Study On Optimized Sizing Of Hybrid Energy Storage Devices For Co-phase Power Supply Systems

The power quality issues represented by voltage unbalance and the electrical sectioning issues have severely restricted the safe,high-quality,and high-efficient operation of traction power supply system(TPSS)under existing traction power supply scheme.Co-phase power supply technology is an ideal solution,which is based on the symmetrical compensation theory.By integrating the photovoltaic(PV)power generation system and the hybrid energy storage system(HESS)into the DC bus of power flow controller(PFC),the utilization of regenerative braking energy and peak-shaving and valley-filling of traction load can be further realized,and the PV penetration rate can be improved.How to actively control the peak load based on controllable components to alleviate the contradiction between supply and demand,take the voltage unbalance power quality issue into account,and conduct hybrid energy storage device capacity planning and design is worth further research.This thesis focuses on this issue and conducts the following research:1)Optimal operation of co-phase traction power supply system with the integration of PV and HESS.For the two scenarios of a single traction substation and multiple co-phase traction substations in the flow-through mode,we set up the target of the lowest day-to-day operating cost of the same-phase traction substation,with hybrid energy storage device charging and discharging strategies,PV output,and The optimal operation model of the cophase traction power supply system whose power of the power flow controller is a decision variable,especially considering the grid-side voltage imbalance constraint.By linearizing the non-convex and nonlinear constraints in the original optimization model,a mixed integer linear programming(MILP)model is obtained and solved using the commercial optimization solver CPLEX.2)Optimal operation of co-phase traction power supply system under uncertain environment.Taking into account the uncertainties of PV output and traction load,a two-phase robust optimization(TSRO)model of the co-phase traction power supply system was established.The first stage is based on the PV output and traction load prediction information,formulating the charging and discharging strategy of hybrid energy storage devices and the electricity trading scheme with the grid;the second stage aims to find the worst-scenario of PV output and traction load and the corresponding optimal power flow.Finally,the two-stage robust optimization model is solved based on the column and constraint generation algorithm(C&CG).The analysis of a numerical example validates the advantages of the proposed twostage robust model over the deterministic model in terms of optimality and robustness.3)Optimized sizing of hybrid energy storage device.Aiming at the project planning and design scenario,a two-level planning model for hybrid energy storage devices is proposed:the upper-level model is the optimal sizing model of hybrid energy storage device with the target of lowest total cost during the project lifetime;the lower-level model is the optimal scheduling model of hybrid storage device with the target of lowest daily electricity cost.The grey wolf optimizer(GWO)with embedded CPLEX solver is proposed.The algorithm is optimized to obtain the rated energy capacity and power capacity of the hybrid energy storage device.In addition,the sensitivity of different parameters and the convergence of the algorithm are analyzed as well.