Omer Caglar Onar

As artificial intelligence (AI) computing densities continue to increase, industry is pursuing megawatt-scale rack architectures that require tightly coordinated advances in electrical power delivery, thermal management, operations, and infrastructure integration. This document summarizes the primary technical challenges for achieving this target.

Wireless power transfer offers safe, convenient, and efficient way of charging electric vehicles. Ongoing research is targeting wireless charging pad design optimization; designing the magnetic component is the most important part of the coupler design because the magnetic part determines the coupling factor and efficiency. Optimizing the coil layout and geometry as well as ferrite design requires finite elements analysis based modeling and simulation for minimized core losses, maximized magnetic coupling, and minimized material use for cost-effectiveness. Although parametric finite element analysis or emerging artificial intelligence methods can generate very accurate results, simulation times are extremely long. To address this issue, this study proposes a simple, effective core design called A TOpographic Mapping (ATOM). The proposed design is based on the design of magnetic core by using the magnetic flux distribution. The thickness of the core increases with increasing magnetic flux density, forming a variable thickness core design with less material and minimized core losses compared to conventional designs. A superimposing method is used to create an optimal design for a rotational magnetic field-based system. According to simulation results, the ATOM design reduces the required material volume by 13.19% and yields the lowest core loss and highest mutual inductance compared to other designs. In addition, misalignment, electromagnetic interference, and thermal performance were evaluated for the proposed design.

On-road wireless charging of electric vehicles (EVs) in motion could potentially reduce range anxiety or battery size with widespread deployment. The planning and implementation of such systems are greatly complicated due to their susceptibility to load variation inherent to traffic flow. This article proposes a method for derisking the potential for traffic slowdowns by compensating for reduced vehicle speed and investigates how implementation may affect system performance. A load modeling case study is presented at 200 kW for a mile of high-speed roadway employing speed-based power regulation with results indicating average power usage, and maximum car hosting capability can be reduced by 20% and increased by 30%, respectively. An 85-kHz power electronics model is developed based on designs and prototypes for an 11-kW, 190-m airgap static system and a 200-kW dynamic wireless track. The simulation is validated in the 11-kW experimental prototype and modified for 200-kW operation to compare with simulated performance. Sensitivity studies are performed in MATLAB/Simulink to evaluate how parameters influence system performance and confirm the capability to reduce output power and maintain efficiency at 11 and 200 kW. The static 11-kW experimental system operates at 93.6% efficiency and multiple options exist to reduce power while maintaining efficiency greater than 90%. The capability to dynamically modify power output from wireless power transfer (WPT) coils, in an experimentally validated simulation, enables techniques to significantly mitigate load variability due to reductions in vehicle speed.

In spite of the high energy efficiency and environmental benefits of electric vehicles (EVs), adoption rates are increasing at a relatively slow pace, primarily because of EVs’ limited range and long charging durations. To reduce EV charging times to be comparable to refueling times of conventional vehicles, extreme fast charging (XFC) systems are required. Such charging systems would reduce drivers’ range anxiety and enable long-distance interstate travel with EVs. This substantial target in charging rates with 15–20 min of recharging times requires research and development from grid to batteries with advanced charging systems. Wireless power transfer (WPT) systems for EV charging applications are flexible, convenient, and highly efficient, and they allow automated charging. This article reviews the power electronics and winding and resonant tuning network configurations for polyphase WPT systems for high-power wireless charging applications.

This project proposes improving the technology level of the three-phase wireless charging technology developed at Oak Ridge National Laboratory (ORNL). Successful commercialization of wireless charging systems require that they meet strict safety standards for electromagnetic field emissions and interoperability with other wireless charging technology. ORNL has previously demonstrated a 50kW three-phase wireless power transfer system with 95% efficiency. This prototype system weighed less than 50% of similar high-power wireless charging system while simultaneously exhibiting better safety characteristics. Due to better material utilization, the reduction in mass is expected to translate into similar cost reduction for the magnetic coupler. Additionally, the smaller footprint of the system can ease vehicle integration difficulties that would be encountered using other technology. Furthermore, the three-phase design can be made to operate with existing single-phase coupler design more easily and without intentional physical misalignment which would otherwise pose safety issues. This project developed ORNL’s WPT technology to satisfy the specifications and requirements for electric vehicle (EV) charging. The result of the project will be a prototype and reference design for a high-power wireless charging system—including magnetics, power electronics, and controls—serving as a baseline for product development.

Electric vehicles (EVs) can provide power to the grid or buildings similar to distributed energy resources (DER) for energy balancing applications or optimizing the operation of the microgrids in harmony with the other DER assets. This paper presents the operating modes of a bidirectional wireless power transfer (WPT) system designed for a medium-duty package delivery vehicle. The WPT system designed for this study can transfer 20 kW of power across 11 inches of airgap using custom-designed double-D (DD) couplers with LCC-LCC tuning networks. The proposed system utilizes a 480 V 3-phase grid connection, a plug-in hybrid delivery truck with bidirectional WPT, and a stationary energy storage system (SESS) that can be connected to the primary-side dc link. Due to the differences in primary and secondary dc bus voltages; and considering the voltage of the SESS, asymmetric voltage gains were used in the system. Sensitivity analyses of this system with respect to these voltage levels are presented. Five different operating modes of the grid, SESS, and the EV battery are investigated with experimental results. Control algorithms are described for grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operating modes. A bidirectional WPT system is operated with a power factor of 0.99 on the grid side in every operating mode. The EV battery was charged with 20.3 kW with an overall efficiency of 93.02% in the G2V operating mode. In V2G operating mode, the WPT system provided 12.82 kW of power back to the grid with an overall efficiency of 89.08%.

High-power inductive wireless power transfer (WPT) systems for electric vehicles are designed to meet specifications, such as stray field, power level, efficiency, misalignment tolerance, and ground clearance. These metrics are all heavily influenced by the coil geometry. This article proposes a coil design method based on the Fourier analysis method (FAM), which is an analytical method for directly designing coil geometries to meet stray field and power level requirements through an optimization of Fourier basis function coefficients. In this work, two 120 kW WPT proof-of-concept demonstrators with low stray field and high efficiency are built from FAM optimization results to validate the models and show the impact of the FAM design process. Experimental validation of the Generation 2 demonstrator at 120 kW output power resulted in a measured dc/dc efficiency of 97.2% at alignment with a 125 mm airgap. At the 120 kW test point, the stray fields 80 cm away from the center of the airgap between the coil assemblies were 3.4 μ T(rms) on the X -axis and 3.5 μ T(rms) on the Y -axis, much lower than the 27 μ T(rms) ICNIRP limit.

A three-port resonant converter with a high-frequency isolation link for hybrid unmanned/autonomous aerial vehicle (UAV/AAV) applications is analyzed in this study. The rectified engine-generator set output supplies the first input ports while the other is connected to a battery energy storage system. Input ports consist of half-bridge high-frequency inverters, whereas output port utilizes a semi-bridgeless active rectifier. This rectifier is formed by replacing rectifier low-side diodes with active switching devices. A phase-shift duty-cycle control is implemented for switching signals to regulate the power share and flow between ports. The proposed control system implemented achieves zero voltage switching (ZVS), reduces switching losses, and minimum current flow optimization ensures regulation in a wide range of output power. Compared to the existing bidirectional pulse width modulation (PWM) converters, the proposed system decreases the number of power conversion stages and provides centralized control without needing communications between the ports. The proposed control technique operating in closed-loop control achieves the power flow between ports under various load conditions. Theoretical analysis demonstrates the proposed converter’s viability and laboratory experimental validations at 500 W full power.

The output power of an ocean wave energy (WE) system has an intermittent and stochastic characteristic. WE output power can be transferred to the grid without sudden fluctuations when combined with a hybrid energy storage system (HESS) consisting of a battery pack and an ultracapacitor (UC) module. The study presented in this paper identifies the lowest-cost HESS sizing for WE systems by using a genetic algorithm (GA) optimization method. In this study, the system cost was reduced with the HESS cost and sizing study for ocean WE converter systems, and the battery was used effectively for a longer cycle. GA optimization has been applied in the field of HESS in ocean WE systems and has brought innovation to the literature with its optimum cost and sizing study. An optimum design model is presented considering the maximum/minimum voltage and current limits and the energy storage units’ temperature and depth of discharge parameters. The series and parallel connection calculations and the required number of battery and UC cells are given in the sizing section. The GA optimization was performed in MATLAB, and the energy storage rate for the 625-kW system and the power and energy results of the energy storage units were given as a result of the optimum cost analysis.