Real time detection of system oscillations – concepts and applications

Signal oscillations on a power system are a phenomenon caused by unintended exchange of power (real or reactive) between sources on the grid, quantities induced onto the grid or because of a resonance. Historically, the electrical power was generated solely using electromechanical generators. Due to that, the primary source of oscillations was the machine-to-machine hunting which is referred to as inter-area oscillation. With the complexity of the grid increasing other oscillation sources were identified. The frequency spectrum of the oscillations increased as well; in certain scenarios the oscillation not being limited to a single frequency. One type of oscillations is a sub-synchronous oscillation occurring because of interactions between the generation and the series compensated lines. With the advent of inverter-based energy resources the nature of oscillations changed as well, with the power electronic control system being responsible for some of the oscillations. The impact on the local grid differs based on multiple factors however it is important to detect the oscillations to understand the consequence to the wide area electrical grid.