Electric vehicle (EV) adoption continues to rise, yet EV sales still represent a small portion of vehicle sales in most countries. An expansion of the DC fast charging (DCFC) network is likely to accelerate this revolution towards sustainable transportation, giving drivers more flexible options for charging on longer trips. However, DCFC presents a large load on the grid which can lead to costly grid reinforcements and high monthly operating costs – adding energy storage to the DCFC station can help mitigate these challenges. This thesis first performs a comprehensive review of DCFC stations with energy storage, including motivation, architectures, power electronic converters, and detailed simulation analysis for various charging scenarios. The review is closely tied to current state-of-the-art technologies and covers both academic research contributions and real energy storage projects in operation around the world. It is identified that the battery energy storage systems (BESSs) with active front end converter provides high efficiency with reasonable power density in a DCFC station. It is also realized that the isolated DC/DC converter interfacing BESS and EV determines the overall efficiency of a DCFC station with a low grid connection. Secondly, this thesis analyzes the impact of active front end based DCFC stations connected to a grid distorted with background voltage harmonics. In active front end based DCFC stations, background voltage harmonics produce current not only at the frequencies of the distorted voltage, but also at other coupled frequencies. Various mitigation techniques, such as increasing inner control loop gain, grid voltage feedforward, and selective harmonic compensation, have been adopted in industry to reduce the emissions originating from distorted background voltage. However, although these techniques are effective in suppressing the current at the harmonic orders present in the background voltage, they deteriorate the emission at coupled frequencies. This thesis provides the theoretical explanation of this phenomenon, which is verified by simulation of a two-level active front end in PSCAD/EMTDC. This thesis also discusses the proper treatment of current emission due to background voltage harmonics. Thirdly, the thesis identifies the semi dual active bridge (semi-DAB) converter as an ideal candidate as the interfacing isolated DC/DC converter between the BESS and the BEV. A novel control strategy is proposed for the semi-DAB converter to achieve wide voltage gain while increasing the efficiency at operational points with high input voltage and low output voltage, which is a commonly occurring scenario when the BESS is fully charged, and the EV battery is at low charge. Furthermore, this thesis also provides an algorithm to determine the required phase-shift in real time for any operating point, eliminating the need to devise the control trajectory offline. A 550 V, 10 kW experimental prototype is built and tested to validate the proposed control strategy. With a 25 A constant charging current, the prototype shows the proposed control strategy can improve efficiency by up to 3.5% compared to the well-known dual phase shift control at operating points with high input voltage (450 – 550 V) and low output voltage (150 – 275 V), with a peak efficiency of 97.6%. Finally, this thesis proposes a novel variable turns-ratio semi-DAB converter to improve its overall efficiency even further when the input voltage is high and the output voltage is low. Furthermore, a control law is also proposed to determine the turns-ratio, i.e., the operational structure of the converter, which reduces the converter peak and rms current. The 550 V, 10 kW prototype is modified to accommodate the variable turns-ratio high frequency transformer to test the proposed converter and control. The proposed converter with control can further improve the efficiency at many operating points compared to single turns-ratio semi-DAB with DPS control. The peak efficiency achieved is 98.5%. / Thesis / Doctor of Philosophy (PhD)

The global automotive industry is currently experiencing a shift as the sector converts from fossil fuels to electric vehicles (EVs). However, the existing infrastructure for EV charging is facing difficulties in meeting the growingdemand in terms of accessibility and technical performance. In response, companies such as Zpark EnergySystems are actively engaged in the development of chargers to cater to the needs of the next generationchargers. As part of their efforts, Zpark has introduced a new product segment specifically tailored to thegrowing market demand, by creating a fast charger for the residential market. This thesis aims to create anexterior design for the charger and battery storage unit (BSU) suited to Scandinavian residential environments.The project has been divided into three main focus areas. The first area concerns design where primarily formtheory, material science and ergonomics have been researched. To validate the theory which established thedesign elements and features of the charger and BSU, extensive user testing was performed. The second areaconcerns adaptation in terms of how the product design will suit the intended home market. Scandinavian-architecture, -design, -colours and -climate has been studied for this area. The final focus area concerns theinteraction between users and mainly the charger. Research has been conducted to explore the integration ofuser interactive features into the design. The usability of these features has also been thoroughly examinedthrough user testing. Which has been combined with theories related to colour, human-machine interaction, andform theory in order to create a user-friendly interaction experience.The project approach has been divided into the following steps; exploration, ideation, evaluation andimplementation. For the explore phase background theory to the project was researched and methods such asbenchmarking, white space analysis, customer journey, placement analysis, and user research were conductedto gain an understanding of the market and the current pain points. For the ideation phase the goal was togenerate a large number of design concepts for both the charger and BSU. This was achieved through variousinternal ideatios methods within the team as well as external methods at workshops. To narrow down betweenthe design concepts an evaluation matrix was used which resulted in a final concept that was brought forward tothe next project phase, namely the evaluation. The evaluation phase concerned testing the final conceptsthough user testing and making technical specifications according to theory. At the end of this stage a finaldesign was achieved where all details were specified and loose ends tied together. The last phase concerningimplementation was then performed in correlation with the specified design through producing digital 3Dvisualisations and creating an animation of the final designs.The project resulted in an exterior design for the charger as well as the BSU which fulfils the aims of the projectscope. The design incorporates the features found to be necessary in the background research. Further auser-friendly design was established through various user tests investigating the integrated features and revisingthem according to the user test results. Adaptation to the home market is achieved through customisablecolours and modularity of the BSU. The design incorporates the characteristics of Scandinavian design boththrough its form elements and by the use of materials which makes the charger and BSU suit a Scandinavianresidential environment in a visually cohesive and aesthetically pleasing way. / Fordonsindustrin genomgår en omfattande förändring då branschen konverterar från fossila bränslen tillelektriska fordon (EF). Branschen står inför utmaningar de kommande åren då den befintliga infrastrukturen förelbilsladdning har svårigheter att möta den ökande efterfrågan när det gäller tillgänglighet och tekniskprestanda. Därav är företag som Zpark Energy Systems aktiva i utvecklingen av innovativa laddare för atttillgodose dessa behov hos nästa generations laddare. I linje med deras satsningar har Zpark introducerat en nyproduktkategori specifikt anpassad till den växande marknadsefterfrågan genom att skapa en snabbladdaresom är skräddarsydd för bostadsmarknaden. Detta examensarbete syftar till att skapa en exteriör design försnabbladdaren samt tillhörande batterilagringsenhet (BLE) anpassad till Skandinavisk bostadsmiljö.Projektet har delats upp i fyra huvudsakliga fokusområden. Det första området centrerar kring design där främstformteori, materialvetenskap och ergonomi har studerats. För att validera teorin som designelement ochfunktioner för laddaren och BLE har baserats på så utfördes användartester. Det andra fokusområdet i projektetavser anpassning i form av hur produktens design ska anpassas till den avsedda bostadsmiljön. Teori gällandeskandinavisk arkitektur, design, färger och klimat har studerats för att skapa en akademisk grund för dettaområde. Det sista fokusområdet för projektet rör interaktionen mellan användare och främst laddaren.Användartester har genomförts för att utforska integrationen av interaktiva funktioner i designen och dessanvändbarhet. Detta har kombinerats med teorier relaterade till färgsättning, människa-maskin-interaktion ochformteori för att skapa en användarvänlig upplevelse under laddningsprocessen.Projektets tillvägagångssätt är uppdelat i tre huvudmoment: utforskning, idégenerering, utvärdering ochimplementering. Under utforskningsfasen undersöktes bakgrundsteori för projektet och metoder sombenchmarking, white space analysis, customer journey, placeringsanalys och användarstudier användes för attfå en förståelse för marknaden och befintliga utmaningar. Under idégenereringsfasen var målet att generera ettstort antal designkoncept för både laddare och BLE. Detta uppnåddes genom olika interna och externaidégenereringsmetoder och workshops. För att välja bland designkoncepten användes en utvärderingsmatrissom resulterade i ett slutgiltigt koncept vilket sedan togs vidare till nästa projektfas. Utvärderingsfaseninnefattade utvärdering av det valda design konceptet genom användartester och tekniska specifikationer enligtteorin. Vid slutet av denna fas uppnåddes en slutlig design där alla detaljer specificerades och lösa ändar knötsihop. Den sista fasen rör implementering och utfördes i enlighet med den specificerade designen genom attproducera digitala 3D-visualiseringar och skapa en animering av de slutgiltiga designerna.Projektet resulterade i en exteriör design för laddaren och BLE:n som uppfyller projektets mål: Designeninkluderar de funktioner som identifierats som nödvändiga i bakgrundsundersökningen. När det gällerfunktionaliteten skapades en användarvänlig design genom olika användartester som utvärderade deintegrerade funktionerna vilka reviderades utifrån resultatet i testerna. Anpassning till hemmamarknaden uppnåsgenom anpassningsbara färger och modularitet för BLE. Designen innehåller kännetecknen för skandinaviskdesign både genom sina formelement och genom användningen av material vilket gör att laddare och BSUpassar i en skandinavisk bostadsmiljö på ett estetiskt tilltalande sätt med hög funktionalitet.

The move toward electric vehicles (EVs) has a significant impact to reduce greenhouse gas (GHG) emissions and make transportation more eco-friendly. Fast-charging stations play a crucial role in this transition, making EVs more convenient for adoption specifically when driving in long distance. However, the challenge is to create a fast-charging system that can work with the different types of EVs and their varying power needs while still being efficient and effective. In this context, this thesis embarks on this journey by introducing an innovative solution for efficient universal fast charging, spanning both low voltage and high voltage battery systems. A novel, configurable dual secondary resonant converter is proposed, which empowers the charging module to extend its output range without imposing additional demands on the resonant tank components. This solution addresses the pressing need for a wide output voltage range in fast-charging standard in the growing EV landscape. To ensure optimal performance across a broad voltage and power range, the thesis employs an analytical model for LLC resonant converters to optimize the resonant components. This strategic component selection aims to achieve the desired output voltage and power range while minimizing conduction losses. The proposed topology and design methodology are rigorously validated through the development of a 10 kW prototype. Furthermore, the study introduces a two degrees of freedom (2DoF) control scheme for the proposed LLC resonant converter with the configurable dual secondary LLC converter topology. An analytical model is formulated to guide the selection of control parameters, ensuring coverage of the desired output voltage and power range without compromising system efficiency. The steady-state analytical model is utilized for determining optimized control parameters at each operating point within the converter's output range. To enhance the charging module's power density and efficiency, a high-frequency litz-wire transformer design methodology is introduced. The transformer's core size is optimized to achieve high power density and efficiency, while the winding configuration is chosen to minimize conduction losses. Finite Element Analysis (FEA) simulations validate transformer losses and operating temperatures. The culmination of this research is the development of a 30 kW charging module prototype. This prototype features an LLC resonant converter with a configurable dual secondary and two degrees of freedom control for output voltage control. The component ratings, estimated losses, and power board design are carefully considered to create a compact and efficient charging module. Experimental testing across a universal output voltage and power range con rms the effectiveness of the proposed solution. In summary, this thesis presents a comprehensive approach to design of a module for EV fast charging application addressing voltage range, efficiency, and component optimization, resulting in the successful development of a high-performance charging module prototype. / Thesis / Doctor of Engineering (DEng)