Is Velocity Feedback Always Best for Machine Stability Control

A total energy control approach derived from Lyapunov based energy function design and applied in a complex power system is shown to provide satisfactory energy reduction performance for severe disturbances. Most energy-based controllers use a control proportional to velocity, this provides satisfactory damping but may not provide good first swing stability. This paper addresses this implicit problem in switching control using a single-machine-infinite-bus (SMIB) example to characterise the phenomenon. A constant energy surfaces diagram is used in the analysis to demonstrate the key issue in switching control. An angle look-ahead control is derived for a (SMIB) system as an effective solution to the first swing switching stability problem. It is shown that through the understanding of the problem, controller design can be made effective for limiting the first swing without loss of damping performance.