| The construction of a new power system with new energy as the main body is an important means to achieve the goal of "double carbon",and the traditional "source following load" mode is gradually changing to "source and load interaction".Microgrid technology is an effective way to realize local consumption of new energy,while DC microgrid has attracted extensive attention because of its small power loss,strong expansibility and no frequency and phase problems.Meanwhile,with the rapid development of vehicle to grid(V2G)technology,electric vehicles(EVs)have gradually become one of the typical controllable resources on the demand side.The diversity of controllable resources and the new requirements of "source load interaction" make the coordinated control of the DC microgrid more complex.Therefore,taking the isolated island DC microgrid as the research object,this paper carries out the research on the voltage coordination control strategy of DC microgrid based on "source load interaction" around the electric vehicle V2 G technology.The specific work is as follows:(1)Based on the topology of multi-subnet DC microgrid,the basic control methods of typical DC distributed micro source interface converter are analyzed;the basic principle characteristics of photovoltaic,battery and fuel cell and the control method of interface converter are explored in depth,and the corresponding simulation model is established to verify the effectiveness of the control method.(2)In-depth study of V2 G control method for electric vehicles in view of the limitations of conventional droop control in load-side controllable unit power distribution.The expected charging power is used to measure the real-time charging demand of EVs,based on which the conventional droop control is further improved to meet the requirement of EVs to participate in grid-assisted voltage regulation.In the charging control,the initial sag control curve is divided into three parts according to the charging modes of EVs(overpower,constant power and reduced power)with the expected charging power as the reference value,and the actual charging power of the EVs is adjusted in real time according to the expected charging power;In the discharge control,considering the voltage regulation demand on the grid side and the charging demand of EVs on the load side,a method of calculating the limit discharge power of EVs based on the bus voltage and expected charging power is proposed to avoid overdischarging of EVs;A simulation model is established to verify the effectiveness of the proposed strategy in optimizing the charging and discharging power of a single EV in EVs participating in DC microgrid voltage regulation service and in optimizing the charging and discharging power allocation when multiple EVs operate in parallel.(3)To realize "multi-source coordination" and "source load interaction",a coordinated control strategy is proposed for multi-subnet DC microgrid.Multi-subnet DC microgrid improves the reliability of the system,but its power coordination control is more complex.To address this problem,the coordinated control strategy of multi-subnet DC microgrid is studied from the two levels of DC subnet and DC microgrid.In the coordinated control of DC subnet,the power coordination of optical storage or optical charging is realized based on voltage signal;In the coordinated control of DC microgrid,to realize the power coordination between DC subnets,a multi subnet power coordinated control method based on double bus is proposed;In addition,he power coordination control method between DC subnet and the fuel cell is further studied to reduce fuel consumption,and the coordination control strategy based on droop control is proposed to realize the coordinated interaction of four controllable resources of photovoltaic,energy storage,fuel cell and charging,and a simulation model is established to verify the effectiveness of the strategy. |
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