Research On Operating Characteristics Of Microgrid Based On Reachability Analysis Theory

Microgrid is an autonomous system composed of a variety of distributed generators,loads,energy conversion and control devices.With the continuous increase of renewable energy penetration and new loads such as electric vehicles,microgrids can combine multiple fluctuating power sources and loads into a controllable unit and then connect to the main grid.There exist various uncertain factors inside the microgrid at all times,such as the power fluctuation of renewable energy sources and loads,and the errors in measurement,which will significantly affect the security and stability of system operation.The low inertia characteristics of power electronic devices used by a large number of distributed generators make the microgrid more vulnerable to random disturbances,easy to violate the operation limits,or even result in oscillation and instability,which restricts the further development of microgrids.Therefore,it is of great practical significance to study the influence of various uncertain factors on the operation of microgrids and analyze the safety and stability of the system under uncertain conditions.Based on reachability analysis theory,this paper proposes a method for analyzing the operating characteristics of microgrids under uncertain conditions.Firstly,the modeling method of uncertain factors is studied and zonotope is used as set representation to establish the uncertainty set of random inputs such as new energy power injections.Then,for the steady-state operation analysis of the microgrid,a reachability method for static system is proposed.Based on the linearized power flow model,the uncertainty set of operation states such as node voltage and line transmission power can be directly obtained through linear transformation,so as to analyze the steady-state operating range of the microgrid.Finally,for the analysis of dynamic operating characteristics,the dynamic model of the microgrid is established.The calculation method of the reachability set of dynamic system is proposed to analyze the system dynamic response.The results show that the proposed method only needs one simulation to obtain the set of state variables which captures all possible operating conditions,so as to analyze the security of the microgrid under uncertainty.