Mitigating SSR in an HVDC– and renewable-rich grid at Cardiff University

Tibin Joseph, Carlos E. Ugalde-Loo, Jun Liang, et. al – Cardiff University

Cardiff University’s Centre for Integrated Renewable Energy Generation and Supply (CIREGS) is a world-leading research group with over 20 research projects on power system stability and control, DC grids, the integration of renewables, VSC-HVDC, and MTDC. Funded by the UK’s Engineering and Physical Sciences Research Council and the Higher Education Funding Council for Wales, their lab features a multi-terminal HVDC test-rig, RTDS Simulator, power amplifiers, DC grid emulator, wind turbine test-rig, and more.

In recent published work at CIREGS, a hardware-in-the-loop setup has been leveraged to investigate a wideband filter approach to damp the effects of subsynchronous resonance on a renewable- and HVDC-rich AC grid. The threat of SSR in Great Britain’s transmission system has increased due to the recent installation of series compensation near the Anglo-Scottish intertie. While traditional SSR mitigation schemes use filters placed at the generator terminals or integrated with network components, damping at transmission level is also common (via, for example, schemes embedded in HVDC and FACTS converter stations). However, most proposed controllers are designed for specific operating points and are sensitive to system configuration and loading conditions. The wideband filter based damper proposed by CIREGS, embedded in the VSC control system, damps multiple torsional modes and can be used regardless of system configuration and series compensation level. Instead of designing filters for each torsional mode, the wideband filter does not require re-tuning. Given the uncertainty around Great Britain (GB) system data, this flexible approach is highly relevant. Notably, damping via the embedded filter is provided without the need for overrating the converter—the dc voltage and power are within the converter’s existing capabilities.