A Multiple DGs Islanding Detection Method Base onThe DWT and THD of Current

According to the IEEE standards 1547-2003 Islanding concept is a condition in which aportion of the utility system that contains both loads and Distributed Generation (DG)remains energized while isolated from the remainder of the utility system and in thiscondition DG must be disconnected at most within 2 seconds. Generally, if there are largechanges in loading for DG after loss of the main power supply, then islanding conditionsare easily detected by monitoring several parameters: voltage magnitude, phasedisplacement and frequency change. However, in case of small changes in loading for DG,the conventional methods have some difficulty in detecting such a particular islandingcondition. Therefore, propose of this paper is, fast and accurate method for MultipleDistributed Generation (MDGs) islanding detection in the distribution networks based onTHD of current and analysis of DG transient terminal unbalance voltage by using DiscreteWavelet Transform (DWT) and Daubechies mother wavelet. For any possible event in thedistribution network such as : islanding and non islanding (Normal utilization, Faultsinclude 3-ph, 2-ph, 2-ph to ground, 1-ph to ground in all buses, Load switching, DGswitching, Capacitor banks switching) conditions with employing of DWT, requirementfeatures by the third level of decomposition classified and accordingly events divided twogroups islanding and non islanding. Performance of proposed method tested on IEEE 13Node Test Feeder in three scenario include ground fault, load rejection and capacitor bankswitching. This system have two different types of DGs that are synchrounous andinduction generators. The PSCAD/EMTDC sued to simulate the different scenarios studiedand analyzing to be optimized in progress of indices such as: accuracy, speed andreliability. By evaluation, it was determined that proposed method compared withconventional islanding detection method is able to islanding detecting in presence of MDGwith high speed and high accuracy.

کلیدواژه ها:

islanding detection ، Discrete Wavelet Transform (DWT) ، unbalance voltage ، TotalHarmonic Distortion (THD) of current ، Multiple Distributed Generation (MDG)