Protection Of Distribution System Containing Micro-grids

With the national emphasis on new energy resources, the distribution system containingmicro-grids with distributed generation will be the distribution network development trend inthe future. But when the distributed generation accesses the distribution network, which willimpact the distribution network structure, impact the fault current magnitude and direction ofthe grid, and will lead to the traditional three-step current protection can not play the originalrole. In order to solve some problems of protection technologies in the new distributionnetwork, in this paper proposes a directional pilot protection program based communicationnetwork technology. In this paper, it has built a simulated model of the distribution systemcontaining micro-grids with distributed generation based on MATLAB software, has got faultdirectional information from the direction of components, to verify the feasibility of thedirectional pilot protection in the distribution network containing micro-grids with distributedgeneration.When the micro-grids with distributed generation access to the distribution system,which makes the direction of the trend and distribution changed in the network, and alsoaffect the size and direction of the short-circuit current. To create a simple model in thesimulation software MATLAB, when the micro-grids with distributed generation access to thedistribution system, which impacts on the traditional protection as follows: resulting in falseaction and refuse action of this line protection, reducing the sensitivity of the protection, lossof the selectivity of the protection; leading to false action of the adjacent line protection, lossof the selectivity of the protection; expanding the scope of power outages. Because themicro-grids with distributed generation access to the distribution system, affects thetraditional protection, in this paper uses a directional pilot protection program basedcommunication network technology. The principle of the protection scheme is: the intelligentelectronic device (IED) is protection device, which do not make any decision, only to detectthe fault direction information. The IED collects the fault direction information, and transmitthe fault direction information to the Supervisory Control and Data Acquisition (SCADA)system by communication network technology, the SCADA system according to the receivedfault information combines with the location algorithm and the isolation algorithm of theprotection, analyzes and processes the received fault information with the location algorithm,and select to whether or not send trip command for the circuit breakers of the fault section, toisolate the fault. In this paper, protection program in accordance with the order to detect fault.The core content of the protection program is the fault directional element can detect the faultdirection information accurately. In order to ensure the correctness of the fault directional element of judgment, this thesis has established the simulation model of the distributionsystem containing micro-grids with distributed generation in MATLAB software. Accordingto the different types and number of distributed power of simulation and analysis, theconclusion that if the fault directional element collects the fault direction information within150ms after the fault occurs, regardless of the access of the distributed power for thesynchronous generator or asynchronous generator, the fault directional element can bereflected fault direction information correctly in this period. Protection requirements of faultremoval time is generally less than this time, so the fault direction information detected by thefault directional element can be met the requirements of fault location and isolation in thispaper.