Research On Coordination Planning And Networking Forms Of HV And MV Distribution Networks

Based on the load density and its development trend and the technical equipment level of the planning area,it is a strategic planning problem to select a technically and economically reasonable high and medium voltage(HV and MV)distribution network structures.The research on coordination planning and networking forms of HV and MV distribution networks has important theoretical and practical significance.In this paper,the network structure coordination of HV and MV distribution networks is explored based on corresponding reliability coordination evaluation.A reliability and economy analysis based coordination optimization model of HV and MV distribution networks is established and corresponding optimization results can be used as the constraints of networking forms.Mesh and ring networking forms are compared and analyzed,and corresponding optimization methods are puts forward.For the reliability coordination evaluation of HV and MV distribution networks,on the condition that there are generally a few limited load shedding rates(from an HV distribution network)possibly resulting in different reliability results with different load transfer rates(from an MV distribution network)considered,a(4N+2M)-parameter method of an HV equivalent source is proposed: firstly,the idea of(4N+2M)-parameter method is expounded;Secondly,on the basis of the 2-parameter method of equivalent sources,the(4N+2M)-parameter method is put forward,focusing on the calculation of its parameters and reliability index and the comparative analysis of two methods;Finally,two methods are applied to typical examples,showing that the(4N+2M)-parameter equivalent source can effectively avoid calculation error from the 2-parameter equivalent source with a small amount of more computational effort.Based on the investigation of advanced power networks,the classification and characteristics of different networking forms are clarified;the "strength,simpleness and weakness" of power networks and HV and MV distribution networks are defined respectively;reliability and economy evaluation based scheme optimization models for HV and MV coordination planning are established: some reliability indices are estimated by using an(4N+2M)-parameter method,and then the reliability indices are converted into economic indices,and the optimal scheme with the minimum total cost.is selected The calculation and analysis of reliability and economy for classical coordination schemes show that the MV distribution networks must be strong for the requirement of high power supply quality;in general,the HV distribution networks are not necessary to be "strong";"simple" HV distribution networks(such as a double-radiation wiring mode)can reduce the pressure of urban channels and substation locations,and also ensure the reasonable reliability and economy of rural radial power grids.Aiming at the construction of mesh network form(or power supply area division),new models and heuristic methods of power supply area division optimization are proposed for MV distribution network planning: firstly,the layout of regional candidate trunk channels is clearly planned;secondly,based on the minimization of the overall cost of trunk supply lines,the priority is to form inter-station power supply areas that can realize load transfer;Then,the overloaded power supply areas are refined by clustering of sub-supply areas in parallel arrangement;Finally,the exhaustive method is used to optimize the matching of sub-supply areas in each power supply areas and form the appropriate size of inter-station power supply areas,self-loop power supply areas and radiation power supply areas.The example analysis proves that the proposed method is reasonable and effective,and practical.Based on the concept of flexible planning,a new set of ideas,models and methods of flexible planning for distribution networks is proposed.The characteristics and application scopes of two kinds of MV networking forms under uncertain conditions(i.e.mesh and ring networking forms),are compared.The advantages of a ring networking form are elaborated for flexible planning.And the optimization model and corresponding heuristic solution method are proposed to choose between a mesh networking form and a ring one,focusing on the construction method of ring network form.The effectiveness and applicability of the proposed flexible planning methods are shown through numerical examples.