Study On System Modeling And Protection Scheme Of Microgrid

Microgrid is a new single controlled distribution network unit, which can be coordinatedwith the higher concentration of distributed power supply and reduce the burden of grid control,take advantages of the distributed power generation, so as to ensure the efficient use ofdistributedmicro source.But, because of the fault feature of microgrid in different operating modes is different,which makes the traditional relying on current mode value as a three-step current protection isdifficult to be as a micro power grid protection scheme, which meets the four standard ofdistribution system protection namely, selectivity, reliability, sensitivity and quick action.Therefore, micro power grid protection technology becomes the key to obtain furtherdevelopmentofmicrogrid.This paper used PSCAD/EMTDC as the simulation environment, made the modeling,control and protection of thedistributed generation and micro grid as theresearch object.Firstly,analyze the mathematical model and topology of the distributed generation inverter. The P/Qcontrol and the V/f control which is based on the droop characteristics of the distributedgeneration inverter are studied carefully, and established the simulation model of these twokinds of distributed generation. And its output characteristic simulation was done to provide abasis for further research.Secondly, the modeling low voltage micro grid was built, whichincluded photovoltaic power generation system, direct-drive wind power generator and storagebattery. the simulation experiment which included changing power output of micro source,running mode conversion and cutting load under islanding operation. It verified the accuracy ofthe control strategy and the stability of the micro-grid during grid-connecting and islandingoperation.In the end, the special fault characteristics of micro-grid was analyzed through thetheory, the basic principle of the current differential protection and inverse time currentprotection was expounded, and established the protection modules in the simulation software.Micro-grid feeder protection strategy was proposed under different operation, the simulation experiment was done to verify effectiveness correctly of the proposed protection module andprotectionstrategy.