A Calculation Method Of Electrical Distance Based On Transmission Impedance And Reactive Power Optimization Of Distribution Network

At present,the economy of our country has been developed rapidly.The electric power industry has been entered the period of large units,large power grid and high voltage.With the expanding of power grid scale,the system structure is more complicated.Combined with the diversification of power generation and increase of uncertainty factors,the voltage stability problems are becoming more serious.Power system reactive power/voltage control has been considered as the effective method to improve voltage stability.Among them,the voltage hierarchical control is widely used.The premise of voltage hierarchical control is the power grid partition,which is based on the electrical distance.The traditional calculation method of electrical distance is sensitivity method.By deducting the definition and calculation formulas,this paper has found that sensitivity method is lack of concept of spatial position relation,inaccurate,unclear about physical meaning and multivalued.As we all know,when the power source and network topology are fixed,the operation parameters are distributed according to the impedance.Therefore,a new electrical distance calculation method is proposed from the view of impedance,namely transmission impedance method.The method is based on power flow tracing.By constructing generalized branch,the transmission impedance can be got,and then we define the absolute value of transmission impedance as the electrical distance.The electrical distance reflects the connection degree between two power variables by transmission impedance,which conforms to the concept of "electrical".It also satisfies symmetry,that is,the distance from power variable A to power variable B is equal to the distance from power variable B to power variable A,which is in line with the concept of "distance".Calculate electrical distances of the IEEE39 nodes system by using this method and partition the power grid.Comparing the results with the sensitivity method,the rationality of the proposed method is verified.Finally,making partition reactive power optimization according to the results and comparing with the whole optimization,the controlling variables can be reduced so the calculating time is less.It can also verify the accuracy of the partition results.