Novel Decoupled Active and Reactive Power Sub-Synchronous Oscillation Response

This research project investigates assessment and mitigation measures relating to sub-synchronous oscillations occurring on electrical power transmission systems as a consequence of the large-scale deployment of Inverter Based Resources (IBR).

Developing Novel Decoupled Active and Reactive Power Sub-Synchronous Oscillation Response Assessment is a National Energy System Operator (NESO) funded project involving both Brunel University of London and NESO. 

This project performs industry-applied research on Sub-Synchronous Oscillations (SSO) in electrical power systems with high penetrations of renewables and Inverter Based Resources (IBR). The SSO research addresses different classifications, sources, detection, identification, prediction and mitigation.

Understanding sources for classes of SSO involves researching different methods of modelling IBR. The project develops new detection and prediction methods for better understanding of possible mitigation actions.SSO analysis techniques include frequency scanning, eigenvalue, impedance-based model and electromagnetic transient analysis.

Innovative technologies such as, Phasor Measurement Unit data is used for event detection, identification, and source location of SSO in real-time. Novel Co-simulation, Digital Twin and Hardware in the Loop (HiL) studies will develop, identify, test, and assess techniques that can be deployed in electrical power systems for SSO detection and mitigation.

Electrical power systems are shifting towards renewables and net-zero system operation. More renewables penetration and Inverter Based Resources (IBRs) are being connected to electrical power systems and pose great challenges in operating systems securely. In the past, security issues concerned thermal violations, voltage stability, rotor angular stability and to some extent small signal stability due to sub-synchronous resonance.

With the new technologies shifting towards Voltage Source Converters (VSC), whether grid forming or following, new modes of oscillations are starting to emerge. Moreover, conventional methods in determining the strength of the system and hence its resilience to secured events will become inadequate and would not be sufficient to determine the operability of the system. It is evident that new measures and methods will have to be developed to cope with such future scenarios and situations. This would be very useful to electrical power system operators around the globe.

This collaborative project performs industry applied research on Sub-Synchronous Oscillations (SSO) in electrical power systems with high renewables and IBR penetration. The research will address different classifications of oscillations, their sources, methods of detection, identification, source location, ways of prediction, and mitigation. Classification and characterisation of SSO is essential to facilitate detection and identification to enable design modifications or real-time mitigation action implementation.

Understanding the sources for each class of SSO as well as newly developed system strength metrics and their usage is essential as they will lead to deeper understanding of the challenge and will involve researching different methods of modelling IBR and their limitations. This should pave the way to develop new detection and prediction methods/techniques as well as lead the way into better understanding of possible mitigation actions.

SSO analysis techniques that can fit the purpose of the study would include, but not limited to, frequency scanning, eigenvalue, impedance-based model and Electromagnetic Transient Analysis. Mitigation measures can be in design stage or in operational timescale. The first can be addressed in post-event actions as well, while the latter can be such as ramping down (or up) a specific IBR-based resource but could include other actions that can be explored in this research.