Research On Control Strategy Of Distributed Energy Storage System In Islanded Microgrid With Communication Constraints

With the rapid development of science and technology,the problem of environmental pollution and energy depletion is becoming more and more serious.In order to meet the growing demand for power generation and reduce environmental pollution,the concept of microgrid came into being.However,distributed generation as the generation of microgrid has fluctuation and intermittence.To improve power quality and system reliability,energy storage system has attracted attention due to its high flexibility in microgrid operation and control,and multi energy storage system is the hot and difficult point of current application and research.Capacity is a unique and important physical quantity of the energy storage system.When the capacity of the energy storage system is small,how to combine multiple energy storage systems to charge and discharge synchronously should be considered;when the capacity of the energy storage system is large enough(no overcharge and discharge in a long period of time),how to make multiple energy storage systems operate economically should be considered.To improve the economic and stability of the energy storage system and make the energy storage system more robust,this paper adopts hierarchical structure and considers the communication constraints of time delay and time-varying topology in the actual system,studies the energy balance problem of small capacity energy storage system and the economic operation problem of large capacity energy storage system,and gives the energy balance control method and the control method of rate optimal allocation of distributed energy storage system.The main contents of this paper are as follows:(1)Firstly,the model of energy storage device is given,and the charging and discharging principle,the interface circuit of bus and the method of power compensation are analyzed.Then,the primary control layer is designed,and its droop controller and voltage current double closed-loop controller achieve the goal of output voltage amplitude and frequency stability and power sharing.(2)A novel coordinated control strategy is proposed for the energy balance problem and output voltage and frequency deviation of multi energy storage system.First,the secondary control layer is designed by using the distributed consistency method of communication delay and time-varying topology,which can restore the primary control layer and cause the output voltage magnitude and frequency deviation of the energy storage system.Then considering the situation that external auxiliary energy can exchange energy with local energy storage devices and the communication network has time-varying topology,a distributed control strategy which can realize energy balance quickly is proposed.Further consideration is given to the case without external auxiliary energy,that is,using the self-regulation method of each energy storage device,based on the improved droop control and distributed observer with communication constraints Methods the energy balance control strategy of self-regulation of each energy storage system was proposed.The effectiveness of the proposed control strategy is verified by theoretical analysis and simulation experiments.(3)Aiming at the economic operation problem of large capacity energy storage system,considering the supply and demand constraints and power output constraints of multi energy storage system,a third-layer control structure is added to give the economic dispatch control strategy of distributed energy storage system based on communication delay and time-varying topology.The convergence performance of the proposed algorithm is analyzed theoretically,and the effectiveness of the proposed control strategy is verified by simulation experiments.