Static Stability Analysis Of Power System On Tie Line Cut-Set

In the interconnected power grid,we usually put the tie link between two or more areas called a grid section.The sum of the flow in every tie link is called section flow,the change of flow in the grid section reflects the relationship of the power exchange between the regions.Therefore,the static stability analysis for the tie link transmission section between the regionals is necessary,the rapid assessment of static stability limit has important engineering application value.The main reason of the interconnected power system instability is the power transmission capacity limits of the between two regionals on the tie link.To quickly judge the static stability limit of the interconnected power system tie line section,the relatively comprehensive dynamic equivalence method of the power system was proposed in this paper based on thevenin equivalent principle.The method turns the power extremum problem of complex interconnected power system into a simple dynamic equivalent circuit.Combined with the traditional concept and method of transmission section,this paper gives a new definition of the tie line cut section.Based on relative comprehensive dynamic equivalence principle,this paper puts forward the margin index that comprehensively evaluates power system link cut section static stability,the index can reflect current stability of the power system link cut section clearly.Through a simple 3 node system and IEEE 14 bus system to analyse the static stability of the tie line cut section.To rapidly and accurate calculateing transmission power limit of the tie line cut section,this paper adopts the high order Taylor series method,by choosing the appropriate independent variable of Taylor series,the nonlinear equivalent model of the power system is established,the model is described by the Taylor series of the node voltage about the load current.In the initial state,expanding the node voltage as Taylor series about load current,in combination with the transmission power limit criterion of the section,according to the current state,directly and quickly predict the limits of the transmission power.Through simulation analysis in the IEEE 14 bus system and IEEE30 bus system,we can verify the correctness of this method.The indicators and the method can be used in the system safety analysis and operation monitoring,to measure the transmission capacity of the tie line cut section and fragility,quickly find the weak sections,for grid operators directly find the weak area,improve the efficiency and accuracy of the analysis.