Total supply capability of electricity distribution networks considering flexible interconnection of low-voltage service transformers

Abstract

Under the target of ‘emission peak and carbon neutrality’, electricity distribution networks will massively access low-carbon technologies, which will result in problems such as insufficient hosting capacity, unbalanced electricity loads, degraded power quality etc. The low-voltage flexible distribution network (LVFDN), which interconnects its low-voltage service transformers using flexible power electronic devices (flexible interconnected devices [FIDs]) is considered an effective means to deal with the challenges above. The total supply capability (TSC) of LVFDN is proposed. Firstly, the typical structures of LVFDN and their operation modes are proposed. Then, the TSC model of LVFDN, which formulates flexible power flow control and multi-level (medium-voltage feeder and low-voltage flexible interconnection) load transfer is proposed. Due to the non-linear non-convex characteristics of the proposed TSC model, a new algorithm based on the ‘branch and bound algorithm’ is also provided. In the case study, the TSC of an actual electricity distribution network is calculated and tested by the N-1 verification method. Finally, the variations of TSC with different capacities of the low-voltage FID are analysed. Suggestions for the planning and operation of LVFDN are also given. A theoretical basis for the application of flexible interconnection technology in low-voltage electricity distribution networks is provided.