Research On Distribution System With Microgrid Reliability Evaluation

Microgrid, as a novel technology developed in recent years, is playing a increasinglyimportant role in power system. Compared with conventional grid, microgrid can relievepower utility pressure of distribution system effectively; can make use of the generators inmicrogrid to provide various subsidiary services, and can delay construction of thecentralized electrical power transmission and distribution system to improve of powersupply reliability and economical efficiency of union power system as well.In traditional reliability evaluation of distribution systems,feeder lines are supplied bya single sources, which called divergent type power supply.In this mode, Any failure on afeeder line may lead to power failure of all the loads behind this feeder. But whenmicrogrid connected with distribution grid, it turns out to be a grid which combinesmultiple electronic sources and loads. If there is a failure on a feeder line, microgrid canappear isolated network operation mode, corresponding reliability evaluation model andmethods would be changed. In addition, the output power of micro power,compared withthe traditional power supply, is more random and intermittent, which makes the reliabilityassessment more complex.This paper proposed a method of reliability assessment for distribution system whichis including the effect of the arbitrariness and intermittent output power of micro-sources.At first, isolated island is divided by breadth-first search algorithm and based on power-matched-principle. The effect of microgrid in isolated network operation mode after thefailure of the system on the reliability assessment,is fully considered；Then，sequentialMonte Carlo simulation is chosen as the research method for reliability evaluation fordistribution system including microgrid. By this method, proper failure-repair simulationmodel of every components and output power simulation model of the source element inisolated island state are established. And the concrete step for reliability assessment fordistribution system including microgrid which based on Monte Carlo simulation areproposed as well.Finally,according to the microgrid structure given by Consortium for ElectricReliability Technology Solutions(CERTS), the corresponding reliability evaluation testsystem is constituted. The simulation of the test system illustrates the validity of proposed model and algorithm. The results also show that after micro-grid connectedwith distribution system, the local load supply reliability would be effectively improved.At the same time, this paper also explores the influence of Microgrid reliability.