Sizing and Energy Management of a Hybrid Locomotive Based on Flywheel and Accumulators

The French National Railways Company (SNCF) is interested in the design of a hybrid locomotive based on various storage devices (accumulator, flywheel, and ultracapacitor) and fed by a diesel generator. This paper particularly deals with the integration of a flywheel device as a storage element with a reduced-power diesel generator and accumulators on the hybrid locomotive. First, a power flow model of energy-storage elements (flywheel and accumulator) is developed to achieve the design of the whole traction system. Then, two energy-management strategies based on a frequency approach are proposed. The first strategy led us to a bad exploitation of the flywheel, whereas the second strategy provides an optimal sizing of the storage device. Finally, a comparative study of the proposed structure with a flywheel and the existing structure of the locomotive (diesel generator, accumulators, and ultracapacitors) is presented

Opportunities and challenges of power electronics systems in future railway electrification

With the continuous expansion of the railway power systems, the integration of high speed locomotives and the need to increase the overhead catenary line power capacity, the main shortcomings of the conventional railway feeding system are becoming more evident. In order to overcome these drawbacks and to contribute to the technological evolution with innovative and electrically more efficient systems, several solutions have been proposed and implemented. In this context, this paper briefly presents a study of different railway power systems, highlighting emerging concepts, such as regenerative braking, energy storage systems, the inclusion of renewable energy sources, bidirectional power flow and wireless power transfer. Some of these concepts can be implemented in short to medium term, or in the long term. Following these concepts, an overview of the power electronics challenges for the implementation of these emerging concepts is presented and discussed.This work has been supported by FCT –Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project QUALITY4POWER PTDC/EEI-EEE/28813/2017. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT foundation. Mr. Mohamed Tanta was supported by FCT PhD grant with a reference PD/BD/127815/2016

Urban and extra-urban hybrid vehicles: a technological review

Pollution derived from transportation systems is a worldwide, timelier issue than ever. The abatement actions of harmful substances in the air are on the agenda and they are necessary today to safeguard our welfare and that of the planet. Environmental pollution in large cities is approximately 20% due to the transportation system. In addition, private traffic contributes greatly to city pollution. Further, “vehicle operating life” is most often exceeded and vehicle emissions do not comply with European antipollution standards. It becomes mandatory to find a solution that respects the environment and, realize an appropriate transportation service to the customers. New technologies related to hybrid –electric engines are making great strides in reducing emissions, and the funds allocated by public authorities should be addressed. In addition, the use (implementation) of new technologies is also convenient from an economic point of view. In fact, by implementing the use of hybrid vehicles, fuel consumption can be reduced. The different hybrid configurations presented refer to such a series architecture, developed by the researchers and Research and Development groups. Regarding energy flows, different strategy logic or vehicle management units have been illustrated. Various configurations and vehicles were studied by simulating different driving cycles, both European approval and homologation and customer ones (typically municipal and university). The simulations have provided guidance on the optimal proposed configuration and information on the component to be used

Повышение тяговых характеристик тепловоза с гибридной энергетической установкой

The expediency of using a hybrid power system with the use of traction batteries on a diesel locomotive is substantiated since the relevance of the problem being solved lies in the possibility of increasing the weight norm of the train without reducing the performance of the main power equipment of the diesel locomotive, which is of great importance for improving the efficiency of railways.To predict the effectiveness of introduction of autonomous locomotives with a combined power source, traction properties of a diesel locomotive equipped with a set of traction batteries are estimated by mathematical modelling. The basis of the method is a dynamic model of train movement, in which the locomotive is represented as an electromechanical system with a direct current electric drive, where a diesel power generator and a lithium-ion battery are used as the primary energy source. It is shown that the use of a hybrid power source with a storage device with capacity of 1300 ampere-hours on a diesel locomotive makes it possible to increase the weight rate of a train by 18 % when moving along a typical profile. Particular attention is paid to the requirements for operation of traction electric machines to prevent their premature failure. It was found that during movement of a locomotive with a hybrid power plant with a train of the calculated weight and under normal environmental conditions (20°C and normal barometric pressure), an increase in the load current of traction motors does not lead to overheating of their windings at the calculated upward slope.The model suggested is universal and allows calculating the efficiency of a diesel locomotive with a hybrid power plant under any driving conditions.Обоснована целесообразность применения на тепловозе гибридной энергетической системы с использованием тяговых аккумуляторов. Актуальность решаемой задачи заключается в возможности увеличения весовой нормы поезда без снижения ресурса основного энергетического оборудования тепловоза, что имеет большое значение для повышения эффективности работы железных дорог.С целью прогнозирования эффективности внедрения на железных дорогах автономных локомотивов с комбинированным источником энергии методом математического моделирования определены тяговые свойства тепловоза, оборудованного батареей тяговых аккумуляторов. Основой метода является динамическая модель движения поезда, в которой локомотив представлен электромеханической системой с электроприводом постоянного тока, где в качестве первичного источника энергии используется дизельгенераторная установка и литий-ионная аккумуляторная батарея. Показано, что применение на тепловозе гибридного источника энергии с накопителем ёмкостью 1300 амперчас позволяет на 18 % повысить весовую норму поезда при движении по типовому профилю. Особое внимание уделяется требованиям к эксплуатации тяговых электрических машин для исключения их преждевременного отказа. Установлено, что при движении локомотива с гибридной энергетической установкой с составом расчётного веса и при нормальных условиях увеличение тока нагрузки тяговых электродвигателей не приводит к перегреву их обмоток на расчётном подъёме.Приведённая модель является универсальной и позволяет рассчитать эффективность работы тепловоза с гибридной энергетической установкой при любых условиях движения

Prolongation of Battery Lifetime for Electric Buses through Flywheel Integration

Electrification of transportation is an effective way to tackle climate change. Public transportation, such as electric buses, operate on predetermined routes and offer quiet operation, zero local emissions and high energy efficiency. However, the batteries of these buses are expensive and wear out in use. The battery ageing is expedited by fast charging and power spikes during operation. The contribution of this paper is the reduction of the power spikes and thus a prolonged battery lifetime. A novel hybrid energy storage system for electric buses is proposed by introducing a flywheel in addition to the existing battery. A simulation model of the hybrid energy storage system is presented, including a battery ageing model to measure the battery lifetime. The bus was simulated during its daily driving operation on different routes with different energy management strategies and flywheel configurations. These different flywheels as well as the driving cycle had a significant impact on the battery life increase. The proposed hybrid battery/flywheel storage system resulted in a battery lifetime increase of 20% on average

An innovative control strategy for a hybrid energy storage system (HESS)

© 2017 IEEE. Electric Vehicles (EVs) adopting both batteries and supercapacitors have attracted a significant amount of attention in research communities due to its unique power sharing capabilities. A Hybrid Energy Storage System (HESS) can effectively reduce power stress that would otherwise be applied to batteries alone, and whose weight and size is still a common concern when competing against conventional ICE-powered cars. In this paper, a high-level control strategy is developed to adaptively split the load between two sources for an electric vehicle adopting HESS under real-life load fluctuations. A converter - Supercapacitor Pack (SP) coupled HESS upon which such an algorithm is deployed on, is proposed to divert excess power into the SP via a smart Power Converter (PC) which is located in between in order to regulate both behaviors. Such a power split strategy (PSS) is designed in such a way to track real-time load profiles and determines one important variable - the cut-off frequency. A simplified HESS model is first developed. The power split algorithm is coded in Matlab and then applied to this HESS model. Finally, the overall system is tested comprehensively over 4 EPA driving cycles. Simulation results prove its effectiveness in coping with even the harshest driving scenarios in real life

A Novel Flywheel and Operation Approach for Energy Recovery and Storage

Flywheel has intrinsic advantages over other energy storage forms such as hydraulic storage, batteries and compressed airs. These advantages include higher robustness, longer life cycle, great energy density, higher efficiency, lower loss, better discharge depth and relatively easier recycling, etc. In this dissertation a novel shaftless flywheel was developed. The most important feature of our novel design is the integration of the motor generator and the magnetic suspension into the flywheel disk, which removes the need for a support shaft and enables our solid disk design. This design was shown to have big advantages than traditional designs using annular discs press-fitted on shafts. This was illustrated by a comparison between annular and solid 4340 discs in stress levels, SN lives and fatigue lives with cracks. Due to the scale of the system, our rotating speed is relatively lower than traditional designs. This makes possible the usage of unlaminated magnetic bearings to reduce the system cost at partial expense of the system performance. A 4340 steel sample was tested to retrieve its magnetic behavior. The novel magnetic levitation was then designed using ANSYS static analysis based on the measured data. The position stiffness and current stiffness were retrieved with the analysis. The eddy losses of the magnetic bearings were retrieved through FEM motor software CARMENTM by Vector FieldTM. The total bearing loss was calculated based on the simulated eddy loss and measured hysteresis loss on 4340. The system equilibrium temperature was simulated with ANSYSTM. The Frequency weakening effect of the magnetic bearing was analyzed with ANSYSTM harmonic analysis. The closed-loop control stability of the system was investigated based on the results. A motor design concept was proposed with the variable motor/generator gain capability. This capability was a key feature in optimizing the charge/discharge performances of the flywheel in both grid level and hybrid locomotive applications. Based on EPA average data, the benefits of our hybrid locomotives on fuel and NOx savings were simulated on various train operations. The optimization for regenerative braking was also discussed. The dissertation concludes with the discussion of the flywheel system isolation from train operation induced vibrations

Technical and economic feasibility of a regenerative braking system with on-board energy storage for freight trains

This dissertation presents the technical and economic feasibility of a novel regenerative braking system (RBS) for the freight rail industry. A concept for a distributed RBS, integrated into the bogies of freight rail wagons, is proposed in a patent by Transnet SOC Ltd. The system allows for numerous RBSs to be installed on a single freight train, in a distributed manner, which collectively functions together to perform regenerative braking on the train with the goal of reducing the energy consumption of the train. The proposed system would, if implemented successfully, alleviate challenges and limitations with current RBS on diesel-powered freight trains. The patent also proposes that the RBS utilise mechanical energy storage by means of a high-speed flywheel which is connected to the train axles by a continuously variable transmission (CVT). The proposed RBS is conceptualised in this study by first establishing the requirements of the system from in-service train data, followed by the development of the subsystems to deliver workable concepts that would meet the requirements identified. A multi-domain, physical system simulation model is subsequently developed to establish the energy savings performance of each of the system concepts for typical freight train routes. The simulation results show that energy savings of between 10% and 24% can be realised by the feasible system concepts, depending on the configuration of the RBS concept and the duty-cycle of the specific train route. This proves the technical feasibility of the proposed system. Next, the proposed system and the candidate concepts are evaluated in economic terms. A cost-benefit analysis (CBA) is performed in which the cost and benefits over the life cycle of the RBS were combined into a single distribution and analysed. The decision criteria calculated in the CBA provide unanimous results as to which of the candidate concepts are economically feasible. It is shown that four of the candidate concepts, all utilising the same transmission topology incorporating a CVT with different flywheel configurations, are economically feasible. The RBS concepts show good return on investment and provide an internal rate of return (IRR) of 17% and a benefit-cost ratio (BCR) of 2.13. These results therefore indicate that the proposed distributed RBS for freight trains is economically feasible and would deliver favourable financial returns if pursued.Dissertation (MEng)--University of Pretoria, 2018.Mechanical and Aeronautical EngineeringMEngUnrestricte

Energy management strategy to optimise regenerative braking in a hybrid dual-mode locomotive

This study proposes an energy management strategy (EMS) for a dual-mode hybrid locomotive equipped with a fuel cell, supercapacitors, and batteries, and intermittent access to an electrified overhead catenary. It is inspired by the Ragone plot and does not consider information or predictions of future load consumption. It aims to reduce a cost function that considers the cost of hydrogen, the electricity consumed from the network, and the energy sources' degradation. The EMS focuses on maximising the energy recovered during braking. The study introduces a methodology to tune the EMS parameters. Two study cases are used to evaluate the EMS. In the evaluation driving profile, typical for a French freight train, the braking energy is around 12.8% of the total energy. With the proposed EMS, the energy recovered is around 99.8% of the total braking energy. A second EMS not oriented to reduce the energy in the braking resistor is also evaluated. The energy recovered with this strategy is around 91.5% of the total braking energy. The global energy reduction is around 1.1% compared with the second EMS and 12.8% without energy recovering. These results show a real opportunity to increase the energy recovered during braking

Flywheel Energy Storage Systems for Rail

In current non-electrified rail systems there is a significant loss of energy during vehicle braking. The aim of this research has been to investigate the potential benefits of introducing onboard regenerative braking systems to rail vehicles. An overview of energy saving measures proposed within the rail industry is presented along with a review of different energy storage devices and systems developed for both rail and automotive applications. Advanced flywheels have been identified as a candidate energy storage device for rail applications, combining high specific power and energy. In order to assess the potential benefits of energy storage systems in rail vehicles, a computational model of a conventional regional diesel train has been developed. This has been used to define a base level of vehicle performance, and to investigate the effects of energy efficient control strategies focussing on the application of coasting prior to braking. The impact of these measures on both the requirements of an energy storage system and the potential benefits of a hybrid train have been assessed. A detailed study of a range of existing and novel mechanical flywheel transmissions has been performed. The interaction between the flywheel, transmission and vehicle is investigated using a novel application-independent analysis method which has been developed to characterise and compare the performance of different systems. The results of this analysis produce general ‘design tools’ for each flywheel transmission configuration, allowing appropriate system configurations and parameters to be identified for a particular application. More detailed computational models of the best performing systems have been developed and integrated with the conventional regional diesel train model. The performance of proposed flywheel hybrid regional trains has been assessed using realistic component losses and journey profiles, and the fuel saving relative to a conventional train quantified for a range of energy storage capacities and power-train control strategies