Adaptive Bidirectional Droop Control for Electric Vehicles Parking with Vehicle-to-grid Service in Microgrid

With the popularity of electric vehicles(EVs),a large number of EVs will become a burden to the future grid with arbitrary charging management.It is of vital significance to the control of the EVs charging and discharging state appropriately to enable the EVs to become friendly to the grid.Therefore,considering the potential for EVs seen as energy storage devices,this paper proposes a multiport DC-DC solid state transformer topology for bidirectional photovoltaic/battery-assisted EV parking lot with vehicle-to-grid service(V2G-PVBP).Relying on the energy storage function of EVs,V2G-PVBP is able to not only satisfy the normal requirements of EVs’owner,but also provide the function of load shifting and load regulation to the microgrid.In this paper,EVs are categorized into limited EV and freedom EV.Limited EVs are always kept in charging state and freedom EVs can take part in the load regulation of the microgrid.The proposed adaptive bidirectional droop control is designed for freedom EVs to make them autonomously charge or discharge with certain power which according to each EV’s state of charge,battery capacity,leaving time,and other factors to maintain the stability of the future microgrid.Eventually,the simulation and experiment of the adaptive bidirectional droop control based V2G-PVBP are provided to prove the availability of V2G-PVBP.

Steady-state Stability Assessment of AC-busbar Plug-in Electric Vehicle Charging Station with Photovoltaic

Although the deployment of alternating current(AC)-busbar plug-in electric vehicle(PEV)charging station with photovoltaic(PV)is a promising alternative,the interaction among subsystems always causes the instability problem.Meanwhile,the conventional generalized Nyquist criterion(GNC)is complex,and it is not suitable for the design of the AC system.Therefore,this paper proposes a modified infinityone-norm(MION)stability criterion based on the impedance method to assess the stability of the foresaid charging station.Firstly,the typical structure and operation modes of the charging station are studied.Furthermore,each subsystem impedance matrix is built by small-signal method,and the MION stability criterion based on impedance method is proposed to assess the charging station stability.Compared with the previous simplified stability criteria based on the norm,the proposed criterion has lower conservatism.Furthermore,the design regulation for the controller parameters is provided,and the stability recovery way is provided by connecting the doubly-fed line and energy storage equipment,which are selected based on intermediate variable,i.e.,short-circuit ratio(SCR).Finally,the effectiveness and conservatism of the proposed stability criterion are validated through simulation and experimental results.

A Smart Charging Algorithm Based on a Fast Charging Station Without Energy Storage System

With the growing popularity of electric vehicles(EV),there is an urgent demand to solve the stress placed on grids caused by the irregular and frequent access of EVs.The traditional direct current(DC)fast charging station(FCS)based on a photovoltaic(PV)system can effectively alleviate the stress of the grid and carbon emission,but the high cost of the energy storage system(ESS)and the under utilization of the grid-connected interlinking converters(GIC)are not very well addressed.In this paper,the DC FCS architecture based on a PV system and ESS-free is first proposed and employed to reduce the cost.Moreover,the proposed smart charging algorithm(SCA)can fully coordinate the source/load properties of the grid and EVs to achieve the maximum power output of the PV system and high utilization rate of GICs in the absence of ESS support for FCS.SCA contains a self-regulated algorithm(SRA)for EVs and a grid-regulated algorithm(GRA)for GICs.While the DC bus voltage change caused by power fluctuations does not exceed the set threshold,SRA readjusts the charging power of each EV through the status of the charging(SOC)feedback of the EV,which can ensure the power rebalancing of the FCS.The GRA would participate in the adjustment process once the DC bus voltage is beyond the set threshold range.Under the condition of ensuring the charging power of all EVs,a GRA based on adaptive droop control can improve the utilization rate of GICs.At last,the simulation and experimental results are provided to verify the effectiveness of the proposed SCA.