A New PMU Placement Method for the Assessment of the Voltage Stability Margin

Voltage stability margin is a valuable information for the operation in control centers. This index provides the maximum load limit for the power system related to a voltage collapse, or more specifically, the Saddle-Node Bifurcation. Its calculation requires a definition of the direction of load growth and different directions can provide different margins of stability. Thus, measures must be taken to ensure that the reported stability margin estimate is adequate with the direction of load growth in effect in the power system. This paper presents a procedure based on Genetic Algorithms for the phasor measurement unit placement in order to monitor the voltage stability margin in the power system for different load growth directions. A direct method is used to compute the voltage stability margin related to the load condition where the Saddle-Node Bifurcation occurs for each load growth direction definition. Tests were conducted in the IEEE 39-bus system.