Dispatchable Region And Security Region Of Distribution Systems With Distributed Generators

In the context of China's increasing emphasis on environmental pollution and energy transformation,the access of high penetration renewable energy access has become an inevitable trend of China's smart grid development.As an important form of renewable energy,DG is accessing to smart distribution network in a large number,with its advantage such as investment,clean environment and high reliability.High penetration access of DG makes distribution network present closed loop structure and open loop operation,power flow in lines reverse,which has a great influence on the distribution network voltage stability,system planning,system operation and power quality.This paper focuses on the new feature for DSSR with DG.The main work is as follows:1.The theory of DSSR is introduced and the influence of DG access to distribution system is analyzed.Firstly,the theory of traditional DSSR is elaborated.Secondly,DGDR concept is proposed after analyzing influencing factors such as placement,output and penetration of DGs and microgrids(MG).Output power range of DGs and MGs can be calculated with dispatchable region.Thirdly,different types of DG are classified and microgrid is simply introduced.Finally,this paper analyzes the influence on the distribution network voltage,scheduling and grid stability,caused by DG.2.Mathematical model and algorithm of dispatchable region is proposed,with which dispatchable region of different DGs and MGs can be obtained within voltage and power flow constraints.Finally,with numerical example of IEEE 33,validity of the proposed method in calculating PQ and PV type DG is proved.Obtained region is compared to dispatchable region with load buses only.Penetration of DGs or MGs causes DGDR area increase and more complex DGDR topology.Under the same conditions,PV type DGDR area is larger than PQ type.3.The model of active distribution system security region(A-DSSR)based on AC power flow is proposed.Firstly,under constraint conditions such as voltages and N-1 security constraints,the model of A-DSSR and calculation method of security boundary are proposed.Secondly,with a practical calculation example,new features of A-DSSR and security boundaries are studied,after considering AC flow.Through comparative analysis,we can see that the result of A-DSSR is more accurate after considering power flow.The security boundaries are still approximately linear,but they can have an augular offset within 0~±15°,around 45°or 135°.Voltages can have big impacts on DSSR.And the results can have some guiding significance of the location and capacity of the new load or DG in the grid.4.The security boundary and safe distance calculation software of the distribution network with DG are established.Firstly,the programming environment and program functions are determined,according to the requirements of the national grid company's technology project.Secondly,according to the model of A-DSSR,the programming framework and program are given.Finally,the feasibility and validity of the proposed calculation method and software are verified,by using different types of examples and simulation analysis of actual power grid data in Jiaxing area.