Stability Analysis Of Hybrid AC/DC Microgrid Considering The Storage System

Compared with other forms of Microgrids,Hybrid AC/DC Microgrid combine the advantages of DC Microgrid and AC Microgrid:strong compatibility with different types of distributed power sources and loads,effectively reducing converters and Power loss;multiple types of distributed power sources can be connected at the same time,which enhances the system's power supply reliability.Based on the above advantages,many urban communities are increasingly turning to Hybrid AC/DC Microgrid as an alternative source of electricity.Distributed power sources,different types of loads,and energy storage devices need to be connected to the bus through power electronic converters.These power electronic converters will affect each other due to non-linear characteristics,especially after being disturbed,which will negatively affect the stability of the system.These tightly regulated loads could be regarded as constant power loads?CPLs?,usually inducing negative impedance instability problems.Unfortunately,most stability studies have been based on small signal linearization techniques,which is limited to studying system stability under small disturbances.However,in the Hybrid AC/DC Microgrid,there are large disturbances such as a large step power load,microsource removal,and system failure.Therefore,it is necessary to analyze the large signal stability of the system.This paper investigates the large signal stability of the Hybrid AC/DC Microgrid based on mixed potential theory,and considers the influences of the storage system and CPLs.The research focuses on two working modes of grid-connected and islanded the Hybrid AC/DC Microgrid.First,combining the characteristics of different working modes,the entire system is converted to DC systems in dq rotating frame.Then the mixed potential models are constructed and analyzed,and large signal stability criteria are derived.The obtained large-signal stability criterion for grid-connected model gives the relationship between the C_dc,L_s,interconnected converter control parameters and the maximum power of CPL that the system can withstand,when the energy storage changes from charging to discharging,the maximum power of the CPL that the AC-DC hybrid microgrid system can withstand increases;the large-signal stability criterion in island mode gives a quantitative basis for the control parameters of the charging and discharging state of the energy storage unit DC-DC converter,which can ensure the stability of the system under large disturbance conditions.The above criteria provide a quantitative basis for the design of the large signal stability of Hybrid AC/DC Microgrid in different working modes,and have strong theoretical guidance value.Simulink software was used to build simulation platforms for AC and DC microgrid in grid-connected and island mode,respectively,and the validity of the obtained criteria is verified.