Research On Power Quality Of Distribution Network With Large-scale Electric Vehicle Charging

With the continuous promotion of electric vehicles,its adverse effects have begun to appear,including power quality problems caused by large-scale electric vehicle grid-connected charging.The grid connection of electric vehicle charging devices containing power electronics will generate harmonic pollution,and the random grid connection of large-scale electric vehicles will cause fluctuations in node voltage.Therefore,research on the power quality of large-scale electric vehicle grid-connected charging is of great significance for the popularization of electric vehicles and the healthy development of the power grid.In order to explore the power quality problems caused by the charging of large-scale electric vehicles,this article starts from the structure and principle of electric vehicle charging devices and the charging characteristics of power batteries,and establishes an equivalent model of electric vehicle charging.The mechanism of harmonic generation and the influencing factors of harmonics,and the theoretical analysis and simulation verification of various influencing factors are respectively performed.Based on the analysis of the mechanism of the harmonics and the analysis of the influencing factors,an engineering calculation method for the total harmonic distortion rate of the charging station current taking into account the timing characteristics of the electric vehicle is proposed,which greatly simplifies the calculation of harmonics for large-scale electric vehicle grid-connected charging It makes up for the shortcomings that simulation research is difficult to model in terms of timing characteristics.After simulation verification,the algorithm accuracy can meet the engineering requirements.Based on actual surveyed electric vehicle travel data,the timingcharacteristics of different types of electric vehicles are analyzed.Based on this,the harmonic characteristics of different types of electric vehicle charging stations are calculated using the harmonic engineering calculation method proposed in this paper,and the voltage characteristics of different types of electric vehicle charging stations are calculated using dynamic probability flow.The calculation results show that both the current total harmonic distortion rate and the voltage overrun probability of the electric vehicle charging station show certain timing characteristics.There is even a period when the current total harmonic distortion rate is low but the voltage overrun probability is high Opposites.The analysis results show that when planning and operating electric vehicle charging stations,comprehensive consideration should be given to the local electric vehicle travel rules,charging station harmonic characteristics,and charging station voltage characteristics to develop an appropriate planning and operation plan.