| In islanded microgrid,it is an important development direction to realize terminal interconnection with the help of information technology and build a cyber physical system.The application of communication data enhances the observability and controllability of the microgrid system,and will also facilitate the task of operation regulation and energy adjustment.However,with the continuous integration of information technology and physical systems,the adoption of communication data in microgrids also brings new challenges to the physical grid.Among them,the following problems are highlighted for islanded microgrid under the influence of communication uncertainties such as communication congestion,communication disturbances and communication interruptions:1.Based on communication data,how to effectively regulate physical quantities such as voltage,frequency and reactive power to improve the stability of system? 2.Based on communication data,how to reasonably control active power output of resources to achieve economical operation of system? To solve the above problems,this paper carries out the following research works.(1)To improve the operational stability of islanded microgrid,a distributed control strategy is constructed based on the idea of cyber-physical system and event-triggered means to ensure system voltage and frequency stability under the influence of communication congestion and communication perturbation.Firstly,regarding the voltage and frequency regulation problem under the influence of communication congestion,the deviation caused by congestion on the consistency control result and the overshoot in the consistency control are used as two triggering conditions to build a prediction compensation mechanism(combining the extreme learning machine and model prediction)and a virtual leader-following consistency controller to tackle the problem;secondly,regarding the voltage and frequency regulation problem under the influence of communication disturbance,the deviation caused by communication disturbance on the consistency control result is used as the trigger condition to build a consistency controller based on the sliding mode control theory to tackle the problem.Finally,the effect of the proposed strategy on voltage and frequency stabilization under the influence of congestion and communication disturbances is verified by simulation tests.(2)To improve the operational stability of the islanded microgrid,the reactive power allocation and circulating current suppression strategies are constructed based on the idea of cyber-physical system using communication networks and communication data to improve the operational stability of the system.Firstly,to address the problem of reasonable sharing of reactive power among energy sources,a variable impedance design based on Kirchhoff’s law and adaptive methods is carried out to realize the matching of reactive power to each energy source according to the capacity ratio among energy sources;secondly,to address the circulating current problem in the system,a voltage/ multi-source cooperative controller is constructed.Finally,the effect of the proposed strategy on reactive power sharing and circulating current suppression is verified by simulation tests.(3)To improve the operation economy of islanded microgrid,under the influence of communication interruptions,a distributed energy control strategy of islanded microgrid is constructed based on the idea of cyber-physical system using communication networks and communication data.Firstly,for the active power sharing problem in the microgrid,the variable impedance design is carried out to assign the optimal power to each energy resource to reduce the total system generation cost.Furthermore,the secondary control process of the microgrid is studied and the influence of the secondary controller on the system operation state is analyzed using the small signal model theory to ensure the stable operation of the system;finally,the effect of the proposed strategy on distributed energy control under the influence of communication interruption is verified by simulation tests.(4)To improve the economical operation of isolated microgrid,based on the idea of cyber-physical system,a source-load-storage energy management strategy is constructed using communication network and communication data to ensure the smooth operation of centralized energy management under the influence of communication interruption.Firstly,for the power prediction problem of renewable resources,based on empirical modal decomposition,extreme learning machine and model prediction theories,a class of hybrid prediction methods is studied and proposed to improve the prediction accuracy;secondly,regarding the communication path interruption problem between the centralized energy management system and the energy source,based on the cyber-physical integrated vulnerability assessment and prospect theory,an optimal transmission strategy is proposed to tackle the problem and improve the communication reliability;furthermore,based on the predicted data and the optimal transmission strategy,a centralized energy management model is constructed and solved to obtain the optimal management scheme;finally,the effect of the proposed centralized energy management strategy under the influence of communication interruption is verified by simulation tests.. |
