Waveform-Based Method for Fast and Accurate Identification of Subsynchronous Resonance Events

An increasing number of unstable subsynchronous resonance (SSR) has occurred for wind farms recently. These events can lead to significant loss of generation, threatening the safe operation of the system, and even damaging the generators. Accurate knowledge of SSR characteristics (SSR frequency, current magnitude, and damping) at an early stage of the event is critical for its effective mitigation. This paper proposes a method for fast and accurate identification of an SSR event and its characteristics. It takes advantage of time-stamped waveform measurements that are typically available on the terminals of series compensated transmission lines. It uses the known model of the line as a “filter” to extract the SSR components. Case studies demonstrate that the proposed algorithm can accurately compute the SSR frequency, SSR current magnitude, and damping in around one SSR cycle or less. In addition to line parameters uncertainties, the method has also proven to remain robust in the presence of harmonic distortions and reduced waveform sampling rates.