The emergence of wide-bandgap-based (WBG) devices, such as silicon carbide (SiC) and gallium nitride (GaN), have unveiled unprecedented opportunities, enabling the realization of superior power conversion systems. Among the potential areas of advancement are medium-voltage (MV) and high-voltage (HV) applications, due to the growing demand for high-power-density and high-efficiency power electronics converters. These advancements have propelled a wide adoption of electric vehicles (EV), which in the future will require great improvements in the charging time of these vehicles. Thereby, this thesis attempts to address such a challenge and bring about technological improvements, enabling faster, more efficient, and more effective ways of charging an electric vehicle through the application of MV 3.3 kV SiC MOSFETs. The current fast-charging solution involves heavy and bulky MV-LV transformers, which add installation complexity for EV charging stations. However, this thesis presents an alternative power-delivery solution utilizing an MV dual-active-bridge (DAB) converter. The proposed architecture is designed to directly interface with the MV grid for high-power, fast-charging capabilities while eliminating the need for an installation of the MV-LV transformer. The MV DAB converter utilizes 3.3 kV SiC MOSFETs to realize the next 800 V EV charging system, along with an extended zero-voltage-switching (ZVS) scheme, in order to provide an efficient charging strategy across a wide range of battery voltage levels. Lastly, a detailed design comparison analysis of an MV Flyback converter, targeted for the auxiliary power supply for the proposed MV EV charging architecture, is presented. / The field of power electronics, which controls and manages the conversion of electrical energy, is an important topic of discussion, as new technologies like electric vehicles (EV) are quickly emerging and disrupting the current status-quo of vehicle-choice. In order to promote timely and extensive adoption of such an enabling EV technology, it is critical to understand the current challenges involving EV charging stations and seek out opportunities to engender future innovations. Indeed, wide-bandgap (WBG) devices, such as silicon carbide (SiC) and gallium nitride (GaN), have unveiled unprecedented opportunities in enabling the realization of superior power conversion systems. Thus, utilizing these WGB devices in EV charging applications can bring about improved design and development of EV fast chargers that are faster-charging, more efficient, and more effective. Hence, this thesis presents an opportunity in EV charging station applications with the utilization of medium-voltage SiC MOSFETs. Because the current fast-charging solution involves a heavy and bulky transformer, it adds installation complexity for EV charging stations. However, this thesis presents an alternative power-delivery solution that could potentially provide an efficient and fast-charging mechanism of EVs while reducing the size of EV chargers. All things considered, this thesis provides in-depth evaluation-studies of medium-voltage 3.3 kV SiC MOSFET-based power converters, targeted for future fast EV charging applications. The development and design of the hardware prototype is presented in this thesis, along with testing and verification of experimental results.

The Hybrid Electric Vehicle Team (HEVT) of Virginia Tech is participating in the EcoCAR 3 Advanced Vehicle Technology Competition series organized by Argonne National Labs (ANL), and sponsored by General Motors (GM) and the U.S. Department of Energy (DOE). EcoCAR 3 is a 4-year collegiate competition that challenges student with redesigning a 2016 Chevrolet Camaro into a hybrid. The five main goals of EcoCAR 3 are to reduce petroleum energy use (PEU) and green house gas (GHG) emissions while maintaining safety, consumer acceptability, and performance, with an increased focus on cost and innovation. HEVT selected a P3 Plug-in Parallel hybrid electric vehicle (PHEV) to meet design goals and competition requirements. This study presents different stages of the vehicle development process (VDP) followed to integrate the HEVT Camaro. This work documents the control system development process up to Year 2 of EcoCAR 3. The modeling process to select a powertrain is the first stage in this research. Several viable powertrains and the respective vehicle technical specifications (VTS) are evaluated. The P3 parallel configuration with a V8 engine is chosen because it generated the set of VTS that best meet design goals and EcoCAR 3 requirements. The V8 engine also preserves the heritage of the Camaro, which is attractive to the established target market. In addition, E85 is chosen as the fuel for the powertrain because of the increased impact it has on GHG emissions compared to E10 and gasoline. The use of advanced methods and techniques like model based design (MBD), and rapid control prototyping (RCP) allow for faster development of engineering products in industry. Using advanced engineering techniques has a tremendous educational value, and these techniques can assist the development of a functional and safe hybrid control system. HEVT has developed models of the selected hybrid powertrain to test the control code developed in software. The strategy developed is a Fuzzy controller for torque management in charge depleting (CD) and charge sustaining (CS) modes. The developed strategy proves to be functional without having a negative impact of the energy consumption characteristics of the hybrid powertrain. Bench testing activities with the V8 engine, a low voltage (LV) motor, and high voltage (HV) battery facilitated learning about communication, safety, and functionality requirements for the three components. Finally, the process for parallel development of models and control code is presented as a way to implement more effective team dynamics. / Master of Science

Electric vehicles (EVs) are increasing in popularity and play an important role in decarbonizing the transport sector. However, a growing EV fleet can cause problems for power grids as the grids are not initially designed for EV charging. The potential of a power grid to accommodate EV loads can be assessed through hosting capacity (HC) analysis. The HC is grid specific and varies, therefore it is necessary to conduct analysis that reflects local conditions and covers uncertainties and correlations over time. This theses aims to investigate the HC for EVs in existing residential power grids, and to gain a better understanding of how it varies based on how the EVs are implemented and charged. The work is in collaboration with a distribution system operator (DSO) and is based on two case studies using real-life data reflecting conditions in Swedish grids. Combinations of different HC assessment methods have been used and the HC is evaluated based on cable loading, transformer loading and voltage deviation. Additionally, the study investigated three distinct charging strategies: charging on arrival, evenly spread charging over whole connection period, and charging at the lowest spot price.  The results show that decisions on acceptable voltage deviation limit can have a large influence on the HC as well as the charging strategy used. A charging strategy based on energy prices resulted in the lowest HC, as numerous EVs charging simultaneously caused high power peaks during low spot price periods. Charging on arrival was the second worst strategy, as the peak power coincided with household demand. The best strategy was to evenly spread out the charging, resulting in fewer violations for 100% EV implementation compared to the other two strategies for 25% EV implementation.  The findings underscore the necessity for coordinated charging controls for EV fleets or diversified power tariffs to balance power on a large scale in order to use the grids efficiently.

Electric vehicles (EVs) are increasing in popularity and play an important role in decarbonizing the transport sector. However, a growing EV fleet can cause problems for power grids as the grids are not initially designed for EV charging. The potential of a power grid to accommodate EV loads can be assessed through hosting capacity (HC) analysis. The HC is grid specific and varies, therefore it is necessary to conduct analysis that reflects local conditions and covers uncertainties and correlations over time. This theses aims to investigate the HC for EVs in existing residential power grids, and to gain a better understanding of how it varies based on how the EVs are implemented and charged. The work is in collaboration with a distribution system operator (DSO) and is based on two case studies using real-life data reflecting conditions in Swedish grids. Combinations of different HC assessment methods have been used and the HC is evaluated based on cable loading, transformer loading and voltage deviation. Additionally, the study investigated three distinct charging strategies: charging on arrival, evenly spread charging over whole connection period, and charging at the lowest spot price.  The results show that decisions on acceptable voltage deviation limit can have a large influence on the HC as well as the charging strategy used. A charging strategy based on energy prices resulted in the lowest HC, as numerous EVs charging simultaneously caused high power peaks during low spot price periods. Charging on arrival was the second worst strategy, as the peak power coincided with household demand. The best strategy was to evenly spread out the charging, resulting in fewer violations for 100% EV implementation compared to the other two strategies for 25% EV implementation.  The findings underscore the necessity for coordinated charging controls for EV fleets or diversified power tariffs to balance power on a large scale in order to use the grids efficiently.

The battery charger plays an important role in the development of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs).This thesis focuses on the DC-DC converter for high voltage battery charger and is divided into four chapters. The background related to EV battery charger is introduced, and the topologies of isolated DC-DC converter possibly applied in battery charge are sketched in Chapter 1. Since the EV battery charger is high voltage high power, the phase-shifted full bridge and LLC converters, which are popularly used in high power applications, are discussed in detail in Chapter 2. They are generally considered as high efficiency, high power density and high reliability, but their prominent features are also limited in certain range of operation. To make full use of the advantages and to avoid the limitation of the phase-shifted full bridge and LLC converters, a novel hybrid resonant and PWM converter combining resonant LLC half-bridge and phase shifted full-bridge topology is proposed and is described in Chapter 3. The converter achieves high efficiency and true soft switching for the entire operation range, which is very important for high voltage EV battery charger application. A 3.4 kW hardware prototype has been designed, implemented and tested to verify that the proposed hybrid converter truly avoids the disadvantages of LLC and phase-shifted full bridge converters while maintaining their advantages. In this proposed hybrid converter, the utilization efficiency of the auxiliary transformer is not that ideal. When the duty cycle is large, LLC converter charges one of the capacitors but the energy stored in the capacitor has no chance to be transferred to the output, resulting in the low utilization efficiency of the auxiliary transformer. To utilize the auxiliary transformer fully while keeping all the prominent features of the previous hybrid converter in Chapter 3, an improved hybrid resonant and PWM converter is proposed in Chapter 4. The idea has been verified with simulations. The last chapter is the conclusion which summaries the key features and findings of the two proposed hybrid converters. / Master of Science

Defining key parameters for a charge sustaining supervisory (torque split) control strategy as well as an engine and catalyst warm-up strategy for a Split Parallel Architecture Extended-Range Electric Vehicle (SPA E-REV) is accomplished through empirically and experimentally measuring vehicle tailpipe emissions and energy consumption for two distinct control strategies. The results of the experimental testing and analysis define how the vehicle reduces fuel consumption, petroleum energy use and greenhouse gas emissions while maintaining low tailpipe emissions. For a SPA E-REV operating in charge sustaining mode with the engine providing net propulsive energy, simply operating the engine in regions of highest efficiency does not equate to the most efficient operation of the vehicle as a system and can have adverse effects on tailpipe emissions. Engine and catalyst warm-up during the transition from all-electric charge depleting to engine-dominant charge sustaining modes is experimentally analyzed to evaluate tailpipe emissions. The results presented are meant to define key parameters for a high-level torque-split strategy and to provide an understanding of the tradeoffs between low energy consumption and low tailpipe emissions. The literature review gives a background of hybrid and plug-in hybrid vehicle control publications including tailpipe emissions studies, but does not include experimental results and comparisons of supervisory strategies designed for low fuel consumption and low tailpipe emissions the SPA E-REV architecture. This paper details the high-level control strategy chosen for balancing low energy consumption and low tailpipe emissions while the engine is operating. Vehicle testing data from a chassis dynamometer is presented in support of the research. / Master of Science

[pt] Atualmente, uma das principais metas do governo alemão é o desenvolvimento do mercado de veículos elétricos no país. Para tanto, o real potencial de redução de emissões atmosféricas através do uso de carros elétricos precisa ser analisado em detalhes. Para que o impacto ambiental causado por veículos elétricos seja minimizado faz-se necessário o uso de energias renováveis. Considerando-se a intermitência de tais fontes energéticas, baterias estacionárias podem ser utilizadas para aumentar a eficiência do sistema energético. Um método quantitativo se faz então necessário para determinar se o uso de energia renovável produzida em pequena escala, incluindo o sistema de armazenamento, é ambientalmente mais vantajoso quando comparado ao uso da energia fornecida pela rede elétrica Alemã. Essa análise quantitativa é possível através do método chamado análise de ciclo de vida (LCA, sigla em inglês). Esse estudo aborda o caso da concessionária de energia de Braunschweig, Alemanha, BS Energy, que pretende instalar um sistema fotovoltaico com uma bateria estacionária para o carregamento de sua frota de veículos elétricos. Para tanto, o presente trabalho tem como objetivo realizar uma análise do ciclo de vida do sistema de carregamento da frota de veículos elétricos da BS Energy para avaliar o real impacto ambiental provocado por tal sistema e fazer uma comparação com o impacto gerado pelo uso de energia proveniente da rede elétrica de Braunschweig. Para dar suporte ao trabalho será realizada uma revisão de literatura sobre o método análise de ciclo de vida, veículos elétricos, baterias de lítio e geração de energia solar. Baseado em informações disponíveis na literatura, bem como nos dados fornecidos pela BS Energy, é construído e calculado o fluxo do ciclo de vida do sistema em questão. / [en] The stated aim of the German federal government is the market preparation and launch of battery electric vehicles in Germany. The potential of electric vehicles for reducing the harmful environmental impacts of road transport in everyday conditions has to be analyzed and evaluated in detail. If electric vehicles shall realize their potential to reduce emissions and minimize the consumption of resources, the use of renewable energy is necessary. Locally generated and stored energy could increase the use of renewable energy sources for electric vehicles. A quantitative method is necessary to determine if the use of local energy is environmentally advantageous in comparison to the use of renewable energy from the grid. Life cycle assessment is a method which quantifies potential environmental impacts, and, therefore, it is a suitable method to examine the research question. The local energy provider BS/ENERGY uses electric vehicles and plans on the installation of a stationary energy storage. Within this scenario the LCA method is applyed to analyze the environmental impacts of this solution.This work carries out a detailed life cycle assessment for the local energy storage system of BS/ENERGY. To support this work a theoretic background of the method life cycle assessment and of the local generation and storage of renewable energy is presented. Based on this information, a generic workflow for the LCA of the use of locally generated and stored energy for electric vehicles is created. This workflow serves as a basis to evaluate the key parameters for the result of the LCA, identifying hot spots and uncertainties. Finally, the specific case of BS/ENERGY is analyzed, with its specific battery chemistry and use pattern. With this, it is expected that the presente work will be able to support BS Energy decision of whether to invest on the stationary battery or not, from an envirionmental point of view.

Studien syftar till att utforska de faktorer som påverkar svenska konsumenters val avelfordon. Genom en syntes av olika teoretiska perspektiv och empirisk forskninganalyserar studien den ekonomiska, infrastrukturella och beteendemässiga kontextensom formar beslutsprocessen kring köp eller icke-köp av elfordon i Sverige. Viktigafaktorer som påverkar beslutet är den höga initiala investeringskostnaden, otillräckligtillgång till laddningsinfrastruktur, rädsla för räckviddsbegränsningar och osäkerhetkring batteriets livslängd och underhållskostnader. Trots att miljöaspekter ofta vägs in,visar forskningen att ekonomiska och praktiska överväganden oftast har störstpåverkan på konsumentbeslut gällande bilköp.Studien framhäver även betydelsen av statliga incitament och policyåtgärder,teknologisk innovation samt variationer i attityder bland olika samhällsgrupper för attöka antalet elfordon på vägarna. Genom att adressera dessa utmaningar kan en merhållbar transportsektor realiseras i Sverige. Vidare identifierar studien områden förframtida forskning, inklusive djupare undersökningar kring konsumentpreferenser ochattityder gentemot elfordon, effektiviteten av statliga incitament samt den fortsattautvecklingen av batteriteknologi och laddningsinfrastruktur. / The study aims to explore the factors that influence Swedish consumers' choice of electric vehicles. Through a synthesis of different theoretical perspectives and empirical research, the study analyses the economic, infrastructural, and behavioural context that shapes the decision-making process around the purchase or non-purchase of electric vehicles in Sweden. Important factors influencing the decision are the high initial investment cost, insufficient access to charging infrastructure, fear of range limitations, and uncertainty about battery life and maintenance costs. Although environmental aspects are often taken into account, research shows that economic and practical considerations often have the greatest impact on consumer decisions to buy a car.The study also highlights the importance of government incentives and policies, technological innovation, and variations in attitudes among different social groups in increasing the number of electric vehicles on the road. By addressing these challenges, a more sustainable transport sector can be realised in Sweden. Furthermore, the study identifies areas for future research, including deeper investigations into consumer preferences and attitudes towards electric vehicles, the effectiveness of government incentives, and the further development of battery technology and charging infrastructure.

For years the trend in the automotive industry has been toward more complex electronic control systems. The number of electronic control units (ECUs) in vehicles is ever increasing as is the complexity of communication networks among the ECUs. Increasing fuel economy standards and the increasing cost of fuel is driving hybridization and electrification of the automobile. Achieving superior fuel economy with a hybrid powertrain requires an effective and optimized control system. On the other hand, mathematical modeling and simulation tools have become extremely advanced and have turned simulation into a powerful design tool. The combination of increasing control system complexity and simulation technology has led to an industry wide trend toward model based control design. Rather than using models to analyze and validate real world testing data, simulation is now the primary tool used in the design process long before real world testing is possible. Modeling is used in every step from architecture selection to control system validation before on-road testing begins. The Hybrid Electric Vehicle Team (HEVT) of Virginia Tech is participating in the 2011-2014 EcoCAR 2 competition in which the team is tasked with re-engineering the powertrain of a GM donated vehicle. The primary goals of the competition are to reduce well to wheels (WTW) petroleum energy use (PEU) and reduce WTW greenhouse gas (GHG) and criteria emissions while maintaining performance, safety, and consumer acceptability. This paper will present systematic methodology for using model based design techniques for architecture selection, control system design, control strategy optimization, and controller validation to meet the goals of the competition. Simple energy management and efficiency analysis will form the primary basis of architecture selection. Using a novel method, a series-parallel powertrain architecture is selected. The control system architecture and requirements is defined using a systematic approach based around the interactions between control units. Vehicle communication networks are designed to facilitate efficient data flow. Software-in-the-loop (SIL) simulation with Mathworks Simulink is used to refine a control strategy to maximize fuel economy. Finally hardware-in-the-loop (HIL) testing on a dSPACE HIL simulator is demonstrated for performance improvements, as well as for safety critical controller validation. The end product of this design study is a control system that has reached a high level of parameter optimization and validation ready for on-road testing in a vehicle. / Master of Science

As the interest in electric heavy-duty vehicles has grown, so has the need for route planning tools to coordinate fleets of electric vehicles. This problem is called the Electric Vehicle Routing Problem (EVRP) and it can be solved using a Branch-Price-and-Cut method, where routes for individual vehicles are iteratively generated using information from the coordinated problem. These routes are computed in a pricing problem, which is a Resource Constrained Elementary Shortest Path Problem (RCESPP). Because of its iterative nature, the Branch-Price-and-Cut method is dependent on a fast solver for this RCSPP to get a good computational performance. In this thesis, we have implemented a labeling algorithm for the RCESSP for electric vehicles with state-of-the-art acceleration strategies. We further suggest a new bounding method that exploits the electric aspects of the problem. The algorithm's performance and the effect of the different acceleration strategies are evaluated on benchmark instances for the EVRP, and we report significantly improved computational times when using our bounding method for all types of instances. We find that route relaxation methods (ng-routes) were particularly advantageous in test instances with a combination of clustered and randomly distributed customers. Interestingly, for test instances with only randomly distributed customers, ng-relaxation required longer processing time to achieve elementary optimal routes and for these instances, the bounding methods gave better computational performance.