Research On Converter Control And Orderly Charging Strategy Of Electric Vehicle Charging Station

The rapid development of electric vehicles has relieved the global energy and environment pressure. At the same time, electric vehicles access to the power grid has brought new problems. On the one hand, electric vehicle charging facilities designed or controlled improperly, may inject a lot of harmonic current to the power grid,and reduce the power factor, so that it can affect the normal operation of the power grid seriously. On the other hand, the disorder charging of electric vehicles can produce a bad peak load, which will increase the peak load of power distribution network. In view of the above problems, this paper studied the control strategy of electric vehicle charging station and the orderly charging strategy of electric vehicles.Firstly, by modeling the electric vehicle charger, which is consist of thyristor phase-control rectifier and DC/DC power converter, this article analyzed of the influence of e lectric vehicle battery charging on pow er quality. And for the problem of the harmonic pollution and low power factor in the process of charging, designed the charger topology which is consist of H bridge cascade multilevel converter and bidirectional DC/DC power converter. Combined with the characteristics of the battery, the control method of the bidirectional charger was studied.Secondly, based on requirements of the charging and discharging to the charger, the control methods of DC side voltage and the AC side current of the cascaded H-bridge multilevel converter were research. The purpose of DC side control is to make the DC voltage equilibrium of converter output. And by the AC side control, the grid side current is sinusoidal and the harmonic current content is reduced. This paper combined the principle and characteristic of fixed switching frequency PWM current control and hysteresis PWM current control method, and proposes a hysteresis PWM current control method for quasi fixed switching frequency. Through the establishment of battery charging and discharging system model for SOC of battery, charger power factor, line side harmonic, it is verified the effectiveness of the control method.Finally, the power demand of electric vehicle disorder charging is analyzed by using Monte Carlo method when the operation and parking law of electric vehicle are combined. In order to reduce the negative effect of the disorder charging on the daily load curve of power systems, an ordered charging control model for electric vehicles is established, which is aimed at reducing the peak-valley gap of power system and reducing the fluctuation of the load fluctuation, and the model is solved by the particle swarm optimization algorithm. At last, the simulation results of the ordered charge and the disorder charge shows that the coordinated charging control strategy is realized on chipping peak off and filling valley up, and the daily load curves are stabilized.This project was supported by《Intelligent Grid Interfaced Vehicle Eco‐charging》, which is the International(regional) cooperation exchange program of the National Natural Science Foundation of China.