Research On Negative Sequence Compensation And Energy Intensive Optimization Of High Speed Railway Based On Hybrid Energy Storage Of Traction Network Side

The high speed railway system places a greater load on the electricity grid.As the mileage increases,the energy consumption of high-speed railways gradually increases.With the increase of railway operating mileage,its energy consumption is gradually increasing.In response to the goal of "carbon neutral,carbon peak",high speed railway needs to realize low-carbon operation.Due to the random and non-linear characteristics of the train load of the traction power system,there is a negative sequence problem in the traction power system,which affects the safe and stable operation of trains.The regenerative braking energy generated by the trains,which contains negative sequence and harmonic components,affects the power quality of the grid when it is fed back directly into the grid.If this part of the energy is fully utilized,it will help reduce the energy consumption of the train and contribute to the ’double carbon’ target.To realize the negative sequence compensation and regenerative braking energy recycling of high-speed railway traction power system,the hybrid energy storage railway power regulator system is studied.The research contents are as follows.(1)The composition structure of the high speed traction power supply system is analyzed.Based on this,the load characteristics of the traction power system,the negative sequence characteristics of the traction power system and the mechanism of regenerative braking energy generation and the impact on the power system are analyzed by combining the measured load data of a traction substation.(2)The topology structure of railway power conditioner system with hybrid energy storage is described,including traction power supply system,railway power conditioner(RPC)and hybrid energy storage system.The structure and mathematical model of RPC are studied.The structure and mathematical model of a hybrid energy storage system consisting of a lithium battery,a supercapacitor,and a bidirectional DC/DC converter are studied.The circuit model of the bidirectional DC/DC converter in buck and boost modes are analyzed.Based on this,the energy flow characteristics of the hybrid energy storage RPC system under four operating states and the integrated compensation principle are analyzed.(3)The control strategy of hybrid energy storage RPC system is investigated,including three parts: energy management strategy,RPC control strategy,and bidirectional DC/DC control strategy.Firstly,in the energy management strategy,the power of the supply arm is derived and calculated,a charging and discharging strategy of the hybrid energy storage system is proposed,three operation modes of the hybrid energy storage system-peak shaving and energy release,standby and trough filling storage are classified,and the performance of the hybrid energy storage system for each mode is studied.A power allocation strategy based on low-pass filtering algorithms to achieve high and low frequency power decomposition is investigated.Secondly,for the RPC control strategy,the RPC compensation current and the converter control strategy are investigated.Then,the Buck/Boost structure bidirectional DC/DC converter control strategy is studied.Finally,the validation analysis is carried out on the Star Sim power electronics small-step real-time simulator from Shanghai Modeling Tech and MATLAB/Simulink.The results show that the proposed control strategy can achieve peak and valley reduction,negative sequence compensation and regenerative braking energy utilization for traction loads.(4)The negative sequence compensation for hybrid energy storage RPC systems considering limited capacity is optimized.Consider the voltage imbalance problem that occurs on the grid side and study its effect on the V/v traction power system.Under this influence,an optimization model with the negative sequence compensation degree as the optimization objective is established by combining the RPC capacity limitation factors and introducing the compensation coefficient,which is solved by the sequential quadratic programming method.Finally,the simulation is verified on MATLAB/Simulink,and the results show that the proposed negative sequence compensation optimization model can reduce the negative sequence current of the traction power supply system and improve the regenerative braking energy utilization when the grid voltage is unbalanced.