A Fast Calculation Of Voltage Stability Index Based On Network Impedance Matrix Correction

With the scale-up of power network in electric power system,the unsafe factors of electric power system operation also increase followingly.In recent years,many accidents of voltage collapse around the world have brought great impact on people's life and economic development,and the issue of voltage stability has attracted much attention from various countries.Therefore,it is extremely important to find the suitable indicators to assess the voltage stability of the construction.Based on the index of the linearized network's voltage stability,the internal system could be simplified by using the principle of linear thevenin equivalence,in which the internal power and load are equivalent to voltage source and current source respectively.The calculation of this index satisfies the rapidity of computing voltage stability which is not based on the load flow equations.However,in the limit case,the various Node voltages are conservative.It couldn't describes the boundary of voltage stability accurately because it does not tend to the theory of extreme value.Based on the impedance of the dynamic equivalent impedance model margin index,each node has one strict voltage stability border through the principle of mechanics equivalence to simplify internal construction.It could also assess the voltage stability of each node precisely which satisfy the accuracy of the calculation of voltage stability.However,on account of the load wave equations,the indicator will take a lot of work to calculate it in a complex power network.This article will combine two above-mentioned characters of the quickness and accuracy to make assessment of the electric tension stability,and put forward a kind of fast method of calculation which modify the voltage stability index based on network impedance matrix.The main works of the paper are:To come up with one fast method of calculation that the network impedance correction for simple systems is based on dynamic equivalence method.For the load of a constant power model in a power system,the load impedance is a nonlinear function of the node operating voltage,so the static equivalent impedance correction method of the burden cannot be directly applied to analyze the descendant elctric tension stability of the construction.In this paper,the nonlinear system dynamic equivalent analysis method is applied to testify that the internal load of the system can be equivalent to linearized dynamic equivalent impedance,and the dynamic equivalent impedance can be connected to load nodes to form a modified network impedance matrix,so as to judge the voltage stability of the construction exactly.Analysis showed that it can assess the node electric tension stability of power construction quickly and accurately without the need of the load flow equations when the internal load mechanics equivalent resistance is equal to the opposite number of the static equivalent impedance.To come up with one fast method of calculation that the voltage stability of complicated construction is built on network resistance matrix correction.By making constant power load of the node equivalent to the dynamic equivalent impedance and applying the method of increasing the load branch of the impedance matrix correction,it could form the network impedance matrix of the analysis and calculation of voltage stability.In order to judge the limit state of voltage stability accurately,it needs to propose a progressive correction method of impedance angle of load dynamic equivalent,which makes the burden dynamic equivalent resistance angle equal to the thevenin equivalent impedance angle of its construction.According to the modified network impedance matrix,the equivalent impedance of the system can be calculated quickly and accurately,and the indicator of the resistance coefficient border of the node voltage stability can be obtained.Due to the application of strict dynamic equivalence analysis method in the nonlinear electric system,the resistance modulus boundry indicator of all nodes uniformly approaches 1 at the boundary of voltage stability.At the same time,The calculation work is greatly reduced by using the analysis of network impedance matrix instead of the load flow equations.The simulation calculation has verified that it could judge the voltage stability border of the construction accurately based on the fast method for voltage stability calculation of network resistance correction.It could also arrange each nodes through its stability,then focus on monitoring the weakness of voltage stability and improve the overall voltage stability level of the construction.