Reliability Models And Algorithm Of Microgrid Considering Operating Strategy

Due to the energy crisis and environmental pressure, as well as the increasingreliability requirement of load point, microgrid has attracted more and more attentionworldwide. Microgrid is a special power system structure, which can effectivelyintegrate various types of distributed generations and switch freely betweengrid-connected operation and island operation. However, island operation of microgridand uncertain output of distributed generation have brought many tough problems toreliability assessment of microgrid. This thesis does some in-depth study focusing onthe issue of reliability assessment of microgrid. The main results are as follow:①In order to consider the ability of microgrid switching to island operation whenfailure occurs in external network, this thesis proposes the definition of islandprobability, which is the probability of that microgrid can meet the load demand withouttaking the power supply of external network and the failures of distributed generationsinto consideration. Based on the ratio of hours when microgrid can meet its loaddemand to annual operational hours, a calculation model of island probability isestablished by considering the influence of fluctuation of load,distributed generationand storage strategy. The above work provides basis for further mode division. Casestudy shows that maximum discharging power of storage battery and the X%parameterof renewable energy have greater impact on island probability.②Microgrid operational mode is various due to the fluctuation of load and outputof distributed generation. Based on the definition of island probability and differenttypes of distributed generations operating in microgrid during a given time period, thisthesis proposes a dividing principle. According to this principle, microgrid is dividedinto four types of operational mode. Based on the types of main power, three operatingstrategies are proposed in the same time. Selection process of operational mode underdifferent operating strategies has received by considering the transfer characteristicsbetween different operational modes, the above work provides a basis for the reliabilityevaluation of microgrid. Case study shows that maximum discharging power of storagebattery and rated power of diesel generation have greater impact on microgridoperational results.③A reliability evaluation model of microgrid considering operating strategy isestablished by analyzing the effect of different fault types (external network, components of internal distribution network and distributed generation) on load pointsunder different operational modes, deducing analytical formulations of reliability indifferent operational mode and evaluating the probability of different operational mode.Case study shows that increasing maximum discharging power of storage battery andrated power of diesel generation are effective ways to improve reliability of microgrid.