Hierarchical Total Supply Capability Evaluation For Distribution Grids

Distribution grid is the last link of electricity to the user,its reliability directly affects thequality of power supply to user,evaluation and calculation of total supply capability ofdistribution grid becomes one of the important indexes for evaluating the distributionnetwork.TSC(Total Supply Capability) refers to maximum load supply capacity of thedistribution grids in a certain power supply meeting the N-1security standard conditions andtaking into account the actual operation.Reasonable and accurate evaluation and calculation of total supply capability ofdistribution grid are important to improve the reliability of distribution grids,not only canreflect the level of distribution grid power supply,more importantly can find the weak pointsof distribution grids,and give guidance to optimize the load and improve equipmentutilization level.Current research on supply capability mainly concentrated in the construction and thecorrection of calculation model.The main calculating methods contain analytical method andmodel method,typical methods are capacity load ratio method, maximum and minimum loadfactor method, maximum network flow method, based on the DC power flow model andcalculation method ofAC power flow model and fuzzy calculation method etc.This article firstly compares and analyzes the existing methods for calculating TSC,thenestablishes callationg model,capacity matrix of equipments,load transfer matrix,etc.Secondly,estalishes a family of hierarchical TSC index reflecting the main limitation ofTSC.The TSCs of the feeder level, the substation level and the second transmission line levelare defined, respectively. A set of matching index are defined to identify the matching degreeof the TSC of the devices in the adjacent levels. A series of index of fullness degree are alsodefined to represent the difference between the actual load and the load in the ideal condition with maximum TSC on devices.At last,The methodology to find the factors reducing the TSC of the distribution grids onthe bases of the proposed index is described.Examples are given to demonstrate the proposedapproach in detail showing its feasibility and effectiveness.