| In recent years,climate change and sustainable environmental development have attracted wide attention around the world.The rapid development of electrified railway effectively reduces carbon emissions and plays an important role in transportation.As regenerative braking is preferentially used in the braking process,a large amount of regenerative braking energy will be generated.These energies contain harmonic and negative sequence components,which bring serious power quality problems to the power grid and directly affect the economic benefits of railway departments.To develop electrified railway with energy storage technology and rationally utilize regenerative braking energy is an effective method to improve operation economy and save energy.This thesis proposes a regenerative braking energy storage scheme using railway power conditioner(RPC)combined with hybrid energy storage systems,and focuses on its control strategy,which is useful for improving regenerative braking energy utilization and reducing railway operation costs.Firstly,the necessity of regenerative braking energy utilization is studied and the system regenerative braking energy capacity level is determined for the traction load characteristics.The regenerative energy utilization technology of electrified railway based on energy consumption,traction substation energy storage,10 k V power regenerative energy recovery and RPC is compared and analyzed.Various energy storage technologies are evaluated in terms of principle,application scenario and economy,and a hybrid energy storage scheme combining battery and supercapacitor energy storage technology is eventually developed.Secondly,the working principle of RPC is analyzed and the equivalent mathematical model of RPC is constructed.The topological structure of bidirectional DC/DC converter is analyzed,and the working principle of bidirectional DC/DC converter with Buck/Boost circuit is studied.The energy transfer characteristics of both sides of the traction substation are analyzed according to the energy flow of the feeding section.In order to realize energy flow and improve power quality of two feeding sections,RPC optimization control strategy was further studied.Based on the analysis of negative sequence compensation method,RPC optimization compensation control method was proposed.Finally,a top-level energy management control strategy based on threshold detection is proposed to realize complementary technical characteristics of battery and supercapacitor storage media.On the premise of "shallow charging and discharging" of the battery,an internal coordination control method is designed based on the moving average filtering theory for the dynamic adjustment of the limiting power.The simulation model was built in MATLAB/Simulink,and the results show that the scheme can realize regenerative braking energy recovery and utilization while improving the power quality,thus verifying the feasibility of the hybrid energy storage system based on RPC architecture applied to railway high-power regenerative energy scenarios. |
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