Analysis About Impact And Countermeasure Of Electric Locomotive On Power Quality

With the continuous improvement of social economy and national life,electrified railway is rapidly developed in recent years.However,due to the non-linearity and volatility of the traction locomotive,the power quality problems such as harmonics,negative sequence and reactive power are generated to the traction power supply system,which affects the safe and economical operation of the power system.In order to meet relevant standards of the power quality in electrified railway,it is very important to study and manage the power quality of traction power supply system deeply.In this paper,the influence in electric locomotive on the power quality of traction power supply system is studied by means of theoretical analysis,modeling and simulation and testing on the spot.The main research content is listed as follows.Firstly,based on the analysis of the structure type and power supply mode of the electrified railway traction power supply system,the SS9 electric locomotive and the CRH5 type EMU are systematically modeled.The model parameters of the two types of locomotives and the parameter design of the controller are discussed.At the same time,the simulation analysis was carried out for the Rongchang traction power supply system of the SS9 electric locomotive running section and the Yushan traction power supply system of the CRH5 EMU operation section.The simulation results show that the low harmonic content of Rongchang traction power supply system is large,mainly 3 times,5 times,7 times and so on,Yushan traction power supply system is mainly dominated by high harmonics and the lower harmonic content is less,which verifies the influence of the two types of locomotives on the traction power supply system.Secondly,the field test and analysis were carried out for Rongchang traction substation and Yushan traction substation.The main test and analysis in detail for two traction substation such as the power factor,harmonic voltage and current,three-phase voltage imbalance and so on.From the test analysis results can be seen,Rongchang and Yushan traction substation power factor in the case of reactive power back to the original power factor are lower than 0.9,Rongchang traction substation harmonic voltage integrated distortion rate of 95% probability is more than 2%,can not meet the standard requirements.It needs to take an effective power quality management strategy.Finally,based on the analysis of the working principle of the in-phase traction power supply management technology,the in-phase power supply control scheme is designed,which is based on the active symmetric compensation technology of the Unified Power Flow Controller(UPFC).The principle of the equilibrium transformation of the scheme is deduced in detail.The equilibrium equation of system harmonic,negative sequence and reactive power compensation is obtained,and the generation and control method of the instruction current in the UPFC is designed.The simulation results show that the total harmonic distortion rate of current harmonic system can meet the requirement of harmonic current,and the three-phase current is almost free of reactive current.The feasibility and correctness of the scheme are verified.At the same time,the scheme also provides a reference for the management of power quality problems in electrified railway.