW; the transfer distance is increased from less than 1 mm to hundreds of mm; the transfer efficiency is increased from about 30% to over 90%. A double-sided LCLC compensation circuit has been proposed to realize high-power and long-distance capacitive power transfer. The compensation circuit provides resonances with the coupling capacitance, and increases the voltages on metal plates to kV level to achieve kW power transfer. A prototype has been constructed and validates the proposed circuit. Experimental results show that the prototype realizes 2.4 kW power transfer across an air-gap distance of 150 mm with a dc-dc efficiency of 90.8%. The experiments also show that the CPT system has better misalignment performance than the conventional IPT system. An IPT-CPT combined system has also been proposed to integrate the IPT and CPT technology together. The combination can increase the efficiency of the CPT system, and improve the misalignment performance of the IPT system. A prototype has been constructed to validate the combined idea. Experimental results show that the prototype realizes 2.84 kW power transfer across an air-gap distance of 150 mm with a dc-dc efficiency of 94.4%. Using the designed LCLC compensation circuit, a dynamic CPT system has been proposed to realize power transfer to receivers in moving status. A long-track coupler structure is used to reduce the pulsation of received power. A prototype has been constructed to validate dynamic charging. Experimental results show that the prototype realizes 154W power transfer across an air-gap distance of 50 mm with a dc-dc efficiency of 85.4%. Considering practical applications, the safety issues and foreign object influence have been studied in this dissertation. The high voltage issue can be solved by reliable insulation, and the electric field emissions can be reduced through capacitive coupler structure design. The foreign object, either metallic or dielectric, can influence the coupling capacitances in a CPT system depends on the position and size. The CPT system can also influence the voltage and power loss in the foreign object. To sum up, this dissertation has demonstrated that the CPT technology is a good solution to realize the charging of electric vehicles. In future work, the power density and efficiency of the CPT system will be further improved to make it more competitive with the inductive and conductive charging technology.PHDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138493/1/feilu_1.pd

Challenges and Barriers of Wireless Charging Technologies for Electric Vehicles

Electric vehicles could be a significant aid in lowering greenhouse gas emissions. Even though extensive study has been done on the features and traits of electric vehicles and the nature of their charging infrastructure, network modeling for electric vehicle manufacturing has been limited and unchanging. The necessity of wireless electric vehicle charging, based on magnetic resonance coupling, drove the primary aims for this review work. Herein, we examined the basic theoretical framework for wireless power transmission systems for EV charging and performed a software-in-the-loop analysis, in addition to carrying out a performance analysis of an EV charging system based on magnetic resonance. This study also covered power pad designs and created workable remedies for the following issues: (i) how power pad positioning affected the function of wireless charging systems and (ii) how to develop strategies to keep power efficiency at its highest level. Moreover, safety features of wireless charging systems, owing to interruption from foreign objects and/or living objects, were analyzed, and solutions were proposed to ensure such systems would operate as safely and optimally as possible

Overview and Advancements in Electric Vehicle WPT Systems Architecture

Wireless Power Transfer (WPT) system is a rapidly evolving technology with vast potentials in consumer electronics, electric vehicles, biomedicals and smart grid applications such as Vehicle to Grid (V2G). Hence, this article is devoted to present an overview of recent progress in WPT with specific interest in magnetic resonance WPT and its system architectures such as compensation topologies, inputs and outputs, as well as coil structure. The strengths, drawbacks and applications of the basic compensations (SS, SP, PS, PP) and hybrid compensations (LCC and LCL) were presented and compared. Although primary parallel compensations perform well at low mutual inductance, they are rarely used due to large impedance and dependence of coefficient coupling on the load. Hence, the need for extra-compensations forming hybrid topologies, such as LCC, LCL, which usually choice topologies for dynamic WPT application or V2G application

A design technique for geometric optimisation of resonant coil sizes in low to mid frequency inductive power transmission systems.

Wireless power transfer (WPT) is a well-established method of energising electrically-powered devices. Among the different available WPT techniques, Resonant Inductive Power Transfer (RIPT) has been adapted for use in a wide range of applications. The primary reason is the relatively higher Power Transfer Efficiency (PTE) that RIPT can provide. RIPT systems operate on the principle of magnetic resonance coupling between a Transmitter (Tx) and a Receiver (Rx) coil. Maximising the PTE is a key driver for improving the performance of RIPT systems. In a RIPT link the PTE is influenced by three factors: (i) inductive linkage between the Tx and Rx, (ii) terminating circuitry of Tx and Rx sides and (iii) the Tx/Rx coil's geometrical size. In considering these impacting factors, different techniques to improve PTE have been extensively presented in the literature and are comprehensively reviewed in this thesis. The research work undertaken focuses on the geometrical optimisation of Tx/Rx coils to help maximise PTE in RIPT systems for operation over low- and mid-frequency bands (i.e. between few kHz to several MHz). Conventional methods for maximising PTE require defining various design parameters (i.e. figure-of-merits), which assist in finding the optimum Air-Cored Coil (ACC) geometry. However, traditional techniques for working with Figure-of-Merit (FoM) parameters are very time-consuming and process-demanding. In this thesis, the number of required FoMs have been reduced to one and incorporated into a process that will accelerate production of the optimum geometry design. A unique FoM parameter (i.e. Pscf) is developed by consolidating the PTE's impacting factors. Considering the RIPT application and its physical size constraints, a proper selection method for identifying the numerical value of Pscf is investigated. A novel iterative algorithm has been developed to assist in selection of the most favourable Pscf value, which provides the optimum ACC geometry. Theoretical design examples of two RIPT systems - operating at 10 kHz (low-frequency band) and 300 kHz (mid-frequency band) - are used to investigate the functionality of the ACC design approach, for which successful results are achieved. The novel iterative algorithm is also experimentally validated by developing four prototyped Tx/Rx ACC pairs, with real-world applications, which operate over low- and mid-frequency bands: 1:06 MHz, 100 kHz, 50 kHz, 15 kHz. For the designed ACC geometries, maximum PTEs of 85:63% at 1:06 MHz, 83:10% at 100 kHz, 72:85% at 50 kHz and 34:57% at 15 kHz are practically measured in bench top tests. The measured PTE values are in close correlation (within 14%) with the calculated PTEs at these frequency ranges, and thus validate the novel ACC design procedure. The RIPT system's maximum achievable PTE can be further increased by adding ferrite cores to the Tx/Rx ACC pair. In this thesis, an advanced iterative algorithm is also presented to support the design of geometrically optimised coil pairs employing ferrite cores. The advanced iterative algorithm is an extension of the initial work on optimising ACC geometries. Optimum Ferrite-Cored Coil (FCC) geometries, produced using the advanced iterative algorithm, for RIPT systems operating at 10 kHz and 300 kHz have been investigated. In comparing the FCC and ACC geometries designed for these frequencies, it is demonstrated that RIPT systems with ferrite cores reduce the ACC's geometrical size and additionally improve PTE. To validate the performance of the advanced FCC design algorithm over low- and mid-frequency bands, two RIPT systems are physically constructed for operation at 15 kHz (low-frequency) and 50 kHz (mid-frequency). For the prototyped RIPT systems, maximum PTEs of 45:16% at 50 kHz and 50:74% at 15 kHz are practically measured. The calculated and physically measured PTE values are within 2% difference; hence validating the advanced FCC design process