Research On The Optimization Model Of Branch Network Transformation Based On Reliability

Centralized heat-supply system is one of the essential infrastructure in modern city, which has a very important influence on social production and people's life. The reliability of tree-shaped heat-supply network is relatively low and the heating accidents have caused great loss to the production and the life of people, so it is very important to improve the reliability of tree-shaped heat-supply network. Meanwhile, ring-shaped network has a strong spare capacity and ability to withstand accidents. So it has a very good prospect. In this paper, based on the existing research results, tree-shaped heat-supply network was transformed into a ring-shaped network in order to meet the requirements of the structure reservation and the delivery of spare capacity. This paper mainly studies several problems as follows:First, based on the tree-shaped heat-supply network with a low reliability and difficult to meet the limitation of the spare structure, we considered transform tree-shaped heat-supply network into ring-shaped. Namely, it improved the reliability of the tree-shaped heat-supply network by adding chain branches(making it to constitute local ring). This paper analyzed the reliability of heat-supply network and its influence factors, and discussed the theoretical methods to determine how many chain branches and where they should be. Then, taking a tree-shaped heat-supply network as an example, we calculated the position and number of the chain branches, making the reliability increased from 82.34% to 94.81%.Next, a mathematical model for the transformation of tree-shaped heating pipe network was established. This model was established under the most unfavorable accident, and the limitation of heating coefficient was set to 70%. It regarded the diameter of the pipe in the ring after transformation as discrete variable and the reform investment as objective function. Some constraint conditions are considered, including the conservation of mass and energy, restraint of the head pump, the discrete pipe diameter and flow velocity.Finally, according to the characteristics of the mathematical model of ring-shaped heat supply network, it analyzed the advantages and characteristics to solve this problem using genetic algorithm(GA). In order to improve the computing efficiency and convergence rate, some improvement measures to the algorithm were put forward to make a better solution. Then, GA was used to optimize the pipe diameter of the network after transformation, and the solution can reach 70 percent of the nomal condition the quota heating demand in the most adverse accident. At the same time, it also made check calculations of the rest accidents so as to make the system meet all the limitation of the heat requirement under all accidents. After transformation of the heat-supply network, the quota heating can reach 70 percent of the normal under the most unfavorable accidents, and not less than 70% of the others.In view of the optimization design of tree-shaped heat-supply network transformation, this paper analyzed the scheme in structure capacity and spare capacity, greatly improving the reliability of tree-shaped heat-supply network. It has a great practical significance in the field of centralized heat-supply.