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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 901 records · Page 50
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DOE OSTI2022

Thermal Design and Optimization of High- Power Wireless Charging System

In this paper, the thermal design and optimization of a high-power wireless charging system (WCS) is proposed. An integrated electromagnetic and thermal co-optimization is essential to design a high power-density WCS pad. This study presents the thermal analysis and the potential optimization scopes for a polyphase WCS pad. The coil and core causes most of the power losses of a WCS pad and causes thermal hotspot in the pad. In this paper, the thermally conductive epoxy is introduced to balance the effective volumetric loss density in the pad and mitigate the thermal hotspots in the coil and core. The proposed design is simulated through finite element analysis (FEA) and tested experimentally for a 50 kW three-phase WCS. Simulation and experimental results show that the conventional design has localized hotspots in the coil and core. The proposed thermal design mitigates the thermal hotspots without increasing the coil or core volume.

Mohammad, Mostak↗
DOE OSTI2022

Modeling and Analysis of a Polyphase Wireless Power Transfer System for EV Charging Applications

Extreme fast charging is an emerging technology targeting to significantly decrease charging times of electric vehicles to 10–20 minutes, similar to an interstate gas refueling practice. High-power wireless power transfer (WPT) systems with polyphase electromagnetic couplers can be an attractive solution for these applications due to the very high surface power density of polyphase coils with reduced ripple current characteristics on both the primary and secondary sides that result in more compact designs with reduced dc bus bar capacitor requirements. In addition, WPT systems offer automated charging process, which can be an enabling technology for connected and automated vehicles, with high-efficiency, convenience, safety, and flexibility. This study presents a matrix representation of a mathematical model for a three-phase WPT system with series-series connected three-phase resonant compensation networks. Nonzero interphase mutual inductances between the same side phase windings are considered for tuning to obtain a circuit model for parametric sensitivity. Simulation and experimental results presented for a 50-kW experimental prototype to demonstrate the operation of the polyphase WPT system.

Zeng, Rong↗
DOE OSTI2022

A 50-kW Bidirectional Step-up / Step-down DC/DC Oak Ridge Converter for Wireless Charger Applications

This study presents a novel bidirectional concept by using Oak Ridge Converter (ORC) for wireless energy conversion (WEC) technologies such as wireless electric vehicle (EV) chargers, wireless mobile or energy storage systems (MESS / ESS), etc. The presented system can be deployed in a bidirectional wireless power transfer (WPT) structure for different input voltages by using two different operating frequencies. The proposed concept here achieves zero voltage switching (ZVS) in during step-up and step-down configurations. The system overall theoretical design and experimental test results are presented for 50 kW power transfer in both bidirectional operations modes. The laboratory demonstration of the system is presented for the three-phase bidirectional system with 6 inches of airgap between the coils and output of 560 VDC with 95.4% dc-to-dc efficiency.

Asa, Erdem↗
DOE OSTI2022

Design and Analysis of a 200 kW Dynamic Wireless Charging System for Electric Vehicles

Dynamic wireless charging of electric vehicles can significantly alleviate or eliminate range anxiety while reducing the required on-board battery capacity. To achieve an electric vehicle charging balance with minimal infrastructure costs, power transfer levels around 200 kW are required. In this paper, a system architecture with a modularized power electronics and optimized power transfer couplers was adopted to enable efficient power transfer. A DC/DC converter was used for secondary-side charging control of the battery. The system performance was validated in an experimental setup at 120 kW with 91.31% efficiency from the DC input on the primary side to the vehicle battery.

Xue, Lincoln↗
DOE OSTI2022

A 20-kW DC Oak Ridge Converter with Integrated AC & DC Sources for Grid Services and Energy Storage Systems

This paper proposes a wireless power transfer (WPT) platform with integrated energy conversion that has the capability for 1) recharging the energy storage systems (ESSs) from the grid systems, including renewable energy sources such as wind, solar, etc., 2) off grid systems recharging the ESSs from dc grid systems, 3) grid recharging of electric vehicles (EVs), and 4) off grid recharging of EVs from ESSs. The unique aspect of the method is the use of multi-interface power electronic converter for the grid and ESSs and EVs that can support a range of applications with ac / dc and dc / dc energy conversion ability in a single converter system. The key enabling technology to achieve these functionalities is Oak Ridge Converter (ORC) with polyphase coupler coil system both developed at ORNL. This new technology enables higher power density WPT systems while allowing the coils to interface from ac grid at 60 Hz frequency or dc source directly merging with 85 kHz operating frequency of switching component. The experimental results of the proposed system are presented for 20 kW output power with the system overall efficiency around 95.4% from dc source and 93% overall efficiency from ac grid achieving 9-10% current total harmonic distortion (THD) and 0.98-0.99 power factor (PF).

Asa, Erdem↗
DOE OSTI2025

Capacitor Design for Self-Resonant Coils for Long-Distance Wireless Power Transfer System

In this paper, an integrated capacitor design is proposed for higher-order resonant tank topologies for self-resonant coils, such as series, parallel, LCC, LLC, etc. The capacitor is one of the large, lossy, and thermally vulnerable components of a high-frequency resonant tank, and designing a high-voltage, thermally stable resonant capacitor can be highly challenging. Designing the extremely high-voltage capacitor as an integral part of the coil reduces the size and complexity of the coil assembly. This paper proposes a low-loss PCB-based high-voltage capacitor design to achieve that target, which can be implemented as an integral part of the coil. The proposed capacitor designs are simulated using Multiphysics FEA and tested experimentally. A 23 kV, 133 pF capacitor prototype was built and tested as part of a 1 kW long-distance wireless charging system. The test results verify the capacitor’s voltage, current, and thermal resiliency performance.

Mohammad, Mostak [ORNL] (ORCID:0000000256388783)↗
DOE OSTI2019

Modeling of Multi-Loops Related Device Turn-On Overvoltage in 3L-ANPC Converters

An analytical model for the device drain-source turn-on overvoltage in three-level active neutral point clamped (3L-ANPC) converters is established in this paper. Considering the two commutation loops in the converter, the relationship between the turn-on overvoltage and the loop inductances is evaluated. The line switching frequency device usually exhibits higher overvoltage, while the high switching frequency device is not strongly influenced by the multiple loops. A 500 kVA 3L-ANPC converter using SiC MOSFETs is tested, and the model is verified with the experimental results.

Gui, Handong↗
DOE OSTI2018

Coil Power Density Optimization and Trade-off Study for a 100kW Electric Vehicle IPT Wireless Charging System

This paper presents a trade–off study examining the impacts of modifying resonant frequency and coil current density on coil power density for a 100kW electric vehicle charging system. We find that power density can be increased significantly by moving to higher operating frequency and current density with marginal impact to overall coil–to–coil transfer efficiency. A detailed prototype model of a 150 kVA rated coil set is presented along with loss estimates from magnetic field simulations and initial test results up to 50kW.

Pries, Jason↗
DOE OSTI2018

Design and Implementation of an optimized 100 kW stationary wireless charging system for EV battery recharging

This paper presents the design, analyses and implementation of an optimized single stage high power wireless charging system capable of transferring 100 kW at an operating frequency of 22 kHz and a coil-to-coil distance of 5 inches.The detailed design and implementation of the power electronics including the high frequency inverter and rectifier and wireless power transfer coils along with the resonant stage are described. FEA simulation results of the coils and the resonant network analysis are validated by using a Venable frequency response analyzer. Experimental results corresponding to 50 kW operation are presented to validate the design process.

Galigekere, Veda Prakash↗
DOE OSTI2018

Comparison of Si, SiC, and GaN based Isolation Converters for Onboard Charger Applications

This paper presents a comparison of isolation converters based on Si, SiC, or GaN switching devices for level-2 integrated onboard chargers. The isolation converters all employ a dual active bridge for bidirectional power flow for the charger and a buck converter tapped off the same transformer for powering the 14V vehicle loads. Design trade-offs and operating constraints are discussed and performance metrics in terms of efficiency and power density and experimental results are included.

Su, Gui-Jia↗
DOE OSTI2019

Harmonic Analysis of Common-mode Reduction Modulation for Three-level Inverter

This paper presents harmonic analysis of common-mode reduction (CMR) modulation for three-level voltage source inverters. The analytical model to calculate the harmonics of CMR modulation with arbitrary PWM sequence is developed. The impact of alternative PWM sequences of CMR modulation on harmonics is investigated. New three-state and four-state PWM sequences of CMR are proposed which spread the energy centered in the carrier frequency in the conventional CMR, and thus reduce the voltage peaks in frequency domain. Experiments are conducted on a three-level neutral point clamped inverter. Experiment results verify the developed analytical model and harmonic analysis.

Chen, Ruirui↗
DOE OSTI2019

Variable Duty Control of Three-Phase Voltage Source Inverter for Wireless Power Transfer Systems

This paper presents duty control and analysis of the three-phase voltage source inverter (VSI) to adjust the output power for three-phase wireless power transfer (WPT) applications. Analytical results show significant reductions in the inverter dc link ripple current with the three-phase system over single-phase WPT counterparts. Simulation and experimental results for an 18 kW three-phase series-series WPT system are included to validate the duty control and analysis. Experimental results also demonstrated the output voltage can be controlled over a wide range by adjusting the inverter duty.

Su, Gui-Jia↗
DOE OSTI2019

Design of Low Inductance Busbar for 500 kVA Three-Level ANPC Converter

The adoption of SiC devices in high power applications enables higher switching speed, which requires lower circuit parasitic inductance to reduce the voltage overshoot. This paper presents the design of a busbar for a 500 kVA three-level active neutral point clamped (ANPC) converter. The layout of the busbar is discussed in detail based on the analysis of the multiple commutation loops, magnetic canceling effect, and DC-link capacitor placement. The loop inductance of the busbar is verified with simulation, impedance measurements, and converter experiments. The results match with each other, and the inductances of small and large loop are 6.5 nH and 17.5 nH respectively, which is significantly lower than the busbars of NPC type converters in other references.

Gui, Handong↗
DOE OSTI2020

Control of Output Power in Primary Side LCC and Secondary Series Tuned Wireless Power Transfer System without Secondary Side Sensors

The output power of a wireless power transfer (WPT) system varies with load and coupling factor of the inductively coupled coils. This paper presents a method to control the output power of primary side LCC and secondary side series tuned WPT system using information of primary side variables. In this approach, a secondary side control system or secondary side sensors are not needed. Detailed mathematical derivations are given to identify and justify the suitable primary side variable that accomplishes the desired purpose without the need of any secondary side communications. Simulation results presented validate the proposed scheme.

Mukherjee, Subho↗
DOE OSTI2020

Shield Design for 50 kW Three-Phase Wireless Charging System

In this paper, magnetic field emissions (MFE) from a 50 kW bipolar coil-based three-phase wireless charging system (WCS) is investigated. Then, a shield design is proposed to suppress the MFE below the safety limit identified by the International Commission of Non-Ionized Radiation Protection (ICNIRP) guidelines. Bipolar coil-based three-phase (3φ) WCSs provide extremely high power-density; therefore, the 3φ WCSs are highly promising for high-power fast-wireless-charging of the electric vehicles. For the high-power EV application, it is a critical challenge to design a shield to suppress the MFE below the safety limit. The traditional aluminum shield is found ineffective for the bipolar 3φ-WCS. The proposed shield is designed with high-permeability magnetic material, i.e. ferrite, nanocrystalline material, etc. The proposed shield is simulated in finite element analysis (FEA) and the FEA results show that the proposed magnetic shield effectively suppresses the magnetic field emission below the ICNIRP limit. The generalized design of the proposed shield can be used for even higher power bipolar coil based WCSs.

Mohammad, Mostak↗
DOE OSTI2023

A High-Power Density Segmented Traction Drive Inverter

High power density is one of the requirements for traction drive inverters for meeting increasing demand for higher power and performance electrical vehicles (EV). This paper presents design and preliminary experimental results for a 100 kW high-power density inverter for EV traction drive applications. The inverter design was based on the segmented inverter topology that can significantly reduce the inverter DC filter capacitor and employs low-profile planar double-sided cooled SiC MOSFET-based power modules, compact mini-channel heat sinks with fin-profile optimized using genetic-algorithms, and high-ripple current capacitors. The design produced a compact inverter package with a total volume less than 1 litter, exceeding the power density goal of 100 kW/L. Experimental results are included to demonstrate the cooling and electrical performance.

Su, Gui-Jia↗