INVESTIGATION INTO FULLY – ELECTRIC AND HYBRID – ELECTRIC POWERTRAINS FOR ROLLING STOCK ATHANASIOS IRAKLIS SUPERVISORS: CHARALAMPOS DEMOULIAS ROB HENSEN, KASPER VAN ZUILEKOM, ERIC VAN BERKUM FACULTY OF ELECTRICAL AND COMPUTER ENGINEERING DEPARTMENT OF ELECTRICAL ENERGY ARISTOTLE UNIVERSITY OF THESSALONIKI THESSALONIKI, GREECE 2015 Acknowledgements Foremost, I would like to express my sincere gratitude to Charalampos Demoulias, my supervisor from Aristotle University of Thessaloniki, for supporting my work and providing me with immense knowledge and insightful comments. Also, special thanks to Kasper van Zuilekom and Eric van Berkum, my supervisors from the University of Twente, for providing me with great amount of knowledge, information and support. Their guidance helped me a lot during the research and writing of this thesis. Also, sincere thanks to Rob Hensen for the dream, Ellen Linnenkamp and Rudi Broekhuis for the support, and of course Erik Hoogma for being there for me, everytime I needed help. Thanks for the amazing journey, your patience, your enthusiasm and the high degree of freedom I was generally given during this investigation. I would also like to thank Edwin de Kreij, Rene Cohlst, and Martijn Elias for the assistance they provided at various levels and their helpful comments along the way. I dedicate this thesis to my brother, Chris Intentionally Blank Page Index Acknowledgements - Chapter 1: 1.1 Brief Introduction 1 1.2 Thesis Objective 2 1.3 Thesis Outline 3 Chapter 2: 2.1 Battery-Powered and Hybrid Operations 5 2.1.1 General Considerations and Goals 5 2.1.2 Previous Developments in HEVs and Energy Storage 7 2.1.3 Control Strategies in Different Hybrid-Electric Configurations 10 2.1.3.1 Series HEV powertrain operating modes 11 2.1.3.2 Parallel HEV powertrain operating modes 12 2.1.3.3 Power-Split HEV powertrain operating modes 13 2.1.3.4 Complex HEV powertrain operating modes 15 2.1.3.5 Full-Hybrids 18 2.2 Energy Storage for EVs and HEVs 19 2.2.1 Electrochemical Batteries (Lithium-Ion) 19 2.2.2 Supercapacitors 23 2.3 Energy Management And Distribution 25 2.4 Integrated System Optimization 28 2.5 Generic Modeling Structure 31 Chapter 3: 3.1 Modeling methodology 36 3.2 Internal Combustion Engine Modeling 38 3.3 Electric Motor/Generator Modeling 40 3.4 Energy Storage Modeling 45 3.4.1 Electrochemical Battery Modeling 45 3.4.2 Supercapacitor Modeling 49 3.4.3 Temperature Estimation of Energy Storage cells 53 3.5 Power Demands Calculation 55 3.5.1 Acceleration Resistance 56 3.5.2 Running Resistance 57 3.5.2.1 Running Resistance in General 57 3.5.2.2 Rolling Resistance 63 3.5.2.3 Aerodynamic Resistance 66 3.5.3 Other Resistances 73 3.6 Power division 75 3.7 Verification of Energy Demands 83 3.7.1 Case I - Gelede Tram Lang (GTL8) Tram 83 3.7.2 Case II - NS Intercity Passenger Train (VIRM) 98 Chapter 4: 4.1 CASE I - Elimination of a Tram's Overhead Catenary System Through Battery Electrification 102 4.2 CASE II - Hybridization of a Diesel-Electric Configuration 110 Chapter 5: 5.1 Summary - Conclusions 116 5.2 Future Work and Modeling Improvements 117 References 119 Appendix 123 CHAPTER 1 1.1 Brief Introduction Mass transportation rail systems have historically relied on high voltage DC or AC overhead catenary lines, third-rail lines or primary energy carriers – mostly fossil liquid hydrocarbons - to satisfy their power and energy demands. In Europe, approximately half of the continent’s transit systems run on electricity but still, there are many locomotives and trains running on fossil fuels by using low efficiency internal combustion engines. The International Energy Agency (IEA) recently published information on the percentages that took part in the rail sector for the year 2012, regarding the total energy consumption and where this energy came from. By that year, worldwide, 73% (19 Mtoe) of the total energy used was extracted from oil products by the process of combustion and 27% (7 Mtoe) of it relied on electricity, by using overhead or third-rail systems. In Greece, 100% (0.03 Mtoe) of the total energy demands relied on oil products, although it is known that currently, main train and tram lines rely on electricity, while the percentages for the Netherlands were 17% (0.03 Mtoe) for oil products and 83% (0.15 Mtoe) for electricity. [IEA: 1 toe is equal to 41.868 GJ, 11.63 MWh or 0.99 t of diesel] Figure 1.1.1: Rail Sector Energy Consumption - 2012, www.iea.org, left: Greece, center: Worldwide, right: Netherlands However, catenary-free hybrid-electric and fully-electric operations, with maximized energy efficiency, minimized local and global emissions and which eliminate the installation and maintenance costs of overhead and third-rail high-voltage power transmission lines, are fast gaining prominence, especially in developed countries. Better and low cost energy storage devices, with high energy density and high discharging and charging rates, providing greater lifetime and efficiency, are also affecting the break-even point of the transformation of the rail sector as we know it. Hybrid-electric and fully-electric powertrains with on-board energy storage are already considered technologies leading to the direction of reducing fuel consumption and emissions by increasing total system efficiency, not only for on-site combustion systems but also for electric 1 propulsion systems. Power for such operations is extracted either by using a combination of fuel consuming units, such as internal combustion engines/fuel cells, and energy storage devices along with specific power/energy-flow strategies, or by simply charging and discharging an on/off–board energy storage package, complying of one or more devices with different characteristics and operation limits, while fulfilling certain technical, performance and comfort constraints. Meeting maximum performance and efficiency criteria is always of top priority. In general, catenary–free and innovative hybrid solutions could offer various benefits to the railway sector, compared to existing used technologies. They are very promising towards the reduction of the construction costs, lifetime maintenance costs, as well as costs associated with design and approval of catenary systems and pantographs, while reducing the local and global energy/fuel consumption and emissions by using regenerative braking, smart control systems and optimized power/energy–flow concepts for achieving high system efficiency. Furthermore, they could allow more flexibility in rolling stock design because many conditions are relaxed (such as specified headroom and vehicle height) while being less susceptible to severe weather conditions such as snow, blizzard and storms, which may damage overhead or third-rail systems. Many approaches that could allow the elimination of overhead catenary and third-rail lines and reduce the energy/fuel consumption of existing fuel consuming systems have been introduced so far and are already proven technology in the automotive industry and in applications where a wireless high efficiency power supply is needed, thus an on-site energy providing unit is required. One drawback of the current proposed approaches in the automotive sector is the high investment cost because of high system complexity, adoption of expensive components and the lack of optimized vehicle parameters and the power-flow strategy for given driving schedules used worldwide. Regarding the modeling and simulation of such powertrains, it is important to mention that in most – if not all – cases, these new systems have a higher degree of complexity than the traditional approaches. Additional electric motors, special internal combustion engines, energy storage devices, torque converters-splitters, electronically controlled clutches and operation and/or energy management units are added with the intention to improve the system's behavior. For the investigation into such complex systems (sizing of components, defining the power/energy–flow strategy and optimizing the driving performance), where simulation of different driving scenarios may take place while looking at the total power demands, energy demands and components' outputs, special modeling of the vehicle's powertrain and its behavior is required. 1.2 Thesis Objective The primary objective of this study, is to develop a mathematical/simulation model of fully-electric and hybrid-electric powertrains for investigations into mass transit rolling stock systems within the environment of 2 Matlab/Simulink. The outcome of this assignment could provide an open-source low-complexity system with high degree of freedom, in terms of changeability, capable of calculating the total power and energy demands, estimating the fuel consumption and emissions of fuel consuming units and approximating the behavior of on- board or off-board energy-storage devices that interact with the rest of the powertrain or an existing overhead catenary or third-rail line in different configurations, adopting different power/energy-flow strategies and for different driving scenarios/schedules, while staying within certain operating limits, for given vehicle parameters. The ultimate goal of this investigation is to provide a tool capable of cooperating with optimization algorithms mostly used for optimum sizing of powertrain components and efficiently optimum definition of the power/energy-flow strategies chosen for different drivetrain topologies. Furthermore, the validation of the energy demands calculated by the developed model for given speed profiles, is not of less importance,