Research On Co-phase Hybrid Energy Storage And Power Supply Technology In Electrified Railways

The characteristics of electrified railway traction load such as asymmetry and nonlinearity not only cause the problems of phase separations and negative sequence technically,but also cause the problems of low utilization of traction transformer capacity and regenerative braking energy feedback economically.Using co-phase power supply technology can eliminate phase separations and accomplish better compensation of negative sequence than before.Using the "peak-shaving and valley-filling" characteristics of the energy storage devices,the capacity utilization rate of traction transformer can be improved and the regenerative braking energy can be recovered.Therefore,based on the single-phase combined co-phase power supply system and energy storage technology,this thesis carries out research on the co-phase hybrid energy storage and power supply technology of electrified railway,so as to achieve good governance of negative sequence,rational utilization of traction transformer capacity and efficient utilization of regenerative braking energy.The main research contents are as follows:Based on single-phase combined co-phase power supply technology,combined with the energy storage characteristics of batteries and supercapacitors,the energy management strategies for co-phase hybrid energy storage and power supply system that take into account the negative sequence compensation and the operation economy of traction substation are proposed respectively.Firstly,aiming at improving the negative sequence,with the national standard limit as the constraint,three different kinds of negative sequence compensation modes are divided according to the degree to which the negative sequence exceeds the national standard.Accordingly,the negative sequence compensation model is established,and the compensation current calculation formula of the port of the hybrid energy storage device under each negative sequence compensation mode is derived.Then,aiming at improving the operation economy of the traction substation,the functional relationship between the capacity of the traction transformer and the electricity fee paid by the traction substation is analyzed.Correspondingly,the capacity replacement model of traction transformer is established,and the compensation power calculation formula of the port of hybrid energy storage device under the model is given.Finally,the feasibility of the proposed two energy management strategies is verified with the measured data.A power allocation method based on adaptive piecewise and smoothing filtering is proposed.In order to improve the negative sequence and increase the utilization rate of traction transformer capacity,based on the energy management strategies considering the negative sequence compensation and the operation economy of the traction substation,the calculation formula of the target power of hybrid energy storage system is derived.Considering the complementary characteristics of battery and supercapacitor,a target power allocation strategy based on adaptive piecewise and smoothing filtering algorithm is proposed for hybrid energy storage system,and the effectiveness and rationality of the power allocation strategy is verified with the measured data.The allocation optimization model of hybrid energy storage system is established and solved.Firstly,based on the life prediction model of the energy storage equipment,the allocation optimization model of the hybrid energy storage system is established by taking the daily operating cost of the hybrid energy storage and power supply system as the objective function and the energy saving rate and the power shortage rate of the load as the operating index.And the adaptive particle swarm optimization algorithm is established as the solution algorithm of the model.Finally,combined with the measured data,the allocation results of the hybrid energy storage system with different schemes and different operating indexes are analyzed,and the reliability of the allocation results is verified.Finally,the work of this paper is summarized and the shortcomings of this research are prospected.