Coordinated Control Strategy Of Hybrid Microgrid Considering Battery’s State Of Charge

In microgrids,energy storage devices are often used to smooth the power fluctuations of the system.Due to the advantages of mature technology,high reliability,and low cost,batteries are often the first choice for energy storage links.When the state of charge(SOC)’s difference between the two sides of the battery in the hybrid AC/DC microgrid is too large,it will cause overcharge and overdischarge of one side of the battery,which will not only shorten its own life,but also threaten the stable operation of the system.However,the power coordinated control when the microgrid adopts master-slave control lacks sufficient consideration of the battery’s SOC.Therefore,this paper studies the power coordinated control strategy of hybrid AC/DC microgrid considering the battery’s SOC,which mainly includes the following work contents:First,for the typical topology of hybrid AC/DC microgrid,the control strategy of distributed generations(DGs)in the AC and DC side subnets in the system when the microgrid adopts master-slave control is studied.The mathematical model and the characteristic parameter SOC of the battery is analyzed,and divide the system operation mode according to SOC of the batteries on both sides in order to lay the foundation for the subsequent chapters to further analyze the influence of the battery’s SOC on the operation and control of the hybrid microgrid.Secondly,when the hybrid AC/DC microgrid is during grid-connected and island operation,the power coordinated control strategies considering the battery’s SOC threshold are respectively proposed,and corresponding simulation verifications are carried out.In grid-connected operation,according to the battery’s SOC and the power status of the DC subnet,the system’s working condition division and switching are studied,and the grid-connected power coordinated control strategy is proposed.In island operation,the system operation mode is divided into four types:normal operation,over-limit on the DC side,over-limit on the AC side,and over-limit on both AC and DC sides according to the SOC of the subnets on both sides,and the system’s working condition division and switching are studied based on the batteries’s SOC and the power status of the subnets on both sides.The design principles and the power coordinated control strategy for island operation is proposed.Finally,aiming at the constant power and standby operation of the interlinked converter(ILC)in the island hybrid AC/DC microgrid,the improved control strategies of the interlinked converter and photovoltaic array are proposed and verified by simulation.When the interlinked converters operate at constant power,in order to effectively prolong the service life of batteries and improve the stable operation ability of the system,with the goal of converging the state of charge on both sides,an improved control strategy is proposed to quantitatively determine the transmission power of interlinked converter based on the state of charge of the batteries on both sides.When the interlinkd converter is standby,there is no power exchange between the two subnets on both sides.In order to make the photovoltaic array and the battery work together to maintain the stable operation of the system,an improved control strategy is proposed to adjust the output of the photovoltaic array according to the change rate of the battery’s state of charge.