Real-time local voltage stability monitoring based on PMU and recursive least square method with variable forgetting factors

This paper implements recursive least square method with variable forgetting factors (VFFRLS) in local real-time voltage stability monitoring scheme based on the application of Thevenin equivalent model and PMU to reform the existing methods which present weak performance in tracking the time-varying parameters of equivalent model for power system. The selections of variable forgetting factor and initial value, identification of the time-varying parameters of system component models, and condition of locking are discussed. The IEEE 39-bus system is used to validate the method. Simulation results show that this approach provides more accurate results in tracking the time-varying parameters. The numerical results also show that the design of locking conditions can deal with the typical contingency, such as large generating unit or transmission line tripped, to achieve more reliable real-time voltage stability monitoring.