Assessment of the stability of a multimachine power system by the transient energy margin

摘要

This research develops a tool for the direct assessment of the transient stability of a multimachine electric power system that is subject to a large disturbance. The tool is the Transient Energy Margin. The transient of interest is the first swing (or inertial) transient;The Transient Energy Margin is computed by evaluating an energy function using the relevant unstable equilibrium point and the system states at the instant the disturbance is removed. In evaluating the function, a significant portion of the fault kinetic energy is identified as not contributing to system instability. The resulting energy value is a measure of the margin-of-safety for the disturbed system;A distinction is proposed between assessing system stability and assessing system security. The Transient Energy Margin is used first to assess the stability of the system by creating a transient energy margin profile of the system. This profile ranks various disturbances to display the strengths and weaknesses of the system. A modified Transient Energy Margin is then proposed as an assessment of security; the transient energy margin profile is repeated to evaluate the system response in terms of the local minimum energy conditions approached by the critical trajectories. Both techniques are applied to a practical, 17 generator test system.