Research On Cooperative Control Based On Multi-Agent System Of Microgrid In Public Buildings

Public buildings consume a large amount of electric energy.Conventionally,the public buildings were powered by a large-scale power system,which could not meet the requirements of the quality and reliability for key loads,and accelerates the energy crisis and greenhouse effect.Microgrid is a new type of energy structure,which integrates distributed generations,energy storage devices and local loads effectively.Microgrid also has two operation modes: grid-connected mode and islanded mode.In grid-connected mode,microgrid could provide or absorb power to the main grid.Once the main grid encounters faults,the microgrid could be disconnected from the public coupling point and run in the islanded mode.Since the flexible operation characteristics of microgrid,it could be a powerful complement of the main grid,and provides stable power support for some key loads in public buildings.In the islanded mode,a hierarchical control structure is adopted in the microgrid,and droop control is mainly adopted in the primary control layer.This control strategy does not depend on communication and is a decentralized and autonomous control method.However,primary droop control causes the system frequency and voltage deviating from the rated values.The distributed cooperative control method based on multi-agent system is adopted in the secondary control level,which has high reliability and robustness,and it is easy to be implemented in the microgrid system.In this paper,the distributed cooperative control strategy is applied in the secondary control layer of an islanded microgrid to realize the secondary frequency and voltage restoration,and the proportional active power sharing.The innovations of this paper are summarized as follows(1)In order to address the problem of frequency and voltage deviation of islanded microgrid system caused by the primary droop control strategy,and consider the communication and computational burden of the system,the distributed asymptotic cooperative consensus control method is utilized.A decentralized event-triggered mechanism is adopted to trigger the controller when the event-triggered conditions are satisfied,the secondary frequency and voltage restoration control are realized.The control efficiency of the distributed secondary cooperative controllers is improved.(2)In view of the previous asymptotic cooperative consensus control algorithm cannot estimate the setting time,and the convergence time could approach infinity,and consider the microgrid powered by distributed battery energy storage system,a distributed fixed time secondary cooperative control strategy is put forward.Through applying the proposed control scheme,the frequency and voltage magnitude restoration are achieved with a fixed settling time upper bound,and obtain the consensus of energy level and the expected active power sharing.The proposed control algorithm could estimate the convergence time in advance.The advantage of this control method is that the upper bound of the setting time is independent of any initial states of the system,which ensures the timeliness of the fixed time control of the islanded microgrid system.(3)Considering the problems of fixed time control of frequency,voltage magnitude and active power in an islanded microgrid system,and consider the communication and computational burden of the system,a new distributed fixed time secondary control protocol is proposed,and a new centralized event-triggered mechanism is adopted.Through the proposed control scheme,the local controllers of the system trigger the control algorithms at the same event-triggered time,and the controllers are updated with the latest sampling measurement values,the secondary control objectives of an islanded microgrid are achieved in a fixed time.The continuous communication is avoided through applying the proposed control approach,the communication burden of the system and the frequency of the controllers update are also reduced.(4)Considering the problem of computational and communication burden of an islanded microgrid system,a new distributed event-triggered fixed time secondary cooperative control scheme is proposed,and a fully distributed event-triggered mechanism is designed.The distributed fixed time control protocol only utilizes the latest sampling measurement values of frequency,voltage magnitude and active power when the event-triggered conditions are satisfied.The proposed distributed control strategy could achieve the secondary control objectives of the islanded microgrid system within a fixed time,and the communication burden of the system and the frequency of the controllers update are also reduced,the control efficiency of the system is improved.Since the proposed control scheme is completely distributed,the reliability and scalability of the system are improved accordingly.