title: Intelligent Train Operation with On-Board Energy Storage Device: An Energy-Saving Perspective
Creators: name: Wu, Chaoxian
Publisher: name: University of Liverpool Repository
Year: 2023

description: Railway transportation is applied extensively in urban transportation to satisfy the increasing travel demand as well as reduce CO2 emission from the road transportation. However, energy consumption of the railway transportation is observed to increase due to its boosting construction and usage. In this case, energy efficiency of the railway transportation has become a popular research topic in the past few decades. At the same time, as an emerging technology, the on-board energy storage device (OESD) is utilised in many modern railway systems to help improve the energy efficiency. This thesis focuses on the investigation of the intelligent train operation with OESD, in which the optimal train operation strategy, OESD discharging/charging strategy, mutual influence between the train operation strategy and OESD, and study on different types of energy storage as OESD in train operation are given. First, the intelligent train operation with OESD in single inter-station section is discussed. An integrated mathematical model to optimise the train speed trajectory with OESD to minimise the net energy consumption of the system for a single inter-station section is established. The influence of the OESD capacity, energy status of OESD and OESD degradation on optimal train operation solution is revealed based on the proposed model. The results show that with a general railway case, the net energy consumption can be significantly reduced by the intelligent management of both the train operation mode and OESD discharging/charging process. Second, the intelligent train operation with OESD in a service cycle is discussed. The OESD is allowed to discharge/be charged when the train dwells at each station. A two-step method, which overcomes the drawbacks of the originally proposed mathematical programming model, is proposed to locate the optimal train speed trajectory, timetable and OESD discharging/charging strategy for both inter-station running and dwelling at stations with high computation efficiency. Beijing Yizhuang line as numerical experiment is given in this thesis, where the reduced energy consumption is observed when compared to other scenarios by using the optimised solution, showing the effectiveness of the proposed method. Third, the intelligent train operation with OESD in a network is investigated. By considering the train network and power network as the environment information, an agent-environment model for the train with OESD is proposed. In the model, the available regenerative braking energy from other trains in the railway power network is formulated into the time-variant expectation based on the stochastic running time distribution of the train network, which can be used by train and OESD during the running. This further utilises the OESD to receive as much as the regenerative braking energy in the environment to reduce the energy waste. The results shows that the proposed method is able to improve the utilisation of the regenerative braking energy in the power network, and also lead to the significantly reduced energy consumption. Fourth, impact of the different types of energy storage as OESD on the optimal train operation strategy is studied. The dynamic discharging/charging power limits with respect to the energy status of each type of OESD, supercapacitors, flywheels and Li-ion batteries, are taken into account. In addition, the optimal sizing problems of the above three types of OESD are also investigated. The results show that the introduction of different type of OESD will lead to the change of the optimal train operation strategy and the resulted energy-saving performance. Using Beijing Changping line as numerical experiment, it is found that choosing the right type and right sized OESD are important due to the significantly different engineering characteristics, energy cost and monetary cost brought to the system when introducing different OESD. In summary, this thesis gives a systematic discussion and exploration on the intelligent train operation with OESD in a perspective of energy saving from small operation scale to large operation scale, and the OESD is also studied as general/no specific type to multiple/specific type to ensure both of the academic and industrial value of the thesis.