Distributed Coordinated Voltage Control Of AC/DC Microgrid Containing Electric Vehicles

Microgrid is the organic unit of future energy internet.AC/DC hybrid microgrid combines the advantages of AC microgrid and DC microgrid,overcomes their shortcomings,will be the trend of microgrid development in the future.However,the large-scale access of renewable energy in AC/DC hybrid microgrid poses serious challenges to the voltage stability of microgrid system.In this paper,the optimal voltage regulation of AC/DC hybrid microgrid containing electric vehicles is studied.Electric vehicles are used as the voltage regulation resources.The optimal charging and discharging power of electric vehicles in AC/DC microgrid is obtained by distributed coordinated control to restrain the voltage fluctuation of AC/DC hybrid microgrid.The main highlights of this paper are follows:(1)Based on the development status of AC/DC hybrid microgrid,the current research on the V2G(Vehicle-to-Grid)and the voltage regulation control mode of microgrid system,the output models of micro-sources and electric vehicles in AC/DC hybrid microgrid are established,and the voltage regulation resources available in AC/DC hybrid microgrid are analyzed.Thus in this paper,a distributed coordinated control structure and control strategy for AC/DC hybrid microgrid by coordinating the output of electric vehicles is proposed;(2)By analyzing the relationship between node power and voltage in AC/DC hybrid microgrid,the power flow calculation model of AC/DC hybrid microgrid is established.Using the idea of equivalence,the DC microgrid is equivalent to an active load unit of the AC microgrid,and the AC microgrid is equivalent to a generation unit of the DC microgrid.The power flow is solved by combining the alternating iteration method,and the voltage distribution of each node at the same time is analyzed;(3)Taking the voltage variance as the objective function,the output of micro-sources and the electric vehicles as the optimization variables,the voltage distributed optimization regulation model of AC/DC hybrid microgrid based on Gossip algorithm is established,and the optimal charging and discharging power of the distributed optimization electric vehicle is obtained.(4)The AC/DC hybrid microgrid simulation platform is built.The simulation platform is composed of the low-voltage AC microgrid based on Siemens Benchmark 0.4kV on the ac side and 8-nodes low-voltage DC microgrid on the dc side.The simulation results of distributed coordinated control and centralized control under grid-connected/off-grid operation modes show that both control strategys can restrain the voltage fluctuation of AC/DC hybrid microgrid,but the distributed control strategy better than centralized control strategy in terms of operation speed and voltage regulation effect.