Braking Energy Research Articles

Energy-Efficient Optimization Method of Urban Rail Train Based on Following Consistency

Because of the short distance between stations in urban rail transit, frequent braking of urban rail trains during operation will generate a large amount of regenerative braking energy. Urban rail trains can reduce their actual traction energy consumption using regenerative braking energy. Therefore, an energy-efficient optimization method for urban rail trains is proposed. By taking the punctuality of trains as the premise, the weighted acceleration of trains is taken as the synergetic variable, the synergetic coefficient is introduced to construct the following consistency model, and its convergence is proved. By analyzing the influencing factors of the following consistency coordination time, an adaptive parameter adjustment strategy is designed to solve the latest secondary traction time and the corresponding maximum speed of the primary traction. In order to save communication resources, the event trigger function is used to construct trigger conditions, and the consistency algorithm is used to update the cooperative controller. The simulation results show that the weighted acceleration of the follower train achieves the following consistency on the premise of ensuring punctuality, and the actual traction energy consumption of the follower train is reduced by 5.73%. The proposed method provides a new strategy for the energy-efficient operation of urban rail trains.

Regenerative Braking Algorithm for Parallel Hydraulic Hybrid Vehicles Based on Fuzzy Q-Learning

The use of regenerative braking systems is an important approach for improving the travel mileage of electric vehicles, and the use of an auxiliary hydraulic braking energy recovery system can improve the efficiency of the braking energy recovery process. In this paper, we present an algorithm for optimizing the energy recovery efficiency of a hydraulic regenerative braking system (HRBS) based on fuzzy Q-Learning (FQL). First, we built a test bench, which was used to verify the accuracy of the hydraulic regenerative braking simulation model. Second, we combined the HRBS with the electric vehicle in ADVISOR. Third, we modified the regenerative braking control strategy by introducing the FQL algorithm and comparing it with a fuzzy-control-based energy recovery strategy. The simulation results showed that the power savings of the vehicle optimized by the FQL algorithm were improved by about 9.62% and 8.91% after 1015 cycles and under urban dynamometer driving schedule (UDDS) cycle conditions compared with a vehicle based on fuzzy control and the dynamic programming (DP) algorithm. The regenerative braking control strategy optimized by the fuzzy reinforcement learning method is more efficient in terms of energy recovery than the fuzzy control strategy.

A New Electrohydraulic Hybrid Energy-Saving System Used on the Reversible Rolling Mills

In the face of the global energy crisis, the use of hybrid technology is an important way to achieve efficient energy storage and utilization. Hybrid systems have been successfully applied to automobiles and construction machinery, but no research study has been conducted on the design and application of energy recovery systems for reversible rolling mills. This article proposes a new type of noncoaxial parallel electrohydraulic hybrid drive system configuration for reversible rolling mills to save energy. It is proposed to collect the braking energy of the previous pass of the reversible rolling mill roll and the surplus power of the original primary drive motor and then start or accelerate the process for the next roll pass. A test experiment was established and the energy-saving efficiency of the proposed system was verified. By rolling 14 passes, 255.892 kJ of energy can be recovered. The overall energy efficiency rate is around 71.547%. The system will significantly promote energy saving, low carbon, green, and other aspects of the reversible rolling mills.

Study on Braking Energy Recovery Control Strategy for Four-Axle Battery Electric Heavy-Duty Trucks

Regenerative braking can extend the driving range and reduce PM emissions from abrasion for battery electric heavy-duty trucks (BETs). The composite braking control strategy including torque distribution and dynamic coordinated control for the four-axle BET equipped with the electromechanical braking system is studied. A segmented torque distribution strategy is proposed to maximize energy recovery while ensuring braking stability. The simulation results reveal that the strategy shows better comprehensive braking performance than the two benchmark strategies, and the energy recovery rate in different load states under CHTC-D is above 40%. The proposed coordinated control strategy takes advantage of regenerative braking’s rapid response and precise control to compensate for torque deviations caused by the hysteresis of friction braking. For two common braking mode transition conditions, regenerative braking torque correction and advance of the mode switching timing are adopted to enable the motor to obtain the torque compensation ability. This method leads to a slight loss of braking energy, and the maximum torque deviation during the mode switching process is suppressed to less than 1.4 kN·m, and the jerk and braking distance is reduced accordingly, which is of great importance in improving driving comfort and braking safety.

Design and implementation of a series hydraulic hybrid propulsion system to increase regenerative braking energy saving range

Environmental contamination has prompted researchers to offer approaches and solutions in a variety of fields, including hybrid drive train. A novel series hydraulic circuit for a regenerative braking system has been presented in order to expand the energy-saving range of regenerative braking and remove friction braking. In various driving scenarios, the generated hydraulic torque performs deceleration. On the basis of the type of deceleration, the single and dual braking modes are examined. In the single braking mode, the required torque is produced by a change in pump output flow, but in the dual braking mode, the torque is provided by simultaneous changes in flow and pressure. The controllers are applied to change the pump output pressure and flow based on the braking mode. Due to the existence of numerous situations for parameters influencing the choice of braking method and the significant difference in the amount of recovery energy in two scenarios an artificial neural network has been employed to decide between single and double braking. To validate the suggested model, a setup for experimentation has been created to simulate various circumstances. Compared to conventional circuits, the modification to the hydraulic circuit increases the initial cost and complexity of the control structure andmaintenance. The evaluation of braking performance and the amount of energy stored under various braking conditions resulted to an average energy storage of 63 percent in single braking mode and 17 percent in dual braking mode. The maximum speed error in single braking is 3.5 at 60 RPM and 7 at 132 RPM in double braking. Thus, the maximum speed error during single and double braking is 5.8 and 5.3 percent, respectively. Unlike typical hybrid systems, all braking conditions resulted in the storage of energy.

Energy Efficiency Improvement with Reversible Substations for Electrified Transportation Systems

More and more often overall energy efficiency of an electrified transportation system appears as target of new constructions, sometimes with incomplete definitions of performance indexes to assess that target has been reached. A worked out example is based on the introduction of reversible substations. Reversible substations are a method to improve energy efficiency, whose application in an existing system can be progressive and does not require large traffic intensity to be effective. Their effectiveness depends on some system parameters (nominal catenary voltage in particular). A simulation model fed with experimental data from a line section of Metro de Madrid is used to demonstrate the operation and optimization of reversible substations. Background The ambitious reduction of CO2 greenhouse gas emission within 2050 declared by the European Commission also involves transportation systems. In this context an optimum recovery of the electric braking energy produced by railway vehicles is more and more relevant. Several strategies to completely recover the braking energy are being developed and applied. A methodology that allows the accurate determination of the amount of recovered energy in real operating conditions becomes then a valuable tool. Objective Reversible substations are one of the braking energy recovery methods that are widely applicable. Their effect is analyzed in a system perspective, considering them integrated in the transportation system with its dynamics and various operating points. The effectiveness and consequences of the operation of one or more reversible substations are evaluated by identifying relevant system conditions and scenarios. Methods An electric network model is provided, fed by measured timetable and traction current. Simulation results are analyzed and compared with some experimental results: simulation configurations will be selected to match those of the available experimental data. Results The selected substation no-load output voltage level has a significant effect on efficiency and performance of reversible substations. A reduction of 50 V, from 1700 V to 1650 V produces a decrease of the energy dissipated by the braking rheostat on-board trains of about 13%. The voltage increase caused during braking phases is kept under control better for track positions close to reversible substations: tests show that line voltage increase is 2.5% of nominal value with a reversible substation, and only 0.5% when it is operated. Trimming the thresholds that trigger the operation of the on-board braking chopper (intermingling regenerative and dissipative braking) has a dramatic effect on regenerability: a reduction of 50 V causes an improvement of 19%. Conclusion The paper presents a methodology that merges measurements and circuital model to investigate on the energy saving provided by reversible substations supplying railway system. The methodology has been applied to a real case. Preliminary results regarding the impact of supply voltage level, reversible module position and threshold levels of the braking chopper control system on the dissipated braking energy and power quality has been carried out.

Research on bi-directional four-port converter of solar electric vehicle

Existing electric vehicles are mainly powered by batteries, which have short driving miles, inconvenient charging, still a large proportion of charging electricity from fossil-fuel power plant, and still not solving the pollution problem from the source and other defects. Connecting solar power to electric vehicles to form a complex energy system can help solve these problems. A bi-directional four port converter consisting of one BOOST and three SEPIC/ZETA circuits is presented to control the composite energy system consisting of photovoltaic panels, battery and super capacitor. BOOST circuit enables maximum power tracking of the solar panels and delivers energy to the DC bus. The first bi-directional SEPIC/ZETA circuit enables the bi-directional flow of energy between the battery and the DC bus during discharge and charging. The second bi-directional SEPIC/ZETA circuit enables the bi-directional flow of energy between the super capacitor and the DC bus during discharge and charging. The third bi-directional SEPIC/ZETA circuit converts the DC bus voltage to a suitable load voltage or feeds the load braking energy back to the DC bus. The bi-directional four-port converter enables multiple modes of operation for complex energy systems, such as maximum power tracking of the photovoltaic panel, battery power to the load, high power density output from the super capacitor, return of braking energy from the load, power supply from the photovoltaic panel to the load, and charging of the photovoltaic panel to the battery and super capacitor, and so on. Simulations and experiments demonstrate that the proposed bi-directional four-port converter can manage multiple operating modes of the complex energy system well and ensure the stability of voltage and power during mode switching. It also proves that the addition of solar energy can effectively reduce the consumption of battery energy, thus improving the driving miles and battery life and contributing to the pure green operation of electric vehicles.

Control of braking energy recovery of lifting machines

The increase in the energy consumption of machines when operating in unsteady modes is caused by many reasons, the main of which are deviation from the calculated operating modes and braking of the machine with irretrievable energy losses. When driving cars from electric motors, the recovery of braking energy can be carried out by switching them to the electric generator mode and returning the braking energy to the general power supply network. However, the absence of parallel consumers in the general power supply network requires the presence of an electric energy accumulator to recover braking energy. Effective recovery of braking energy can be carried out in a flywheel energy storage device with a high service life and high specific indicators of stored energy per unit weight of the storage device using differential gear mechanisms having two degrees of freedom.

Improving vehicle energy efficiency with braking energy recovery

In these days, improving energy efficiency of transport vehicles become one of the priorities. A vehicle must have enough traction power to overcome rolling, aerodynamic, acceleration and road grade resistances. Fortunately, acceleration and road grade resistances consume energy that is possible to recover at significant levels. At the present work, the operating characteristics affecting the braking energy of a 12 m long and 15 tons loaded weight city bus were analysed. The results indicated that Campus route has a cumulative braking energy of 26 kW-h. It is about 80% of the traction energy for the route, However, Karaman route has a cumulative braking energy of 38 kW-h. It is about 65% of the traction energy for the route. If 50% of the braking energies are recovered, percentages of the energy savings for the Campus and Karaman routes will be approximately 40% and 30%, respectively.

Smart Metering and Machine Learning for the Quantification of Regenerative Braking Energy on the d.c. Railway Systems

Nowadays, there is a great interest in improving the energy efficiency in DC railway systems. The recovery of braking energy is one of the most promising solutions. However, this solution requires to engage modifications on the railway system such as installing braking energy storage or transforming the existing DC substations in reversible substations. Thus, before engaging such costly modifications, it is necessary to have a reliable quantification of the energy that can be saved. In this paper, we are concerned with this problem. For this purpose, a novel approach based on smart metering and machine learning is proposed to detect the regenerative braking patterns from collected data. The performed experiments show the efficiency of the considered method.

Research and analysis on brake energy recovery of pure electric vehicles

Environmental pollution and other problems are becoming increasingly serious with the energy crisis. Pure electric vehicles, as a new green and pollution-free means of transportation, are increasingly favoured by the public. Compared with traditional fuel vehicles, pure electric vehicles have a shorter range, and brake energy loss accounts for approximately 10-30% of the total energy consumption. Brake energy recovery technology can effectively improve the energy utilization rate of pure electric vehicles and increase their range. This article focuses on studying different methods of braking energy recovery for electric vehicles, using comparative analysis and selecting several sets of schemes with higher recovery efficiency for analysis, pointing out the advantages and disadvantages of different methods. Research indicates that electrochemical energy storage represents a superior approach for recycling energy due to its ability to enhance energy recovery efficiency through algorithmic optimization of motor braking force distribution. However, the application of mechanical energy storage and hydraulic energy storage in pure electric vehicles necessitates further improvements to address various technical challenges.

ANALYSIS OF THE DRIVE OF ELECTRIC VEHICLESWITH ITS DIFFERENT CONFIGURATIONS

In the process of car development, its drive is continuously improved. The properties of different types of driving with an internal combustion engine (ICE) are well-studied [1]. ICE's bleak future has forced major automotive manufacturers to turn to electric mobility. The motor, integrated with final drive and differential, is compact and takes up little axle space, making it easier to assemble the drive into one axle or all-wheel drive. Electric vehicles have many advantages over vehicles with ICE: no emissions, high efficiency, quiet and smooth operation, braking energy recovery, simplified maintenance, etc. The functional and fundamental principles of electric vehicles and vehicles with ICE are similar, but there are some features. The characteristic of the electric motor (hereinafter referred to as the motor) is ideal for the drive — it has a large zone of constant maximum power, and the maximum torque appears immediately during starting. The motor, integrated with final drive and differential, is compact and takes up little axle space, making it easier to assemble the drive into one axle or all-wheel drive. Possible drive designs without a differential with two motors and two final drives on the axle, or with low-speed motors without final drives. The heavy battery is placed in the floor, so the stability of the electric car is high. The maximum possible recovery of braking energy is added to all the positive properties of all-wheel drive in the case of an electric car. To reduce the power consumption in the drive, two motors provide a drive mode with only one motor. Among electric vehicles with one-axle drive, front-wheel drive prevails due to using multi-energetic front-wheel drive platforms, stable stability and handling performance and good traction properties in winter conditions. The advantage of rear-wheel drive is the ability to realize greater traction forces during acceleration or movement on the rise due to the dynamic redistribution of the load on the rear axle. However, during braking, due to the dynamic redistribution of the load on the front axle, the possibility of recuperation of braking energy decreases. For a more detailed analysis of the drive, typical electric vehicles are selected, the characteristics of their drive motors are given, traction characteristics are calculated and constructed in the traction force coordinates — speed of movement, the realized adhesion coefficients are determined, and appropriate conclusions have been drawn.

Method for Recovery of Vehicle Braking Energy with Electric Drive Powered by DC Network and Device for Its Implementation

Designing and creating new energy efficient and cost-effective systems is an integral part of the development of the transport industry. An effective solution to the problem of high operational fuel consumption of vehicles is the improvement of braking energy recovery systems, which will significantly increase the range of the vehicle. The paper considers the existing types of braking energy recovery systems for various vehicles. An own scheme for improving the recuperation system is proposed, which makes it possible to increase the efficiency of recuperation while maintaining the overall dimensions of the device.

Recovering and accumulating energy in regenerative braking of a garbage truck using hydro-mechanic power split transmission

Hydro-mechanical power-split transmissions (HPSTs) are a kind of continuously variable transmission; HPSTs integrated with the hydraulic energy recovery and accumulation function are the most coherent selection to im-prove the energy efficiency of the garbage truck. With an accumulator located in the speed-increasing hydraulic converter of the HPSTs, it is possible to recover and accumulate energy during braking and reuse energy when starting, accelerating or using other technologies in the process of garbage collection and transportation. Some results of simulation research and analysis of the energy recovery and accumulation process introduced in this paper can be used as a scientific basis for the complete design of energy saving powertrain systems, quality, and environmental friendliness for garbage trucks. In this study, the results of the simulation and analysis of the energy recovery and accumulation process were reported. Our findings can be used as a scientific basis for the complete design of energy saving powertrain systems, quality, and environmental friendliness for garbage trucks.

Combining Urban Fleet Vehicle Operation with Reducing Energy Wastage in Light Rail Systems

Fleet electric vehicles offer excellent potential for vehicle-to-grid operation, as a result of their predictable use patterns. This paper investigates the potential for linking up urban fleet electric vehicles with wasted energy from urban light rail networks. Vehicle-to-grid charging could be deployed to reduce energy wastage from regenerative braking, while serving as temporary energy storage on the light rail system to reduce energy requirements during acceleration and providing an energy supply for fleets of electric vehicles based in urban areas. This paper uses GPS data from real light rail journeys to estimate regenerative braking energy availability for Edinburgh's light rail network. Findings indicate that electric vehicle charging linked to Edinburgh's light rail network would be beneficial for both parties.

Optimisation of braking energy recovery for rear-drive electric vehicles based on fuzzy control

Optimisation of braking energy recovery for rear-drive electric vehicles based on fuzzy control

Operation-Aware System Design for Synergistic Integration of Regenerative Braking Energy of Railway Systems into EV Fast Charging Stations

Operation-Aware System Design for Synergistic Integration of Regenerative Braking Energy of Railway Systems into EV Fast Charging Stations

Integrated Regenerative Braking Energy Utilization System for Multi-Substations in Electrified Railways

This article proposes an integrated regenerative braking energy utilization system (RBEUS) to improve regenerative braking energy (RBE) utilization in electrified railways. The proposed RBEUS uses a traction substation energy storage system and two sectioning post converters to achieve coordinated RBE utilization in three consecutive traction substations via power-sharing and storage, and the power quality can also be improved. A hierarchically coordinated control strategy is developed based on the operation principle to provide real-time power management and control for the RBEUS. In the system layer, a centralized power management strategy is designed for operation mode management and active power command generation. It uses a sequential quadratic programming-based algorithm to solve the objective function to achieve optimal RBE utilization under different operation modes. In the converter layer, local controllers of the RBEUS enable converters to respond to the active power commands from the system layer and reactive power commands generated by themself for power flow control. The effectiveness of the proposed RBEUS is comprehensively verified by using a hardware-in-the-loop experiment. Besides, a comparison analysis of the proposed RBEUS and literature methods is conducted to testify the superiority of the RBEUS. The feasibility of RBEUS implementation is also discussed from fault protection and economy.

Energy-Saving Train Operation Synergy Based on Multi-Agent Deep Reinforcement Learning on Spark Cloud

With the development of urban rail transit, energy conservation has been highly concerned by the worldwide railway industry. The existing energy-saving control methods are hard to meet the requirements of large-scale multi-train intelligent cooperation. Furthermore, in order to optimize the overall energy consumption and make effective utilization of regenerative braking energy (RBE), the micro train driving strategies must be taken into account in the macro train schedule regulation. This article aims to establish a systematic optimization model to describe the train traffic environment and design a deep reinforcement learning (DRL) approach using multi-agent cooperative actor-critic (MACAC) to reschedule multiple trains for energy saving. Due to the high dimensional characteristic of control actions, the action representation technique is applied for generalization. The multiple agents are deployed on the Spark cloud platform to effectively improve the learning efficiency through multi-node parallel computing. The proposed MACAC approach on Spark cloud is capable of dealing with the intelligent learning and computing efficiency of large-scale train operation synergy, and saving energy to the maximum extent on the premise of satisfying various time constraints. The evaluation was carried out through the field data of Beijing Yizhuang subway line. The results show that the proposed MACAC approach can effectively learn to improve the energy efficiency, and the parallel computing method on Spark cloud is suitable for practical applications.

Train-Network-HESS Integrated Optimization for Long-Distance AC Urban Rail Transit to Minimize the Comprehensive Cost

In order to solve the problem of the serious stray current existing in DC urban rail transit, and to improve the utilization rate of the regenerative braking energy (RBE) generated by locomotive, an AC traction power supply system (TPSS) for long-distance urban rail transit is proposed, in which the network power flow distribution is affected by the train trajectory, the parameters of network and hybrid energy storage system (HESS) configuration. For achieving the minimum comprehensive cost including the electricity cost and the life cycle cost (LCC) of HESS, this paper aims to develop a Train-Network-HESS integrated model to optimize network power flow distribution. The train trajectory is illustrated based on time-space conversion method and HESS control strategy is discussed to increase the utilization of the RBE. Furthermore, the optimized configuration of the AC TPSS for urban rail transit is obtained by the hybrid GA-PSO algorithm. Finally, the effectiveness of the proposed model is verified by detailed case studies and the comprehensive cost can be reduced up to 39.08% compared with conventional TPSS.