Power systems with increasing penetration of wind and other renewable energy sources face operational challenges, including reduced inertia, diminished short‑circuit strength, and voltage stability concerns. These issues stem from the displacement of traditional synchronous generation and the growing reliance on inverter‑based resources (IBRs). To address these concerns, Hybrid Synchronous Condenser Systems (H‑SCS)—which integrate a Synchronous Condenser System (SCS) and a Static Synchronous Compensator (STATCOM) via a common point of coupling—have emerged as a possible solution. This work presents operational experience from the Phoenix project in Scotland and previews further developments underway at the Eccles site.

The Phoenix installation, operational since 2020 at the 275‑kV Neilston substation, represents the first full‑scale deployment of the H‑SCS concept. Rated at 140 Mvar capacitive, 103 Mvar inductive, and providing 94 MJ of inertia, it has demonstrated the ability to increase renewable energy transfer capability by at least 280 MW through existing transmission lines while simultaneously improving system strength, reactive‑power support, and disturbance response. The live trial program (2020–2022) tested the coordinated operation of the SCS and STATCOM under varied grid conditions, including voltage and reactive‑power setpoint changes, mode transitions between Voltage Control and Reactive Power Control, and activation of advanced features such as Loss Reduction Mode, Power Loss Minimization, and Fast Transients Compensation. Trial observations also captured system behavior during nearby switching events, power imbalances, and short‑circuit disturbances, verifying the responsiveness and robustness of the hybrid control scheme known as the Master control.

The Eccles project, scheduled for operation in 2027, extends the concept with two larger H‑SCS units rated at 300 Mvar capacitive, 220 Mvar inductive, and 750 MJ of inertia, each equipped with flywheels. Building upon lessons learned from Phoenix, the Eccles design incorporates new features such as grid‑forming converter control, Power Oscillation Damping capability, parallel H‑SCS operation, and load‑balancing strategies. These additional H‑SCS units are expected to enable higher wind energy penetration, reduce dependence on traditional fossil-fuel-based generation, and improve system stability and performance in steady state and during disturbances.

The conclusions indicate that H‑SCS technology is a scalable, ready-to-deploy alternative for strengthening grids with high penetration of IBRs. By combining synchronous condenser inertia with the speed and controllability of STATCOM systems, H‑SCS installations mitigate rates of change of frequency (RoCoF) issues, minimize the risk of protection system mis-operation, provide dynamic reactive power support, and contribute with power oscillation damping, thus enhancing system security, improving voltage stability, supporting reliable energy transfers, and ensuring power quality. The work gives insights into a validated solution for integrating large volumes of wind energy while maintaining a secure and resilient grid operation.