Study Of Hybrid Power Supply System Of Light Rail Transit Based On Onboard Energy Storage System

Since the LRT(Light Rail Transit) has the advantage of large volume, convenient, safe and lower cost than subway, so in recent years, LRT developed very quickly in many big and medium cities all over the word. The braking mode of traditional LRT vehicles is generally the resistance braking or mechanical braking. So a lot of braking energy is dissipated as heat and it’s causing a huge waste of energy. Thus how to use energy storage technology to recover braking energy and reduce energy consumption of LRT has become a hot topic in the LRT research area.The emergence of new power type titanate lithium battery nearly two years makes the rising of power density, discharge-charge speed and cycle life of lithium battery. The new titanate lithium battery has unique advantages and prospects to recover the LRT braking energy, avoid regeneration failure and achieve feeder-free operation. So this thesis will focus on the energy management, control strategy, simulation model structures and capacity configuration of the on-board lithium battery energy storage system.Firstly, the thesis summarizes of the LRT energy storage technology and completes the experimental analysis of the charge-discharge performance of the new titanate lithium battery. The on-board lithium battery energy storage system includes bi-directional DC/DC converter and lithium batteries. This thesis describes the working principle and the parameter design of bi-directional DC/DC converter circuit in detail.Based on the shortcomings of typical DC grid voltage control strategy, this thesis presents a new SOC optimization control strategy for the on-board energy storage device. The strategy achieves the charge-discharge control and energy management of battery from the power perspective, so it’s more straightforward. In addition, this control strategy can also gently cut the battery energy storage device when it’s at a low battery level or fully-charged state, thus it is valid to avoid a series of "step-index" voltage and current caused by the rapid removal of storage device. Therefore the new control strategy is conducive to the stable and secure operation of the system. At the meantime, the thesis also builds the corresponding single train and multiple trains simulation model and uses a semi-physical hardware test platform to validate this new control strategy.Finally, based on the above findings and the Japanese LRT line parameters, we use MATLAB software to optimize the capacity of on-board energy storage system with the purpose of seeking the maximization economic benefits of the whole system, and assess the effect of recovering braking energy and stabilizing DC grid voltage of on-board lithium battery energy storage system in all domains.