Study On Optimized Sizing Of Hybrid Energy Storage Devices For High-speed Railway

The power quality issues represented by voltage unbalance and the electrical sectioning issues can be effectively solved by co-phase power supply technology.By integrating the hybrid energy storage system into the co-phase power supply system,the peak-shaving of traction load and utilization of regenerative braking energy can be further realized.Due to the violent fluctuations of traction load and the particularity of electricity price,research on suitable energy management strategy for the hybrid energy storage system of the high-speed railway becomes an urgent problem.On the other hand,the capacity of an energy storage device is closely related to its investment cost.How to take the traction load characteristics into account and conduct hybrid energy storage device design is also a key issue of economic operation.This thesis focuses on the above issues and conducts the following research:1)Demand analysis of hybrid energy storage system for high-speed railway.According to the traction load,the peak-valley characteristics of traction load are studied.The demand peak-to-average ratio of the traction load is about 300% and the regenerative braking energy accounts for about 5% of the total energy consumption.Based on the two-part tariff,the impact of the peak-valley characteristics on the electricity cost is analyzed,which also describes the practical significance of the peak-shaving and valley-filling and the demands of energy storage system.Based on the comparison of different traction substation energy storage schemes,this thesis proposes a scheme of hybrid energy storage system for high-speed railway and establishes the mathematical model to provide support for the subsequent research.2)Energy management strategy of the hybrid energy storage system in traction substation.A two-layer structure of energy management strategy is proposed in this section.Proposed an outer control strategy to control energy storage system discharging in periods counted by historical data.Then,an inner power distribution strategy based on wavelet packet transform is proposed,to dispatch low-frequency power components to the battery and deliver highfrequency power components to SC.Finally,the configuration process of the hybrid energy storage system is established and the effectiveness of the configuration scheme and the energy management strategy is verified by an example.3)The optimization sizing model of the hybrid energy storage system based on the life cycle.The sizing model aims at the optimal economic benefit during the life cycle process,considers the impact of energy management strategy and the time cost of capital.A battery loss model is established for battery service life evaluation.An improved particle swarm optimization combine with cross mutation is studied by taking thresholds of energy management strategy and capacity configuration of the energy storage system as undetermined parameters.The algorithm is used to solve the optimization model,the convergence performance of the algorithm is analyzed as well.This thesis mainly proposes an energy management strategy for the hybrid energy storage system of high-speed railway and then establishes an optimization sizing model,which provides effective support for the application of high-speed railway hybrid energy storage technology.