Thevenin Equivalent Of The Grid And Reserch On Static Voltage-Stability

The voltage stability of power system is an important issue.Especially since the the 70's of 20th century,such accidents of power system's disintegration and collapse ocuured at home and abroad,which was caused by voltage's destabilization.Long-term and large acreage power failure of the world has caused tremendous economic losses.Therefore,reserching on the increasingly prominent problem of voltage stability is of great significance,which is also the direction for which the power workers have a lot of enthusiasm.As the power grids interconnect,power system topology becomes more complex.So the studying of the entire power grid is increasingly difficult.If there is a model to simplify the grid,research on the grid will become more simple and convenient.This is also the hard goal which is pursued by a number of electrical workers.Thevenin equivalent of the power system is the outstanding representative.It makes a complex power system changed into a two-node system,so that researchers can rapidly make a stability analysis and evaluation to the node interested in.However,how to obtain or track accurate Thevenin equivalent parameters is the key to analysis the state of the running system.Thevinin equivalent simplified the network to be simple and intuitive,so that which is a hot direction reserched a lot by many reserchers.This paper proposes a fast method,which uses differential equations to simplify a parameters's time step changes to track the Thevinin equivalent parametres of the power system.Through utilizing the grid's initial state parameters and power flow datas,a continuous time differential equations,which is simpfied to reflect the time step changes of the parameters,we can trace and calculate the current time Thevinin parameters.The method'procedure is concise,through the differential form of the dynamic changes in response variables,we can avoid the current popular two-points or multi-points method'error of considering the parameters unchanged to track Thevenin equivalent parameters.A new algorithm of calculating Thevenin equivalent parameters is mainly proposed with sensitivity based on Thevenin equivalent's model.Making use of node voltage partial pressure principal on initial status and active power disturbance status,equations set can be listed.This equations are simple and linear,which are sloved only with triangular decomposition and whithout two points or more points flow datas as convetional algorithm.It is less computation.After Gaining Thevenin equivalent parametres by Thevenin's equivalent on load bus node,static voltage analysis of all load nodes is proceeded using resistance module margin indicator,and the whole system's load margin can be estimated.Tested on IEEE 30-bus and IEEE57-bus systems verify the correctness and practicability of this method.