On-board Energy Storage Device Research Articles

Impacts of On-board Energy Storage Devices on the Energy Consumption of Train Operations

Urban rail transit systems consume significant electrical power, with traction accounting for 50% of the total energy (from China Urban Rail Transit Association [1]). As operational mileage and vehicle counts rise, so does energy consumption, underscoring the importance of vehicular energy conservation. This study evaluates the impact of on-board energy storage devices on train energy efficiency. Using operational data from Changsha Metro Line 5 and incorporating literature reviews and simulations, the energy-saving potential was assessed. Integrating these storage devices with vehicle energy monitoring systems shows promising potential for energy conservation and operational efficiency. This research presents a viable strategy to reduce energy consumption in urban rail vehicles, enhancing system competitiveness.

Analysis of operation modes of shunting diesel locomotives when performing shunting work

An overview of modern trends in updating shunting locomotives, which are based on the installation of on-board energy storage devices, multi-diesel propulsion power plants, and power plants operated on hydrogen energy sources, was carried out. The necessity to take into account the operating conditions of a shunting diesel locomotive when choosing an upgrade option is shown. The operation modes of shunting diesel locomotives during shunting operations at the Козятин-I freight station during three shifts were considered. By analyzing the data of the БІС-Р onboard system and processing the route sheets, the parameters of the operating modes were determined. Calculations of diesel engine power utilization indicators were performed, according to which it was determined that the full use of the installed diesel generator power is 7.5...8.4%, and the maximum diesel power recorded under the studied operating conditions is about 50%. The duration of work with traction loads is 49.5...68.8% of the shift time. The longest - 55...60% of the total duration of work under traction - are modes with a power of 0...50 kW. The duration of work without load is 18.1...36.9% of the duration of the shift. The shunting work performed is related to the formation and disassembly of trains, including the use of a sorting slide, as a result of which the traction power transmission operates with a low efficiency. In order to reduce the consumption of fuel and energy resources when performing shunting work, it is necessary to update the fleet of locomotives for shunting work, the characteristics of which are adapted to the operating modes. Key words: hybrid locomotive, modernization, shunting, energy efficiency, energy storage

Method to Design Power and Energy Capacity of Onboard Energy Storage Device for Emergency Operation Based on Simple Formulation

Method to Design Power and Energy Capacity of Onboard Energy Storage Device for Emergency Operation Based on Simple Formulation

Efficiency coefficients of the energy storage device in the contact network of the city electric transport

The efficiency of stationary and on-board energy storage devices in the contact network of mountain electric transport (tram, metro) is considered. The efficiency coefficients of storage devices are derived depending on the completeness of consideration of storage systems and methods of their application. In accordance with the established formulas for calculating different types of efficiency, the operation indicators of domestic energy storage devices of various types on mountain electric transport are analyzed. It has been established that, other things being equal, stationary energy storage devices are more efficient than those of the on-board version.

COMPARATIVE ANALYSIS OF APPROACHES TO DETERMINING THE PARAMETERS OF A CAPACITIVE ENERGY STORAGE FOR ELECTRIC ROLLING STOCK

The article deals with the main existing approaches to determining the parameters of on-board capacitive energy storages for electric rolling stock and their comparative analysis. The advantages and disadvantages of each of the ten considered approaches are set out. Each of the approaches is described and their comparative analysis is performed according to such criteria as the level of research complexity, the financial component of research, the possibility of taking into account the real operation conditions of electric rolling stock while carrying out the research, the method of evaluating the parameters of the on-board capacitive energy storage, the possibility of determining rational parameters, the universality of the approach, considering the technical and economic component and limitations on weight and size of indicators. The power and energy capacity of on-board capacitive energy storage devices, their weight-size indicators when applying each of the considered approaches for the same given operating conditions of the electric rolling stock are determined. A five-car articulated vehicle with an asynchronous traction drive and recovery systems, consisting of metro cars of models 81-7080, 81-7081, 81-7081-01, was chosen as the electric rolling stock. The experimental section between the final stations of the SviatoshynskBrovary line of the utility company “Kyivskyi Metropolitan” was chosen as the specified operating conditions. The payback period and the impact of storage systems with the selected parameters on the performance indicators of the given electric rolling stock while using various approaches are determined. It was found that the most developed approaches, the key point of which is the selection of rational parameters using theoretical research with the help of application-specific software and multi-criteria evaluation methods. The feasibility of using a multi-criteria approach, which allows choosing rational parameters of the capacitive energy storage for electric rolling stock based on three important evaluation criteria, i.e., weight, volume and payback period, is demonstrated. It was established that it is rational to use an on-board capacitive energy storage device of low power and energy intensity.

Impact of On-Board Hybrid Energy Storage Devices on Energy-Saving Operation for Electric Trains in DC Railway Systems

To improve the energy-efficiency of transport systems, it is necessary to investigate electric trains with on-board hybrid energy storage devices (HESDs), which are applied to assist the traction and recover the regenerative energy. In this paper, a time-based mixed-integer linear programming (MILP) model is proposed to obtain the energy-saving operation for electric trains with different constraints of on-board HESDs, such as their capacity, initial state of charge (SOC), and level of degradation. The proposed integrated power flow model based on the train longitudinal dynamics, power split of on-board HESDs, and line impedance is discretized and linearized, aiming to minimize the net energy consumption (NEC). The results reveal that on-board HESDs with a higher capacity does not necessarily lead to a higher energy-saving rate; a lower or excessive initial SOC could undermine the energy-saving potential; considering the long-term train operation, the degradation of the Li-ion battery will influence the energy-saving operation for electric trains, as well as result in an energy-saving rate that ranges from 41.57% to 31.90%. The practical data from Guangzhou Metro Line 7 were applied in the simulations, which enhanced the practicality and effectiveness of the proposed method.

PROSPECTS OF USING AUTONOMOUS ELECTRIC TRAINS WITH ONBOARD STORAGE STORES

Purpose. Improving the efficiency of passenger traffic on non-electrified sections of the railway of Ukraine by optimizing the structure and creating principles for building a traction electric drive of a promising autonomous electric train powered by traction engines from the system of onboard storage of electricity. Methods. The methodological basis of the study are the general theoretical provisions and principles of the system approach of theoretical electrical engineering, theoretical mechanics, theory of electrical machines and converters. The basic principles of management theory and the basics of decision theory are used. Results. The general principles of construction of the traction electric drive of the perspective autonomous electric train with power supply of traction engines from onboard energy storage devices are formulated. The functional scheme of the traction electric drive of the perspective autonomous electric train is offered, the analysis of work of the electric drive in the modes of traction and regenerative braking is carried out. The mass parameters of two types of energy storage devices, namely electrochemical batteries and supercapacitors, have been determined. The basic requirements to the system of automatic control of the traction drive of the electric train are formulated. It is shown that in the future the use of autonomous battery electric trains will be technically possible and economically justified on non-electrified sections of Ukrzaliznytsia.

Joint optimization combining the capacity of subway on‐board energy storage device and timetable

On-board energy storage devices (OESD) and energy-efficient train timetabling (EETT) are considered two effective ways to improve the usage rate of regenerative braking energy (RBE) of subway trains. EETT is less costly but has lower ceilings, whereas OESD, although expensive, maximizes the reuse of RBE. To make the RBE usage rate of the train group reach the required target, a typical problem is how to use the OESD with the minimum capacity to reduce the cost. With this consideration, this paper proposes an optimization method that combines EETT and OESD. In this method, the joint optimization of timetable and OESD capacity allocation in case OESDs of different capacities can be carried between trains is considered to further improve the optimization. A non-linear programming model is built to minimize the total OESD capacity of the train group under the constraint of reaching target RBE usage. An efficient heuristic algorithm is designed to simultaneously obtain the optimal timetable and the matching capacity allocation scheme of OESDs. Finally, some simulation cases based on real-line data are designed to verify the effectiveness of the method.

Electrical power supply system planning for a modern catenary-free rapid charging

Electric power supply system planning is practically an important function of the modern light rail transit system with catenary free operation and rapid charging. Installing a modern dynamic load of the traction power supply system with the local electric distribution network needs to consider its capacity and feeder to support enough and efficiently. In this paper, the design of the electrical power supply system of the pilot project of Nakhon Ratchasima Green Line light rail system with 11.6-km line length and 21 passenger stations operated with catenary-free and powered with an on-board energy storage device has been proposed and planned to replace the old local transportation. The traction power supply of the light rail system drawn power from the MV distribution feeder practically consist of receiving power substation, MV power feeding system power feeder substation, charging power supply and service power supply have been designed provided the configuration circuit. A rapid charge system to delivery high power to fulfill the on-board energy storage is considered to recharge at passenger stations with an overhead conductor or wireless power transfer during a short dwell time. A number of charging station is determined accordingly the capacity of the power substation and its positions. The traction power drawn by a train service round-trip that related to the capacity of the power substation as a charging station has been calculated by the simulation of the train movement. The regenerative braking energy during train operated in braking mode is also considered as a partial charging energy the on-board energy storage device. From the proposed design, the motive energy consumption of each scenario charging formations obtains the maximum charging energy drawn by the train between charging points, the capacity of on-board energy storage devices, maximum charging power and the total charging points.

Optimal Sizing of Onboard Hybrid Energy Storage Devices Considering the Long-Term Train Operation

With the fast development of energy storage technology, more applications of Energy Storage Devices (ESDs) have been found in rail transportation in recent years. This paper aims to address the optimal sizing problem of on-board Hybrid Energy Storage Devices (HESDs) which are installed to assist train traction and recover the regenerative braking energy. On-board HESDs combining Li-ion battery and supercapacitor can further enhance the capacity and instant power rating. In this paper, a mixed integer linear programming (MILP) model is proposed to minimize the economic cost in terms of energy consumption and installation, and the degradation cost of on-board HESDs considering the long-term train operation constrained by the initial investment of on-board HESDs. Train operation is found to be highly related to characteristics of on-board HESDs including the maximum power, capacity, and state of health (SOH). By changing the investment ratio between Li-ion battery and supercapacitor, the energy-saving rate and economic cost for various investment ratios have been obtained. Compared with the results of train optimal control with Li-ion battery only, supercapacitor only and no on-board HESDs, the results indicate an energy-saving rate up to 25.59%, from the perspective of the long-term train operation. When the allowable capital cost is relaxed from 20 k$ to 60 k$, the cost per kilometer is reduced from 0.55 USD/km to 0.53 USD/km, showing higher capital cost is closely linked to higher cost reduction in the long-term train operation.

MANAGEMENT STRATEGIES FOR ENERGY PROCESSES IN ELECTRIC ROLLING STOCK WITH ON-BOARD ENERGY STORAGE DEVICES

The article deals with the main existing strategies for management strategy of energy exchange processes in the electric rolling stock with onboard capacitive energy storage devices. When considering strategies, it is assumed that the onboard capacitive storage has low power and capacitance. Therefore, this capacitor storage is not able to accept the full amount of regenerative braking energy of the electric rolling stock. The purpose of the paper is to consider and analyze management strategies for energy exchange processes in the electric rolling stock with onboard capacitive energy storages; to define the advantages and disadvantages of each of the existing strategies and propose a concept for the effective management of energy exchange processes in the electric rolling stock. The block diagram of electric rolling stock with the onboard capacitive energy storage which is used for the analysis of management strategies for energy exchange processes is presented. The modes of operation of electric rolling stock with onboard capacitive energy storages are described. Five main strategies for management of energy exchange processes on the electric rolling stock with onboard capacitive energy storages are determined. The advantages and disadvantages of each strategy are set out taking into account the given conditions (characteristics of the electric rolling stock, conditions of the rolling stock motion, oscillograph charts, etc.). The general advantages and shortcomings of each strategy are defined, which allowed to propose the concept of creating an adaptive strategy for managing energy exchange processes in electric rolling stock with onboard capacitive energy storages. The main concept of this management strategy is to implement efficient energy exchange between the traction equipment, the onboard capacitive energy storage, the overhead contact system, both in normal and emergency modes of traction power supply, taking into account the dynamics of energy exchange processes in the overhead contact system, which will generally allow safety and energy efficiency of the transportation process. The obtained research results will contribute to the development and implementation of effective strategies for managing energy exchange processes in the electric rolling stock.

A Two-Step Method for Energy-Efficient Train Operation, Timetabling, and Onboard Energy Storage Device Management

This article proposes a novel two-step approach to concurrently optimize the train operation, timetable, and energy management strategy of the onboard energy storage device (OESD) to minimize the net energy consumption for a whole urban railway line. In Step 1, approximating functions representing the minimum net energy consumption of each specific interstation operation is obtained by data fitting based on the previous research outcomes. In Step 2, the optimal running time, initial state of energy (ISOE) of OESD, train speed profiles, discharge/charge management of the OESD during each interstation journey and at each station are obtained by applying convex optimization formulated by approximating functions gained in Step 1. The method is first tested with several general train cases to show its robustness and adaptability. Then, a real-world case based on Beijing metro Yizhuang line is studied and the optimal solution is found to reduce the net energy consumption 1.04%, 2.09%, and 23.77% for a service cycle of a single train when compared to other operation scenarios, i.e., fully charged, no management, and no OESD scenario, respectively. The approach is also computationally efficient with a computational time less than 1 min, namely 38.86 s for the upline and 48.38 s for the downline, spent on finding the optimal solution.

Adaptive Eco-Driving Strategy and Feasibility Analysis for Electric Trains With Onboard Energy Storage Devices

With the rapid progress in railway electrification and energy storage technologies, onboard energy storage devices (OESDs) have been widely utilized in modern railway systems to reduce energy consumption. This article aims to develop the optimal driving strategy of electric trains with three popular types of energy storage devices, namely supercapacitors, flywheels, and Li-ion batteries, as the OESD to minimize the net energy consumption. With the given OESD investment cost, the dynamic power limits of different types of OESDs are fully considered to optimize the dynamic discharge/charge behavior of the OESD in the train operation. The case studies investigate the train operation on fully electrified railways, discontinuously electrified railways, and catenary-free railways, showing that the optimal eco-driving strategy of the train and discharge/charge behavior of the OESD is significantly different for a different type of OESDs. The obtained train speed, OESDs' state of energy (SOE), power profiles, and energy-saving potential for each type of OESDs under various scenarios are compared comprehensively, and the results also reveal that the flywheel has the best performance for its energy-saving rate ranging from 0.15 %/k $\$ $ to 0.86 %/k $\$ $ , while a Li-ion battery is observed with the weakest performance with the energy-saving rate being only 0.01 %/k $\$ $ -0.26 %/k $\$ $ . The error rate analysis also confirms a satisfactory modeling accuracy of the proposed method.

A New Low-Frequency Oscillation Suppression Method Based on EMU On-Board Energy Storage Device

Low frequency oscillation (LFO) in the electric multiple units (EMUs)-traction network cascade system (ETNCS) can lead to traction blockade and abnormal operation. Using the Chinese CRH3 EMUs as an example, a new LFO suppressing method by applying the energy storage (ES) device on EMUs is proposed in this paper and the ES is connected to the DC-link on board. The equivalent model of the ETNCS is established at first. The critical condition of LFO in the ETNCS is analyzed via impedance ratio criterion and Bode diagram. Then, the proposed on-board bidirectional DC-DC converter integrated with the ES system is controlled via a virtual DC machine (VDCM) strategy, and the VDCM small signal model derivation and the parameter design are carried out. Using the Bode diagram of the impedance ratio, the system stability with the ES device controlled by the proposed VDCM scheme is analyzed again; simulation results verify the effectiveness of the control algorithm to suppress the LFO adaptively. Compared with the traditional PI controller, the system steady-state and dynamic performance can be improved with the proposed method, including decreased overshoot, fluctuation, response time, and increased gain margin of the DC-link voltage.

A Novel Optimal Power Control for a City Transit Hybrid Bus Equipped with a Partitioned Hydrogen Fuel Cell Stack

The development of more sustainable and zero-emissions collective transport solutions could play a very important measure in the near future within smart city policies. This paper tries to give a contribution to this aim, proposing a novel approach to fuel cell vehicle design and operation. Traditional difficulties experienced in fuel cell transient operation are, in fact, normally solved in conventional vehicle prototypes, through the hybridization of the propulsion system and with the complete fulfillment of transients in road energy demand through a high-capacity onboard energy storage device. This makes it normally necessary to use Li-ion battery solutions, accepting their restrictions in terms of weight, costs, energy losses, limited lifetime, and environmental constraints. The proposed solution, instead, introduces a partitioning of the hydrogen fuel cell (FC) and novel optimal power control strategy, with the aim of limiting the capacity of the energy storage, still avoiding FC transient operation. The limited capacity of the resulting energy storage systems which, instead, has to answer higher power requests, makes it possible to consider the utilization of a high-speed flywheel energy storage system (FESS) in place of high energy density Li-ion batteries. The proposed control strategy was validated by vehicle simulations based on a modular and parametric model; input data were acquired experimentally on an operating electric bus in real traffic conditions over an urban bus line. Simulation results highlight that the proposed control strategy makes it possible to obtain an overall power output for the FC stacks which better follows road power demands, and a relevant downsizing of the FESS device.

Optimal Sizing of Onboard Energy Storage Devices for Electrified Railway Systems

For improving the energy efficiency of railway systems, onboard energy storage devices (OESDs) have been applied to assist the traction and recover the regenerative energy. This article aims to address the optimal sizing problem of OESDs to minimize the catenary energy consumption for practical train operations. By employing a mixed-integer linear programming (MILP) model based on energy flow and the law of conservation of energy, three types of widely used OESD—supercapacitors, Li-ion batteries, and flywheels—have been studied in a real-world case of the Beijing Changping line. Results show that without the constraints of capital cost and volume, the supercapacitor, Li-ion battery, and flywheel with optimized capacity can save the catenary energy consumption by 23.6%, 22.9%, and 23.7% compared with the cases without OESDs, respectively. The minimum catenary energy consumption for each type of OESD has also been found with the constraints of capital cost and volume. The study shows that with a volume constraint less than 0.6 m3 and a higher allowed capital cost more than 20 k$, flywheel tends to achieve the least catenary energy consumption. When the volume is relaxed to go beyond 0.6 m3, supercapacitors always achieve the minimum catenary energy consumption disregarding the constraint of capital cost.

On-Board and Wayside Energy Storage Devices Applications in Urban Transport Systems—Case Study Analysis for Power Applications

This paper investigates the benefits of using the on-board energy storage devices (OESD) and wayside energy storage devices (WESD) in light rail transportation (metro and tram) systems. The analysed benefits are the use of OESD and WESD as a source of supply in an emergency metro scenario to safely evacuate the passengers blocked in a metro train between stations; the use of OESD for catenary free sections, the benefits of using the WESD as an energy source for electrical car charging points and tram traction power supply; the benefits of using a central communication system between trams, cars, WESD and electrical car charging points. The authors investigated the use of: OESD with batteries for a catenary free section for different scenarios (full route or a catenary free section between two stations); the charge of OESD between stations (in parallel with tram motoring) to decrease the charging dwell time at stations and to help in achieving the operational timetable; the thermal effect of the additional load on the overhead contact system (OCS) when the tram is charging between stations; the sizing of OESD and WESD for emergency feeding in a metro system. The authors investigated the use of the WESD as a source of energy for the electrical car charging points to reduce the car pollution and carbon emissions. Presented in the paper is the enhanced multi train simulator with WESD prepared for the analyses conducted. The paper describes the DC electrical solver and WESD control method. A validation of the software has been conducted in regard to the substation voltage, WESD energy balance and WESD control.

Selection of the capacity of the onboard energy storage device for a high-mobility wheeled vehicle wear-resistant brake system with an electric machine

With the growth of the average speed of wheeled vehicles, the wear-resistant brake system which would increase their mobility by improving their braking performance and lower the heat loads on the service brake system is gaining interest of the manufacturers. At the same time, a good option for increasing power efficiency of the high-mobility wheeled vehicles is to use an electric machine in the wear-resistant brake system. The electric machine can operate in the generator cycle and provide energy recuperation during braking. Recuperation at braking requires accumulation of high values of electric energy in a storage device (usually a molecular storage device), which brings to the forefront the problem of its efficient capacity selection. The article deals with the selection of the required capacity of an onboard energy storage device providing better power efficiency of the vehicle due to the use of an electric machine in the wear-resistant brake system. The method for the selection of the required capacity of the onboard energy storage device is based on the calculation of the energy spent by the vehicle for maintaining the given speed. The following strategy of the electric machine control was used in the research: the energy accumulated in the storage device after braking will be spent at the next acceleration. Therefore, the power efficiency can be increased only due to such compensation of the high frequency oscillations of the spent/accumulated electric energy in the potential storage device that would prevent reaching its maximum charge level in a typical driving cycle. Based on the results of the research the capacity of the storage device is assessed by the peak-to-peak amplitude of the time history of the accumulated/stored energy when driving along a given route. A method that allows formulation of the specifications for the onboard energy storage device used as an element of the wear-resistant brake system, the method uses statistical data on the road conditions of vehicles operation. The method provides selection of the optimal parameters (required capacity) of the electric energy storage device which would guarantee effective operation of high-mobility wheeled vehicles in typical driving cycles.

Train Speed Trajectory Optimization With On-Board Energy Storage Device

Rail transportation is used extensively in urban areas to reduce CO2 emission and increase road capacity. As a result, the energy efficiency of rail transportation is becoming a popular research topic. Energy-efficient train operation involves four types of control: maximal traction, cruising, coasting, and maximal braking. With the rapid development of energy storage devices (ESDs), this paper aims to develop an integrated optimization model to obtain the speed trajectory with the constraint of on-board ESD properties such as capacity, initial state of energy (SOE), and the degradation of the on-board ESD. Mixed integer linear programming is implemented on the discretized distance-based model to find the solution. In addition to the optimal speed trajectory, the on-board ESD discharge/charge operation strategy will be obtained. Results show that with high on-board ESD capacity, a train tends to apply more braking to recover more energy by using ESD; high initial SOE leads to more traction operation but undermines the energy-recovering process; degradation of on-board ESD influences the train operation and net energy consumption by affecting discharge/charge frequency. Additionally, in the case with on-board ESD, more than 11.6% of net energy consumption can be reduced compared with the one without on-board ESD. This paper indicates that the proposed method is an effective and robust way to study how on-board ESD influences optimal train operation as well as to achieve optimal train speed trajectory with on-board ESD.

On-Board Energy Storage Devices with Supercapacitors for Metro Trains—Case Study Analysis of Application Effectiveness

This paper presents an analysis on using an on-board energy storage device (ESD) for enhancing braking energy re-use in electrified railway transportation. A simulation model was developed in the programming language C++ to help with the sizing of the ESD. The simulation model based on the mathematical description has been proposed for a train equipped with on-board ESD for analysis of effectiveness of its application. A case study was carried out for a metro line taking into consideration train characteristics, track alignment, line velocity limits and a running time table. This case study was used to assess the energy savings and perform a cost-benefit analysis for different sizes of the on-board ESD by applying the proposed approach. It was shown that when additional environmental benefits (reduction of CO2 emissions) are considered, this may significantly improve effectiveness of the investments due to CO2 European Emission allowances.