Research On Cooperative Black-start Of Internal And External Power Sources In Large Power Grids

As the last line of defense for power grid security,black start is of great significance to national security,social stability,economic development and political strategic needs.At present,the type of black-start power supply is single,and it relies heavily on the reliability of specific black-start power supply.The tie lines between power grids have strong support ability and can also be used as emergency power supply for black-start.In order to strengthen the last line of defense of the large power grid and accelerate the process of system recovery,this paper conducts three aspects of research around the problem of coordinated black-start of power sources inside and outside the large power grid.The main work and contributions are as follows:(1)A method for selecting internal and external black start power sources in large power grids is proposed.Firstly,the self start characteristics of various types of units in the power grid are studied,and a two-level black start capability evaluation system is established to obtain the internal black start power supply set;Secondly,the external black start power supply set is determined through the connection relationship with adjacent power grids and the transmission capacity of the connection lines;The research shows that the two sets obtained are the basis for studying black start zoning and path optimization.Internal and external black start power supplies can complement each other’s advantages and achieve synchronous recovery.(2)A method for coordinated partition and path optimization of black-start power sources inside and outside power grid based on Dijkstra algorithm is proposed.Firstly,based on the knowledge of graph theory,the original power network is transformed into an undirected weighted graph,and a method for solving the shortest electrical path using Dijkstra algorithm is proposed.Based on this,a strategy and solution flow for the coordinated black start of a pair of internal and external power sources with the closest electrical distance are proposed;Finally,taking an actual power grid as the solution object,the collaborative mapping relationship and partition number of internal and external black start power sources are obtained,and the optimal path set for the startup tasks of each black start power source in the region is also obtained.(3)A method for collaborative black start of internal and external power sources in the power grid considering safety and speed has been proposed.Firstly,based on the problems encountered during the black start operation,a comprehensive safety verification and control method for the black start process is presented;In order to shorten the charging time of the line segment by segment,a method for putting no-load line into operation by grouping is proposed with the minimum number of line groups and corresponding voltage regulation measures as the optimization objectives.Finally,taking an actual large power grid as a simulation case and comparing it with conventional black start strategies,it is shown that the proposed optimization strategy has a greater safety margin and faster recovery speed.