Definition, Model And Calculation Method Of Total Supply Capability Of Distribution System

As the key-ligament between the customer and the generation&transmissionsystem, distribution system plays a very important role in ensuring the continuouspower supply for customers in safety and in high reliability. The future distributionsystem of smart grid will possess fast network transfer capability and new N-1securityboundary. Within these new N-1security boundaries, load can be transferred from onesubstation to others through feeders with tie-lines, besides the load transfering withinsubstation through bus switch. The fast network transfer capability will bring significantchanges to future distribution system operation, which is one of main motivation of thetheory of Total Supply Capability (TSC). This paper introduces the developing processof power supply capability calculation, and analyzes the N-1security of substationtransformer and feeder. Based on these, this paper proposes the definition of TotalSupply Capability (TSC) of distribution system, and a model and calculating methodof TSC is set up. This paper also proposes a method to evaluate the accuracy of TSCcalculating.First, this paper introduce the definition of TSC of distribution system accordingto the Total Transfer Cabability(TTC）in transmission system. Based on de definitionof TSC, concept of Substation Supply Capability (SSC), Network Transfer Capability(NTC) and Available Supply Capability (ASC) etc. is proposed.Second, this paper proposes the model and calculating method for TSC. Themodel of TSC is set up as the solving of linear programming problem. The modelconsiders capacity and N-1security of transformers and feeders and the topology ofdistribution network as constraints. The objective function is TSC, and the optimalsolution of the linear programming model is load of transformers and feeders at TSC.The TSC model is composed of two parts, one is the maximum TSC model; the otheris the load balance model, which can be transferred into the format of matrix andsolved by Lingo respectively.Third, this paper proposes the evaluating method of TSC calculating, whichconsists of two parts. The first part is accuracy determination, which is based on theN-1security simulation test of distribution system and the definition of TSC, this partcan decide the calculating is accurate or not. The second part is error assessment, in this part, a hybrid approximation method to calculate TSC is presented, andcalculation of TSC is evaluated through a series of indices, which provides the errorof the TSC calculating.Finally, the case study has shown the application of the TSC model and theevaluating method, which proves the effectiveness and accuracy of the proposed TSCmodel and calculating method.