Madhu Chinthavali

Primary-Side Power Flow Control of Wireless Power Transfer for Electric Vehicle Charging

Various noncontacting methods of plug-in electric vehicle charging are either under development or now deployed as aftermarket options in the light-duty automotive market. Wireless power transfer (WPT) is now the accepted term for wireless charging and is used synonymously for inductive power transfer and magnetic resonance coupling. WPT technology is in its infancy; standardization is lacking, especially on interoperability, center frequency selection, magnetic fringe field suppression, and the methods employed for power flow regulation. This paper proposes a new analysis concept for power flow in WPT in which the primary provides frequency selection and the tuned secondary, with its resemblance to a power transmission network having a reactive power voltage control, is analyzed as a transmission network. Analysis is supported with experimental data taken from Oak Ridge National Laboratorys WPT apparatus. This paper also provides an experimental evidence for frequency selection, fringe field assessment, and the need for low-latency communications in the feedback path.

A 55-kW Three-Phase Inverter With Si IGBTs and SiC Schottky Diodes

Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Currently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si insulated-gate bipolar transistor-SiC Schottky diode hybrid 55-kW inverter by replacing the Si p-n diodes in Semikrons automotive inverter with Crees made-to-order higher current SiC Schottky diodes. This paper presents the developed models of these diodes for circuit simulators, shows inverter test results, and compares the results with those of a similar all-Si inverter.

Investigation on the parallel operation of discrete SiC BJTs and JFETs

This paper presents an analysis of single discrete silicon carbide (SiC) JFET and BJT devices and their parallel operation. The static and dynamic characteristics of the devices were obtained over a wide range of temperature to study the scaling of device parameters. The static parameters like on-resistance, threshold voltage, current gains, transconductance, and leakage currents were extracted to show how these parameters would scale as the devices are paralleled. A detailed analysis of the dynamic current sharing between the paralleled devices during the switching transients and energy losses at different voltages and currents is also presented. The effect of the gate driver on the device transient behavior of the paralleled devices was studied, and it was shown that faster switching speeds of the devices could cause mismatches in current shared during transients.

A 55 kW three-phase inverter with Si IGBTs and SiC Schottky diodes

Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Presently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si IGBT-SiC Schottky diode hybrid 55kW inverter by replacing the Si pn diodes in Semikrons automotive inverter with Crees made-to-order higher current SiC Schottky diodes. This paper presents the developed models of these diodes for circuit simulators, shows inverter test results, and compares the results to those of a similar all-Si inverter.

Temperature dependent Pspice model of silicon carbide power MOSFET

This paper provides a behavioral model in Pspice for a silicon carbide (SiC) power MOSFET rated at 1200 V / 30 A for a wide temperature range. The Pspice model was built using device parameters extracted through experiment. The static and dynamic behavior of the SiC power MOSFET is simulated and compared to the measured data to show the accuracy of the Pspice model. The temperature dependent behavior was simulated and analyzed. Also, the effect of the parasitics of the circuit on switching behavior was simulated and discussed.

18 kW three phase inverter system using hermetically sealed SiC phase-leg power modules

Power electronics play an important role in electricity utilization from generation to end customers. Thus, high-efficiency power electronics help to save energy and conserve energy resources. Research on silicon carbide (SiC) power electronics has shown their better efficiency compared to Si power electronics due to the significant reduction in both conduction and switching losses. Combined with their high-temperature capability, SiC power electronics are more reliable and compact. This paper focuses on the development of such a high efficiency, high temperature inverter based on SiC JFET and diode modules. It involves the work on high temperature packaging (>200 °C), inverter design and prototype development, device characterization, and inverter testing. A SiC inverter prototype with a power rating of 18 kW is developed and demonstrated. When tested at moderate load levels compared to the inverter rating, an efficiency of 98.2% is achieved by the initial prototype without optimization, which is higher than most Si inverters.

Comparison of Si and SiC inverters for IPM traction drive

In this paper a comparison of performance of an hybrid electric vehicle with an all-silicon (Si), hybrid (Si and SiC), and an all-Silicon Carbide (SiC) inverters simulated for the standard US06 driving cycle is presented. The system model includes a motor/generator model, a boost converter model, and an inverter loss model developed using actual measured data. The drive train simulation results will provide an insight to the impact of SiC devices on overall system efficiency gains compared to Si devices over the drive cycle at different operating conditions.

A 55 kW three-phase automotive traction inverter with SiC Schottky diodes

Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Presently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si IGBT-SiC Schottky diode hybrid 55 kW inverter by replacing the Si pn diodes in Semikrons automotive inverter with Crees made-to-order higher current SiC Schottky diodes. This paper shows the results obtained from testing this inverter and compares it to a similar all-Si inverter.

High-temperature and high-frequency performance evaluation of 4H-SiC unipolar power devices

Silicon carbide (SiC) unipolar devices have much higher breakdown voltages because of the ten times greater electric field strength of SiC compared with silicon (Si). 4H-SiC unipolar devices have higher switching speeds due to the higher bulk mobility of 4H-SiC compared to other polytypes. Four commercially available SiC Schottky diodes at different voltage and current ratings, an experimental VJFET, and MOSFET samples have been tested to characterize their performance at different temperatures. Their forward characteristics and switching characteristics in a temperature range of -50degC to 175degC are presented. The results of the SiC Schottky diodes are compared with those of a Si pn diode with comparable ratings

Characterization and modeling of silicon carbide power devices and paralleling operation

This paper presents recent research on several silicon carbide (SiC) power devices. The devices have been tested for both static and dynamic characteristics, which show the advantages over their Si counterparts. The temperature dependency of these characteristics has also been presented in this paper. Then, simulation work of paralleling operation of SiC power MOSFETs based on a verified device model in Pspice is presented to show the impact of parasitics in the circuit on the switching performance.