Research On Resilience Assessment Theory And Fault Restoration Strategy Of Resilience Microgrid

Microgrid is not only an important way to realize the utilization of renewable energy and the development of distributed generation,but also a powerful supplement and effective support for large power grid.However,the microgrid itself has the characteristics of variable structure,small inertia,weak support,and easy disturbance.With the small probability high loss large disturbance（such as extreme events,mode conversion,system fault shutdown,etc.）,large probability small loss small disturbance events(such as intermittent power generation,converter state conversion With the increasing number of power fluctuations and load disturbances caused by load access uncertainty and the increasing demand for clean and reliable distributed power,microgrid with the concept characteristics of "resilience" has become a very meaningful direction in the field of smart grid.The resilient of microgrid means that microgrid has sensitive and reliable resistance,rapid and effective adaptability and rapid and stable recovery ability after interference.Resilience microgrid can quickly adapt and adjust after disturbance events,improve power supply integrity and ensure power supply quality by reasonably allocating available resources,and quickly return to normal working state after disturbance.Before and after disturbance,the response of resilience microgrid is divided into four processes:prevention,resistance,adaptation and recovery.Resilience is an index to measure the resilience ability of resilience microgrid to prevent disturbance,response autonomy and fault recovery.Therefore,this paper mainly studies the resilience evaluation of resilience microgrid system and the recovery scheme in fault recovery stage.The specific work is as follows:Firstly,the resilience evaluation index of resilience microgrid is constructed and calculated.The connotation and influencing factors of resilience of resilience microgrid are described;Aiming at the problem of complex factors affecting the resilience of microgrid,based on the complex network model modeling method,considering the structure and operation characteristics of resilience microgrid system,a fault occurrence model of resilience microgrid based on modal transformation is established by using Markov chain;Define the recovery strength index of resilience microgrid;Then the calculation of resilience index value of resilience microgrid system is realized.An example is given to verify the feasibility of the proposed evaluation index.Secondly,aiming at the runaway shutdown of most micro sources in the resilience microgrid caused by the large disturbance of the microgrid,this paper analyzes the similarities and differences of the characteristics of distributed micro sources,studies the "semi black state" of the resilience microgrid system,comprehensively considers the stability and rapidity of the system,and designs a self recovery scheme in the semiblack state of the resilience microgrid based on the grey start method,The purpose is to improve the reliability and recovery ability of resilience microgrid after fault caused by large disturbance.Aiming at the micro source start-up priority in microgrid,the quantitative evaluation of micro source start-up capability based on Improved BP neural network is carried out,and the evaluation results of micro source importance are obtained;According to the evaluation results,considering the electrical constraints of the resilience microgrid in the grey start-up process,the recovery models of the distributed micro sources,loads and lines of the system are constructed respectively,and the optimal fault recovery scheme of the resilience microgrid system is obtained by using branch and bound and improved particle swarm optimization algorithm.The effectiveness of the proposed scheme is verified by numerical simulation.Finally,aiming at the problem of voltage sag during the restoration process of the resilience microgrid system,a fault recovery control scheme based on gray start is proposed to maintain the stability of the system.This method improves the stability and rapidity of the resilience microgrid during the restoration process.The effectiveness of the proposed strategy is proved by comparing and verifying the simulation with the traditional control strategy.