Distributed Large Signal Stability Based on Input-to-State Stability Conditions for DC Microgrid Clusters
DC microgrid cluster(DCMGC)is formed by the flexible interconnection of multiple DC microgrids that are geographically neighbored,representing the vital direction of future distribution power systems.However,DC microgrids and DCMGCs exhibit weak network properties characterized by low inertia and high impedance,mainly due to the high penetration of distributed energy resources(DERs)and widespread adoption of power electronic converters.Meanwhile,the systems are subject to large disturbances,such as DER intermittence,load switching,plug-and-play operation,mode transitions,and short-circuit faults.These factors collectively present a stringent requirement to achieving stable large-signal operation in DCMGCs.In this regard,large signal stability analysis of DCMGCs becomes imperative.However,the complex system,featured as higher-order,strong coupling,nonlinearity,and dynamic variation,renders excessive signal stability analysis of the DCMGC.Conventional centralized modeling methods require dynamic models for the entire system,which leads to infeasible solutions and a lack of scalability with the increase of microgrids.With the generalization of DCMGCs into large-scale systems interconnected by multiple subsystems,this paper proposes a distributed large signal stability analysis method based on the input-to-state stability(ISS)conditions.Firstly,the DCMGC with hierarchical control is divided into two parts,i.e.,the power stage and the control loop.Each is further decomposed into multiple subsystems,consisting of a single islanded microgrid and its coupling dynamics(tie-lines and tertiary control).Thus,a distributed large-signal equivalent circuit model around each microgrid is built.Secondly,the ISS-Lyapunov function is constructed based on the ISS theory for the distributed model of every subsystem,and the large signal stability criterion in a distributed fashion is derived.Finally,a large signal stability region is estimated by the six-microgrid DCMGC.The relationship between the key parameters and the stability region is then analyzed.Besides,the comparison between the centralized and the distributed large signal stability analysis on the minimum DCMGC example with the interconnection of two microgrids is performed.The distributed large signal stability analysis is slightly more conservative than the centralized method.However,its modeling exhibits complexity,solvability,and scalability.The numerical analyses are verified by the hardware-in-the-loop(HIL)experiment.The following conclusions can be drawn.(1)The distributed large-signal stability criterion transforms the previous centralized modeling approach into a"divide and conquer"strategy,simplifying the calculation process and offering scalability for the large signal stability analysis of DCMGCs.Especially for the analysis under dynamic connections and disconnections of microgrids and comprising units,there is no need to re-model and re-calculate the system.(2)The ISS theory can effectively handle the external gains and internal dynamic characteristics of DCMGC subsystems.Given the large-signal stability conditions of the DCMGC,the proposed method facilitates the disturbance magnitude determination that the system can tolerate.
DC microgrid clusterdistributed modelinglarge signal stabilityinput-to-state stability
国家科技期刊平台
NSTL
万方数据
