The Method Of Using Dynamic Impedance Matrix To Analy Voltage Stability And Determine Its Application In Power System

In recent years,with the gradual development of power system,the time of power grid has come to us.There are so many large voltage collapsed accident occurred in the world.It has brought great instability to society and people's lives.Voltage stability has become the main issues affecting the safe and stable operation of the power system.The nonlinear dynamic analysis method is used to define nonlinear dynamic impedance matrix with the basis of the comprehensive dynamic equivalence principle.Diagonal elements are called dynamic self-impedance,but off-diagonal elements are called dynamic mutual impedance in dynamic impedance matrix.According to the characteristics of the dynamic impedance matrix,we put forward the dynamic mutual impedance analysis method,and thus propose the voltage dynamic mutual impedance and current dynamic mutual impedance.The voltage dynamic mutual impedance indicates that the changes of all nodes' current effect on one of the node's voltage,the average of voltage dynamic mutual impedance is applyed to the determination of weak points and preliminary determine the reactive power compensation point.Yet,the current dynamic mutual impedance shows that the change of one node's current effect all the nodes' voltage in power system,the average of current dynamic mutual impedance was setted for evaluating the reactive power compensation device on the basis of the whole voltage comprehensive compensation system.Testing the effectiveness of the dynamic mutual impedance analysis method in IEEE14 and IEEE30 buses system.The requirement of reactive power compensation is not only ensuring the voltage stability of compensation point,but also the rest of the nodes' voltage having the biggest ascension.This paper combine the average of voltage and current dynamic mutual impedance which introduce the load weight,and applys it to reactive power compensation in the configuration.Firstly,the average of voltage dynamic mutual impedance can identify weak areas of the system.And then,the weights which combine the average of voltage and current mutual impedance,could select the reactive power compensation point in weak area.Given the importance of voltage stability in the grid security and stability,we can take voltage stability margin as the objective function.After setting the appropriate threshold,we arrive at a final configuration of reactive power compensation.Through the simulation and analysis ofIEEE30 buses system to verify the correctness of the method which combine the average of voltage and current dynamic mutual impedance in determining optimal reactive compensation point.