Research On Technology Of Photovoltaic DC Microgrid With Hybrid Energy Storage Connected To Traction Power Supply System

Photovoltaic DC microgrid with hybrid energy storage connected to traction power supply system is not only conducive to the construction of low-carbon and clean green railway and the development of rail transit Internet,but also can promote the nearby consumption of photovoltaic power and the recycling of regenerative braking energy,which has significant economic and social benefits.Due to the particularity of traction power supply system,the access of new energy is subject to many constraints,the current research rarely consider the balanced distribution between new energy output and regenerative braking energy recovery,and lack the optimization analysis of hybrid energy storage power distribution and system operation.Therefore,this paper will focus on the topology,energy management strategy and capacity optimal configuration of photovoltaic DC microgrid with hybrid energy storage connected to traction power supply system.Building a model of photovoltaic DC microgrid with hybrid energy storage is the basic work of this paper.According to the principle of photovoltaic cell and maximum power point tracking control,the simulation model is established,and the output characteristics of photovoltaic power generation system under different environmental conditions are analyzed.A hybrid energy storage system model is studied,and its topology and control strategy are determined.The topology and control strategy of bidirectional DC / AC converter are given,and the microgrid simulation model is built.According to the established microgrid model,the scheme and operation characteristics of microgrid connected to traction power supply system are studied.The principle and topology of traditional traction power supply system and co-phase traction power supply system are analyzed,and the topology and operation of connected to the two traction power supply systems are studied and analyzed,explained the advantages and disadvantages of the two methods,and the co-phase traction power supply system is selected as the basis for subsequent research.The traction load characteristic is analyzed and the regenerative braking process is studied.A simulation model is built in Matlab/Simulink,and the simulation results verified the feasibility of the proposed scheme.According to the proposed scheme,the energy management strategy of microgrid connected to traction power supply system is proposed.The energy flow of the system under different working conditions is analyzed,and the maximum charging and discharging power of hybrid energy storage is determined by using probability and statistics method.According to the photovoltaic power and load power,the target output value distribution strategy of hybrid energy storage system is proposed.In order to realize the complementary characteristics of the battery and supercapacitor and prolong the cycle life of the battery,a charging and discharging protection method is proposed,which makes the battery conform to the principle of "shallow charge and shallow discharge".A low-pass filtering algorithm with real-time adjustment of the filtering time constant is used to distribute the power,and a power coordinated distribution strategy of the hybrid energy storage system with amplitude limiting dynamic adjustment in the state of charging and discharging is proposed.For example simulation analysis,verified the effectiveness of the energy management strategy.Based on the topology and energy management strategy,the optimal configuration model of hybrid energy storage system is established and solved.A two-level optimal allocation model of hybrid energy storage based on the life cycle cost is established,the objective function of the outer model is the minimum daily cost of system operation,and the objective function of the inner model is the electric energy saved by system operation.The cycle life of energy storage is calculated by rain flow counting method,and the loss model of energy storage is established to calculate the daily cost of energy storage.The model solving process is designed based on particle swarm optimization algorithm,the single energy storage and hybrid energy storage are solved respectively.The solution results of the optimization model and the operation of the system are analyzed.It proved that the superiority of hybrid energy storage,the correctness of the solution results and the effectiveness of the proposed scheme.