| Microgrids bring a better solution to the integration of distributed renewable energy sources and follow the development trend of new energy in the future,thus becoming an important part of modern intelligent power distribution system.Compared with AC microgrid,DC microgrid has gradually become a research hotspot with fewer energy conversion links and simpler control loop.Moreover,as multiple DC microgrids are further interconnected to form clusters,energy complementarity and maximum utilization of distributed energy can be achieved among the microgrids.In addition,the hierarchical control strategy can be used in order to achieve multi-objective decoupled design of the cluster system.Where primary control is used as local decentralized control with a controller in each unit;the implementation of secondary and tertiary control is based on high quality communication.Compared with traditional centralized communication,distributed communication has reliable operability in network link failure,and effectively avoids the negative impact of single point failure.However,in the absence of central controller,the ability of distributed communication global monitoring is weakened,which will inevitably expose the cyber layer of the system to potential security problems.In addition,the distributed communication will provide conditions for the spread of attacks,which will have a negative impact on the entire cluster system and increase the difficulty of detection.Therefore,this thesis carries out the research related to attack detection and attack recovery in DC microgrid cluster communication network for the security problem of DC microgrid cluster communication network,and the main work accomplished contains the following three aspects.Firstly,this thesis analyzes the system architecture of DC microgrid cluster,conducting research on physical layer and network layer respectively.Then,the hierarchical control structure of the DC microgrid cluster is analyzed.Local decentralized primary control and distributed secondary control of DC microgrids achieve local voltage stability and energy distribution,providing the basis for interconnection.The two-layer distributed tertiary control of the cluster achieves overall energy management of the cluster and generates voltage set points for each DC microgrid,thus achieving overall load balancing.And the stability of DC microgrid cluster operation under hierarchical control strategy is verified by Matlab/Simulink simulation.Secondly,the thesis proposes cyber security strategies for individual DC microgrids and DC microgrid clusters respectively based on the need of cyber security.For individual DC microgrid cyber anomalies,this thesis implements the detection of attacks based on the Kalman filter.The DC microgrid cluster detects the presence of network attacks by the proposed cyber security policy as well as restores the stable and reliable operation of the system during the attack duration.In addition,this thesis considers the classification conditions of false data injection attacks and obtains the design requirements for stealth attacks.And the proposed network security strategy is verified by DC microgrid cluster simulation.Finally,taking the three interconnected DC microgrid cluster systems as the verification model,the hardware-in-the-loop real-time simulation experiment platform and the all-physical hardware experiment platform are built respectively,and then the experimental waveforms of DC microgrid cluster under normal operation state are given.In order to verify the effectiveness of the proposed alternative-based cluster detection strategy and recovery strategy,experiments and waveform acquisition related to the impact of network attacks on clusters and clusters under the effect of network security policies are completed.The experimental results show that the proposed DC microgrid cluster cyber security strategy can effectively detect the attacked nodes,and the cluster can still maintain stable operation under the recovery strategy. |
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