Study On Power Quality Control And Regenerative Braking Energy Utilization Of Traction Power Supply System

Nowadays,"low-carbon development" has become an important concept of global economic development,and the implementation of low-carbon transportation has also become the strategic choice of each country.Electrified railway has become an important way of low-carbon transportation due to its advantages of energy conservation,environmental protection,economic convenience and strong transportation capacity.Therefore,the birth and success of electrified railway has made the world re-examine the value of railway.The load of electrified railway is mainly traction load of electric locomotive,which has the characteristics of single-phase,nonlinear,random fluctuation and energy generation when braking,which will bring complex power quality problems and regenerative braking energy utilization problems to traction power supply system.Traditional Railway Power Regulator(RPC)can deal with the Power quality problems such as negative sequence and harmonics,but it cannot solve the problem of the utilize of regenerative braking energy.Based on this,this paper proposes to install Hybrid Energy Storage System(HESS)on RPC(HESS-RPC)is constructed,and the corresponding control strategy is studied.To comprehensively solve the problem of power quality control and regenerative braking energy utilization in traction power supply system.At the same time,aiming at the power distribution problem of internal charge and discharge of HESS,a method of dynamically adjusting the charge and discharge power of HESS is proposed based on the change of the State of Charge(SOC)of the supercapacitor.The main research contents of this paper include:(1)The structure of traction power supply system model is established,and on this basis,analyzes the causes of the traction power supply system of power quality problems,and then presents the process of regenerative braking energy,and illustrates several common ways of energy use for later in this paper,we solve the traction power supply system power quality management and utilization of regenerative braking energy provides a theoretical basis.(2)Aiming at the limitations of the traditional RPC,a system topology structure which can take into account both power quality management and regenerative braking energy utilization was designed.In this system,HESS is connected to RPC’s intermediate DC capacity link through a converter,and the HESS-RPC structure is obtained.Then,on this basis,the comprehensive compensation principle and energy utilization principle of the whole system are analyzed,and the control strategy of the system is designed with the comprehensive realization of negative sequence,harmonic compensation and regenerative braking energy utilization as the control objectives.Finally,the simulation experiment and result analysis prove that the topology and control strategy can not only improve the power quality of traction power supply system,but also effectively utilize regenerative braking energy.(3)Aiming at the problem of charging and discharging power distribution in HESS,this paper proposes a method to dynamically adjust the charging and discharging power of HESS based on the SOC of the supercapacitor,aiming at the shortcomings of traditional charging and discharging power distribution methods.This method can maintain the power regulation ability of the supercapacitor,reduce the discharge depth of the battery and the frequency of power change,improve its service life,and enhance the economy of the system.Finally,a simulation test is carried out with the simulated working condition data,and the advantages of the proposed dynamic power allocation method are verified by comparative analysis.