The Dissipating Energy Flow method for analysing generator contribution to power system damping -- evaluation and interpretation

Abstract: Electromechanical oscillations is a power system phenomenon where generator rotors oscillate, leading to oscillatory power flows. Damping of such oscillations is important for system stability. Forced oscillations is a special case where one faulty component is the source of the oscillation. This report concerns the Dissipating Energy Flow (DEF), which is an energy-based method for analysing damping performance of individual network components through synchrophasor measurements. It has shown promise in being able to locate the source of a forced oscillation. Through simulations in simple systems the method is evaluated in its ability to 1) locate the source of forced oscillations and 2) indicate the performance of power system stabilisers (PSS). The method succeeds in locating the sources of forced oscillations, while the simulations show no use of the method in indicating PSS performance when the system is disturbed by a forced oscillation. The former is in line with existing literature, but the latter is in conflict with the proposed equivalence between dissipating energy and damping. The results further suggest that the $P$-$f$ term of the DEF integral alone is responsible for its utility. The simulations indicate that the method's functionality builds on the fact that the source always exhibits a leading phase in an oscillation. This leading phase is demonstrated using data from a real oscillation event. With the help of a mechanical analog the net damping done by the power due to relative rotor angles between machines is analysed, which gives an understanding of the connection between the phase-leading characteristics of the source generator and its dissipating energy flow.