In this paper, an inductively coupled multiphase resonant converter is presented for wireless electric vehicle charging applications As an alternative to the traditional frequency and phase shift control methods, a hybrid phase-frequency control strategy is implemented to improve the system efficiency A theoretical analysis of the proposed system is carried out considering a wide battery state-of-charging range In order to confirm the proposed converter and control technique, a laboratory prototype wireless charger is designed using 8-in air-gap coreless transformer and rectifier The proposed control is compared with the conventional control methods for various load conditions at the different power levels In comparison results, the proposed hybrid control methodology demonstrates the efficiency improvements of 11% at the heaviest load condition and 57% at the lightest load condition

Analysis and Control of Multiphase Inductively Coupled Resonant Converter for Wireless Electric Vehicle Charger Applications

A 25 kW wireless charger design for electric vehicles is presented in this paper. The wireless charger consist of three phase power factor corrector (PFC), three phase resonant inverter, primary and secondary coils with series resonant compensation, and a rectifier. In the proposed design, PFC provides a constant voltage DC Bus and the whole output regulation is done by the resonant inverter. It simplifies the rectifier structure to the simple full-bridge topology. The design is verified with experiments at the output power from 0 W to 25 kW. The measured system efficiency was up to 91%.

A 25 kW industrial prototype wireless electric vehicle charger

In this study, the analysis of a three-coil wireless power transfer (WPT) system, which can be divided into source, communication and load circuits, is discussed in details. Among the three-coil WPT systems features, it is demonstrated, for instance, that maximum efficiency ( η MAX ) and maximum power transferred to the load (P 3MAX) do not depend on the load resistance, neither on the mutual inductance between communication and load coils. In fact, it is shown that η MAX and P 3MAX depend only on source and communication circuits parameters. Practical results are also presented, showing good agreement with the developed theory and validating the proposed analysis.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2016.0492

Analysis and optimisation of three-coil wireless power transfer systems

With resonant wireless power transfer systems in operation, objects and/or humans having divers material properties come into the vicinity of the resonant coils. To model such systems efficiently, a novel full-wave multisolver is developed where the tangentially continuous vector finite element (FE) method is coupled with a method of moments (MoM) technique. The MoM technique is based on an electric field integral equation specifically designed to model the singular behavior of the thin coil wires, while the FE method is used to model the scattered field due to material inhomogeneities. A simplified sequential solver similar to the scattered field formulation is derived from the linear system of the multisolver in order to be applied as an efficient preconditioner, thereby speeding up the solution time significantly. The impedance change due to the material inhomogeneities can be calculated directly by applying the reaction concept. This ensures that the accuracy of the impedance change does not depend on the relative magnitude of the impedance change compared with the total impedance. The performance of the multisolver is illustrated by solving a test problem with a helical coil and a dielectric sphere with moderate conductivity, and comparing the multisolver results with the full FE solutions.

Finite-Element-Integral Equation Full-Wave Multisolver for Efficient Modeling of Resonant Wireless Power Transfer

In this study, we analyzed the internal electric field E and specific absorption rate (SAR) of human biological tissues surrounding an air-core coil transcutaneous energy transmission transformer. Using an electromagnetic simulator, we created a model of human biological tissues consisting of a dry skin, wet skin, fat, muscle, and cortical bone. A primary coil was placed on the surface of the skin, and a secondary coil was located subcutaneously inside the body. The E and SAR values for the model representing a 34-year-old male subject were analyzed using electrical frequencies of 0.3–1.5 MHz. The transmitting power was 15 W, and the load resistance was 38.4 Ω. The results showed that the E values were below the International Commission on Non-ionizing Radiation Protection (ICNIRP) limit for the general public exposure between the frequencies of 0.9 and 1.5 MHz, and SAR values were well below the limit prescribed by the ICNIRP for the general public exposure between the frequencies of 0.3 and 1.2 MHz.

Analysis of specific absorption rate and internal electric field in human biological tissues surrounding an air-core coil-type transcutaneous energy transmission transformer

Transcutaneous Energy Transmitters (TETs) transfer wireless energy through an inductive link established between two pancake coils placed, respectively, outside and inside the body of a patient. The simulation of the misalignment between the coils must be performed in 3-D, e.g., with a Finite Element (FE) method. This paper introduces a homogenization method to minimize the cost of the expensive 3-D FE computation in the frequency domain. Its originality lies in the non-homogeneous TET geometry during the meshing process. The results of this technique are compared with those obtained by considering regular stranded TET coils. They showed improvements mainly at kilohertz frequencies, the typical TET operating frequency range.

https://hal.archives-ouvertes.fr/hal-00807074/document

Homogenization Methods in Simulations of Transcutaneous Energy Transmitters

Coreless transformers are used in several applications, operating in a large range of frequencies. Their equivalent circuit model is very important to allow the proper design of any electronic circuit or load that may be electrically coupled to them. Especially, in cases where the coils of these devices are modeled with a relatively large wire gauge (when compared with the skin depth), the losses due to eddy currents must be included, otherwise their circuit simulation will be incorrect. This paper proposes a method that allows modeling the lumped parameters of coreless transformers, including the eddy currents. The method uses an optimization algorithm search through a genetic algorithm solver. Although the scope of this paper lies within coreless transformers, the whole method was designed in a generic way to model different types of electric equipment.

Modeling Coreless Transformers With a Relatively Large Wire Gauge Using an Optimization Method

The use of artificial organs completely implanted in the patient's body requires a transcutaneous energy transmitter (TET) design that provides more comfort and reliability to the patient, i.e., a TET as small as possible with the least increase of temperature and that meets several project requirements. The multiobjective genetic algorithm optimization method is used here to minimize volume and dissipated power per coil area of round spiral TETs. It ensures the transmission of 13 W of power and load voltage within limits defined by electronic circuits at coil gaps of up to 25 mm. A variable resistance that absorbs a defined active power is used instead of a fixed resistor load to best represent the artificial organ with regulator. Modeling issues, such as the influence of the misalignment between the coils on the coupling of the TET, are also discussed.

https://hal.archives-ouvertes.fr/hal-00807076/document

A Design Proposal for Optimal Transcutaneous Energy Transmitters

This work studies a Transcutaneous Energy Transmitter (TET) which uses electromagnetic fields to transfer power from outside the body to an artificial organ in the body, working like a high frequency transformer with the skin being part of the magnetic coupling between the primary (external coil) and secondary (internal coil). For this reason, this project made two different kinds of analyses of the efficiency and the induced current density in a biologic tissue: first, simulations were performed using core types of distinct geometries, each with multiples sizes, ranking which type is more recommended; second, the sensitivity of the chosen core type to misalignments was evaluated for different dimensions. In addition, the sensitivity to the core permeability was also investigated for both analyses.

/pdf/a-systematic-sensitivity-analysis-of-the-performance-of-a-5dak2fqfj2.pdf

A systematic sensitivity analysis of the performance of a transcutaneous energy transmitter for design purposes

/pdf/topics-in-design-and-analysis-of-transcutaneous-energy-2rc3qk1ysa.pdf

Daniela Wolter Ferreira

Papers

Homogenization Methods in Simulations of Transcutaneous Energy Transmitters

Modeling Coreless Transformers With a Relatively Large Wire Gauge Using an Optimization Method

A Design Proposal for Optimal Transcutaneous Energy Transmitters

A systematic sensitivity analysis of the performance of a transcutaneous energy transmitter for design purposes

Topics in design and analysis of transcutaneous energy transfer to ventricular assist devices.