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Quasi-static simulation method for evaluation of energy consumption in hybrid light rail vehicles
Abstract
The presented article will describe an 'effect-cause' model for the purpose of simulating the energy consumption of DC fed light rail vehicles. The model will assess the advantages of hybrid vehicles in terms of energy consumption, network power and voltage variations, line current and losses; and will help sizing and designing a supercapacitor based energy storage system (ESS) for both on-board, and stationary applications. The proposed modeling needs to allow the ESS sizing according to the objective that needs to be achieved, being braking energy recovery, voltage drop compensation and peak power shaving the most common goals of ESS use in hybrid vehicles. The needed power and energy levels will vary in function of the vehicle features and the driving cycle followed. This all can be determined by the quasi-static simulation tool to ease the design process. Another objective of the modeling tool is to evaluate the behaviour of the vehicle power flow controller, which manages the power from/to the ESS in function of the state of several variables.
... We solve the siting and sizing problem using a particle swarm optimisation (PSO) based algorithm and the obtained results are compared and discussed. The metro network model is implemented in a simulation routine based on the 'quasi static' backwards looking method, described in [15], [16]. The proposed design solution allow to maximize energy efficiency, to minimize the number and capacity of SCs and then, consequently, to reduce the costs. ...
... Substations are represented by ideal DC voltage sources, series resistance and series diode only if the substations are not reversible, [10]. The contact wire is modelled as a set of electric resistances that change their value according to the vehicle position [6], [15]. If x(kΔt) is the metro train position at the time kΔt, the value of the resistance upstream Ra and downstream Rb to the metro vehicle towards a generic node of the railway feeding system (electric substation, ESS or another train) are calculated by: ...
... [km] is the distance between the train and the upstream node at the each time step kΔt. Finally, the electric model of the overall network with the substations, the SC storage units, and the metro vehicle is shown in Fig. 2. Furthermore, it is necessary to improve the model with some small capacitances in parallel to the vehicles in order to describe the receptivity of the network under regenerative braking conditions [15]. They models the voltage rise along the contact wire during the first phase of the regenerative breaking that is used by the ESS control to detect the availability of breaking energy along the track. ...
In this paper, we investigate the design of stationary ESSs based on supercapacitors (SCs) for metro network (MN). We implement a simulation tool in order to estimate the power flow among the metro vehicles and the ESSs through the MN. A new formulation of the ESSs siting and sizing optimisation problem is proposed and solved using particle swarm algorithm. The optimisation process minimises the energy supplied by the electrical substations and the whole ESSs capacity taking into the electrical line constraints in the metro network simulator. Several simulations are performed in order to design the number, the position along the track and the required capacity of the SCs. Using commercially available modules, a realistic design solution is compared with the theoretical one obtained by solving the optimisation algorithm. Finally, we estimate the energy delivered from the electric substations and the energy saved using the real ESSs configuration.
... The metro vehicle is modelled by using the mass-point model, frequently used in literature, [4], [12]. The train longitudinal dynamic is described by the Newton's second law and kinematics equations: ...
... Finally, the electric model of the overall network with the substations and the metro vehicle is shown in Fig. 3. In order to describe the receptivity of the network under regenerative braking conditions, the train model is completed by adding some small capacitances in parallel to the metro vehicles, [12]. Their effect is a voltage rise when trying to feed back to the line an amount of power higher than the power consumed by other vehicles at the same instant. ...
... The energy constraints are evaluated by using a metro network simulator able to calculate the energy supplied by the electrical substation for a particular drive cycle. The metro system models presented in the previous section are implemented in a software simulator based on the 'quasi static' backwards looking method, able to estimate the energy consumption of vehicles following a given driving cycle in a short simulation time [4], [6], [12]. Fig. 4 shows the block diagram of the proposed validation algorithm: for each sub track, the algorithm performs the PSO procedure. ...
In this paper, we propose a validation procedure of energy consumption patterns implemented in a steady-state railway system software simulator by using experimental measured data. The software tool is able to evaluate the energy supplied by the feeding line to move a metro vehicle implementing different speed profiles. In particular, we suggest a simply methodology aimed to calibrate the metro system models by minimizing the mean squared error (MSE) between the estimate values of the model parameters and the real ones. The optimization problem we formulated, takes into account the equality constraints between the measured energy consumption at specific instants, and that computed by the software simulator. The effectiveness of this energy validation procedure is showed on a real case study comparing the energy consumption of metro vehicle implementing eco-drive speed profiles. The encouraging results are presented and discussed.
... In Refs. [21][22][23][24], stationary ESS has been applied to save the regenerative energy in a metro network. Stationary ESS has been proposed for voltage regulation of weak points in Ref. [25]. ...
... In comparison to previous modeling methods presented in Refs. [21][22][23][24], the proposed approach presents a good physical insight into the network model. Moreover, it can be extended easily. ...
... Moreover, it can be extended easily. Unlike [21][22][23][24] which use trial and error method to find the best ESS configuration with the highest energy saving, in this paper, an effective method is proposed to calculate the maximum instantaneous regenerative energy of each station analytically. Then, appropriate ESS configuration is suggested for each station. ...
... This model allows computing all mechanical variables, from track profile and driver behavior. It should be noted that driver behavior is a difficult part of modeling procedure [6, 11]. In our case, the driver is more than a simple controller; he has also to anticipate speed limitations and stops. ...
... These results are more obvious between substations, where the differences can reach 2 points on efficiency and 20 V on DC voltages.Fig. 5. Efficiency of presented supply systems Finally, this simulation tool allows light rail designers to evaluate global performances of a given power supply topology with a reasonable computing time. Moreover, this tool allows calculation of the energetic efficiency of a structure which can be interesting for structure with embedded storage, in order to design and optimize the power of power sources as substations and storage [11]. ...
In this paper, a new HVDC power supply system for light rail systems is presented and compared to classical distribution networks based on AC/DC controlled converters. A simulation tool has been developed to simulate such a complex system, taking into account vehicle motion and HVDC electrical distribution. Then, an optimization of HVDC structure and control will be presented using Lagrangian formulation. All the results are compared to classical distributions, and show the effectiveness of the proposed power supply distribution used for light rail systems.
... What is optimal if things would stay the same forever is normally not optimal when the modeling includes the changes of the system. Optimization in the time dimension will typically be useful for studies of on-vehicle Ciccarelli et al., 2012;Barrero et al., 2008) and railside (Barrero et al., 2008;Iannuzzi et al., 2011) energy storage. ...
... What is optimal if things would stay the same forever is normally not optimal when the modeling includes the changes of the system. Optimization in the time dimension will typically be useful for studies of on-vehicle Ciccarelli et al., 2012;Barrero et al., 2008) and railside (Barrero et al., 2008;Iannuzzi et al., 2011) energy storage. ...
... Electrical substations (ES) are described by an ideal DC voltage sources, a series resistance and a series diode because conventional and mainly widespread substations are not reversible, [3], [12]. Electric resistances changing their value according to the train position, model the contact wire: ...
... The constant d [km] is the distance between two consecutive nodes (ES, or another train) located downstream and upstream the current position of the EMTS's vehicle, whereas d -x(kΔt) [km] is the distance between the vehicle position and the downstream stationary node at the same time step. Finally, the electric model of the overall network with the substations and the vehicle is shown in Fig. 4. In order to describe the receptivity of the network during regenerative braking phases, the vehicle model is completed by adding a small capacitance in parallel to the ideal current source, [12]. Its effect consist of a voltage rise when the vehicle tries to feed back to the line an amount of power higher than the power consumed by other vehicles at the same time. ...
Currently, lithium batteries are characterized by higher energy density but they require an accurate charge and discharge profile to increase its lifetime, and it is not easily to be obtained feeding urban railway systems. On the other hand, supercapacitors are powerful components, which can deliver very high power pulse for both traction and braking phases. The hybridization of these energy storage systems allows obtaining the advantages of the two different technologies improving overall performance but it needs an accurate sizing and energy management. This paper describes a methodology for designing energy storage systems (ESS) for urban railway applications composed of lithium batteries and supercapacitors. The sizing procedure takes into the account both the energy management strategy and power limitations of the two storage technologies. The effectiveness of the hybrid ESS is shown on a real case study presenting catenary-less zones. The encouraging results are presented and discussed.
... Thus, they can be used in urban rail transit or metro systems mainly for voltage compensation and energy saving applications, [13]- [14]. In addition, in [15] the use of trackside flywheel-based ESSs to increase energy saving and to reduce the TPS peak load in DC metro systems is proposed, whereas [16] and [17] consider ultracapacitor-based ESSs. ...
... where Cn is the annual operations cost of year n including both fixed (Cf) and variable (Cv) costs. In(17) we expressed Cn for ABS and TPS by using the abs and tps subscripts, respectively,[29]-[31]. ...
Auxiliary battery-based substations (ABSs) can enhance conventional railway feeder systems. In particular, ABSs make DC feeders located in areas far from the AC grid, able to power high-performance passenger and freight trains and store their braking energy. The paper proposes a techno-economic method to define size, position along the track, and control parameters of an ABS, with the goal to minimize the annual cost of energy (ACOE). Our approach takes into account the replacements of battery modules within the ABS expected lifetime in order to reduce costs. Numerical simulations are carried out assuming a new generation high-performance train on a real Italian 3 kV DC railway system equipped with one ABS. Although in some cases ABSs are already cheaper solutions compared to new traditional substations, the proposed sizing method allows obtaining a further reduction in the ABS cost.
... The power conversion is considered to have 95% efficiency. The representation of the ESS as an ideal current source is adopted in [12,[24][25][26][27][28][29][30][31][32][33] to simplify solving the power flow. Since the ESS is ideal and its type is not specified, operation within 100% and 0% SOC boundaries are imposed. ...
In DC electric railways, energy storage systems (ESSs) have been addressed to assist in the energy efficiency improvement, which is achieved by exploiting the captured excess braking energy of decelerating trains in order to reduce the traction energy demand of the accelerating trains. Conventionally, stationary ESSs are assumed to have access to the substations and grid, which is being a significant shortcoming since the ESS in many locations such as the London Underground has neither access to the traction substations nor external sources. Since ESSs cannot have infinite capacity and have practical restrictions on the state of charge (SOC), much of the regenerative energies during braking are being lost, which reduces the benefits of ESSs in enhancing energy efficiency of electric railways. In this paper, boosting the energy efficiency of the system is achieved by proposing a new adaptive control method based on fuzzy logic control (FLC) to dynamically control a stationary ESS connected to a DC track system. Therefore, the power flow between the track and the ESS with respect to the storage capacity is managed without affecting the benefits yielded by the system. The proposed control method is simulated and tested experimentally on a real prototype including a supercapacitor ESS. Three traffic scenarios are applied to evaluate the feasibility and the performance of the proposed controller with respect to the undefined traffic scenarios matching the case in the London Underground. The proposed control method applied to three traffic scenarios have achieved energy savings of 39.2–41.4%. The experimental results are compared against the simulation results, showing a percentage error ranging from 1.8 to 3.6%.
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... Some papers have been written on stationary EES implementations, [4], [13]. SCs sizing is designed simply equating the maximum kinetic energy of the metro vehicles with the energy that can be stored by SCs, [14] and [6], or using an optimization approach without considering the related siting, [15]. ...
The design of an Energy Storage System (ESS) based on SuperCapacitors (SCs) for Metro Network (MN) regenerative braking energy recovery system is investigated. A simulation tool is implemented in order to estimate the power flow among the metro vehicles and the ESSs through the MN. Several simulations are performed in order to design the number, the position along the track and the required capacity of the SCs. The energy delivered from the electric substations and the energy saved using a particular ESS configuration computed by joint sizing and siting approach are estimated to show the effectiveness of the proposed method.
... Its main objective being to reduce the number of required iterations, thus increasing the speed which the system solution is generated. Different simulation methods for electric railways have been proposes in extant literature [11,12,13,14]. However, these approaches provide only the voltages experienced by the trains and not the track voltage. ...
This paper uses Newton–Raphson method for DC power flow analysis of the Addis Ababa light Rail Transit (AALRT). The study focuses onthe line section from Menilik II square station up to Lideta station. First the tractive effort required by the trains for different scenarios such as train movement in a straight line, a curved line, and a line with gradient is computed as the chosen line section contains all these scenarios. Then the total input power will be calculated using computed tractive effort obtained for each scenario and using other input parameters obtained from AALRT, and different papers. The input power for the different loads is computed, and the input power is used to analyse the bus voltage for different loads and train positions. Newton Raphson Method is used to solve the DC Power bus problem assuming that the train requires constant power while moving between two feeding stations. Even if using the rail as the return conductor for DC traction systems has economic advantages, it has some limitations like the rail potential and stray current. A rail potential study is carried out and conclusions are drawn. The result shows that the maximum voltage drop was 0.1 p.u and the train power consumption increases by 136.73 kW as the train takes a gradient of 3.92% and keep increasing again by 29.17kw with a curve resistance (100 meters). The Rail potential moves from 6.0139V to 29.85V proportionally with the variation of the total ground resistance.
... Chymera et al. [12] used the drive cycle measured by GPS (global positioning system) in Renfrew et al. [13] to find that an energy saving of 30.6% could be obtained by means of super-capacitor storage. Barrero et al. developed a mathematical model for the evaluation of energy consumption in hybrid light rail vehicles using constant efficiencies and a DC (direct current) fed LRT train, however a test cycle intended for buses was used and no cost aspects were covered [14]. Later Barrero et al. studied the effects of implementing supercapacitors on-and off-board of metro trains based on a train model and a drive cycle, including altitude differences and multiple operating trains [15]. ...
The introduction of flywheel energy storage systems in a light rail transit train is analyzed. Mathematical models of the train, driving cycle and flywheel energy storage system are developed. These models are used to study the energy consumption and the operating cost of a light rail transit train with and without flywheel energy storage. Results suggest that maximum energy savings of 31% can be achieved using a flywheel energy storage systems with an energy and power capacity of 2.9 kWh and 725 kW respectively. Cost savings of 11% can be obtained by utilizing different flywheel energy storage systems with 1.2 kWh and 360 kW. The introduction of flywheel energy storage systems in a light rail transit train can therefore result in substantial energy and cost savings.
... The mass-point model has been used to model the metro vehicle [6]. In particular, the longitudinal dynamics of train is described by the Newton's second law and kinematics equations: ...
This paper proposes a procedure for detecting the optimal speed profile of a metro vehicle. The proposed approach provides an energy-efficient driving in terms of optimal speed profile. The speed profile is obtained through the solution of a single objective optimization problem based on the minimization of the train energy consumption while satisfying specified technical and operating constraints. Advantages obtainable through recovery of energy are also taken into account. The proposed procedure was applied to an actual urban railway system and the results compared to those obtained through an operation strategy based on the maximization of the vehicle performances.
... In most cases, the nonreversibility of TPS is neglected or is considered with a variation of resistance values [19]- [21]. Other works propose the switching of models to improve the consideration of nonreversible aspects [22], [23]. ...
Simulation is a valuable way to develop cleaner transportation systems. Nevertheless, the complexity of this kind of system leads to complex models, particularly when taking into account nonlinear aspects of traction power substations (TPSs). Thus, this paper proposes different TPS models based on energetic macroscopic representation. An appropriate model is deduced from comparisons between the different models to realize energetic studies. It is finally applied to the simulation of a simple subway line, which is experimentally validated.
... ESS model and supercapacitor electric model.A c c e p t e d P a p e r the receptivity of the network under regenerative braking conditions[17]. Indeed, if these capacitances were not present, it would not be possible to simulate the braking phase when the energy is given back to the line and all the paths for the current flow would be closed. In fact, if substations are not reversible and there are not vehicles consuming energy, ESSs cannot absorb braking energy if ESS controller does not detect a growth of line voltage. ...
In this paper, we investigate the performances of two different algorithms for calculating the metro vehicles speed profiles minimizing the energy consumption of a given path. The optimization problem, formulated as a Mixed-Integer Nonlinear Programming (MINLP) problem, take into account constraints related to the trip (timetable , distances, acceleration limits, etc.) and constraints related to the electric feeding system (line voltage, substations supplied power, etc.). We implement a deterministic algorithm based on Dynamic Programming Optimization (DPO) method, and a heuristic one based on Particle Swarm Optimization (PSO) method, and we evaluate the performances in terms of the time spent on search of a feasible solution and the goodness of the obtained solution. The resulting speed profiles are tested in a metro network simulation tool, based on the 'quasi static' backwards looking method, and taking into account the track topology, the characteristics of the metro system. The results in terms of energy saved, current supplied by the electric substations and line voltage stabilization are evaluated and discussed.
... The use of supercapacitors (SCs) for transportation vehicles has received a wide attention in the hybrid automotive vehicles research field, see among others [1]. Supercapacitors have been recently studied as an attractive solution to improve energy efficiency also in railway networks [2], [3], [4] and vehicles [5], [6]. Different architectures and the corresponding energy management issues have been analyzed in the literature, among others the integration of a SC with on board fuel cells [7], the exploitation of the overvoltage durability of the traction motors [8], the advantages of using modern SCs in substation architectures [9], the energy management for hybrid vehicles with diesel engines [10], [11]. ...
In this paper a state feedback control strategy for supercapacitors used in energy storage systems of railway vehicles is proposed. The control goal consists of guaranteing good performance in transient and steady state operating conditions, also in the presence of line voltage and motor current variations. Numerical results on a realistic example show the effectiveness of the proposed control strategy, also for missing line contact scenarios.
... In most cases, the nonreversibility of TPS is neglected or is considered with a variation of resistance values [19]- [21]. Other works propose the switching of models to improve the consideration of nonreversible aspects [22], [23]. ...
The aim of this paper is to propose an Energetic Macroscopic Representation (EMR) of the dynamic model of a traction power substation based on 6- pulse diode rectifier. This model is validated by comparing the wave forms with PSIM169; software. Furthermore, it is applied to the energetic simulation of a subway line by combining the substation model with supply rail and vehicle models. This last part allows a good representation and comprehension of the real system.
... According to [103], regeneration may save up to 40 % of in-fed power, and 20 % will be re-consumed by neighboring trains when the traffic is dense and feeding back to public grid is forbidden. A moving load model for super-capacitor energy storage is presented, where it is concluded that energy storage is of more use if traffic is sparse, because energy passing through storage if not necessary will induce extra losses. ...
Railway power supply systems (RPSSs) differ mainly from public power
systems from that the loads are moving. These moving loads are motoring
trains. Trains can also be regenerating when braking and are then power
sources. These loads consume comparatively much power, causing substantial
voltage drops, not rarely so big that the loads are reduced. By practical
reasons most RPSSs are single-phase AC or DC. Three-phase public grid
power is either converted into single-phase for feeding the railway or the RPSS
is compartmentalized into separate sections fed individually from alternating
phase-pairs of the public grid. The latter is done in order not to overload any
public grid phase unnecessarily much.
This thesis summarizes various ways of optimally operating or designing
the railway power supply system. The thesis focuses on converter-fed railways
for the reasons that they are more controllable, and also has a higher potential
for the future. This is also motivated in a literature-reviewing based paper
arguing for the converter usage potential. Moreover, converters of some kind
have to be used when the RPSS uses DC or different AC frequency than the
public grid.
The optimal operation part of this thesis is mainly about the optimal
power flow controls and unit commitments of railway converter stations in
HVDC-fed RPSSs. The models are easily generalized to different feeding,
and they cope with regenerative braking. This part considers MINLP (mixed
integer nonlinear programming) problems, and the main part of the problem
is non-convex nonlinear. The concept is presented in one paper. The subject
of how to model the problem formulations have been treated fully in one
paper.
The thesis also includes a conference article and a manuscript for an idea
including the entire electric train driving strategy in an optimization problem
considering power system and mechanical couplings over time. The latter
concept is a generalized TPSS (Train Power Systems Simulator), aiming for
more detailed studies, whereas TPSS is mainly for dimensioning studies. The
above optimal power flow models may be implemented in the entire electric
train driving strategy model.
The optimal design part of this thesis includes two aggregation models for
describing reduction in train traffic performance. The first one presented in
a journal, and the second one, adapted more useful with different simulation
results was presented at a conference. It also includes an early model for
optimal railway power converter placements.
The conclusions to be made are that the potential for energy savings by
better operation of the railway power system is great. Another conclusion
is that investment planning models for railway power systems have a high
development potential. RPSS planning models are computationally more
attractive, when aggregating power system and train traffic details.
... Energy storage systems application and usage: the most typically analysed applications are tramways or metro, where energy storage systems allow to save energy, reduce line voltage fluctuations and optimize both energy and infrastructure costs. In particular, Teymourfar et al. [18] analysed the possibility to perform energy recovery within a metro network, Ceraolo and Lutzemberger [19] , using the Modelica TM environment, analysed and compared different configurations useful to increase the efficiency of tramways, Barrero et al. [20] analysed the energetic efficiency of light railways, investigated the sizing of Ultra- Capacitors for the Brussels tramway [21] and performed an analysis on a set of on-board supercapacitors for a tram, evaluating also the effect of power converter (Barrero et al. [22] and Van Mierlo et al. [23]), while González-Gil et al. [24,25] analysed different strategies to enhance the energetic efficiency of urban railway systems, including regenerative braking. Furthermore , Iannuzzi et al. [26] proposed a technique to optimize the sizing of ultracapacitors for light railways and Mir et al. [27] designed a supercapacitor storage system for tramways. ...
... Quasi-static backwards looking method has been used for simulation of energy consumption of the train in [15]. As [16], stationary ESS has been used to save the regenerative energy. Stationary ESS has been proposed for voltage regulation of weak points in [17]. ...
This paper discusses the control strategy for energy management in railway transit network with wayside (substation) supercapacitor (SC) energy storage system (ESS). Firstly, the structure of the wayside energy storage system is introduced. Secondly, the model of energy storage system is built and the control strategy is described. Thirdly, in order to estimate the required energy storage system, a useful method is proposed to predict the instantaneous regenerative energy magnitude which is delivered to each substation. Finally, the ESS configuration for each substation is determined. A simplified mathematical model of the whole metro network is established and the main features of the control strategy are developed. Numerical simulations show the efficacy of suggested control strategy and the energy saving obtained for railway transit network.
... The model also did not incorporate an energy regeneration module. Some of the state-of-the-art models [17][18][19][20][21][22] considered an average constant regenerative braking energy efficiently that mainly depended on the train's average speed. The major limitation is that these models cannot capture vehicle transient behavior and model energy regeneration at a microscopic level. ...
The paper develops an electric train energy consumption modeling framework considering instantaneous regenerative braking efficiency in support of a rail simulation system. The model is calibrated with data from Portland, Oregon using an unconstrained non-linear optimization procedure, and validated using data from Chicago, Illinois by comparing model predictions against the National Transit Database (NTD) estimates. The results demonstrate that regenerative braking efficiency varies as an exponential function of the deceleration level, rather than an average constant as assumed in previous studies. The model predictions are demonstrated to be consistent with the NTD estimates, producing a predicted error of 1.87% and −2.31%. The paper demonstrates that energy recovery reduces the overall power consumption by 20% for the tested Chicago route. Furthermore, the paper demonstrates that the proposed modeling approach is able to capture energy consumption differences associated with train, route and operational parameters, and thus is applicable for project-level analysis. The model can be easily implemented in traffic simulation software, used in smartphone applications and eco-transit programs given its fast execution time and easy integration in complex frameworks.
... In order to calculate the power flow and the energy consumption in light railway/metro system, two models have been pointed out and merged: the first one is based on calculus of traction effort necessary to implement the timetable, taking into account both the track and railways behaviours; the second one, starting from the mechanical effort, evaluates the power flow on the feeding system. The obtained model has been implemented in a simulation tool based on the 'quasi static' backwards looking method [21]. This method is usually applied in railway and metro simulations, due to its relatively simple models and short simulation times for energy consumption estimation of vehicles following an imposed speed cycle. ...
The calculation of optimal driving speed profiles for metro vehicles that improve energy saving and, thus, reduce costs, are investigated. The optimization problem is solved in two different steps: in the first one, a Dynamic Programming Optimization (DPO) algorithm (including slopes and curves effects) is used to find a set of pseudo-optimal speed cycles; the objective is to minimize the electrical energy used for traction subject to constraints such as travel time, trip distance, acceleration limits, etc. In the second optimization step, the speed profiles set are evaluated in a simulation tool implemented to estimate the power flow among vehicles through the metro network. A test campaign monitoring the saved energy and main electric variables have been implemented and the presented results showing the effectiveness of the performance of the proposed optimization algorithm.
... In parallel with the data logging setup a HEV simulation platform has been developed [6,7,8]. ...
In this article the development and use of a data acquisition system for the optimization of hybrid propulsion systems is proposed. This versatile system can be used for different hybrid driveline architectures and for off- and on-road data logging. It retrieves the necessary parameters to develop or assess the power flow control algorithm of the vehicle under test, in order to optimize the driveline and reduce energy consumption and emissions. It is based on a cRIO™s programmable controller of National Instruments in combination with dedicated sensors and interfaces for the data acquisition of electrical and mechanical parameters. The assets and configuration of the system are discussed. Experimental data are given and discussed. In addition the HEV simulation platform developed in parallel is briefly described.
... The modeling of the train motion is based on the masspoint model [13]. The longitudinal dynamics of train is obtained by means of the Newton's second law and kinematics equations, so the following equation system has to be solved: -R o and are the basic resistance and the line resistance, respectively. ...
This paper focuses on three alternative railway systems (i.e., railway, urban metro and city tram). An approach to assess the size of an on-board energy storage unit is proposed. The unit is designed to supply the three trains along a catenaryfree track. The equations of motion are formulated in a common case. The approach solves the system of equations by means of an optimization procedure where a set of constraints on the representative variables is assigned. Service duty cycle and energy requirements are characteristics of the three alternative systems. The results of the numerical simulations focus on the
design of a battery-based storage unit to be equipped in the rolling stock vehicles. Specifically, the performance required to the storage units in the three alternative configurations are investigated and compared. Some final notes pointed out the
impact of the design constraints on the unit sizing.
... Different simulation methods for electric railways have been proposed in extant literature [14][15][16][17][18][19][20]. However, these approaches provide only the voltages experienced by the trains and not the track voltage. ...
Electrical modelling of rail tracks with multiple running trains is complex due to the difficulties in solving the power flow. The train positions, speed and acceleration are constantly varying resulting in a nonlinear system. In this work, a method is proposed for modelling DC electric railways to support power flow analysis of a simulated metro train service. The method exploits the MathWorks simulation tool Simscape, using it to model the mechanical and electrical characteristics of the rail track system. The model can be simulated to provide voltages at any position in the track and additionally, the voltages seen by any train. The model includes regenerative braking on trains, this is demonstrated to cause overvoltage in the feeding line if it is higher than the power demand of the other trains at that time. Braking resistors are used to protect the network from overvoltage by burning the excess energy. Through the implementation of Energy Storage Systems (ESSs), it will be possible to improve the energy efficiency and remove timetabling restrictions of electric railways by effectively controlling the rail track voltage. The paper proposes several methods to validate the model.
... However, the control algorithm, the optimal positioning and ESS sizing have not been discussed in these papers. References [13], [14] have employed " Quasi-static backwards looking method " in order to simulate energy consumption in a metro trains. ...
In this paper, the metro supply network and metro trains are modeled using real official data obtained from Tehran metro. This data includes speed cycles of trains, travelling times of trains and technical characteristics of electric trains with considering the return line, which are necessary to design an appropriate energy storage system (ESS). Regenerative current in each station is analyzed and possible energy savings per year are estimated. Stationary supercapacitors are employed to store regenerative currents and necessary capacitance for each station is calculated.
... In [38], modeling of two trains running on the same line with both onboard and wayside supercapacitor ESS is presented. Simplified modeling of multi-train operation with both wayside and onboard supercapacitor is presented in [39]. In [40], a modified current injection power flow algorithm is used to model multi-train operation. ...
... Detailed impact analysis using QSTS has been performed in literature, covering all three of the above mentioned aspects. QSTS analysis is performed for solar PV in [3]- [6], wind in [7], plug-in electric vehicles in [8] and energy storage in [9]. In [10]- [12], the authors evaluate various types of dynamic reactive power control strategies of DERs using high resolution QSTS analysis. ...
Significant changes in the regulatory environment, coupled with economic viability, has led various electric utilities to consider distributed photovoltaic (PV) systems as an alternative to traditional circuit upgrades. Increased penetration of distributed PV can result in the overload of the distribution system infrastructure, which can lead to premature failures and costly repairs. Quasi-static time series (QSTS) analysis is the state-of-the-art for evaluating distributed PV impacts, however, existing QSTS methods require significant computational time. To address this issue, this paper presents a fast, scalable, and novel method to estimate the current-related PV impact metrics including circuit element loading, overload duration, and line losses for a yearlong, 1-second resolution QSTS simulation. The efficacy of the proposed algorithm is tested on a utility-provided 2969-bus distribution system model, demonstrating a 99.3% reduction in computation time.
... In most cases, the nonreversibility of TPS is neglected or is considered with a variation of resistance values [19]- [21]. Other works propose the switching of models to improve the consideration of nonreversible aspects [22], [23]. ...
... It consists in the estimation of the energy consumption of a vehi- cle, following an imposed speed cycle. This speed cycle is divided in small time steps during which the vehi- cle variables are supposed to be in the steady state [28][29][30]. ...
This article will compare the benefits and constraints of onboard and stationary energy storage systems (ESS) with the aim of reducing the overall energy consumption on a low DC voltage metro network.
A dedicated simulation tool that models a metro line with conventional or hybrid trains and stationary supercapacitor (SC)-based ESSs has been developed for this purpose. The model can simulate the energy exchange among simultaneously running vehicles of a conventional metro line and evaluate the effect of a stationary ESS when installed along the line. Different traffic scenarios are considered for the study: high, moderate, and low traffic volume as this element has a strong influence on the energy exchange among the running vehicles and therefore on the energy available for storage in the ESS. This will eventually determine the energy consumption reduction.
This simulation tool is used to study the most convenient ESS alternative for the case of a Brussels metro line. When compared with a conventional metro line, the total energy consumption reduction achieved with stationary ESS varies in function of the traffic conditions, ESS size, and ESS distribution along the line. With efficient metro trains, values of energy savings up to 18.7, 25.1, and 36.4 per cent can be obtained at high, moderate, and low traffic volumes, respectively. In contrast, using onboard ESS on every vehicle, the maximum energy savings achieved vary between 27.3 and 36.3 per cent at high and low traffic volumes, respectively.
Results show that even though the energy savings achieved are higher with onboard ESS, the amount of SC cells needed is lower when using stationary ESS. However, benefits such as peak power shaving, voltage drop reductions, and reduced line losses are better attained by onboard ESS.
... If the voltage is between 23 kV to 24 kV, the batteries will neither charge nor discharge. A similar no-operation mode is also used in [32]. This makes a barrier and helps to avoid a sudden transition between charging and discharging modes caused by heavy train loads. ...
Innovative advancement in power electronics is not only reshaping the conventional high voltage (HV) transmission systems, but has also opened a new paradigm for researchers to consider its benefits in the railway electrification system (RES). In this regard, the medium-voltage direct current (MVDC) RES is a key area of interest nowadays. In this paper, a secondary energy source (SES) consist of renewable energies (REs) and energy storage systems (ESSs) is proposed to solve the issues of catenary voltage regulation, stray current, and rail potential in MVDC-RES. Some of the major integration topologies of the SESs are analyzed for MVDC-RES and the most effective one is proposed and implemented. The voltage at the point of connection (PoC) of the SES is used as a reference for controlling different operating modes of REs and ESSs. Moreover, feedforward control is used at the ESS converter to attain the quick response from the batteries for the desired operation. The proposed scheme improves catenary voltage, and reduces the stray current and rail potential. Besides this, the scheme provides higher energy density and reduces line losses. Simulation results are provided to validate the operating modes and advantages of the proposed interconnection scheme.
The paper suggests an energy management control strategy of wayside Li-ion capacitor (LiC) based energy storage for light railway vehicles (LRV). The installation of wayside supercapacitor (SC) storage devices, as widely recognized, allows the recovery of the braking energy for increasing the system efficiency as well as a better pantograph voltage profile. A new type of SC, LiC, interfaced with dc-interleaved converter has been presented. This technology has an energy density comparable to batteries and power density much higher than the batteries. The authors propose a control strategy based on the maximum kinetic energy recovery throughout braking operations of the running vehicles. The stored energy comes back to the vehicles during the accelerations. The strategy stays on the knowledge of the state of charge of LiC device and the actual vehicle speeds. In particular, the control algorithm evaluates, in real time, the actual value of LiC voltage and current references on the basis of the vehicles inertial forces and acceleration estimations, taking into account the power losses of the system. Experimental tests made on electromechanical simulator, equipped with a 136-V, 30.5-F LiC module, fully confirm the validity of the suggested control. Finally, experimental characterization of LiC module has been achieved.
The paper focuses on an innovative energy management control strategy of a wayside supercapacitor (SC) applied in DC electrified light transit networks. In order to achieve minimum energy demand from the electric feeding substations, the target of the control is the optimal tracking of the storage device voltage subject to the minimization of the mean square of the supply currents and, consequently, the reduction of power losses along the line. Hence, optimization theory has been used for the analytical determination and implementation of real time control strategy. Therefore the proposed strategy has been verified and validated via numerical simulations with reference to realistic LRV operation and different headway among the operating vehicles. A comparison with a classical energy storage system (ESS) state of charge control has been also carried out, as well as the energy saving improvement has been highlighted and the energy storage system integration and challenges are addressed. The results validate the theoretical approach and prove that the suggested control strategy is quite effective, putting in evidence its potentiality and the possibility of an actual implementation.
In this paper, the feasibility of using stationary super-capacitors to store the metro network regenerative braking energy is investigated. In order to estimate the required energy storage system (ESS), a very simple model for metro network is developed. Using the model of metro network for a particular station, a new approach is proposed to find an appropriate cost function for sizing the ESS components. By minimizing the proposed cost function, the optimum rating of components and appropriate control strategy for dc-dc converter can be realized. A case study is provided and simulated for station five of line three of Tehran metro network using Matlab software optimization toolbox.
This article will assess the installation of stationary super capacitor based energy storage systems (ESS) along a metro line for energy savings purposes. The influence of the ESS size and distribution along the line will be studied taking into account different traffic conditions.The ESSs will be configured with regards to energy content, voltage variation, maximum current and power losses. To carry out the study, an 'effect-cause' or 'backwards looking' model of the light rail vehicles and the electric network has been developed in Matlab/Simulink. A power flow controller to handle the energy flow in function of the network voltage and ESS state of charge will be proposed.
Railway rapid transit systems are key stones for the sustainability of mass transit in developed countries. The overwhelming majority of these railway systems are direct-current (DC) electrified and several energy-saving techniques have been proposed in the literature for these systems. The use of regenerative-braking in trains is generally recognised as the main tool to improve the efficiency of DC-electrified mass transit railway systems but the energy recovered in braking cannot always be handled efficiently, above all in low traffic-density situations. Several emerging technologies as energy storage systems or reversible traction substations have the potential for making it possible to efficiently use train-braking. However, a systematic evaluation of their effect is missing in the literature.
The proposed work discusses pros and cons of electric mobility in smart cities: it describes innovative solutions able to effectively and reliably manage the microgrids due to overload and / or fault of the transmission line or of the generation unit. It is also proposes a smart charging solution able to reduce the absorption peak from the network, maximize the use of energy from renewable sources and thus reduce the cost of energy to the user. Finally, they are proposed some innovative solutions to increase energy efficiency in electrified transport: in particular, the attention is focused on the benefits introduced by the energy storage systems and by the modulation of the train speed trajectories.
An energy storage system based on Supercapacitor (SC) for metro network regenerative braking energy is investigated. The control strategy according to the various power requirements in metro line and differing characteristics of these storage devices are proposed to manage the energy and optimize the power supply system performance. In order to estimate the required energy storage system (ESS), line 5 of Beijing metro network is modeled through a novel approach, in different running interval conditions based on the real data obtained from Beijing metro office. A useful method is proposed to predict the instantaneous regenerative energy which is delivered to each substation before applying ESS and based on that the ESS configuration for each substation is determined. A simplified mathematical model of the whole metro network has been developed and the main features of the control strategy have been developed. Numerical simulations show the efficacy of suggested control and the energy saving obtained for metro trains.
This paper presents a control strategy for the power flow management of a wayside energy storage system based on a supercapacitor technology installed in a tramway network. The control is based on the management in real time of voltage levels at catenary point connections in order to optimize the energy flow among the running tramcars and substations with the goals of improving the energy saving and reducing the voltage drops in the supply network. The suggested control algorithm was experimentally validated using a laboratory-scale model to verify the effectiveness of the strategy. A lithium-ion capacitor module with 72 series-connected laminated cells of the JSR Micro ULTIMO type was used. Thus, an emulation of a real tramway network in the city of Naples (ANM) was implemented to evaluate the potential impact in terms of costs/benefits of the next installation on the ANM network.
In regional and local 3kV DC railway lines, Energy Storage Systems (ESS) along the catenary can manage energy coming from electrical braking; in the actual low-carbon economy scenario, besides environmental considerations, better energy utilization goes to a general rationalization of the existing and future electrical substations. Modular multiport converters based on Power Electronic Transformers (PET) and ESS can be used for this purpose. This work analyzes as case study a regional 3kV DC line, obtaining by simulations and GPS measurements the train current and the pantograph voltage profile on the catenary. Energy savings are calculated placing ESS and multiport converters inside existing substations.
Hardware-In-the-Loop (HIL) simulation of a simplified subway line is developed for experimental validation of subway line simulator. Energetic Macroscopic Representation (EMR) is used to organize models and controls. A subway supplied by a Traction Power Substation (TPS) through a DC energy rail is studied. The HIL simulation is based on the current control of an inductor, which reproduces the same behavior than the subway. A flexible and quasi-static model of the whole system is used and experimental results are provided.
The railway traffic is rising and implying an increase in electrical power consumption. However, reducing the energy consumption is required. The railway traffic system is observed as a chain of distributed loads while trains are in the accelerating mode and also as distributed generators while trains are in the decelerating mode. Therefore a distributed smart energy management is needed to take full advantages of the braking energy and to reduce the tracking energy by planning the energy consumption at the accelerating time. This paper proposes a distributed control by Multi Agent System (MAS) in a railway micro-grid consisting on a hybrid substation with stationary storage. The strategy of energy management proposes a smart energy storage system designed to allow balancing the energy flows between accelerating and decelerating trains, while the objective is to reduce the railway energy consumption.
In regional and local 3 kV DC railway lines, Energy Storage Systems (ESS) along the catenary can manage energy coming from electrical braking; in the actual low-carbon economy scenario, besides environmental considerations, better energy utilization goes to a general rationalization of the existing and future electrical substations. Modular multiport converters based on Power Electronic Transformers (PET) and ESS can be used for this purpose. This work analyzes as case study a regional 3 kV DC line, obtaining by simulations and GPS measurements the train current and the pantograph voltage profile on the catenary. Energy savings are calculated placing ESS and multiport converters inside existing substations.
The electrical modelling of rail tracks with multiple
running trains is complex due to the difficulties of solving the
power flow. The trains’ positions, speed, and acceleration change
instantly which makes the system nonlinear. Additionally, the
nonreversible substations are another reason for the nonlinearity
of the system. These nonlinear characteristics of the rail system
make the power flow analysis more complicated. In this paper, a
simple method for modelling electric railways has been used to
avoid complicated algorithms to solve the power flow. The method
depends mainly on modelling the mechanical and electrical
characteristics of the full rail track system using the simulation
tool Simscape, which has been developed by MathWorks. The
model is able to provide the track voltage and also the trains
voltages. Through the implementation of Energy Storage Systems
(ESS) it will be possible to improve the energy efficiency of electric
railways by effectively controlling the rail track voltage and the
trains contact voltages.
Electric rail transit systems are the large consumers of energy. In trains with regenerative braking capability, a fraction of the energy used to power a train is regenerated during braking. This regenerated energy, if not properly captured, is typically dumped in the form of heat to avoid overvoltage. Finding a way to recuperate regenerative braking energy can result in economic as well as technical merits. In this comprehensive paper, the various methods and technologies that were proposed for regenerative energy recuperation have been analyzed, investigated, and compared. These technologies include: train timetable optimization, energy storage systems (onboard and wayside), and reversible substations.
Hybrid energy storage system (HESS) helps to lighten the power supply equipment of light rail vehicles (LRVs), and the static wireless power transfer (WPT) technology can improve the disadvantages of wired charging. This paper focuses on the WPT-based charging strategy for HESS, the efficiency and cost of WPT system are focused. Considering the specific of the HESS in the application of LRV, a charging strategy is designed and optimized to achieve the optimal efficiency tracking of WPT system, and the strategy can also avoid the wireless communication between the primary side and secondary side. In addition, the bidirectional power flow is proposed to reduce the power level of the WPT system, which helps save system costs. Furthermore, the dynamic power allocation of HESS is improved based on the LRV operating situations, and the WPT system parameters and HESS charging parameters are optimized correspondingly. Finally, the feasibility of the charging strategy is verified by 27.8 kilowatts WPT charging experiments.
Laser powder bed fusion technique has been considered as one of the best metal additive manufacturing processes considering the part quality and dimensional accuracy. However, the high cost of metal powders makes it difficult to afford for all kinds of applications. Reusability of the powders can overcome this issue, but the effect on various material properties is still in research stage. This paper analyzes the morphology and powder size distribution of 15-5 precipitation hardening stainless steel powders which were reused up to ten times. The powder size distribution was found to be slightly different for ten times reused powder as compared to raw powder and consisted of finer as well as agglomerated particles. The oxygen content was found to be more for the one time and five time recycled powder; however, for the ten time recycled powder, the oxygen content was found to be less.
Les systèmes d'énergie électrique embarqués ou semi autonomes connaissent des évolutions marquées. Parmi elles, on peut citer l'introduction massive d'électronique de puissance permettant d'améliorer significativement les performances via leur commande et l'interfaçage de sources de stockage. A contrario, de nombreux problèmes se posent lors du dimensionnement et du choix de l'architecture de commande du système : quelle stratégie de gestion énergétique doit-on mettre en œuvre au préalable pour optimiser les flux et le dimensionnement des sources ? Quelle commande permet d'intégrer à la fois des critères de performances dynamiques, de stabilité et de robustesse vis-à-vis des incertitudes paramétriques inhérentes à un processus de dimensionnement ? Enfin, quels outils et modèles doit-on mettre en œuvre pour garder un lien fort entre paramètres du système et critères de performances tout au long de ce processus ? Les travaux présentés dans ce mémoire proposent des premières réponses à ces questions, via l'utilisation de techniques de commande avancées comme la commande optimale ou la commande robuste. Des outils originaux de modélisation, basés sur les systèmes d'ordre non entier seront également présentés pour la modélisation de dispositifs diffusifs (machines électriques, générateurs électrochimiques) ou modélisés par des équations aux dérivées partielles.
An advanced vehicle simulator model called ADVISOR has been developed at the National Renewable Energy Laboratory to allow system-level analysis and trade-off studies of advanced vehicles. Because of ADVISOR`s fast execution speed and the open programming environment of MATLAB/Simulink, the simulator is ideally suited for doing parametric studies to map out the design space of potential high fuel economy vehicles (3X) consistent with the goals of the Partnership for New Generation of Vehicles (PNGV). Five separate vehicle configurations have been modeled including 3 lightweight vehicles (parallel, series, and conventional drivetrains) along with 2 vehicles with 1996 vehicle weights (parallel and conventional drivetrains). The sensitivity of each vehicle`s fuel economy to critical vehicle parameters is then examined and regions of interest for the vehicles mapped out through parametric studies. Using the simulation results for these vehicles, the effect of hybridization is isolated and analyzed and the trade-offs between series and parallel designs are illustrated.
In this book the longitudinal behavior of road vehicles is analyzed. The main emphasis is on the analysis and minimization of the fuel and energy consumption. Most approaches to this problem enhance the complexity of the vehicle system by adding components such as electrical motors or storage devices. Such a complex system can only be designed by means of mathematical models. This text gives an introduction to the modeling and optimization problems typically encountered when designing new propulsion systems for passenger cars.
This article will assess the installation of stationary super capacitor based energy storage systems (ESS) along a metro line for energy savings purposes. The influence of the ESS size and distribution along the line will be studied taking into account different traffic conditions.The ESSs will be configured with regards to energy content, voltage variation, maximum current and power losses. To carry out the study, an 'effect-cause' or 'backwards looking' model of the light rail vehicles and the electric network has been developed in Matlab/Simulink. A power flow controller to handle the energy flow in function of the network voltage and ESS state of charge will be proposed.
The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3–5 Wh/kg with a power density of 300–500 W/kg for high efficiency (90–95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1–2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 Ω cm2.Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.
A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy they can store is low and does not allow a large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the needed high power amount to reach short refill times, a solution is proposed which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power. In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power-level, in order to achieve a fast energy transfer between two supercapacitive tanks.
Resulting from Ph.D. research, a vehicle simulation program is proposed and continuously developed, which allows simulation of the behavior of electric, hybrid, fuel cell, and internal combustion vehicles while driving any reference cycle. The goal of the simulation program is to study power flows in the drivetrains of vehicles and the corresponding component losses, as well as to compare different drivetrain topologies. This comparison can be realized for energy consumption and emissions, as well as for performance (acceleration, range, maximum slope, etc.). The core of this program, consisting of a unique iteration algorithm, will be highlighted in this paper. This algorithm not only allows the calculation of the limits of vehicle acceleration in the function of drivetrain component characteristics, but at the same time is able to develop and evaluate the different power-management strategies of hybrid vehicles, combining combustion engines and electric motors. Furthermore, the comprehensive iteration algorithm is demonstrated to be very efficient in handling any type of working limit for all components in different types of drivetrains, which results in an accurate and modular vehicle simulation program with high data flexibility.
A supercapacitive-storage-based substation for the compensation of resistive voltage drops in transportation networks is proposed. It allows to feed as a current source in any voltage conditions of the line. The system has been designed as a compensation substation to be placed at weak points like end-of-line stations, instead of additional feeding substations. A dedicated power-electronic converter with an associated control system for the stabilization of the voltage level at the point of coupling in case of strong perturbations is proposed. Practical results are also presented, which have been recorded from a reduced size prototype.
A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy they can store is low and does not allow a large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the needed high power amount to reach short refill times, a solution is proposed which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power . In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power-level, in order to achieve a fast energy transfer between two supercapacitive tanks.
How to compare the environmental damage caused by vehicles with different fuels and drive trains? This paper describes a methodology to assess the environmental impact of vehicles, using different approaches, and evaluating their benefits and limitations. Rating systems are analysed as tools to compare the environmental impact of vehicles, allowing decision makers to dedicate their financial and non-financial policies and support measures in function of the ecological damage. The paper is based on the "Clean Vehicles" research project, commissioned by the Brussels Capital Region via the BlM-IBGE (Brussels Institute for the Conservation of the Environment) (Van Mierlo et al., 2001). The Vrije Universiteit Brussel (ETEC) and the Université Libre de Bruxelles (CEESE) have jointly carried out the workprogramme. The most important results of this project are illustrated in this paper. First an overview of environmental, economical and technical characteristics of the different alternative fuels and drive trains is given. Afterward the basic principles to identify the environmental impact of cars are described. An outline of the considered emissions and their environmental impact leads to the definition of the calculation method, named Ecoscore. A rather simple and pragmatic approach would be stating that all alternative fuelled vehicles (LPG, CNG. EV, HEV. etc.) can be considered as 'clean'. Another basic approach is considering as 'clean' all vehicles satisfying a stringent emission regulation like EURO IV or EEV. Such approaches however don't tell anything about the real environmental damage of the vehicles. In the paper we describe "how should the environmental impact of vehicles be defined?", including parameters affecting the emissions of vehicles and their influence on human beings and on the environment and "how could it be defined ?", taking into account the availability of accurate and reliable data. We take into account different damages (acid rain, photochemical air pollution, global warming, noise, etc.) and their impacts on several receptors like human beings (e.g.: cancer, respiratory diseases, etc), ecosystems, or buildings. The presented methodology is based on a kind of Life Cycle Assessment (LCA) in which the contribution of all emissions to a certain damage are considered (e.g. using Exposure-Response damage function). The emissions will include oil extraction, transportation refinery, electricity production, distribution, (Well-to-Wheel approach), as well as the emission due to the production, use and dismantling of the vehicle (Cradle-to-Grave approach). The different damages will be normalized to be able to make a comparison. Hence a reference value (determined by the reference vehicle chosen) will be defined as a target value (the normalized value will thus measure a kind of Distance to Target). The contribution of the different normalized damages to a single value "EcoScore" will be based on a panel weighting method. Some examples of the calculation of the Ecoscore for different alternative fuels and drive trains will be calculated as an illustration of the methodology.
In the framework of a PhD research programme [1] a vehicle simulation program is developed. It is a modular user-friendly interactive programme that allows the simulation of the behaviour of electric (battery, hybrid and fuel cell) as well as internal combustion (petrol, diesel, CNG, etc.) vehicles. The goal of the simulation program is to study power flows in drivetrains and corresponding component losses as well as to compare different drivetrain topologies. This comparison can be realized at the level of consumption (fuel and electricity) and emissions (CO2, HC, NOx, CO, particles, etc.) as well as at the level of performance (acceleration, range, maximum slope). The main modelling aspects and research ‘trigger points’, including its innovative iteration algorithm, will be highlighted in this paper.
In this paper, a new mathematical model in semi-empirical form for lead-acid batteries is presented, which describes the relationship between the battery terminal voltage and the variable discharge current. Based on the proposed model, a new estimation method of the battery available capacity (BAC) in the presence of variable discharge currents is developed. The method involves the real-time identification of the model parameters which are then used to estimate the BAC according to the predefined cutoff voltage and the trend of battery terminal voltage during discharging. Thus, both temperature and aging influences on the BAC are considered inherently. Comparisons between the calculated results and the measured data confirm that the proposed method can provide an accurate real-time estimation of the BAC under variable discharge currents.
This article gives an overview of the various possibilities of increased energy efficiency in electrical railway systems. Not only the power systems in the main traction circuit are emphasized, but also efficient solutions arising from auxiliary-optimization, reduced weight of the vehicles, aerodynamics and efficient rail automation. The main focus is on the application of energy storage in traction systems. The stationary installation in substations is described and the advantages demonstrated in a number of applications using different main strategies. A wide and varied range of benefits arise from the typical application situation
The proposed energy storage on board of a railway vehicle leads to a big step in the reduction of consumed energy. Up to 30% energy saving are measured in a prototype light rail vehicle, at the same time reducing the peak power demand drastically. Additionally, operation without catenary for several hundred meters was successfully demonstrated with the prototype light rail vehicle driving with switched off pantograph. This prototype vehicle is in passenger operation since September 2003, the implemented software is optimized on energy savings. About two years experience is available and the results are convincing. Applying the energy storage to diesel-electrical multiple units leads to fuel savings and provides a "booster" effect on the acceleration performance. The stored energy is adding additional power on top of the diesel engine power during acceleration. Compared to original diesel power, this additional power can be provided with a relatively low additional weight. Finally, the energy savings of up to 30% and the corresponding emission reduction will already fulfill the targets of various local and global energy saving programs set up by e.g. European Union and big railway operators
Improving the braking energy recovery efficiency in light rail systems can reduce their energy consumption. In order to compare and quantify contribution of different technologies with respect to traditional light rail systems, a quasi-static decoupled load flow modelling of a power supply network with AC-DC converters has been developed by the authors. It uses an empiric model of uncontrolled rectifiers based on abacuses determined by simulation.
The on board energy storage system with Ultracaps for railway vehicles presented in this paper seems to be a reliable technical solution with an enormous energy saving potential. Bombardier Transportation has equipped one bogie of a prototype LRV (light rail vehicle) for the public transportation operator RNV in Mannheim with a MITRAC Energy Saver. Outstanding feature is the daily operation of the energy storage unit in daily passenger service, and this even since September 2003. The experiences are very positive. The measured traction energy saving of approximately 30% confirmed fully the former calculations. Running the energy storage device on board of a tram brings additionally following benefits: (i) a dramatic reduction of the peak power demand (ii) catenary free operation" on several hundred meters without power supply from the catenary (iii) catenary free city center by on board storage and recharging stations. Applying the energy storage devices in Metro systems has a similar effect as in case of LRVs. However the savings distribution in the whole system will be a little bit different. Due to higher regeneration capability of metro systems the expected share of the train propulsion saving will be lower. It will be compensated by a considerable reduction of the line losses, especially for systems with low rated catenary voltages (600 V or 750 V). Very promising are energy storage applications in propulsion systems of diesel-electrical multiple units (DEMUs). These vehicles lack possibilities to use the braking energy of the train. Energy storage systems on board of DEMUs bring high fuel savings together with the corresponding emission reduction. On top of that the energy storage leads to a booster effect - extra power during acceleration from the storage, by adding the limited weight of the MITRAC Energy Saver.
This paper proposes and studies new strategies for an increase of the energetic efficiency of an urban transportation network fed with catenaries. A simulation tool has been developed to determine the energy efficiency on the global transportation system (vehicles, feeding line and substations). The system energy consumption is identified by calculating the energy injected by the substations to the feeding line. It takes into account all the line losses and the interactions between the different vehicles on the line. The development of a new tool was necessary as other simulation tools calculate the energy consumption of the tram without taking in account the line properties and the interactions between the vehicles. Using this simulation tool, the energetic efficiency of a tram is studied while on board of the vehicle a supercapacitive energy storage has been added. The energy storage allows local energy recovery and injection of energy to the catenaries during braking phases. The results of simulations with or without on-board energy storage and with overhead lines with high resistive or standard behavior are presented. The results show that the global energy efficiency of the system (trams, feeding line and substations) is increased by a factor between 19.4 and 25.6% (depending on the vehicle auxiliaries power) by adding a supercapacitive energy storage for both cases presented in this paper: high and standard line resistance. The use of a high line resistance instead of a standard line resistance increases the efficiency of the total system by an additional 5%.
Two rating systems assessing the environmental damage caused by vehicles are compared: a Brussels one, ECOSCORE and a European one, CLEANER DRIVE. Both vehicle rating systems were developed for the assessment of vehicles with alternative types of fuels as well as different types of drive train, such as electric, hybrid and fuel cell vehicles. A simplified life cycle assessment following a well-to-wheel approach is used to compare the methodologies. Total emissions involve oil extraction, transport and refinery, fuel distribution and electricity generation and distribution as well as tailpipe emissions from the use phase. Different types of pollution such as acid rain, photochemical air pollution, noise pollution and global warming are examined and their impact on numerous receptors such as ecosystems, buildings and human beings (cancer, respiratory diseases, etc.) are investigated. Examples illustrate both methodologies and sensitivity analysis is used to examine the robustness of the systems.
A supercapacitive-storage based substation for the compensation of resistive voltage-drops in transportation networks is proposed. It allows to feed as a current-source in any voltage conditions of the line. The system has been designed as a compensation-substation to be placed at weak points like end-of-line stations, instead of additional feeding substations. A dedicated power-electronic converter with an associated control system for the stabilization of the voltage level at the point of coupling in case of strong perturbations is proposed. Practical results are also presented, which have been recorded from a reduced-size prototype.
With the more stringent regulations on emissions and fuel economy, global warming, and constraints on energy resources, the electric, hybrid, and fuel cell vehicles have attracted more and more attention by automakers, governments, and customers. Research and development efforts have been focused on developing novel concepts, low-cost systems, and reliable hybrid electric powertrain. This paper reviews the state of the art of electric, hybrid, and fuel cell vehicles. The topologies for each category and the enabling technologies are discussed
Ultracapacitors -improving energy storage for hybrid vehicles
- J Auer
- G Sartorelli
- J M Miller
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Reduced Energy Consumption And Environmental Impact From Road Vehicles Through The Development And Implementation Of Simulation Tools
- J Swann
J. Swann, "Reduced Energy Consumption And Environmental
Impact From Road Vehicles Through The Development And
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Innovative Modular Computer Program For Calculation Of Vehicle -Longitudinal Dynamics
- J W Biermann
J.W. Biermann, "Innovative Modular Computer Program For
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The Use Of Simulation Software To Asses Advanced Power Trains And New Technology Vehicles
- R Noons
- J Swann
- A Green
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Software To Asses Advanced Power Trains And New
Technology Vehicles", Proc. of EVS-15, AVERE, Brussels,
Belgium, October 1998
System-Optimization Of The Drivetrain Of Electric Vehicles To Reduce The Energy Consumption
- P Mauracher
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Electric Vehicles To Reduce The Energy Consumption", Proc.
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How to Define Clean Vehicles? Environmental Impact Rating of Vehicles
- J Van Mierlo
- G Maggetto
Van Mierlo J, Maggetto G, et al., "How to Define Clean
Vehicles? Environmental Impact Rating of Vehicles",
International Journal of Automotive Technology (IJAT),
KSAE,SAE, ISBN 1229-9138, Vol 4, Nr 2, Pg 77-86, 2003
Vehicle Propulsión Systems. Introduction to Modeling and Optimization
- L Gazella
- A Sciarretta
Gazella L., Sciarretta A., 'Vehicle Propulsión Systems.
Introduction to Modeling and Optimization', Springer Verlag
Berlin Heidelberg 2005. ISBN-10 3-540-25195-2