Research On The Operating Characteristics Of Integrated Charging System In The V2G Application

The popularity of electric vehicles has promoted the development of energy conversion technology(Vehicle-to-Grid,V2G)between power grids and electric vehicles.Electric vehicles can’t achieve high power in the energy conversion due to the limitation of the size and power level of the charger.However,if the drive system components with higher power levels are added to the charger,the limited space will be saved and the power level of the system can be increased.So the integrated charger for V2G service has become a hot issue in the energy-information management.In the V2G mode,the charger needs to have a wide output power,faster response speed,and also meet the harmonics requirements of grid current in the process of feeding power to the grid.Based on the above conditions,this paper mainly researches the output characteristics of the integrated bidirectional charger when feeding power to the grid.Firstly,this paper analyzes the choice and working principle of the bidirectional charger topology,including the boost principle,modulation technology and so on.Then the control strategy is proposed by establishing the mathematical model of the system and combing the regulation of the power grid,which is prepared for the analysis of integrated systems and the construction of the experimental platform.Because of the limitations of the electric vehicles’ space,this paper presents an integrated approach that replaces the filter inductances with the motor windings.By changing the connection method of the motor windings to ensure that no electromagnetic torque is generated in the V2G mode.The simulation results show that the maximum rotor torque ripple generated by the three-phase stator windings is small.In order to reduce the influence of the mutual inductances between the windings,this paper improves the system control method that the sample variable is multiplied by the corresponding coefficient matrix.In addition,the active damping control of integrated systems has reduced the harmonic current at the resonant point of grid current.In grid experiment,the closed loop formed by the feedback capacitance current in the control system suppresses the resonant spikes generated by the third-order filter structure at the resonant frequency.For reducing the instability caused by current sensors and saving the system cost,the estimation algorithm of filter capacitor current is used for replacing the current sensor.In the algorithm,the integral operations are instead of two series-connected low-pass filters.The experimental results show that the estimation algorithm can also achieve good active damping effect.