International Journal of Electric and Hybrid Vehicles (17 papers in press)
State estimation method for power lithium-ion battery based on dynamic equilibrium voltage
by Qiuting Wang, Wei Qi, Duo Xiao
Abstract: The state parameters of power lithium-ion battery include the State of Charge (SOC), the State of Health (SOH) and the State of Power (SOP). These three parameters are used to indicate the current remaining mileage, the maximum endurance mileage, and the acceleration performance, respectively. The dynamic equilibrium voltage (DEV) based on electrical characteristics is studied in this paper. The online state estimation problems for battery cells under dynamic working conditions is discussed in depth. We chose the DEV value as the characteristic parameter to estimate the SOC and SOH values online. The main results of our researches are (1) the mathematical model of power lithium-ion battery is established based on the dynamic behaviour;(2) the state space equations are derived to describe the model parameters and the working performance; (3) the SOC and SOH values are estimated accurately, according to only the DEV curve results under all-new state. Our experiments were processed under different temperatures and different ageing degrees to investigate the new model and new estimation method.
Keywords: lithium-ion battery; dynamic equilibrium voltage; SOC; SOH; SOP; online estimation.
Power factor correction and load demand peak shaving in residential town using electric vehicle fleet in smart parking
by Chia Lailypour, Dariush Nazarpour
Abstract: This paper presents an algorithm for compensating the active and reactive power simultaneously in a real residential distribution household system using the amount of energy saved in plug-in hybrid electric vehicles (PHEVs) or in electric vehicles (EVs) parked in smart parking. The system and vehicle's specifications are discussed in separate sections. Moreover, the effects of the algorithm on active power peak shaving, reactive power compensation, and power factor correction are discussed as well. The economic effect of the algorithm on costumer energy payment bills in Iran's distribution market is depicted in section VІ. Reactive power compensation leads to correction of the power factor and power loss reduction. The main reason for connecting vehicles to the grid is to charge them in their departure time to the desired state of charge (SOC). This algorithm guarantees that all vehicles will reach their desired state of charge at least a half-hour before departure. Finally, the positive effect of algorithm on all items is demonstrated.
Keywords: charging vehicles; distributed systems; electric vehicle; plug-in hybrid electric vehicle; peak shaving; power factor correction; residential grids; smart grid; smart building; smart home; smart parking.
Smart accelerating and braking achieving higher energy efficiencies in electric vehicles
by Guido Wäger, Jonathan Whale, Thomas Bräunl
Abstract: To maximise the use of the relatively small energy storage in mainstream electric vehicles (EV), an efficient operation is critical. Regardless of the traction power or energy regeneration capabilities (recuperation), each EV motor controller operates more efficiently under certain motor rotational speeds (rpm) and loads than others. Unlike internal combustion engine (ICE) cars or hybrid cars, EVs do not have variable gearboxes that allows the rpm to be adapted to adjust the engine speed towards more efficient regions. However, the driver can actively influence the load by changing acceleration or deceleration rates. This can lead to a more efficient operation of the EV's motor and controller. Although EV efficiency tests, modelling, and multi gearbox efficiency tests have been conducted, many of these studies focused on following a speed profile with relatively small changes in acceleration and deceleration rates. This study exposes an EV to a series of high load variations in acceleration and deceleration, in order to investigate the impact on energy consumption. The results show significant improvements in efficiency and a reduction in energy consumption by applying high loads at low vehicle speeds. However, the study also found increased losses under certain high acceleration rates, which outweighed the benefits of loading an EV so that its engine speed is in its most efficient region.
Keywords: electric vehicle efficiency; motor controller efficiency; smart acceleration.
Research status of structure optimisation design for in-wheel motor-driven system
by Di Tan, Haitao Wang, Fan Song, Lidong Miao
Abstract: As one of the key technologies of the next generation 'pure electric drive' electric vehicle, the in-wheel motor-driven electric vehicle has been paid great attention by the auto industry, because of its obvious technical advantages in the overall arrangement of the vehicle, the chassis active control and the convenience of control. Domestic and international automobile group companies, scientific research institutes and automobile components suppliers have invested considerable research and development efforts on these vehicles. The in-wheel motor-driven system integrates the motor, the speed reducer, the brake and so on into a narrow space and its integrated structure and performance directly affect the driving/braking performance of the driving wheels and the driving performance of the vehicle. Therefore, as one of the core technologies of these vehicles, the optimisation design of the integrated structure has always been a difficult and hot spot in the research institutes. In this paper, the development status of the optimisation design technology for the integrated structure of the in-wheel motor driven system at home and abroad is analysed and summarised, and on the basis of this, the future research directions are discussed.
Keywords: in-wheel motor-driven system; optimisation design; electromagnetic design; thermal design; lightweight design.
Modelling and control of a bidirectional single-phase single-stage converter for plug-in electric vehicles
by Reza Sabzehgar, Yaser M. Roshan
Abstract: In this paper, the modelling and control of a bidirectional single-phase single-stage converter for plug-in electric vehicles is presented. A nonlinear sliding mode controller with boundary layer solution and a redefined sliding manifold are proposed to enforce a pseudo-resistive relation between the input voltage and current. Based on the pseudo-resistive relationship obtained between the input voltage and current, the sliding mode control approach is used to regulate the input resistance of the converter to a desired value, hence allowing charging and discharging of PEVs. Numerical simulation results are presented that evaluate performance of the proposed modelling and feedback control scheme.
Keywords: plug-in electric vehicle; vehicle-to-grid; grid-to-vehicle; bidirectional charger; power electronics converter; modelling and control; sliding mode control; sliding manifold redefinition; chattering compensation.
Electrical vehicle bearings: technological impact, applications and requirements
by Maruti Khaire
Abstract: The automotive industry is going through a major technological shift from internal combustion engines to Electric Vehicles (EV). The EV technologies are governed mainly from cleaner energy and environmental concerns besides falling fossil fuel reserves. This major technological shift is having a long-term and significant impact on the bearings industry. Bearing usage per vehicle is expected to come down with electrification of bearings. This paper discusses the impact of vehicle electrification on the bearings industry and the technological requirements for successful development of EV bearings. Enhanced bearing life, reliability improvement, power dense bearings, smart bearings capable of sensor implementation, optimised friction, NVH characteristics, special attention to lubricants and sealing are some of the key technical requirements for EV vehicle bearings. Surface engineering and application of specialty coatings have the potential to increase bearing application coverage and optimised cost of bearing for EVs. EV bearings are going to add new bearing damages, such as electrical pitting and lubricant burning. Electrical pitting and lubricant burning are going to generate internal contamination in the bearings, which may reduce the life of bearings. It is imperative for bearing engineers to build a deeper understanding of the new technological requirements for EV bearings to fulfill the new market requirements.
Keywords: electrical vehicle bearings; reliability improved bearing; power dense bearing; smart bearing; friction optimisation in bearing.
Modelling of inductive resonant transfer for electric vehicles.
by Luca Pugi, Alberto Reatti, Rosa Anna Mastromauro, Fabio Corti
Abstract: Wireless recharge of electric vehicles is an important field of research deeply connected to the diffusion of electric vehicles. In particular, the design of induction power transfer systems involves the development of resonant power circuits electromagnetically coupled through inductive coils. In this work, by means of the tools used for the modal analysis of the vibrating systems, we propose an innovative approach for modelling and design based on an innovative bond-graph physical similitude. In particular, the proposed approach is applied to the study of an inductive power transfer system with series-series compensation. With respect to the proposed case study, we have been able to verify how methods that are usually adopted to perform modal analysis of mechanical systems should be also used for an optimal design of the system. In particular, one of the main advantages of the proposed approach is the possibility of an intuitive physical interpretation of system behaviour as an equivalent mechanical one. Another contribution of the work is represented by the definition of a new dimensionless parameter, briefly called weighted modal damping, that is quite useful to optimise an applied load respect to efficiency issues. The accuracy of the proposed methodology is verified on a couple of numerical test cases: the first one refers to experimental activities performed by the authors, and the second one is taken from the literature. Further verifications are also performed using finite element methods of the modelled systems. All the performed experimental activities and numerical simulations substantially converge to the same conclusions, confirming the validity and feasibility of the proposed approach.
Keywords: inductive power transfer; bond-graph approach; optimisation of vibrating systems.
Mathematical modelling of energy harvesting in piezo embedded electric vehicle tyres together with self-health assessment of suspension system
by Raziq Yaqub, Kaveh Heidary
Abstract: This paper proposes embedding piezoelectric material inside the Electric Vehicle (EV) tyres in order to harvest otherwise wasted energy and monitor the health of the tyres and suspension system. The discussion will focus on two aspects of the proposed system. One pertains to the mathematical modelling of energy harvesting through piezoelectric energy conversion process inside the tyre, and the other with collecting and processing the mechanical stress data obtained from the embedded piezoelectric material. The energy generated from the piezoelectric material, which entails conversion of mechanical strain of the embedded piezoelectric material to electrical energy, is utilised to charge the battery and extend the driving range of the EV. Concurrently, the material stress-strain data generated by and collected from the piezoelectric material is used to extract valuable real-time information that may be used for condition-based maintenance pertaining to the tyres' remaining useful life, uneven or excessive tyre wear, the need for wheel balancing, assessment of the suspension system health condition, and an alert for vehicle maintenance, such as wheel alignment. Thus the proposed system will not only reduce the driving range anxiety, it will also enhance vehicle health and safety and lead to concomitant savings.
Keywords: Energy harvesting; Piezoelectricity; Electric Vehicles; Mechanical stress-to-electricity conversion; automobile tyres and suspension system; data acquisition and display.
Analysis and research of in-wheel motor temperature field for electric vehicles
by Jiwen Ren, Juanlin Huang, Qiping Chen, Qiang Xiao, Sheng Kang
Abstract: Electric vehicles with in-wheel driving motors have broad market prospects. The in-wheel motor is regarded as the key component of electric vehicles, it has important theoretical and engineering application value to analyse and research. This paper describes the current situation and existing problems of the in-wheel motor, analyses the mechanisms of iron loss, copper loss, and mechanical loss, and studies four types of motor temperature field analysis method, including the equivalent heat road method, the equivalent thermal network, the finite element method, and the coupling method of temperature field and fluid field. By comparing the methods of gas cooling and liquid cooling, the research progress of in-wheel motor cooling is analysed, and the development trend of in-wheel motor cooling technologies is discussed.
Keywords: electric vehicles; in-wheel motor; temperature field; cooling; motor loss.
Optimisation of control strategy of a range-extended electric bus
by Yunfei Zha, Jinlong Song, Qingyong Zhang, Guoqing Liu, Ronghui Guo
Abstract: The aim of the present study was to optimise the cycle fuel consumption and energy consumption of a range-extended electric bus. The optimal variables included the final drive ratio of the main decelerator, the upper and lower limits of the power unit, and the speed threshold. NSGA-II was used as the optimisation algorithm. The optimisation results showed that the overall economy behaviour of the bus was improved, while climbing performance increased by 43.77%. The stability of dynamic performances was acceptable because only slight fluctuations were found in the maximum speed and the acceleration duration from 0 to 50 km/h. Although the power consumption increased by 0.6%, the per 100 km fuel consumption decreased by 32.98%. The results showed that the optimisation strategies, optimisation objectives and optimisation variables applied were reasonable and effective.
Keywords: range-extended vehicle; control strategy; CRUISE simulation; optimisation.
Torque coordination control strategy in engine starting process for a single motor hybrid electric vehicle
by Yupei Lin, Datong Qin, Minghui Hu, Guochang Jiang
Abstract: To troubleshoot the oversized output torque ripple during engine starting process of a parallel hybrid electric vehicle (HEV), the engine starting process is divided into cranking phase, speed synchronisation phase and after-ignition phase. In this paper, the expressions of the vehicle jerk are derived from the vehicle dynamic formula in each phase, and the influences of various parameters on the jerk are analysed. The coordinated control strategy between the clutch pressure and motor torque, and that between the motor torque and engine torque are proposed. The simulation for the single shaft HEV model is carried out through Matlab/Simulink, by which rationality of the control algorithms was checked. Finally, a bench test is implemented whose results prove the determined change rate of clutch pressure, motor torque, and engine torque can effectively coordinated to meet the need of vehicle ride performance in engine starting in-motion process.
Keywords: engine starting process; torque coordination control; hybrid electric vehicle.
Study on the influence of sorting parameters on lithium-ion battery pack life-cycles Based on cell consistency
by Qiuting Wang
Abstract: Lithium-ion batteries have been applied as the most extensive and stable power sources in electric vehicles (EVs). The variation of cell parameters is a critical factor to the safety, energy density, life and stability of the battery pack. The main efforts of our studies are, firstly, the current distribution of two parallel cells is obtained based on the equivalent circuit method (ECM) in actual operation condition; the distribution model was verified and can be used in serial, parallel and mixed constructions. Secondly, the self-discharge rate is certificated as an important parameter to affect cell-consistency in the ageing process. The rate value was deduced based on the solid electrolyte interface (SEI) membrane growth model. Thirdly, a reliable theoretical basis for optimising the cell sorting method is provided. Lastly, the ageing tests using 18 cells in parallel construction were conducted. The experimental results indicate that our new sorting method and sorting parameters can improve the cell consistency performance in the ageing process.
Keywords: lithium-ion battery; sorting parameters; current distribution; cell consistency; equivalent circuit method; solid electrolyte interface.
Improvement of economic and ecological characteristics of a car with a start-stop system
by Vladimir Dvadnenko, Shchasiana Arhun, Aleksandr Bogajevskiy, Svitlana Ponikarovska
Abstract: The work analyses the existing start-stop systems. Most of them have the following drawbacks: low efficiency, increased load on the battery, starter and engine, noise, jerks and vibrations at the start, the start delay time, etc. The proposed improvements to the start-stop system allow increasing its efficiency. The main feature is a second generator, and, thanks to it, the increased time and power of recuperative braking; besides, the engine can be stopped in a vehicle that is running by inertia or downward. At a certain speed of the car the engine is started without a starter, and the energy of recuperative braking is used for electrical heating of the coolant. The paper presents a kinematic diagram of the transmission of a car with an improved start-stop system. A poly-V-belt drive has been chosen as a drive of the second generator. Experimental studies of the engine start in various modes have been carried out, and graphs of the dependence of the vehicle speed on the time are presented.
Keywords: energy recuperation; environmental safety; hybrid car; start-stop system.
Second-hand electrical vehicles: a first look at the secondary market of modern EVs
by Gabriel Pedrosa, Helena Nobre
Abstract: The first mass-produced electrical vehicles (EVs) reached the ten years mark and their future remains uncertain. Both practitioners and researchers have devoted much attention to the marketing of new EVs. However, the secondary market remains unapproached. In the automotive sector, this market can be as much as three times the size of the new car market. Yet, it remains unknown how EVs will be received. This study takes the first step to understanding the reception of second-hand EVs by addressing this research gap through a qualitative design based on 17 in-depth interviews with drivers of conventional fuel vehicles. Based on the analysis of the drivers attitudes towards second-hand EVs, willingness to pay, and the role of battery condition and warranty options, the paper proposes some recommendations for the practice and future research venues on the secondary market of EVs.
Keywords: electric vehicle; secondary market; second hand EV; battery; warranty.
Development and analysis of series/series resonant wireless system for electric two-wheeler battery charging
by Panugothu Srinivasa Rao Nayak, Kishan Dharavath
Abstract: In recent years Wireless Power Transfer (WPT) for electric vehicle battery charging is a developing technology. It allows electric power transfer without any physical connection between a transmitter and a receiver over a certain distance. However, to improve the power transfer capability over a longer distance, the coupled coils must be compensated with an appropriate capacitor. This paper deals with implementation and analysis of series/series resonant wireless battery charging system for electric two-wheeler at resident parking garages or at public parking places. The charging profiles such as charging current and time with various misalignment conditions of the coupled coils are presented and also the efficiency of the system is analysed. The experimental result conveys the appropriateness of the proposed design can be implemented for real-time heavy-duty vehicles.
Keywords: wireless power transfer; series/series compensation; Buck converter; mutual inductance.
Parameter design and characteristic analysis of the interior non-uniform air-gap permanent magnet synchronous motor for electric vehicles
by Ma Shilun, Zhang Xueyi, Du Qinjun, Geng Huihui
Abstract: Aiming at the demand for high torque and wide speed range of permanent magnet synchronous motor (PMSM) used in electric vehicles, a PMSM with fractional slot concentrated winding and the rotor of non-uniform airgap is designed. Fourier harmonic analysis theorem is used to calculate the harmonic content and peak value of cogging torque of different rotor eccentricities. Combined with finite element simulation software, the influence of rotor of uniform airgap and the rotor of non-uniform airgap on the q axis and d axis magnetic circuit is analysed, so the optimal rotor eccentricity is determined. Compared with the rotor of uniform airgap, the peak value of cogging torque and the waveform distortion rate is reduced, while the salient rate is increased. Performance tests are done and results show that reasonable rotor eccentricity can effectively improve the motor of flux weakening
Keywords: permanent magnet synchronous motor; non-uniform air gap; harmonic; salient ratio; flux-weakening expansion rate.
Using the health benefits of electric vehicles to justify charging infrastructure incentives.
by Mitchell House, David Wright
Abstract: Health benefits from switching from internal combustion vehicles to electric vehicles (EVs) include reduction of healthcare costs from treating cardiopulmonary illness, less sick leave taken from work, and quality and length of life improvements. This paper compares the financial value of those benefits with the cost of building an EV charging infrastructure. When the number of charging stations increases with the number of EVs the net benefit is positive, unless the cost of all charging stations is at the high end of the empirical range or when the number of charging stations per EV is higher than in Norway. In scenarios with a rapid build-out of charging stations over 2-4 years, there is a net cost during the build-out period and net benefits from 2021 onwards. These results justify the use of government incentives for charging station deployment and this paper quantifies the impact of different levels of incentive.
Keywords: electric vehicles; charging infrastructure; health benefits; government policy; risk analysis.