Research On Key Technologies Of Energy Internet Router Charging Pile

With the widespread application of distributed new energy sources,such as photovoltaics,and the rapid increase in the number of electric vehicles,research on multi-port energy router charging pile has important application values.Due to the flexibility of ports,the multi-port energy router charging pile can effectively integrate distributed new energy,energy storage,and electric vehicle charging piles,improving the self-consumption rate of the distributed generation,using the buffer of each node’s energy router to avoid the impact of large-scale electric vehicle disorderly charging on the grid in the area,when necessary,dispatching the energy router to support the grid.However,because of the intermittent nature of new energy’s output,the randomness of electric vehicle’s access,and so on,multi-port energy router charging pile involves multiple operating conditions.It is of difficulty to study seamless switching and coordinated control during multi-mode operations,as well as multi-mode operations of ports in different operating conditions.Based on this,the main parts of this dissertation are as follows:1.Based on the four-port energy router charging pile topology,the coordinated control of multi-mode operating conditions of the energy router is studied.Based on grid dispatching,on/off grid,electric vehicle pitching in or cutting off,vehicle to grid,energy storage’s state of charge,and so on,the specific working conditions and switching conditions of the four-port energy router charging pile are designed.Adopting hierarchical control and based on the proposed new droop control method based on current tracking,the energy router can coordinatly operate under multiple working conditions,thereby achieving seamless switching of planned operating conditions.The effectiveness of the proposed unified coordinated control strategy is verified by simulation.2.Based on the problems of excessive bus voltage fluctuation and imprecise power allocation caused by unplanned switching of operating conditions,a unified distributed control strategy for energy router charging pile is proposed.Combining current control and droop control,the local controller responds to upper-layer instructions through current control to achieve seamless switching of planned operating conditions and accurate power distribution;adds virtual inertia control and current feedforward in the droop loop to satisfy fastness and reliability requirements,thus suppressing DC bus voltage fluctuations during unplanned switching.The correctness and effectiveness of the proposed control strategy is verified by simulation comparison.3.Aiming at the voltage control of photovoltaic and energy storage in extreme cases,a multi-mode operation control strategy for photovoltaic and energy storage is proposed.Based on state following,seamless pitching in,seamless switching between constant current mode and constant voltage mode of energy storage are achieved;By secondary voltage compensation based on droop control,indirect realization of photovoltaic voltage control is realized,and thus achieving off-grid coordination control of photovoltaic and energy storage without communication.The effectiveness of the proposed control strategy is verified by simulation.