Showing papers by "Burak Ozpineci published in 2006"

A cascade multilevel inverter using a single DC source

Abstract: A method is presented showing that a cascade multilevel inverter can be implemented using only a single DC power source and capacitors. A standard cascade multilevel inverter requires n DC sources for 2n + 1 levels. Without requiring transformers, the scheme proposed here allows the use of a single DC power source (e.g., a battery or a fuel cell stack) with the remaining n-1 DC sources being capacitors. It is shown that one can simultaneously maintain the DC voltage level of the capacitors and choose a fundamental frequency switching pattern to produce a nearly sinusoidal output.

Hybrid Cascaded H-bridges Multilevel Motor Drive Control for Electric Vehicles

Abstract: This paper presents a hybrid cascaded H-bridge multilevel motor drive control scheme for electric/hybrid electric vehicles where each phase of a three-phase cascaded multilevel converter can be implemented using only a single DC source and capacitors for the other DC sources. Traditionally, each phase of a three-phase cascaded multilevel converter requires n DC sources for 2n + 1 output voltage levels. In this paper, a scheme is proposed that allows the use of a single DC source as the first DC source with the remaining n − 1 DC sources being capacitors. It is shown that a simple 7-level equal step output voltage switching control can simultaneously maintain the balance of DC voltage levels of the capacitors, eliminate specified low order non-triplen harmonics, and produce a nearly sinusoidal three-phase output voltage. This scheme therefore provides the capability to produce higher voltages at higher speeds (where they are needed) with a low switching frequency method for motor drive application, which has inherent low switching losses and high conversion efficiency. This control scheme especially fits fuel cell electric vehicle motor drive applications and hybrid electric vehicle motor drive applications.

A 55 kW Three-Phase Inverter with Si IGBTs and

Abstract: 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 Semikron's automotive inverter with Cree's 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. I. INTRODUCTION There is a growing demand for more efficient, higher power density, and higher temperature operation of the power converters in transportation applications. In spite of the advanced technology, silicon (Si) power devices cannot meet some transportation requirements. Silicon carbide (SiC) has been identified as a material with the potential to replace Si devices in the near term because of its superior material advantages such as wider bandgap, higher thermal conductivity, and higher critical breakdown field strength. SiC devices are capable of operating at high voltages, high frequencies, and at higher junction temperatures. Significant reduction in weight and size of SiC power converters with an increase in the efficiency is projected (1-5). SiC unipolar devices such as Schottky diodes, VJFETs, MOSFETs, etc. have much higher breakdown voltages compared to their Si counterparts which makes them suitable for use in traction drives replacing Si pn diodes and IGBTs (6-14). Presently, SiC Schottky diodes are the most mature and the only commercially marketed SiC devices available. These diodes are commercially available up to 1200V/20A or 600V/20A.

System Modeling and Characterization of SiC Schottky Power Diodes

Abstract: Most of the present models of silicon carbide (SiC) Schottky diodes are not suitable for evaluating their performance from a system level. The models presented in this paper are specialized for system-level simulations. They are based on basic semiconductor theories and synthesis of some models in the literature. Theoretical and experimental characterization of SiC Schottky power diodes is also involved. The models describe both static and dynamic behaviors of SiC Schottky power diodes. Thermal effects are considered as well for a better evaluation of power losses evaluation and cooling system design. The models were also used to estimate the efficiencies of Si IGBT/SiC Schottky diode hybrid inverter. To validate the simulation, a Si IGBT/SiC Schottky diode hybrid inverter and a Si IGBT inverter were built and tested

A SiC-Based Converter as a Utility Interface for a Battery System

Abstract: The purpose of this work is to provide validated models to estimate the performance of a SiC-based converter as a utility interface in battery systems. System design and modeling are described in detail. Simulations are done for both a SiC JFET converter and its Si counterpart based on the quality of tested devices. The simulation results indicate that in both charging and discharging modes, the SiC converter has a better performance compared to the Si one. (1) With the same heatsink size and ambient temperature, great advantages in efficiency and junction temperatures were found in the SiC-based converter. (2) With the same thermal limit, large savings in system weight and volume combined with a high efficiency were found in the SiC-based converter.

Enhancing power electronic devices with wide bandgap semiconductors

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

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

Abstract: 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 Semikron's automotive inverter with Cree's 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.

Design, modeling, testing, and spice parameter extraction of dimos transistor in 4h-silicon carbide

Abstract: In this paper, an analytical model for a vertical double implanted metal-oxide semiconductor (DIMOS) transistor structure in 4H-Silicon Carbide (SiC) is presented. Simulation for transport characteristics of the SiC MOSFET with the exact device geometry is carried out using the commercial device simulator MEDICI. A rigorous experimental testing and characterization is done on a 4H-SiC DIMOS transistor test device. SPICE parameters are extracted from the measurements, and a SPICE model for the DIMOS transistor has been developed. The presented work is a part of team efforts of material, device, and power electronics researchers at the University of Tennessee and Oak Ridge National Laboratory.