Research On The Optimization Of The Tie Lines In Urban Distribution Network Based On Two-Tie Connection Mode

Generally, urban distribution network is composed of 10kV feeders. By making full use of current distribution equipments and line corridors, it is vitally important to implement the objective distribution network on the basis of current network gradually as to improve power supply reliability and transmission capability of the distribution network. To adapt the characteristics of urban power load development and reduce the customer outage costs, it is necessary to set the reasonable tie lines so that the distribution substations or feeders can connect each other with the power quality and reliability improved.In this passage, through summarizing many actual cases of various areas and cities in China, practical methods and process of urban objective distribution network planning are presented; Transition mechanism of various typical connection modes are analyzed and studied, mainly including overhead lines transit from single loop network to multi-fraction three-tie loop mode, cable lines from single loop network to two-tie two"∏"mode and"4-1"connection mode emphatically. The study of transition mechanism is significant for adapting the characteristic of power loads increasing gradually and urban diversified construction, making urban objective distribution network more flexible and reliable.A bi-level optimization method based on two-tie connection mode is also proposed to optimize the tie lines in the distribution network. Outer optimization employs genetic algorithm(GA) to search for an optimal traverse sequence of substations based on contemporary distribution network. Differently, inner optimization, which is a traverse sequence based on outer optimization, optimize the tie lines configuration between different substations or in the same substation in sequence to form the two-tie connection mode network.Through analysis and research of typical connection mode transition mechanism and the bi-level optimization method based on two-tie connection mode in this passage, it achieves perfect results and can provide reasonable references to the power planners and operators.