| In the distribution network,the resilience mainly evaluates the support and recovery capability of the distribution network for critical loads in extreme disturbance events.The microgrid and distributed generation improve the redundancy of the power grid,which can greatly satisfy the reliable and continuous power supply of the load under various conditions,and improve the resilience of the distribution network under extreme accidents.In addition,the microgrid has flexible operation mode,good frequency regulation and voltage regulation capability,fast response and faster self-starting capability,which is of vital significance in coping with emergencies and maintaining critical loads.In this paper,Taking the photovolatic-battery-diesel microgrid as an example,the Virtual Synchronous Generator(VSG)control for the energy storage inverter,islanding detection strategy,off-grid switching,and isolated micro-network black start technology are studied,from the three indicators of evaluating the resilience of the distribution network as the entry point: the self-healing recovery rate,self-healing speed,self-healing sustainable time.The work is as follows:1.The topology structure and control strategy of battery energy storage,photovoltaic power generation and diesel power generation system in microgrid system are discussed.The mathematical model of VSG control is established.The overall architecture of optical storage microgrid is given.It is built on Matlab/Simulink platform.The complete optical storage diesel microgrid system is verified,and the basic voltage regulation and frequency modulation function of the battery energy storage and diesel power generation system and the frequency response of the photovoltaic power generation unit are verified.The optimal virtual inertia and damping parameters of the VSG control are calculated.2.The effects of microgrid related control technology on improving the flexibility of distribution network are analyzed according to the resilience index,and the island detection strategy affecting the resilience index,seamless switching technology and pre-synchronous control operation,and the black start technology of isolated micro grid are analyzed.On this basis,it is verified that the seamless parallel/off-grid switching of the optical storage and firewood micro grid under the VSG micro-source can be completed in milliseconds,and it is better than the parallel/off-grid operation under the traditional PQ/Vf control switching mode.3.A black start scheme was developed to start the energy storage and diesel generator network at the same time,and then starting the grid connection of photovoltaic power generation units,verifying the self-recovery ability after microgrid failure to prevent the magnetizing inrush current in the black start process of the microgrid containing transformers.The inverter control is improved to VSG zero-start boost control.4.Apply online optimization of virtual synchronization control strategy,so that VSG has good dynamic response characteristics after failure on the distribution network side,and enhance self-healing sustainable time;adaptability and regularity of dynamic response characteristics of online self-optimizing VSG The simulation and comparison of VSG's grid strength adaptability proves that the former has important significance for improving the resilience of the distribution network. |
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