Regenerative Braking Energy Research Articles

Modeling of Regenerative Braking Energy for Electric Multiple Units Passing Long Downhill Section

The process of electric multiple units (EMUs) passing long downhill sections is inevitable in the construction of mountain railways. Moreover, huge regenerative braking energy (RBE) will be sent back to the traction network, threatening voltage safety. Due to the lack of accurate vehicle-grid integrated models considering slope parameters in studying the RBE, this article proposes a modeling scheme, taking China railway high-speed 3 (CRH3) EMUs as an example. First, based on the extended dual pulsewidth modulation (PWM) mathematical model, the quantitative formula for calculating the motor braking power of the CRH3 EMUs is established. Moreover, the slope parameters are introduced into the vehicle-grid model via force analysis and regenerative braking power calculation. Then, by substituting the calculated results into the extended dual PWM mathematical model, the target instruction parameters are solved. Next, the accurate electrical characteristics, including catenary voltage, electromagnetic torque, and converter voltage, are simulated to evaluate the voltage safety. Finally, by comparing the simulation and semi-physical experiment results with the experimental data from the Chengdu to Chongqing railway line, the feasibility, validity, and accuracy of the model are verified.

Real-Time Control Strategy of Tractive Load Peak Clipping and Valley Filling Based on Model Predictive Control

Access to energy storage devices (ESDs) is an effective way to solve the peak traction load shock and Regenerative Braking Energy (RBE) recycling. However, in the real-time operation of the system, there are problems of prediction errors affecting the control results and the problem of energy storage “dead time.” This article analyzes the mechanism of the energy storage “dead-time” problem and aims to solve this problem without increasing the energy storage capacity. Therefore, this article combines the ideas of rolling optimization and predictive control in the model predictive control (MPC) method and proposes an MPC method based on the adaptive correction (AC-MPC) of the State of Charge (SOC) of ESD. The predictive control can ensure the accuracy of power correction; the rolling optimization can reduce the global impact of each correction and reduce the complexity of the calculation. In addition, the rolling prediction in the rolling optimization link reduces the prediction error by reducing the prediction time scale, thus reducing the impact of the prediction error on the control results. The experimental data show that the proposed control strategy can effectively solve the two problems mentioned above, ensure the effect of peak reduction and RBE recovery, and improve the economy of system operation.

Study on Energy-Saving Optimization of Urban Rail Transit Train Timetable under Regenerative Braking

Energy-saving driving and regenerative braking energy utilization are two main ways to realize energy-saving optimization of urban rail transit train timetables. On the basis of the more mature energy-saving driving achievements of the predecessors, the absorption utilization rate of regenerative braking energy is improved by adjusting the dwell time of trains in the station so that while a train is braking, other trains in the same electric section are just under traction. In this paper, the overlap time between the traction and braking processes of different trains is used as a measure of the proportion of regenerative braking energy that is absorbed. In order to maximize this overlap time, an energy-saving optimization model of urban rail transit train timetable based on regenerative braking technology was established. To facilitate the solution, the nonlinear constraints are converted to linear at the time of model construction in this paper. In the solution, the spatio-temporal local rolling algorithm and the commercial optimization software ILOG CPLEX are used for the solution. The solution results show that the method in this paper can effectively improve the absorption and utilization of regenerative braking energy.

Optimal dispatching of high-speed railway power system based on hybrid energy storage system

High-speed railway power system consists of traction power system and station power system. High-speed railway locomotives generate electrical energy that is fed back to the grid during regenerative braking, and the grid company adopts the policy of ignoring the reverse transmission, which wastes energy on the railway system. In this paper, based on the interconnection of 10kV station power system and 27.5 kV traction power system, a hybrid energy storage system (HESS) composed of supercapacitors (SCs) and batteries is added to recover the regenerative braking energy, and roof photovoltaic (PV) is installed in railway station to reduce the power consumption of the system, and an energy management strategy with grid peak shaving characteristics is proposed. Then, the optimal dispatching model of high-speed railway power system is established, and the daily operation cost of the system is reduced by using the mixed integer linear programming method. Finally, according to the actual data of a domestic railway station, the proposed optimization method is verified. The results show that the strategy not only reduces the total daily operation cost, but also effectively reduces the peak power purchase of the peak load. The scheme proposed in this paper saves 11.86% of the daily operation cost.

A Multifunctional Energy Storage System With Fault-Tolerance and Its Hierarchical Optimization Control in AC-Fed Railways

To better recycle the regenerative braking energy (RBE) and improve the power quality (PQ) in asymmetric AC-fed railways, a novel multiplex back-to-back energy storage system (MB2ESS) with fault-tolerance ability is proposed, where individual subsystems not only independently operate as self-controlled entities, but also collaborate with adjacent subsystems to resist system disturbances and local faults. On this basis, a hierarchical optimization control method with three-layer structure is designed for the flexible and effective operation of MB2ESS, including the global optimization layer based on finite state machine, the regional decision-making layer with event-driven distributed coordination controller, and the local execution layer via multi-converter autonomous control. It can be used to seamlessly switch different operation modes, coordinately manage the multidirectional transmission of RBE, dynamically control PQ optimization compensation, and rapidly perform fault response behaviors. Subsequently, through typical scenarios, comparative study, and field case of a traction substation in Beijing-Shanghai Railway, the feasibility and effectiveness of proposed scheme are verified. The engineering capability assessment results also show that this scheme can effectively make up for the structure and function deficiencies of conventional railway energy storage systems, which has well adaptability and application potential.

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.

Study on Speed Planning of Signalized Intersections with Autonomous Vehicles Considering Regenerative Braking

In order to reduce the energy consumption caused by the frequent braking of vehicles at signalized intersections, an optimized speed trajectory control method is proposed, based on braking energy recovery efficiency (BERE) in connection with an automated system for vehicle real-time interaction with roadside facilities and regional central control. Our objectives were as follows; firstly, to establish the simulation model of the hybrid energy regenerative braking system (HERBS) and to verify it by bench test. Secondly, to build up the genetic algorithm (GA) optimization model for the deceleration stopping of the HERBS. Then, to obtain signal light status and timing information to be the constraints; the BERE is to be the optimized objective, resulting in optimization for the speed trajectory under the deceleration stopping condition of a single signalized intersection. Finally, vehicle simulations in ADVISOR software are utilized to validate the optimization results. The results show that the BERE during deceleration stopping at a single signalized intersection after the speed trajectory optimization is 36.21% higher than that of inexperienced drivers, and 7.82% higher than that of experienced drivers.

Optimal linearized operation of electric railway system in the presence of flexible renewable sources and switchable capacitor banks considering supply and demand sides’ uncertainties

The electric train (ET) is a great energy consumer in an electrical network, which regenerates a high amount of energy into the grid at the braking moment. Therefore, in this paper, the optimal operation of the electric railway system is proposed considering renewable sources, hybrid storage systems (battery and ultracapacitor units), switchable capacitor banks, and regenerative braking energy of ET at the same time to attain a favorable economic, environmental and operational condition. Renewable sources reduce operating costs and environmental pollution. The storage system is utilized as a flexible source along with renewable generations. The ultracapacitor stores the ET braking energy, and the capacitor bank regulates the voltage. The scheme minimizes the expected network operating cost, while the AC optimal power flow and other technical limits are considered. This problem is nonlinear, and a linearized approximation formulation is implemented to achieve a unique optimal solution with the best and minimum computation time. The unscented transformation method is used to model uncertainties of load, ETs’ energy consumption, and renewable energies. Finally, by evaluating the numerical results, it is illustrated that the efficiency of the proposed method simultaneously improves the economic, environmental, and operational features of the network.

Modeling, simulation, and experiments on waste kinetic energy utilization

Saving energy is as important as energy production. In systems like cars, trains, elevators, and machines that require frequent start/stop operation, a significant amount of kinetic energy is wasted during braking. It may be necessary to employ a sophisticated breaking mechanism to catch waste kinetic energy for later usage. Several criteria influence the proposed braking mechanism. A hydraulic test bench is developed and built to investigate how much kinetic energy can be absorbed and stored during braking using a hydraulic circuit. The test bench’s driving power is a variable voltage and variable frequency electric motor that drives a flywheel that constitutes the majority of the kinetic energy with speeds ranging from 876 to 2975 rpm. A positive displacement gear pump, flow control valve, non-return valve, on/off valve, direction control valve, and an accumulator are the major components of the hydraulic circuit. The use of an automated contactor and a magnetic clutch allows for alternate operations between the mechanical system and the hydraulic brake circuit. The entire system is theoretically modeled, and a MATLAB code is created to investigate the impact of various parameters on the braking mechanism’s performance. Four groups of experiments were conducted to investigate the features of the driving and braking systems, as well as the influence of various factors on the amount of energy that may be collected during braking. The results indicate that 18% to 55% of the kinetic energy may be absorbed and transformed into hydraulic power stored in the accumulator. The amount of hydraulic power gained is governed by the operating speed and restriction ratio (hydraulic system resistance). At certain rotational speeds and restriction ratios, maximum gain hydraulic power could well be produced. Not only can braking energy regeneration improve system efficiency, but it also provides environmental benefits. Alexandria, Egypt is used as a case study to investigate the economic and environmental benefits of employing this technology in cars.

Timetable Optimization and Trial Test for Regenerative Braking Energy Utilization in Rapid Transit Systems

Rapid transit systems play a significant role in supporting rapid social and economic development in large cities all over the world. However, the systems consume a large amount of energy, which brings increasing environmental concerns. A number of energy-saving technologies have been studied on railways. However, few of the outcomes have been tested and evaluated in practice. This paper presents the development of a timetable optimization and trial test on a metro line to reach the full potential of the train regenerative braking system. To achieve this purpose, a timetable optimization algorithm has been developed, and a trial test of the optimal timetable has been arranged on a metro line for a whole day. In the test, all the trains running in the network were organized to operate in accordance with the optimal timetable. The trial test results indicate that by applying the optimal timetable, the regenerative braking energy utilization can be improved, thereby reducing the overall network energy usage.

Integrated Rail System and EV Parking Lot Operation With Regenerative Braking Energy, Energy Storage System and PV Availability

A significant advancement regarding the electrification of transportation has occurred in recent years due to technological developments, environmental concerns, and geopolitical issues in the energy areas all over the world. In this study, a new concept for the integration of rail-based public transportation systems with electric vehicle (EV) parking lots operated by a “park and ride” strategy is propounded, including also renewable resources based energy production. In the proposed structure, the charging power demand of the EV parking lot is supplied by different charging strategies considering the existing unused energy infrastructure capacity and the regenerative braking energy of the railway system, altogether. Here, the design of a photovoltaic (PV) based carport type renewable energy production unit is also realized in the existing local parking area. The development of an optimal energy management system to effectively manage these inputs is realized and the uncertainties pertaining to EVs’ demand are also taken into account. To demonstrate its efficacy, the concept is tested considering a bench of case studies and comprehensive results are obtained.

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.

Control strategy for high speed flywheel energy storage system based on voltage threshold of DC1500 V transit transportation traction grid

Energy storage equipment can play a unique advantage to recycle the regenerative braking energy of metro, of which flywheel energy storage system (FESS) has a good application prospect. At present, the control topology of FESS is two-level converter, and the DC voltage of FESS is mostly DC 750 V. High speed maglev-flywheel energy storage system (HSM-FESS) is used to recycle the braking energy in transit transportation. In order to achieve stable operation of the HSM-FESS, the control strategy based on the voltage threshold of the DC1500 V traction grid is adopted. At the same time, the Neutral Point Clamped (NPC) three-level control method of high speed maglev-permanent magnet motor (HSM-PMM) based on square wave modulation-two phase conduction (SWM-TPC) is proposed. A starting and braking simulation model of metro with HSM-FESS is built in MATLAB/Simulink, and the relevant simulation verification is completed.

An Adaptive Energy Management Strategy of Stationary Hybrid Energy Storage System

In order to further improve the energy-saving and voltage stabilizing effect of the stationary energy storage system (ESS), this article tries to adopt the battery-supercapacitor (SC) hybrid ESS (HESS) as stationary ESS. The advantages of stationary HESS are verified by an example. An adaptive energy management framework for stationary HESS is proposed. A power distribution strategy is proposed to solve the adaptability of two energy storage media to the load variation of rail transportation power system, and to a certain extent, the battery degradation is delayed. The proposed strategy can not only realize the reasonable power-sharing between battery and SC considering the influence of headway on regenerative braking energy but also can keep the battery’s charge and discharge capacity for a long time by using fuzzy logic control (FLC). A simulation is carried out to illustrate the advantages of the proposed energy management strategy (PEMS). Finally, the PEMS is compared with two conventional strategies by the hardware-in-the-loop experiment platform, where it is shown to provide better performance (inferred through increases of 1.1% and 5.7% in energy conservation rate, 0.82% and 6.4% in voltage stabilization rate, and reduction of 2.26 and 0.36 A in the root-mean-square value of battery current at different headway).

An effective utilization scheme for regenerative braking energy based on power regulation with a genetic algorithm

To ensure that regenerative braking energy is fully utilized by traction trains in the whole railway power supply systems, an effective utilization scheme of the regenerative braking energy based on power regulation with a genetic algorithm (GA) is proposed in this paper. This scheme consists of railway power conditioners (RPCs), energy transfer converters (ETCs) and a central controller. A RPC connects the two power arms of each TS, and an ETC connects the two power arms of each section post (SP). The RPCs and ETCs are controlled to transfer the regenerative braking power distributed by the central controller, which is calculated by the GA. The detailed calculation steps are described. Moreover, the principle and control strategies of the negative sequence current compensation by the RPCs are given based on the optimization results of the GA. Finally, optimization calculations and hardware in loop (HIL) experiments were performed. The results show that the utilization rate of regenerative braking energy is about 93.3% and the three-phase current imbalance is reduced by about 98.6% in the case system with the proposed scheme. This result verifies the effectiveness and feasibility of the proposed scheme.

Techno-Economic Model-Based Capacity Design Approach for Railway Power Conditioner-Based Energy Storage System

The railway power conditioner-based energy storage system (RPC-based ESS) is a promising technology to improve the regenerative braking energy (RBE) utilization and power quality of ac direct-fed (25 kV) and AT-fed (2 × 25 kV) railway power systems. However, despite its benefits from the technical perspective, economic viability must be concerned in industrial applications. The capacity is one of the critical issues affecting ESS performance in technical and economic aspects. Therefore, this paper presents a comprehensive approach to designing the capacity for the RPC-based ESS by considering multiple objectives, including the RBE utilization rate, power quality standard, and net lifetime benefit. The proposed approach develops a technical-economic model for the RPC-based ESS based on variables such as the system capacity for RBE utilization and power quality improvement, lifetime cost, and electric charge-based benefits. Moreover, the master-slave control strategy is employed to control the RPC-based ESS to implement the capacity design objectives. Finally, the correctness and effectiveness of the proposed method are validated by sufficient tests based on field load data of a Chinese traction substation.

Net Hydrogen Consumption Minimization of Fuel Cell Hybrid Trains Using a Time-Based Co-Optimization Model

With increasing concerns on transportation decarbonization, fuel cell hybrid trains (FCHTs) attract many attentions due to their zero carbon emissions during operation. Since fuel cells alone cannot recover the regenerative braking energy (RBE), energy storage devices (ESDs) are commonly deployed for the recovery of RBE and provide extra traction power to improve the energy efficiency. This paper aims to minimize the net hydrogen consumption (NHC) by co-optimizing both train speed trajectory and onboard energy management using a time-based mixed integer linear programming (MILP) model. In the case with the constraints of speed limits and gradients, the NHC of co-optimization reduces by 6.4% compared to the result obtained by the sequential optimization, which optimizes train control strategies first and then the energy management. Additionally, the relationship between NHC and employed ESD capacity is studied and it is found that with the increase of ESD capacity, the NHC can be reduced by up to 30% in a typical route in urban railway transit. The study shows that ESDs play an important role for FCHTs in reducing NHC, and the proposed time-based co-optimization model can maximize the energy-saving benefits for such emerging traction systems with hybrid energy sources, including both fuel cells and ESD.

Super-capacitor energy storage system to recuperate regenerative braking energy in elevator operation of high buildings

<span>In operating phases of elevators, accelerating, braking modes occur frequently, so braking energy recuperation of elevators has contributed considerably to decrease the total electric energy consumption for operating elevators in multi-floor buildings. In this paper, the supercapacitor energy storage system is used to recover regenerative braking energy of elevators when they operate down full-load and up no-load, reducing fluctuation of voltage on DC bus as well. Therefore, super-capacitor energy storage system (SCESS) will be parallel with line utility to recuperate regenerative braking energy in braking phase and support energy for acceleration phase. The surplus energy will be stored in the supercapacitors thanks to a DC-DC converter capable of exchanging energy bidirectionally in buck/boost modes, and designing control strategy including two control loops. Inner loop-current loop: controlling charge/discharge process of supercapacitors by current iL complying with operation characteristic of elevator; Outer loop-voltage loop: managing UDC-link at a fixed value. Simulation results with elevator system of the ten-floor building, Hanoi, Vietnam installed SCESS have been verified on MATLAB Simulink, SimPowerSystem with saving energy level about 30%.</span>

Optimal Scheduling of FTPSS With PV and HESS Considering the Online Degradation of Battery Capacity

To improve the power quality (PQ) and eliminate the neutral zone (NZ), a flexible traction power supply system (FTPSS) was proposed to provide flexible interfaces for hybrid energy storage system (HESS) and photovoltaic (PV). However, in order to realize the optimal scheduling of FTPSS, it is necessary to further study the high cost of HESS and battery available capacity. In this study, a two-layer model with the lowest comprehensive cost as the goal is proposed, which includes the cost of investment, replacement, operation and maintenance (O&M), and electricity. In the upper layer, the HESS sizing and replacement strategy are performed to achieve the lowest daily comprehensive cost within the project period. In the lower layer, based on the piecewise linear method, the battery capacity degradation is formulated as a linear mathematical model concerning the depth of discharge (DOD). Then, with the aim to achieve the lowest electricity charge, a mixed-integer linear programming (MILP) model is formulated by associating PV, regenerative braking energy (RBE), and HESS. Sparrow search algorithm (SSA) with CPLEX solver embedded is utilized to solve this two-layer nonlinear model. Finally, the simulation results show that the proposed model can achieve a 13.55% cost reduction.

Energy Management Strategy Adopting Power Transfer Device Considering Power Quality Improvement and Regenerative Braking Energy Utilization for Double-Modes Traction System

Energy Management Strategy Adopting Power Transfer Device Considering Power Quality Improvement and Regenerative Braking Energy Utilization for Double-Modes Traction System