Research On Harmonic Modeling Of Electric Vehicle Charging Station Based On Data-driven Method

In the background of the global energy crisis,the energy revolution,which is gradually replacing traditional energy sources with clean energy,is quietly taking place.As a new generation of vehicles,electric vehicles have the incomparable advantages over traditional vehicles and ushered in a major opportunity for its development.However,EV chargers are non-linear loads mainly composed of power electronic devices,and harmonics are injected into the distribution network after large-scale grid connection,which is not conducive to the safe and stable operation of the power grid,and will also have adverse effects on other electronic equipment in the power grid.Therefore,it is of great practical significance to study the harmonic influence on the distribution network when the electric vehicle charging station is connected to the grid for charging.This paper presents a data-driven dynamic harmonic source modeling method for charging stations of electric vehicles.Firstly,based on the research on the mechanism of harmonic generation in the charging process,an equivalent nonlinear resistance model based on battery state of charge(SOC)is established,and the electric vehicle charging based on the model is built on the PSCAD/EMTDC simulation platform.The equivalent model is used to simulate a complete charging cycle;harmonic characteristics such as current and voltage harmonic contents in the dynamic charging process are analyzed,and relevant parameters that can reflect the harmonic characteristics of electric vehicle charging process are extracted.Then,the whole equivalent modeling strategy is adopted for the electric vehicle charging station.The relationship between the harmonic current amplitude and phase angle at the grid-connected point of charging pile(station)of EV and the fundamental voltage,the charging state of battery and the type of rectifier circuit is mapped non-linearly by RBF neural network.Taking the simulation data of the complete charging cycle of single/multiple electric vehicle chargers as an example,the effectiveness of the modeling method is verified.The results of calculation examples show that the modeling method can well reflect the harmonic characteristics of charging stations' parallel nodes,and has fast simulation speed and high accuracy.It is an effective harmonic source modeling method.Finally,the harmonic effect caused by grid-connected charging stations of electric vehicles are analyzed by the proposed model,and the situation that the power supply voltage contains harmonic is predicted and discussed.