| With the vigorous development of electric power system and electrified railway,China’s high-speed railway has rapidly gone to the world in recent years.While constantly refreshing the "Chinese speed",the development of high-speed rail has injected new vitality into the rapid development of cities and regions.In the past decade,China’s high-speed railway has transformed itself from a "follower" into a "leader" in the world,connecting numerous large and small cities,and changing China’s urban pattern at an unprecedented speed.With the development of high-speed railway,the asymmetric,nonlinear,high-impact and high-power characteristics of traction load will cause a series of power quality problems,among which reactive power,negative sequence and harmonic problems are more obvious.At the same time,for the special load characteristics of traction load,the rationality of measurement method also needs to be further explored.This paper first analyzes the relationship between the power system and the traction power supply system,and using the general transformation between traction substation electric parameters,set up for different connection types of three-phase equivalent model of traction power supply system,and considering the system impedance,balanced load(linear load)under the condition that the three-phase equivalent model of power system is established.Based on this model,the distribution characteristics of the positive sequence,negative sequence,fundamental wave and harmonic power flow in the system are derived.As a harmonic source,the traction load injects harmonic power into the system,which is eventually absorbed by the system impedance and linear load.Secondly,this paper expounds the imbalance in the sine with the main imbalances in the system according to the positive sequence active power measurement,foldback are meter measurement methods and considering equivalent of apparent power factor measurement methods,the advantages and disadvantages of three kinds of measurement methods are analyzed,and based on the IEEE Std 1459-2010 power theory is proposed in view of the unbalanced traction load of electric energy metering.Finally,a power factor assessment model is established,and the power factor limits are fitted by a large number of measured data and voltage offset constraints. |
