Research On Hierarchical Partitioning Method For High Voltage Regional Power Grid

With the development of national economy,the capacity of power system is increasing,China's primary energy base and energy demand region has a long distance reverse distribution characteristics,electrical energy needs to be transported in a long distance.In order to ensure the economy and safety of power transmission,the traditional solution is to increase the system voltage with the increase of the system capacity.In the early stage of a new higher voltage level,the network can not be very strong in structure.In the process of improving and strengthening,in order to obtain large network transmission power and use cheap resources,the electromagnetic loop network is generated.After the operation of the power network closed loop,the short circuit impedance of the system will be reduced,which makes the short circuit current increase.On the other hand,along with the electric power market continues to advance,higher requirements are raised about power transmission capacity and reliability of the main frame.Aiming at the serious situation of short circuit current,the selection method of the power network hierarchical model,and the selection method of the interval tie line and the selection of the access point of the large power source are studied.A new method of power network partition is presented,and the selection method of access point of large power source is provided,which provides a new way to solve the problem of short circuit current.Taking into account the traditional power grid partitioning method does not fully consider the power grid structure,in this paper,the method for power grid division based on improved automotive relay is presented with a 500 kV grid as the main frame.The proposed method can be implemented by programming and multiple partitions can be carried out simultaneously without repeatedly solving.According to this rules,the sites near the initial station can be found,and then partition.After the network partition,when a partition generated power shortage for component failure,the tie line between the partitions is an important measure to solve the power shortage by providing power supply or load transfer.At the same time,the interval tie line not only ensures the linkage between the partitions,but also can effectively avoid the occurrence of cascading failures.Therefore,the selection of the interval tie line is very important.In this paper,the selection of the interval tie line is studied,and a new evaluation system for the selection of the interval tie line based on the relative entropy combination weighting method is proposed,considering the short circuit current,power flow,the overall power flow,the node voltage stability,short circuit capacity,to ensure the integrity and rationality of the evaluation.The method for determining the access point of the existing large power supply access network is mainly based on the expert experience,and the subjective dependence is too large.This paper constructs a relatively complete index system which can be used to evaluate the rationality of the selection of large power access points.The index system takes into account of the system power flow distribution,short circuit current,N-1 fault,stability,network loss,so that the evaluation results are more reasonable.In order to avoid the limitation of the single weighting method,firstly,the combined weighting method to determine the comprehensive weight of each index is used,and then the improved gray correlation analysis method based on the comprehensive weights is used to evaluate the scheme of the access point of the large power supply connected to the power grid comprehensively.From the perspective of power grid planning,it provides a practical method for the selection of access point for large power supply access network.Finally,the PSD power system analysis software is used to carry out the simulation of data from Tangshan.The effectiveness and feasibility of the proposed method are verified by the simulation example.