Trends, features and recent research efforts in the field of hybrid electric vehicles

Transcription

1 Int. J. Alternative Propulsion, Vol. 1, No. 1, Trends, features and recent research efforts in the field of hybrid electric vehicles Amr A. Adly Department of Electrical Power and Machines, Faculty of Engineering, Cairo University, Giza 12211, Egypt amradlya@intouch.com Ahmed F. Zobaa* Department of Electrical Power and Machines, Faculty of Engineering, Cairo University, Giza 12613, Egypt a.zobaa@eng.cu.edu.eg *Corresponding author Greg J. Nolan PSEG Power, LLC, 80 Park Plaza, Newark, NJ , USA Gregory.Nolan@pseg.com Abstract: Hybrid Electric Vehicles (HEVs) have attracted tremendous attention as a commercially viable alternative to either traditional vehicles or electric vehicles. Successful HEV design requires optimal sizing of its key mechanical and electrical components. Recently, energy management strategies for HEV have been extensively studied. In addition, for a HEV to be as efficient as possible, proper management of its energy elements is required. Several research studies have been focused on the optimal sizing of HEV components. In this case, a fixed control strategy is employed. On the other hand, there are a number of studies on the optimisation of HEV power management strategy to find the optimal control parameters. In this case, the component sizes are fixed. This paper presents an overview on HEVs including trends, features and recent research efforts in this field. Keywords: Hybrid Electric Vehicle (HEV); vehicle modelling; hybrid dynamical system; series hybrid vehicles; optimisation; energy management. Reference to this paper should be made as follows: Adly, A.A., Zobaa, A.F. and Nolan, G.J. (2006) Trends, features and recent research efforts in the field of hybrid electric vehicles, Int. J. Alternative Propulsion, Vol. 1, No. 1, pp.1 5. Copyright 2006 Inderscience Enterprises Ltd.

2 2 A.A. Adly, A.F. Zobaa and G.J. Nolan Biographical notes: Amr A. Adly received a BS and an MS degree in Electrical Engineering from Cairo University, Egypt, in 1984 and 1987, respectively, and a PhD in Electrical Engineering from the University of Maryland, College Park, Maryland, USA, in Since 1994, he has been working as a Faculty Member in the Electrical Power and Machines Department, Faculty of Engineering, Cairo University, and was promoted to a Full Professor in the same department in He also worked in the USA as a Visiting Professor at the University of Maryland, and as a Senior Engineer/Scientist at LDJ Electronics, Michigan. He has authored and co-authored more than 75 papers. He holds one US Patent, is the recipient of several national and regional awards and has been a Senior IEEE Member since Currently, he is a member of the IEEE Magnetics Society Technical Committee. His research interests include electromagnetics, electrical machines, magnetic recording, magneto-hydrodynamics and superconductivity. Ahmed F. Zobaa received a BSc (Hons), an MSc and a PhD in Electrical Power and Machines from the Faculty of Engineering at Cairo University, Giza, Egypt, in 1992, 1997 and Currently, he is an Assistant Professor in the Department of Electrical Power and Machines in the same faculty. His areas of research include harmonics, compensation of reactive power, power quality, photovoltaics, wind energy, education and distance learning. He is an Editorial Board member, Editor or Associate Editor of a dozen international journals. He is a member of the IEEE Power Engineering, Industry Applications, Industrial Electronics and Power Electronics Societies, the Institution of Electrical Engineers, the International Association of Science and Technology for Development and the International Solar Energy Society. Greg J. Nolan has 30 years of experience in the engineering and design of numerous generating station, substation, industrial and infrastructure projects. For the majority of these projects, he was incharge of all engineering activities. He holds a BS in Electrical Engineering from the Pennsylvania State University and an MBA from Temple University. He is a senior member of IEEE, former Chair of the IEEE IAS/I&CPS Energy Systems Committee, and currently the Vice Chair Technical of the IEEE IAS/I&CPS Department. He is a Registered Professional Engineer in six US states and a certified Project Management Professional (PMP) in the Project Management Institute. Currently, with PSEG Power LLC, he is the project engineering manager for a new, 750 MW, combined-cycle generating station near Albany, NY. 1 Introduction It is well known that electric motors have a higher efficiency than the equivalent internal combustion ones. Until the 1940s, the energy source of small vehicles propelled by electric motors was solely confined to lead-acid batteries. Owing to the fact that such vehicles had a much shorter mobility range in comparison with other widely available liquid fuel vehicles, their use was mainly limited to areas where exhaust emissions were not favourable such as on golf courses and inside factory installations. At a later stage of the 19th century, petroleum prices fell sharply. This fact, in addition to the low energy densities of electric batteries and impractical methods of classical electric drive control

3 Trends, features and recent research efforts 3 strategies, result in significant developments in electric vehicles being pushed back. In the later years of the last century a few major factors revived the interest and research efforts related to these types of vehicles. These factors are as follows: great advances in the area of power electronics which can provide very attractive and smooth means of drive control modified electric motor designs which are more suitable for such applications development of new batteries with higher energy density increasing prices of petroleum and potential long-term depletion of world reserves increasing awareness and stricter legislations related to environmental protection and pollution control. 2 Hybrid electric vehicle trends and main features A Hybrid Electric Vehicle (HEV) is simply one which uses both electrical and mechanical energy to propel it (Hermance and Sasaki (1998)). It is supposed to combine the long mobility range provided by liquid fuels and the expected high efficiency of electrical drive systems. Earlier designs assumed that HEVs would get most of their power simply from wall electric sockets. For longer trips, it was believed that an on-board generator powered by an internal combustion engine would be the best option to extend the power needed. Such a system would be expected to yield a more efficient vehicle with far fewer exhaust emissions. However, recent design approaches for HEVs have significantly changed. While automakers have been carrying out efforts to come up with design methodologies that would help reduce the emissions and maximise fuel efficiency, focus was directed towards the concept of HEVs. An important feature of HEVs is the minimised need for an on-board electrical energy storage unlike in pure electric vehicles. This results in a reduced mass as well as cost. In fact, several conceptual cars have already been commercially introduced. An example of such HEVs is the Toyota Prius which is a five-passenger car. This car demonstrated a remarkable energy-saving record to the extent that it can be driven for 850 miles on 13 gallons of gasoline at low speed as well as under intermittent stopping conditions. It was, thus, no surprise that most fuel efficient vehicles in some classes for the year 2004 model were HEVs. Some of these HEVs, as well as their miles/gallon (MPG) records are given in Table 1 (see for more details It should also be pointed out that HEVs for military purposes have also been under development for some time. Such vehicles redirect and/or fully utilise some of HEV features towards military applications (Fish and Savoie, 2001; Traci and Acebal, 1999). A typical example includes the redirection of absorbed braking energy from the traction motors towards providing the burst power for electromagnetic launching weapon systems. Basically, HEVs may be classified as either parallel or series in configuration. In a parallel HEV, the drive system may be simultaneously powered by a mechanical internal combustion engine and an electric motor. Examples for situations necessitating the

4 4 A.A. Adly, A.F. Zobaa and G.J. Nolan simultaneous drive mode include acceleration, passing and hill climbing. The internal combustion engine in such HEV also serves to charge the on-board battery unit that powers the electric motor. On the other hand, in a series HEV, the drive system is solely powered by the electric motor that draws its power from the on-board battery unit. Charging the battery unit is accomplished via a generator driven by the mechanical internal combustion engine. It should be mentioned that some slight variations from the aforementioned two main HEV configurations also exist. Such variations include the involvement of mechanical flywheels, ultracapacitors as well as a dual series-parallel design configuration. Table 1 Some HEVs which were cited among the most efficient vehicles in 2004 HEV IC engine size (L) Maximum MPG Honda Insight Honda Civic Hybrid Toyota Prius Chevrolet C15 Silverado Hybrid GMC C15 Sierra Hybrid Chevrolet K15 Silverado Hybrid GMC K15 Sierra Hybrid Some recent HEV research efforts Research efforts related to all aspects and components of HEVs have been on the rise in the last few decades. In fact, a considerable number of HEV-related publications have been reported in 2005 (see e.g. Chai et al., 2005; Kou et al., 2005; Wang et al., 2005a,b; Zheng et al., 2005). Though not exhaustive, a representative sample of such research efforts is included in this special issue. In his paper, Schulz discusses the determination of set values for the real-time control of power-split HEVs as well as their different operating modes and drivetrain losses. He stresses the fact that the model of the drivetrain losses involved in the modelling strongly influences the fuel consumption of the vehicle. Wiegers et al. describe in their paper, the development of a computer model to modelling the performance of ultracapacitor arrays as battery replacements in HEVs. Computation results of their model were compared to data obtained from the University of Idaho s ultracapacitor hybrid Future Truck. They demonstrated that their model was capable of accurately predicting the fuel economy. They also demonstrated that ultracapacitors were a viable replacement to battery packs. Zhu et al. present in their paper, an innovative method to analyse and design an optimal energy management strategy for a power-split power train HEV. They introduced a hybrid dynamical system theory to formulate the problem of HEV control system design that incorporates both continuous and discrete dynamics. Their simulation results illustrated the applicability of the proposed design method. Montazeri-Gh and Poursamad describe in their paper, the methodological approach for the simultaneous optimisation of HEV is component sizing and control strategy using genetic algorithm. According to their methodology, the whole set of sizing and control

5 Trends, features and recent research efforts 5 variables are encoded as chromosomes and the multiobjective target is defined to minimise the fuel consumption and emissions. Their simulation results demonstrated the effectiveness of their approach in reducing the fuel consumption. He and Yang present in their paper a real-time implementable optimisation-based energy management strategy for a series HEV. They discussed a novel semi-global optimisation formulation to minimise the vehicle fuel consumption. Their simulation results validated their proposed strategy and showed that it could result in an improvement in the vehicle fuel economy. In the paper by Fredriksson an additional degree of freedom is introduced by electrifying the propulsion system of a vehicle to improve the driveability. In this configuration, the electric motor was obviously used to assist the internal combustion engine during transients. He discusses in his paper driveline modelling, control design and verifications by simulations. His simulations suggest an improvement in driveability as well as a reduction in emissions. Koot et al. investigate in their paper the fuel reduction that is possible by applying energy management to the vehicular electric powernet. They consider two strategies: a regenerative braking strategy and a more advanced strategy based on optimisation techniques. Their studies suggested for obtaining a higher fuel reduction, an alternator is required with a maximum power that is much larger than the average requested electric load. As previously mentioned, all of the aforementioned papers reflect some of the hot research issues related to HEVs. It is hoped that this special issue would be useful and educative to potential readers and other researchers involved in this topic. References Chai, F., Cui, S. and Cheng, S. (2005) Performance analysis of double-stator starter generator for the hybrid electric vehicle, IEEE Transaction on Magnetics, Vol. 41, No. 1, pp Fish, S. and Savoie, T. (2001) Simulation-based optimal sizing of hybrid electric vehicle components for specific combat missions, IEEE Transaction on Magnetics, Vol. 37, No. 1, pp Hermance, D. and Sasaki, S. (1998) Hybrid electric vehicles take to the streets, IEEE Spectrum, November, pp Kou, B., Li, L., Cheng, S. and Meng, F. (2005) Operating control of efficiently generating induction motor for driving hybrid electric vehicle, IEEE Transaction on Magnetics, Vol. 41, No. 1, pp Traci, R.M. and Acebal, R. (1999) Integrated thermal management of a hybrid electric vehicle, IEEE Transaction on Magnetics, Vol. 35, No. 1, pp Wang, S., Zhan, Q., Ma, Z. and Zhou, L. (2005a) Implementation of a 50-kW four-phase switched reluctance motor drive system for hybrid electric vehicle, IEEE Transaction on Magnetics, Vol. 41, No. 1, pp Wang, T., Zheng, P., Zhang, Q. and Cheng, S. (2005b) Design characteristics of the induction motor used for hybrid electric vehicle, IEEE Transaction on Magnetics, Vol. 41, No. 1, pp Zheng, P., Liu, Y., Wang, Y. and Cheng, S. (2005) Magnetization analysis of the brushless DC motor used for hybrid electric vehicle, IEEE Transaction on Magnetics, Vol. 41, No. 1, pp