Casey T. Morris

More Electric Aircraft: Review, Challenges, and Opportunities for Commercial Transport Aircraft

Similar to the efforts to move toward electric vehicles, much research has focused on the idea of a more electric aircraft (MEA). The motivations for this research are similar to that for vehicles and include goals to reduce emissions and decrease fuel consumption. In traditional aircraft, multiple systems may use one type or a combination of types of energy, including electrical, hydraulic, mechanical, and pneumatic energy. However, all energy types have different drawbacks, including the sacrifice of total engine efficiency in the process of harvesting a particular energy, as with hydraulic and pneumatic systems. The goal for future aircraft is to replace most of the major systems currently utilizing nonelectric power, such as environmental controls and engine start, with new electrical systems to improve a variety of aircraft characteristics, such as efficiency, emissions, reliability, and maintenance costs. This paper provides an in-depth look into how the systems have-or will be-changed. Future aircraft capabilities such as electric taxi and gas-electric propulsion for aircraft are also included for discussion. Most recent commercial transport aircrafts are described as the current state-of-the-art electric aircraft system. Future goals, including those of NASA, are presented for future advances in MEA.

Reduction of Common Mode Voltage and Conducted EMI Through Three-Phase Inverter Topology

This letter presents a three-phase voltage source inverter (VSI) topology to reduce the common mode (CM) voltage and electromagnetic interference (EMI) of electric motor drives. Instead of using filters, active or passive, or specific pulse width modulated (PWM) techniques to reduce the CM voltage, the proposed topology has inherently less CM voltage generation. With the addition of two switches placed in series on the dc lines, this topology effectively reduces the CM voltage during zero switching states by “floating” the inverter from the dc source. This topology can be implemented with any PWM method and does not add any additional complexity to the standard control techniques. The operation and CM reduction capability of the topology is first demonstrated in simulation and then verified with experimental results. A comparison of both common mode voltage and EMI is made to a conventional three-phase VSI to demonstrate the effectiveness of the proposed topology.

Common-Mode Voltage Cancellation in PWM Motor Drives With Balanced Inverter Topology

This paper proposes a novel inverter topology for canceling the common mode voltage of motor drives, and thus reducing or eliminating the ground leakage current, bearing current, and common mode electromagnetic interference. The proposed topology splits one of the switches on each phase-leg of a conventional inverter into two half-voltage rated switches, and creates two complementary sets of balanced three phase output voltages, whose common mode voltages cancel each other in the driven motor, and is named as “balanced inverter”. The balanced inverter topology does not involve additional passive components, modification of the modulation strategy, or increase of the total device rating. Theoretical analysis, simulation, and testing results are presented to verify this concept.

Driving Toward Accessibility: A Review of Technological Improvements for Electric Machines, Power Electronics, and Batteries for Electric and Hybrid Vehicles

Electric and hybrid vehicles continue to demand a considerable share of the automotive market. This movement has been enabled by the recent technological improvements in the areas of electric motors, power electronics, and energy storage. While many electric vehicles (EVs) are on the market, they are not as cost competitive as conventional vehicles, and affordable cost is necessary for large-scale market penetration. For this to become a reality, continued research is needed to develop new cost-efficient technologies. This article presents the metrics and benchmarks used to gauge the performance of various electric drivetrains. In addition, current state-of-the-art technologies are presented in terms of these metrics as well as the future goals and trends in the industry. With ongoing development, the market for electric and hybrid vehicles will continue to increase.

Comparison Between Output CM Chokes for SiC Drive Operating at 20- and 200-kHz Switching Frequencies

The adoption of silicon carbide (SiC) MOSFETs in variable speed drives (VSDs) makes it possible to increase the inverter switching frequency up to several hundred kilohertz without incurring excessive inverter loss. As a result, the harmonic currents and related losses in the machine can be significantly reduced, and the dynamic performance of motor will also be improved. However, the high switching frequency will increase the common mode (CM) electromagnetic interference (EMI) emission of the drive system presenting new challenges on CM choke design. In the literature, chokes designed for VSDs operating above 100 kHz are rarely found. Hence, this paper presents a case study on the output CM chokes for a SiC-based VSD switching at 20 and 200 kHz. A comprehensive comparison is made between the chokes for two switching frequencies regarding design, sizing, and performance, through both calculation and experiments. The results show that the CM choke designed for 200 kHz switching frequency is significantly larger and heavier than the 20 kHz choke, due to the higher inductance value required to meet the EMI limit and the lower permeability of the core material. Meanwhile, the 200 kHz choke is also less effective in noise attenuation as a result of the larger winding capacitance compared with the 20 kHz choke.

Achieving high efficiency using SiC MOSFETs and reduced output filter for grid-connected V2G inverter

This paper describes a comprehensive analysis of a three-phase two-level silicon carbide (SiC) MOSFET V2G inverter including the LCL filter design. The efficiency is compared between the SiC MOSFET and Si IGBT. Using a SiC device enables the inverter to operate at high switching frequency and this leads to improved efficiency up to 99.05% at 10 kHz and 97.71% at 100 kHz switching frequency. The output LCL filter is also designed based on a specific switching frequency and the filter value is most significantly reduced at the highest switching frequency. The SiC inverter and LCL filter is simulated using LTSpice and MATLAB Simulink.

Determination of CM choke parameters for SiC MOSFET motor drive based on simple measurements and frequency domain modeling

The adoption of silicon carbide (SiC) MOSFETs in variable speed motor drives makes it possible to increase the inverter switching frequency up to several hundred kilohertz without incurring excessive inverter loss. As a result, the harmonic currents and related losses in the machine can be significantly reduced, and the dynamic performance of motor will also be improved. However, the increased switching frequency of SiC drives will increase the ground leakage current in the common mode (CM) path, presenting new challenges on CM choke design. This paper aims at understanding the CM choke design under this new circumstance. First, a simple and accurate frequency domain CM circuit modeling approach suitable for SiC motor drives is proposed and subsequently verified through experimental tests. Based on the model, required choke parameters are then determined through analytical calculation. Through comparative analysis, the impact of increased switching frequency on CM choke design is studied.

Benchmarking of electric and hybrid vehicle electric machines, power electronics, and batteries

Electric and hybrid vehicles continue to demand a share of the automotive market. This movement has been mainly enabled by recent technological improvements in the realm of electric motors, power electronics, and energy storage. While many electric vehicles are on the market, they are not as cost competitive as the conventional vehicles, and this is needed for large-scale market penetration. In order for this to become a reality, continued research is needed to develop new technologies. This paper presents the metrics and benchmarks used to gauge the performance of various systems. In addition, the current state-of-the-art technologies are presented in terms of these metrics as well as the future goals and trends in the industry. With continued development, the market for electric and hybrid vehicles will only continue to increase.

Minimizing switching losses in high switching frequency GaN-based synchronous buck converter with zero-voltage resonant-transition switching

GaN power switching devices are promising candidates for high switching frequency and high efficiency operations due to their lower on-resistance and faster switching capabilities compared to conventional silicon power devices. As the switching frequency increases up to the MHz-level, soft switching plays an important role to further minimize the switching losses and improve the efficiency. In this paper, a GaN-based synchronous buck converter operating with zero-voltage resonant-transition (ZVRT) switching in synchronous conduction mode is proposed. The ZVRT switching converter offers a favorable trade-off between switching and conduction losses especially in GaN-based DC-DC converters. The efficiency of the ZVRT switching converter providing 20 W output power from 28 V input voltage improves up to 7% at 3 MHz switching frequency.

A novel flux-switching permanent magnet motor-compressor with integrated airfoil-shaped rotor design

The purpose of this paper is to propose a novel flux-switching permanent magnet motor with an integrated airfoil-shaped rotor. Some of the conventional axial-flow compressor systems need an electric motor to provide mechanical energy input to the compressor. The proposed novel flux-switching motor-compressor can integrate both an electric motor and an axial-flow compressor into a single entity and perform axial-flow compression using the airfoil-shaped rotor. This integrated motor-compressor design eliminates the connection between the electric motor and compressor and makes the entire system more compact. Due to the high-speed nature of the integrated motor, no gearbox is needed in the proposed design so that reliability is improved. The principle of design for the proposed integrated motor-compressor is discussed. Analytical studies for the thermodynamics and electromagnetics are elaborated in this paper. A case study design is done to investigate the effect of rotor airfoil curvature to the torque production capability, and the results are demonstrated by finite element analysis.