Determining an appropriate partitioning method to reduce the power system dimensions for real time voltage control

One of the ways to increase the speed of adaptive optimal coordinated voltage control (OCVC) is the reduction of the power system dimensions. To this end, after occurrence of a disturbance, the power system is initially partitioned into interior, boundary and exterior zones. Partitioning is based on the fact that voltage instability is a local phenomenon at the early moments after fault occurrence; therefore the variation of boundary and exterior variables is small. Then, the equations of boundary and exterior zones are linearized, and the variables and equations of exterior zone-except for control variables-are removed. This will lead to a considerable decrease in the number of power system equations. Three partitioning based on admittance matrix system, active and reactive power flow in transmission lines are taken into consideration and the appropriate method resulting in the minimal linearization error is selected. This paper also uses the multi-objective evolutionary algorithm based on decomposition (MOEA/D) to increase the problem solving speed in adaptive optimal coordinated voltage control. The simulation results on the New England 39-bus and IEEE 118-bus systems demonstrate that calculations speed have been remarkably improved while retaining the required precision.