Subsynchronous Resonance Control in Wind Energy Systems

Subsynchronous resonance (SSR) arises when wind‐turbine generators interact with series-compensated transmission networks, causing oscillations at frequencies below the grid’s synchronous frequency. In modern wind farms, converter-interfaced machines such as doubly-fed induction generators (DFIGs) and full-scale converters introduce additional control loops and non-linear dynamics that can exacerbate SSR and related subsynchronous control interactions. Effective control of SSR combines accurate system modelling—often based on impedance or state-space representations—with active damping strategies implemented in power‐electronic converters or grid­side devices. These strategies include supplementary damping controllers, adaptive sliding-mode techniques and converter-based stabilisers, as well as network-side controllers such as STATCOMs or VSC-HVDC links. Achieving robust SSR mitigation is essential for grid stability, safe operation of turbines and the economic integration of large-scale wind power, particularly in regions employing series compensation to enhance transmission capacity.

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Subsynchronous Resonance Control in Wind Energy Systems publication trend

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Technical terms

Subsynchronous resonance (SSR): An oscillatory instability that occurs when energy is exchanged between wind generators and series-compensated lines at frequencies below the system’s synchronous frequency.

Doubly-fed induction generator (DFIG): A wind-turbine generator type with partial power conversion via a back-to-back converter, offering variable-speed operation and reactive power control.

Series compensation: The insertion of capacitors in series with transmission lines to increase power transfer capability, which can lower network impedance and trigger SSR.

Impedance modelling: A frequency-domain representation of converter and network dynamics used to identify resonant peaks and design damping controls.

Supplementary damping controller: An auxiliary control loop added to converter or FACTS devices to inject damping torque or reactive power modulation at resonant frequencies.

References

1. Review of sub-synchronous interaction in wind integrated power systems: classification, challenges, and mitigation techniques. Protection and Control of Modern Power Systems (2023).
2. Frequency-Coupled Impedance Modeling and Resonance Analysis of DFIG-Based Offshore Wind Farm With HVDC Connection. IEEE Access (2020).
3. Variable-Gain Super-Twisting Sliding Mode Damping Control of Series-Compensated DFIG-Based Wind Power System for SSCI Mitigation. Energies (2021).
4. Real-Time Estimation and Damping of SSR in a VSC-HVDC Connected Series-Compensated System. IEEE Transactions on Power Systems (2018).
5. Sub‐synchronous resonance mitigation by a STATCOM in doubly fed induction generator‐based wind farm connected to a series‐compensated transmission network. The Journal of Engineering (2018).