Assessment Of Power Supply Capacity For Distribution Network Based On Interval-affine Analysis Method

As the key-ligament between the customer and the generation and transmission system,distribution system plays a very important role in ensuring the continuous power supply for customers in safety and in high reliability.Therefore,the scientific evaluation on the power supply capability of urban distribution network is of enormous social and economical significance.As the distributed power generation system(DG)integrated into the distribution network,its output power is uncertain,while the load power is also random,which makes power flow calculation of the system stochastic and brings new challenges to the evaluation of power supply capacity.Considering the uncertainty of DG's output power and the randomness of power load,this paper evaluates the power supply capability of distribution network.To avoid the extension of results when interval arithmetic calculates power flow,the paper calculates power flow through Interval-affine Analysis.The interval-affine analysis is part of repeated power flow arithmetic when evaluating power supply capability.The results indicate that this method combines the advantages of the interval and affine analysis together and effectively reduce the intervals range and obtained more accurate results.Considering the uncertainty of DG's output power and unbalanced three-phase loads,the three-phase repeated affine power flow is put forward to evaluate power supply capability.In the last,on the basis of traditional repeated power flow arithmetic,while the uncertainty of node power is expressed by affine model,the paper put forward the three-phase affine repeated power flow arithmetic to calculate power supply capability.In the calculation,the three-phase affine back/forward sweep method is used to calculate power flow.The results indicate that this method can obtained more accurate results and deal with the situation of unbalanced three-phase systemConsidering that in the past we can only analyze that how multiple DGs result on the power supply capability of distribution system,and we cannot analyze that how single DG result on it.The paper proposes the index of influence of the DG's uncertain output power on power supply capability.Based on tracking principle of isotope,while the DG's output power is integrated into affine models containing noise elements,the paper obtain the tracking analysis of power supply capacity.The results indicate that this method can quantitatively evaluate the impact of DG on power supply capacity.