Research Of Grid-connection Control Strategy Under The Vehicle To Grid Mode

To develop the Electric Vehicle（EV）industry plays the important part in the new energy strategy.Promoting not only energny conservation and consumption reduction in vehicles but fuel vehicle’s electrification program,that can alleviate the energy and environmental problems faced by our country at this stage to a certain extent.In recent years,the number of EVs has increased rapidly.For the power system,how to deal with large-scale plug-in EVs so that between the EVs and the grid can exchange power in a ’friendly’ and ’orderly’ manner,that is a real problem faced by both sides.Therefore,the concept of Vehicle to Grid（V2G）has been proposed.The bi-flow of energy between EV and the grid is carried out.EVs are used not only as loads,but as energy storage mic-sources to participate in the regulation of the power system.In this thesis,the key technologies of the V2 G system are deeply studied according to the overall V2 G system structure.The research is divided into three aspects,including the research on the power control strategy of the EV charging and discharging interface’s converter,the frequency regulation method with distributed V2 G system connecting to grid,the research on the power quality control strategy of EVs’ charging and discharging interface.The research work is as follows:According to the overall structure of the V2 G system,this thesis is analyzed the operation principle of the converter in the EV of charging and discharging device.The voltage equation and torque characteristic equation of the synchronous machine are introduced into the control strategy of the three-phase converter,so that the interface between EV and grid can simulate the characteristics of the synchronous machine.The model in which single EV in charging and discharging condition plugs into the power grid is built,the results demostrate that the designed control strategy could simulate the characteristics of the synchronous machine and realize the bi-flow of power between the EV and the grid.Based on the regional grid’s frequency control system model adopts the Auto SelfGeneration（AGC）system.For a school of EVs with adopting the Virtual Synchronous Machine（VSG）control strategy,the frequency regulation control strategy with EVs participating is designed and used in the frequency regulation of the power grid.The frequency regulation control strategy takes into account the battery’s State of Charge（SOC）partition of EV and the frequency deviation of the power grid,so determines the weighting factor of the droop cruve’s coefficient by formulating fuzzy control rules when the V2 G system pulgs into grid,which is applied to AGC system frequency regulation considering the distributed V2 G system participates in.The simulation results shows that the control strategy can participate in the primary frequency regulation of the power system in a rational and orderly manner according to the partition of the battery SOC and the frequency deviation.The power electronic devices in the EV’s charging device has a certain impact on the power quality of the grid Point of Common Coupling（PCC）.On the basis of virtual synchronous control,this thesis carries out system description and state space modeling of the structural hardware circuit parameters of the three-phase converter in the charging device,so obtains the system state equation at the interface of the three-phase plug-in converter.It is transformed into a mixed sensitivity problem in H∞ control,that solves suitable compensator function.A harmonic suppression control strategy for EV’s plug-in three-phase converters is designed.It can fully utilize the EVs’ behavior of energy storage to realize grid-connected power control,at the same time suppress the harmonic problem generated during the EVs is in charging and discharging process.