A brief review: basic coil designs for inductive power transfer

The inductive power transfer (IPT) has contributed to the fast growth of the electric vehicle (EV) market. The technology to recharge the EV battery has attracted the attention of many researchers and car manufacturers in developing green transportation. In IPT charging system, the coil design is indispensable in enhancing the EV battery charging process performance. This paper starts by describing the two charging techniques; static charging and dynamic charging before further presents the IPT system descriptions. Afterwards, this paper describes a brief review of coil designs which discusses the critical factors that affect the power transmission efficiency (PTE) including their basic designs, design concepts and features merits. The discussions on the basic coil designs for IPT are of the circular spiral coil (CSC), square coil (SC), rectangular coil (RC), and double-D coil (DDC). Furthermore, the significant advantages and limitations of each research on different geometries are analyzed and discussed in this paper. Finally, this paper evaluates some essential aspects that influence the coil geometry designs in practica

High performance battery chargers for full electric and hybrid cars

This Doctoral Thesis aims to study and develop advanced and high-efficient battery chargers for full electric and plug-in electric cars. The document is strictly industry-oriented and relies on automotive standards and regulations. In the first part a general overview about wireless power transfer battery chargers (WPTBCs) and a deep investigation about international standards are carried out. Then, due to the highly increasing attention given to WPTBCs by the automotive industry and considering the need of minimizing weight, size and number of components this work focuses on those architectures that realize a single stage for on-board power conversion avoiding the implementation of the DC/DC converter upstream the battery. Based on the results of the state-of-the-art, the following sections focus on two stages of the architecture: the resonant tank and the primary DC/AC inverter. To reach the maximum transfer efficiency while minimizing weight and size of the vehicle assembly a coordinated system level design procedure for resonant tank along with an innovative control algorithm for the DC/AC primary inverter is proposed. The presented solutions are generalized and adapted for the best trade-off topologies of compensation networks: Series-Series and Series-Parallel. To assess the effectiveness of the above-mentioned objectives, validation and testing are performed through a simulation environment, while experimental test benches are carried out by the collaboration of Delft University of Technology (TU Delft)

Control of wireless power transfer system for dynamic charging of electric vehicles

L'abstract è presente nell'allegato / the abstract is in the attachmen

Analysis and Design of Current-fed Wireless Inductive Power Transfer Systems

Wireless Inductive Power Transfer (IPT) technology promises a very convenient, reliable, and safe way of transferring power wirelessly. Recent research on IPT establishes its indispensable role and suitability in electric vehicle (EV) applications. Efficient design of both converters and IPT coils are essential to make this technology feasible for mass deployment. The existing research on IPT is mainly based on power converters derived from voltage-source inverter (VSI) topologies, where feasibility of current-source inverter (CSI) has received very limited attention. Considering certain limitations of voltage-fed converters, this research is focused on the concept study and feasibility analysis of current-fed power electronics for IPT systems, where the primary application is EV charging. CSI leads to parallel LC resonance in the primary side of IPT. The advantages of the parallel tank networks include lower inverter device current stress, very close to sinusoidal coil current, soft-switching of inverter devices, and natural short circuit protection during fault etc. Considering these merits, a new IPT topology is proposed in this thesis, where the inverter is full-bridge CSI and the compensations in primary and secondary sides are parallel and series types, respectively. Compared with the existing IPT topology with current-fed push-pull inverter, the proposed system does not have startup and frequency bifurcation issues. However, due to weak coupling between IPT coils, the primary side parallel capacitor experiences high voltage stress in higher power levels, and this voltage directly appears on inverter devices. To overcome this, a modified IPT topology fed from a CSI is proposed, where the primary compensation is parallel-series type and secondary compensation is series type. Detailed steady-state operation, converter design, soft-switching conditions, small-signal modelling, and closed-loop control are reported for both the topologies. To verify analytical predictions, numerical simulation is performed in PSIM 10 and experimental results obtained from a 1.6kW lab-built prototype are reported. Considering the requirement of bi-directional power flow capability to support energy injection from vehicle to grid (V2G) for future smart-grid applications, a new bidirectional IPT topology with current-fed converter is proposed. It has current-sharing feature in grid side converter and voltage doubling feature in vehicle side converter. This is the first attempt to implement bidirectional IPT with current-fed circuit and demonstrate grid to vehicle (G2V) and V2G operation. Keeping inverter output power factor lagging, ZVS turn-on of the inverter devices are always ensured irrespective of load variation. Detailed steady-state operation and converter design for both G2V and V2G modes are reported. Experimental results obtained from a 1.2kW lab-prototype are reported to verify the analysis and performances of bidirectional IPT circuit. The last part of this thesis addresses the possible improvements on reducing the number of power conversion stages to achieve higher system efficiency, compact size and reduced cost. This is usually done by using direct ac-ac converter as the primary side converter of IPT. Existing single stage IPT topologies are derived from VSI topology. From source side, these topologies have buck derived structure; therefore, none of them draw high quality current from source. In this thesis a new single stage IPT topology is proposed, which has boost derived structure and thereby capable of maintaining unity power factor at source. Dynamic load demand, source current waveshaping and effective wireless power transfer are achieved with two-loop control method. Experimental results obtained from a 1.2kW grid-connected lab-prototype are reported to justify the suitability of this single-stage IPT topology for practical use

Analysis and design considerations of resonator arrays for inductive power transfer systems

In the frame of inductive power transfer (IPT) systems, arrays of magnetically coupled resonators have received increasing attention as they are cheap and versatile due to their simple structure. They consist of magnetically coupled coils, which resonate with their self-capacitance or lumped capacitive networks. Of great industrial interest are planar resonator arrays used to power a receiver that can be placed at any position above the array. A thorough circuit analysis has been carried out, first starting from traditional two-coil IPT devices. Then, resonator arrays have been introduced, with particular attention to the case of arrays with a receiver. To evaluate the system performance, a circuit model based on original analytical formulas has been developed and experimentally validated. The results of the analysis also led to the definition of a new doubly-fed array configuration with a receiver that can be placed above it at any position. A suitable control strategy aimed at maximising the transmitted power and the efficiency has been also proposed. The study of the array currents has been carried out resorting to the theory of magneto-inductive waves, allowing useful insight to be highlighted. The analysis has been completed with a numerical and experimental study on the magnetic field distribution originating from the array. Furthermore, an application of the resonator array as a position sensor has been investigated. The position of the receiver is estimated through the measurement of the array input impedance, for which an original analytical expression has been also obtained. The application of this sensing technique in an automotive dynamic IPT system has been discussed. The thesis concludes with an evaluation of the possible applications of two-dimensional resonator arrays in IPT systems. These devices can be used to improve system efficiency and transmitted power, as well as for magnetic field shielding

Design optimization of contactless power transfer systems for electric vehicles using electromagnetic resonant coupling

Contactless power transfer (CPT) systems have been gaining considerable attention and have achieved tremendous technology advancements across a wide variety of utilizations in the past decade. CPT technologies offer promising advantages and open up new avenues for development of numerous real-world applications. Of particular importance is the implementation of CPT systems on the charging of electric vehicles (EV), which are considered as a sustainable alternative that will effectively address global fossil energy scarcity and climate change issues in the future. The overarching aim of this thesis is to investigate and improve the operation performance of CPT systems for contactless EV charging. Optimized high-performance CPT systems are expected to be the ultimate goal for EV wireless charging in the following century. In the CPT applications, some certain characteristic outputs and parameters such as overall system efficiency, RMS power transfer, air gap and resonant frequency are considered as key performance metrics to be addressed. These crucial metrics and properties have been emphasized throughout this thesis. The electromagnetic resonant coupling technique has been put forward and adopted for most designed prototypes in this thesis in order to optimize the overall performance of CPT systems. The research methodology development, model designs, implementations and results analysis of the thesis are undertaken from the perspective of both power electronics and electromagnetics towards achieving the main objectives of the research. With focuses on overall system efficiency, real transfer power to load, air gap, frequency, magnetic coupler design, shielding materials, inner shielding distance and misalignment characteristics, a range of studies have been conducted in the thesis based on the proposed methodology, enhanced simulation models and laboratory prototypes. A number of important contributions have been made by the thesis. The four most significant contributions are: Firstly, the originally developed methodology for the CPT research of the thesis – the research flowchart system based on the preliminary natural resonant frequency probe and anticipation method. This uniquely proposed method for this thesis has been used to effectively probe, track and narrow down the most appropriate resonant frequency range to be chosen for CPT systems to perform with, towards reaching an optimized status of electromagnetic resonant coupling in terms of CPT technology-based EV charging. Secondly, the magnetic coupler modular-based CPT designs for investigating overall system performance optimization. As a result, in the thesis, a novel small-sized CPT prototype that is based on a geometrically improved H-shaped magnetic coupler, with ferromagnetic cores, passive aluminium shielding, an SS compensation topology and electromagnetic resonant coupling, has been proposed as an optimal design solution. Thirdly, approximating a CPT system to operate in close proximity to its calculated natural resonant frequency point by tuning and controlling system operating frequency could effectively lead to an overall system performance optimization most of the time in practical applications using electromagnetic resonant coupling, whereas setting the system operating frequency exactly at its calculated natural resonant frequency to make the system maximally operate at an extreme state of magnetic resonance may only produce a partial optimization from perspective of the system parameters and outputs. Fourthly, reasonable trade-offs between performance metrics are required to be considered and evaluated in order to achieve a feasible overall CPT system optimization. Through the detailed analysis of the results, model outcome comparisons, explanations on findings, limitation discussions and holistic system evaluations, this thesis is devoted to report and provide a series of newly proposed solutions and innovatively designed CPT systems. These solutions are supported by empirical findings, conclusions and contributions, which may encourage further pursuits of system performance optimizations for high-power high-frequency CPT charging technologies applied for future EV, despite methodological limitations, experiment restrictions and external uncertainties