MAS-based Cooperative Control Scheme For Microgrid Clusters Considering Time Delay Compensation

With the increased penetration of distributed generation(DG)units on the electrical grid systems,the renewable energy sources(RESs)including photovoltaic(PV)and wind energy have been widely used in the distributed power systems.However,DG units may also bring challenges to the distribution network such as inverse power flow,voltage deviations and voltage fluctuations.When a number of DG units are clustered together,they can form a microgrid(MG).With the development of the microgrid technology,a microgrid cluster(MGC)system,which consist of multiple microgrids,have received considerable attention for its intelligent operation control and load demand customization.In this paper,the hierarchical control for a MG,consensus control for MGC systems and delay compensation for low-bandwidth communication lines have been investigated,which can be summarized as follows:(1)The hierarchical control strategy model is established for the islanded MG system.The primary control is utilized to make the paralle-connected system stable and the small signal model is established to analyze the stability of the MG system.In addition,the secondary controller is proposed to eliminate voltage amplitude and frequency deviations,and then the tertiary control is used to adjust the power generation of the MG system.Furthermore,the correctness of the parameter design and the effectiveness of the control strategy are verified by simulation results.(2)For a MGC system,multi-agent system-based consensus controller is utilized to establish the matrices of the communication network.In addition,the active power,reactive power and harmonic power can be shared by the proposed consensus controller.Furthermore,a consensus-based controller for a MGC system is proposed to adjust the power generation among each microgrid.The effectiveness of the theoretical analysis and the control schemes are verified by simulation results.(3)Considering the communication delay in low/high bandwidth communication lines,the equivalent of BPF-based droop control and secondary control is proposed to eliminate the time delay.In addition,the BPF-based consensus control is proposed to reduce communication transmission data to reduce time delay and communication cost for microgrids.Moreover,the predictive control is proposed to make the MGC system stable within the delay margin.Finally,the hardware-in-the-loop(HIL)results are used to validate the correctness and effectiveness of the proposed compensation scheme.(4)The microgrid experiment platform composed of parallel-connected DG units is built to verify the effectiveness of the hierarchical control.Furthermore,considering each independent converter as a DG unit,the experimental platform of the microgrid with three DG sources is constructed to verify the effectiveness of the consensus-based control strategy of the system in this paper.