Research On Operation Control Technology Of Electric Vehicle Charging,Discharging And Storage Integrated Station Based On V2G

With the rapid development of electric vehicles,disorderly charging causes the load to increase and decrease suddenly,which seriously affects the stable operation of the power grid.At the same time,the proportion of renewable energy continues to increases,and its randomness and volatility also affect the stable operation of the power grid.Vehicle-to-grid(V2G)technology uses a large number of electric vehicles as distributed energy storage units to effectively improve the power system’s renewable energy consumption capacity.Therefore,a new type of V2G-based charging,discharging and storage integrated station for electric vehicles has become a research hotspot,which can not only take advantage of the interactive advantages of the vehicleto-grid,but also efficiently solve the problem of reuse of retired batteries for electric vehicles.This paper takes the V2G-based electric vehicle charging,discharging and storage integration station as the research object,and researches its topology and operation control technology.Analyze the working mode and modulation strategy of the energy storage interface converter,establish a mathematical model,design the controller parameters,and introduce an active power balance management strategy to ensure the positive and negative DC bus voltage balance of the charging station.The charging interface adopts a bidirectional full-bridge three-level LLC resonant converter,analyzes the working principle of the converter in hybrid control mode,uses fundamental wave analysis to establish a mathematical model of the LLC resonant converter,and analyzes its gain formula and soft switching realization conditions.Establish mathematical models of diode-clamped three-level inverters in three coordinate systems.Aiming at the problem of current impact during planned grid-off-grid switching,improve the PQ/VF switching method based on the state follower to achieve smooth switching between gridconnected and off-grid.Establish a calculation model for the charging and discharging energy boundary of electric vehicles.Based on the real-time charging power distribution algorithm,a new charging and discharging control strategy for the management electric vehicles is proposed.The proposed control strategy can provide peak load transfer when meeting electric vehicle battery charging or replacement requirements,and realize orderly charging and discharging.The system experiment platform was built to conduct the orderly charging and discharging experiment of electric vehicles in V2 G mode and the self-balancing experiment in the station in island mode.The experimental results show the effectiveness of the integrated station operation control strategy.