Integrated on-board EV battery chargers: New perspectives and challenges for safety improvement

Thanks to the heavy reduction of cost and volume, integrated On-Board Chargers (OBCs) represent an effective solution to provide a versatile and powerful charging system on board of electric and plug-in electric vehicles, combining the charging function with the traction drivetrain. Such integration foresees the use of the traction motor windings as reactive elements and the traction inverter as AC/DC converter. However, this integration brings several challenges on the table. At first, shaft torque production must be avoided to reduce the losses and mechanical stress. A second challenge is to improve the filtering capability of the motor windings in order to meet the grid standards in terms of current distortion and power factor correction. At last, the most critical issue is to meet the safety standards in terms of leakage current, since it represents a risk to human operators and could also hamper the smooth operation of the charger. Therefore, this paper aims at giving a comprehensive review of the challenges in designing integrated chargers. After reviewing the architectures available in literature, an exemplifying structure of integrated OBC will be analysed in terms of leakage current generation and compliance with the relevant standards, along with an introduction to those solutions which use the machine as isolation transformer. Conclusions are given on the prospect for making integrated on-board chargers safer and more reliable

An Isolated Integrated Charger for Electric or Plug-in Hybrid Vehicles

For electric and hybrid vehicles using grid power to charge the battery, traction circuit components are not normally engaged during the charging time, so there is a possibility to use them in the charger circuit to have an on-board integrated charger.In this Licentiate thesis, an isolated high power integrated charger is proposed, designed and constructed based on a special ac machine with a double set of stator windings called motor/generator.The charger is capable of unit power factor operation as well as bi-directional power operation for grid to vehicle application.The mathematical electromechanical model of the motor/generator is derived and presented. Based on the developed model, new controller schemes are developed and designed for the grid synchronization and charge control. The machine windings are re-arranged for the traction and charging by a controllable relay-based switching device that is designed for this purpose.A laboratory system is designed and implemented based on a $4$ pole $25~kW$ interior permanent magnet synchronous motor and a frequency converter considering the integrated charging features for winding re-configuration. The practical results will be added in the next step of the project. The charging power is limited to $12.5~kW$ due to the machine thermal limit (half of the motor full power in the traction mode) for this system.The whole system is simulated in Matlab/Simulink based on the developed model and controllers to verify the system operation for the charge control. Simulation results show that the system has good performance during the charging time for a load step change. The simulation results show also a good performance of the controllers leading to machine speed stability and smooth grid synchronization. Moreover, the unit power factor operation is achieved for battery charging in the simulations

An Isolated Integrated Charger for Electric or Plug-in Hybrid Vehicles

For electric and hybrid vehicles using grid power to charge the battery, traction circuit components are not normally engaged during the charging time, so there is a possibility to use them in the charger circuit to have an on-board integrated charger.In this Licentiate thesis, an isolated high power integrated charger is proposed, designed and constructed based on a special ac machine with a double set of stator windings called motor/generator.The charger is capable of unit power factor operation as well as bi-directional power operation for grid to vehicle application.The mathematical electromechanical model of the motor/generator is derived and presented. Based on the developed model, new controller schemes are developed and designed for the grid synchronization and charge control. The machine windings are re-arranged for the traction and charging by a controllable relay-based switching device that is designed for this purpose.A laboratory system is designed and implemented based on a $4$ pole $25~kW$ interior permanent magnet synchronous motor and a frequency converter considering the integrated charging features for winding re-configuration. The practical results will be added in the next step of the project. The charging power is limited to $12.5~kW$ due to the machine thermal limit (half of the motor full power in the traction mode) for this system.The whole system is simulated in Matlab/Simulink based on the developed model and controllers to verify the system operation for the charge control. Simulation results show that the system has good performance during the charging time for a load step change. The simulation results show also a good performance of the controllers leading to machine speed stability and smooth grid synchronization. Moreover, the unit power factor operation is achieved for battery charging in the simulations

On the Modeling, Analysis and Development of PMSM: For Traction and Charging Application

Permanent magnet synchronous machines (PMSMs) are widely implemented commercially available traction motors owing to their high torque production capability and wide operating speed range. However, to achieve significant electric vehicle (EV) global market infiltration in the coming years, the technological gaps in the technical targets of the traction motor must be addressed towards further improvement of driving range per charge of the vehicle and reduced motor weight and cost. Thus, this thesis focuses on the design and development of a novel high speed traction PMSM with improved torque density, maximized efficiency, reduced torque ripple and increased driving range suitable for both traction and integrated charging applications. First, the required performance targets are determined using a drive cycle based vehicle dynamic model, existing literature and roadmaps for future EVs. An unconventional fractional–slot distributed winding configuration with a coil pitch of 2 is selected for analysis due to their short end–winding length, reduced winding losses and improved torque density. For the chosen baseline topology, a non–dominated sorting genetic algorithm based selection of optimal odd slot numbers is performed for higher torque production and reduced torque ripple. Further, for the selected odd slot–pole combination, a novel star–delta winding configuration is modeled and analyzed using winding function theory for higher torque density, reduced spatial harmonics, reduced torque ripple and machine losses. Thereafter, to analyze the motor performance with control and making critical decisions on inter–dependent design parameter variations for machine optimization, a parametric design approach using a novel coupled magnetic equivalent circuit model and thermal model incorporating current harmonics for fractional–slot wound PMSMs was developed and verified. The developed magnetic circuit model incorporates all machine non–linearities including effects of temperature and induced inverter harmonics as well as the space harmonics in the winding inductances of a fractional–slot winding configuration. Using the proposed model with a pareto ant colony optimization algorithm, an optimal rotor design is obtained to reduce the magnet utilization and obtain maximized torque density and extended operating range. Further, the developed machine structure is also analyzed and verified for integrated charging operation where the machine’s winding inductances are used as line inductors for charging the battery thereby eliminating the requirement of an on–board charger in the powertrain and hence resulting in reduced weight, cost and extended driving range. Finally, a scaled–down prototype of the proposed PMSM is developed and validated with experimental results in terms of machine inductances, torque ripple, torque–power–speed curves and efficiency maps over the operating speed range. Subsequently, understanding the capabilities and challenges of the developed scaled–down prototype, a full–scale design with commercial traction level ratings, will be developed and analyzed using finite element analysis. Further recommendations for design improvement, future work and analysis will also be summarized towards the end of the dissertation

A comprehensive study of key Electric Vehicle (EV) components, technologies, challenges, impacts, and future direction of development

Abstract: Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more commonplace in the transportation sector in recent times. As the present trend suggests, this mode of transport is likely to replace internal combustion engine (ICE) vehicles in the near future. Each of the main EV components has a number of technologies that are currently in use or can become prominent in the future. EVs can cause significant impacts on the environment, power system, and other related sectors. The present power system could face huge instabilities with enough EV penetration, but with proper management and coordination, EVs can be turned into a major contributor to the successful implementation of the smart grid concept. There are possibilities of immense environmental benefits as well, as the EVs can extensively reduce the greenhouse gas emissions produced by the transportation sector. However, there are some major obstacles for EVs to overcome before totally replacing ICE vehicles. This paper is focused on reviewing all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments. Its objective is to provide an overall picture of the current EV technology and ways of future development to assist in future researches in this sector

Power Semiconductors for An Energy-Wise Society

This IEC White Paper establishes the critical role that power semiconductors play in transitioning to an energy wise society. It takes an in-depth look at expected trends and opportunities, as well as the challenges surrounding the power semiconductors industry. Among the significant challenges mentioned is the need for change in industry practices when transitioning from linear to circular economies and the shortage of skilled personnel required for power semiconductor development. The white paper also stresses the need for strategic actions at the policy-making level to address these concerns and calls for stronger government commitment, policies and funding to advance power semiconductor technologies and integration. It further highlights the pivotal role of standards in removing technical risks, increasing product quality and enabling faster market acceptance. Besides noting benefits of existing standards in accelerating market growth, the paper also identifies the current standardization gaps. The white paper emphasizes the importance of ensuring a robust supply chain for power semiconductors to prevent supply-chain disruptions like those seen during the COVID-19 pandemic, which can have widespread economic impacts.The white paper highlights the importance of inspiring young professionals to take an interest in power semiconductors and power electronics, highlighting the potential to make a positive impact on the world through these technologies.The white paper concludes with recommendations for policymakers, regulators, industry and other IEC stakeholders for collaborative structures and accelerating the development and adoption of standards

Dual Benefits of Adding Damper Bars in PMSMs for Electrified Vehicles: Improved Machine Dynamics and Simplified Integrated Charging

Recently, due to rising environmental concerns and predicted future shortages of fossil fuels, there is a movement towards electrification of the transportation industry. A vast majority of the current research uses permanent magnet synchronous machines as the main traction motor in the drivetrain. This work proposes to add a special damper to a conventional permanent magnet synchronous machine to further improve the suitability of this machine for electrified vehicles. Firstly, an equivalent circuit model is developed to simulate the operation of a conventional PMSM with a damper. A synchronous loading test is proposed to determine the synchronous reactance of the machine. A modified blocked rotor test is used to find the damper parameters assuming that the rotor cage construction is known. Also a single-phase AC test that can be used to determine the damper parameters without prior knowledge of the rotor construction is proposed and presented as an alternative to the blocked rotor test. Thereafter, the models of a 50 kW traction motor and the same machine with damper bars are developed and simulated. The performance of both machines are compared and evaluated. The damper parameters are selected based on the dynamic and steady state performances. It is also shown that the machine with a damper has faster response to a three-phase short circuit fault. In addition, this study also looks into integrated charging which utilizes the existing drivetrain components for vehicle to grid and grid to vehicle operation. The damper is shown to be effective in mitigating the saliency condition caused by the buried magnets of IPMSM at stand-still condition. As a result, the machine windings can be used as line inductors for integrated charging

Oak Ridge National Laboratory Annual Progress Report for the Power Electronics and Electric Machinery Program

The U.S. Department of Energy (DOE) and the U.S. Council for Automotive Research (composed of automakers Ford, General Motors, and Chrysler) announced in January 2002 a new cooperative research effort. Known as FreedomCAR (derived from 'Freedom' and 'Cooperative Automotive Research'), it represents DOE's commitment to developing public/private partnerships to fund high-risk, high-payoff research into advanced automotive technologies. Efficient fuel cell technology, which uses hydrogen to power automobiles without air pollution, is a very promising pathway to achieve the ultimate vision. The new partnership replaces and builds upon the Partnership for a New Generation of Vehicles initiative that ran from 1993 through 2001. The Advanced Power Electronics and Electric Machines (APEEM) subprogram within the Vehicle Technologies Program provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on understanding and improving the way the various new components of tomorrow's automobiles will function as a unified system to improve fuel efficiency. In supporting the development of hybrid propulsion systems, the APEEM effort has enabled the development of technologies that will significantly improve advanced vehicle efficiency, costs, and fuel economy. The APEEM subprogram supports the efforts of the FreedomCAR and Fuel Partnership through a three-phase approach intended to: (1) identify overall propulsion and vehicle-related needs by analyzing programmatic goals and reviewing industry's recommendations and requirements and then develop the appropriate technical targets for systems, subsystems, and component research and development activities; (2) develop and validate individual subsystems and components, including electric motors, and power electronics; and (3) determine how well the components and subsystems work together in a vehicle environment or as a complete propulsion system and whether the efficiency and performance targets at the vehicle level have been achieved. The research performed under this subprogram will help remove technical and cost barriers to enable the development of technology for use in such advanced vehicles as hybrid electric vehicles (HEVs), plug-in HEVs, and fuel-cell-powered automobiles that meet the goals of the Vehicle Technologies Program. A key element in making HEVs practical is providing an affordable electric traction drive system. This will require attaining weight, volume, and cost targets for the power electronics and electrical machines subsystems of the traction drive system. Areas of development include these: (1) novel traction motor designs that result in increased power density and lower cost; (2) inverter technologies involving new topologies to achieve higher efficiency and the ability to accommodate higher-temperature environments; (3) converter concepts that employ means of reducing the component count and integrating functionality to decrease size, weight, and cost; (4) more effective thermal control and packaging technologies; and (5) integrated motor/inverter concepts. The Oak Ridge National Laboratory's (ORNL's) Power Electronics and Electric Machinery Research Center conducts fundamental research, evaluates hardware, and assists in the technical direction of the DOE Vehicle Technologies Program, APEEM subprogram. In this role, ORNL serves on the FreedomCAR Electrical and Electronics Technical Team, evaluates proposals for DOE, and lends its technological expertise to the direction of projects and evaluation of developing technologies