K. Lakshmi Varaha Iyer

Investigation of Permanent-Magnet Motor Drives Incorporating Damper Bars for Electrified Vehicles

Understanding the need for steady-state and transient performance improvement in an interior permanent-magnet synchronous machine (IPMSM) drive, this paper exclusively investigates the IPMSM incorporating damper bars in the rotor of electric motor for electrified vehicles (EVs). First, motivation for the employment of damper bars in IPMSM is provided and justified with a case study. Thereafter, a mathematical model of an IPMSM drive with damper bars in the rotor has been developed based on dq-axis theory and validated through experiments performed on a laboratory IPMSM containing damper bars. The validated mathematical model has been then employed to arrive at satisfactory rotor bar parameters for an existing IPMSM on board a commercially available EV. Moreover, a replica of the existing onboard EV motor with and without incorporating dampers have been designed, and finite-element analysis has been performed to investigate various performance characteristics. Comparative performance analyzes of both the machines with and without damper bars under steady-state and transient conditions have been performed wherever necessary, and the results elicited have been discussed.

Development of a Novel Magnetic Circuit Model for Design of Premium Efficiency Three-Phase Line Start Permanent Magnet Machines With Improved Starting Performance

This paper presents challenges in an ongoing project related to the design of a premium efficiency three-phase line start permanent magnet synchronous motor (LSPMSM) and proposes an exclusive solution through development of a novel magnetic circuit model. Since the LSPMSM is rapidly replacing the conventional induction motors in industrial applications such as pumps, fans and conveyors which require the machine to operate under both frequent start-stop and steady-state conditions for a wide range of time, a trade-off has to be reached between their starting performance and efficiency post-synchronization. Until now this has only been possible with time consuming FEA based design methodology. Hence, understanding the need and scanty availability of literature on simplistic and yet precise magnetic circuit based design of three-phase LSPMSM, this manuscript proposes exclusively a novel magnetic circuit model to design LSPMSM with improved starting performance. Firstly, the aforementioned design issues have been illustrated using different machine configurations developed. Further, a detailed procedure to deal with the design issues with the help of the developed magnetic circuit model is discussed and validated by developing a machine where the trade-off has been reached.

Analysis of stator winding inter-turn short-circuit fault in interior and surface mounted permanent magnet traction machines

Recently, permanent magnet synchronous machines (PMSMs) are widely used in electrified vehicle applications due to their high efficiency and high torque density characteristics. Hence, in an approach towards fault prognosis through online monitoring, it is of paramount importance to analyze inter-turn short-circuit fault whose occurrence is expected as the insulation wears out due to the frequent start-stop duty of both surface-mounted permanent magnet (SPM) and interior permanent magnet (IPM) traction machines. This paper puts an effort to analyze the performance of SPM and IPM machines under the effect of inter-turn short-circuit fault. This research work serves as an initial step towards development of an adaptive fault tolerant control scheme with less computational and hardware complexity for both the aforementioned machine drives.

Investigation of Integrated Charging and Discharging Incorporating Interior Permanent Magnet Machine With Damper Bars for Electric Vehicles

Integrated charging technology in electric vehicles is expected to reduce the overall cost as well as the weight of the vehicle, while leading to fast charging capability in the vehicle. Understanding the above, this paper puts an effort to exclusively investigate interior permanent magnet synchronous machine (IPMSM) drive incorporating damper bars in rotor for integrated charging application in electric vehicles. First, motivation for the employment of IPMSM with damper bars for integrated charging is provided and justified. Thereafter, a novel parameter determination method based on dq-axis theory to determine the parameters of a laboratory IPMSM with dampers is proposed and experimentally validated. The determined parameters are then employed to design, control, and compare the performance of an integrated charging system incorporating an IPMSM drive with and without damper bars. The developed system is then experimentally tested under both vehicle-to-grid and grid-to-vehicle modes, and results elicited from the investigations are discussed.

Study of permanent magnet machine based flywheel energy storage system for peaking power series hybrid vehicle control strategy

Transit agencies are increasingly focused on making bus fleets cleaner, more efficient and cost effective by incorporating new clean propulsion technologies. Increased maintenance cost and lower lifetime of battery packs in existing hybrid electric buses have been major bottlenecks in motivating transit bus operators to rapidly switch to this energy efficient technology. Understanding the demerits of the current battery based energy storage technology and merits of the prospective flywheel based energy storage technology for transit bus application, this paper puts an effort to study the permanent magnet synchronous machine based flywheel energy storage system for the aforementioned application. A series transit hybrid bus with peaking vehicle control strategy has been taken into consideration with a macro objective to compare the performance of the battery based and flywheel based hybrid transit bus in terms of fuel consumption and cost of the installed system. However, the focus of this paper remains on the development and study of a 100 kW flywheel energy storage system based on vector control technique which forms the first step towards this macro objective.

A Novel Two-Axis Theory-Based Experimental Approach Towards Determination of Magnetization Characteristics of Line-Start Permanent Magnet Synchronous Machines

Understanding the importance of saturation of parameters in line-start permanent magnet synchronous machine (LSPMSM) and the scanty available research literature on simplistic methods of determining the magnetizing characteristics of LSPMSM, this paper proposes a novel and yet simplistic approach towards its determination. Experimental investigations have been performed on a laboratory LSPMSM based on the proposed dq axis (two-axis)-based methodology and the measured magnetization characteristics of the machine has been incorporated into the machine model. The measured characteristics have hence been validated through dynamic and steady state performance analyses of the machine under direct online (DOL) starting. Furthermore, performance analysis of the machine has also been performed through the developed machine model with and without incorporating the magnetization characteristics of the machine to elicit the effects of parameter saturation during startup and synchronization of the machine.

Design and Testing of a Multi-port Sustainable DC Fast-charging System for Electric Vehicles

Abstract In this era of electrified transportation, inadequate fast-charging infrastructure and limited driving ranges in vehicles due to current energy storage technology remain bottlenecks in motivating consumers to rapidly shift to these electrified vehicles. Mass integration of these vehicles into the grid in the future would result in huge stress on the existing grid in terms of quantity and quality of power consumed. Understanding these issues in detail, this article exclusively discusses the design, development, and comprehensive testing of a multi-port sustainable fast-charging station involving solar photovoltaic, an in-house battery electric vehicle, the utility grid, multiple power electronic converters, and proper control under various modes of operation of the charging station. Such a charging station would enable quick and conventional charging with a lower power level through sustainable power, if available, hence reducing the impact on the grid and the energy cost of system operation.

Design considerations for permanent magnet machine drives for direct-drive electric vehicles

Understanding the need for improvement in efficiency of an electric vehicle drivetrain system, this paper exclusively discusses various design aspects of a permanent magnet machine drive for direct-drive electric vehicles (EV). Firstly, the motivation to employ a direct-drive configuration in EV is discussed. Thereafter, initial electric machine rating design considerations for a typical Supermini or B-segment EV employing a direct-drive configuration is discussed. Furthermore, employing an existing stator, investigations are performed through analytical equations and designed machines to understand different permanent magnet machine design aspects with regards to selection of: number of poles, type of permanent magnet rotor, stator winding configuration and number of phases. The study performed here will assist in providing decision points on various structural design indices of the machine before venturing into the FEA based permanent magnet machine design and assessment for the direct-drive EV application.

Short term power demand forecasting in light- and heavy-duty electric vehicles through linear prediction method

In this paper a novel method based on linear prediction technique is proposed for short term power demand forecasting in light and heavy-duty electric vehicles for improvement in the overall efficiency of the vehicle. The paper also utilizes filtering of unnecessary information which would have been a major bottleneck in improving the methods accuracy. The predicted demand function is fed to a wavelet function, which apportions the share between the battery and the ultracapacitor of the considered energy management system. The proposed method is validated with empirical power demand data obtained from on road tests of both light and heavy-duty electric vehicles through numerical investigations.

Online stator and rotor resistance estimation scheme using swarm intelligence for induction motor drive in EV/HEV

The usage of niche copper-rotor induction motor (CRIM) in the Tesla Roadster electric vehicle has bolstered the technology of using copper-rotor induction motor for electrified transportation. Understanding the merits, demerits and state of art technology of induction motor and its drive in EV/HEV application, this research manuscript proposes an online stator and rotor resistance estimation scheme using particle swarm optimization (PSO) technique for efficient and accurate control of induction motors in the same application. Firstly, an insight is provided on the state or art CRIM technology in EV/HEV and the need for reliable online rotor and stator resistance estimation scheme. Secondly, a PSO based scheme for resistance estimation is developed through a mathematical model. The developed model is validated and tested on a 10hp CRIM thorough a computer programme. Thereafter, the calculated results obtained from numerical investigations are analyzed.