The Research On Coordination Planning Of High-voltage And Medium-voltage Distribution Networks

The coordinated planning degree of power grid affects the system's reliability and economic running. No "bottlenecks" in some parts, and no waste in the links, and, to make the full coordination of power grid are the important goals for power grid planning. It is our pursuit to improve the coordination degree of high-voltage and medium-voltage distribution networks. In this paper, the main work includes the following contents:First, the paper studies the high-voltage and medium-voltage distribution networks' running situation, power supply ability, and the weakly-coordinated factors. The weakly-coordinated phenomena of high-voltage and medium-voltage distribution networks are summarized from the perspectives of capacity and network structure. And then, the reasons to these uncoordinated phenomena are deeply analysed, the corresponding preliminary suggestions are made also in the end.Second, a differentiation coordination degree evaluation system of high-voltage and medium-voltage is prososed, which considers the 110kV substation, lOkV feeders, and the power suppy zones. This system selects the certain evaluation indexes on the basis of analzing the development of distribution networks. Otherwise, it takes the load characteristics in different power suppy zones, load density, 110kV substation's space interval utilization, feeder-load ratio, transfe power capability of tie lines, and, the trunk line length in considence. The mian analyzing methods used in the system are Analytic Hierarchy Process (AHP1-9 scaling method) and Curve Fitting. Based on the methods and the coordination degree evaluation system, the coordination planning results of 110kV substations in all kinds regions are differentiated evaluated, the possible coordination weaknesses of planning are analyzed, and lastly, the differential solutions are put forward too.Third, Summarizing and comparing the present 110kV substation site's planning grograms, and then, considering the maneuverability, using the "center of gravity", and taking the coordination degree evaluation indexes into accont, a method of 110kV substation site selection is put forward. First of all, This location method will be benifital to reduce the weak links of the high-voltage and medium-voltage distribution networks's operation, because it not only can guarantee the balance of the load, but also can optimizate the medium-voltage distribution networks's structure as a whole.And lastly, an important planning theory for improving the coordination degree of high-voltage and medium-voltage distribution networks is proposed. Substation site selection must be coordinated with power supply area division. They ought to be iteratively planned. The selection of substation site will affect the division of power supply range, and, if the power supply ranges of the new substation are different, the loacationS of this substation will be different too. Lastly, the process of 110 kV substation iteratived coordination planning is proposed.