Power Systems Analysis in the Power-Angle Domain


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Virginia Tech


The idea of performing power systems dynamic analysis in the power-angle domain has been hinted at by previous researchers, but this may be the first published document to develop detailed techniques by which entire power systems can be represented and solved in the power-angle domain. With the widespread deployment of phasor measurement units and frequency data recorders the industry is looking for more real-time analytical tools to turn real-time wide-area measurements into useful information. Applications based on power-angle domain analysis are simple enough that they may be used online.

Power-angle domain analysis is similar to DC load-flow techniques in that a flat voltage profile is used and it is assumed that real power and voltage angle are completely decoupled from reactive power and voltage magnitude. The linearized equations for the dynamics of generators and loads are included in the model, which allows the electromechanical response to be solved using conventional circuit analysis techniques. The effect of generation trips, load switching, and line switching can be quickly approximated with nodal analysis or mesh analysis in the power-angle domain.

The analysis techniques developed here are not intended to be as accurate as time-domain simulation, but they are simpler and fast enough to be put online, and they also provide a better analytical insight into the system. Power-angle domain analysis enables applications that are not readily available with conventional techniques, such as the estimation of electromechanical propagation delays based on system parameters, the formulation of electromechanical equivalents, modal analysis, stability analysis, and event location and identification based on a small number of angle or frequency measurements. Fault studies and contingency analysis are typically performed with detailed time-domain simulations, where the electromechanical response of the system is a function of every machine in the interconnection and the lines connecting them. All of this information is rarely known for the entire system for each operating condition; as a result, for many applications it may be more suitable to compute an approximation of the system response based on the current operating state of only the major lines and generators. Power-angle domain analysis is adept at performing such approximations.



adaptive protection, traveling waves, wide-area monitoring, FNET, state-space analysis, modal analysis, event location, power systems