- Sungrow successfully suppressed broadband oscillations at a 500MW plant in what is claimed as the world's first field test.
- Broadband oscillations can destabilise renewable energy systems and affect grid connections.
- Engineers adjusted power output and inverter control parameters to reproduce the oscillations during the test.
- Sungrow plans to continue developing related technologies to support renewable energy integration.
A Chinese company has reproduced and suppressed broadband oscillations at a 500 MW solar-plus-storage plant, in what is described as the world's first field test of the technique. The test was carried out by Sungrow, a renewable energy company based in Hefei that focuses on solar photovoltaic (PV) and energy storage systems. The test took place in September 2026 at a plant in Qinghai province, China, and was aimed at tackling broadband oscillations — rapid electrical fluctuations that can effectively destabilise renewable energy systems. They can also force generating equipment to disconnect from the grid or shut down altogether.
Because of their unpredictable nature, reproducing these fluctuations at an operating plant has so far proved difficult. Sungrow addressed the problem by deliberately triggering the fluctuations at a real-world plant. "For renewable energy to become a truly stable and reliable source of power, the ability to develop autonomous fault self-healing and grid support capabilities is essential," explained Pan Nian'an, Sungrow's chief engineer.
Successful reproduction of broadband oscillations
To conduct the test, engineers established weak grid conditions at the 500 MW plant, which uses Sungrow's PV inverters. The team identified three factors that trigger oscillations: the plant's power output, the system short-circuit ratio (SCR), and the inverter control parameters. They first adjusted these parameters, then successfully reproduced local broadband oscillations in a controlled environment. They also went on to test how the PV inverters responded under different grid conditions. Sungrow completed what it describes as the world's first oscillation suppression test at the plant.
Sungrow's patented grid strength adaptive technology identified the local grid strength within 40 milliseconds. The equipment then adjusted its control strategy to stabilise voltage and frequency. The demonstration also tested Sungrow's grid-forming control technology. The system is designed to help power electronics actively support grid stability, rather than simply following existing grid conditions. According to the company, its grid-forming control strategy can maintain stable operation across an SCR range of 1 to 40, while also helping to mitigate transient overvoltages.
Potential implications of the test
Broadband oscillations have previously been linked to major disturbances in power systems. For example, Germany's BorWin1 offshore high-voltage direct current (HVDC) project experienced oscillations of 250 to 350 Hz in 2014. The incident damaged filter capacitors and led to roughly six months of downtime. In 2019, the Hornsea offshore wind farm in the North Sea off the UK also experienced a subsynchronous oscillation event, resulting in widespread disconnections, the loss of around 3.2% of system load and affecting approximately one million customers. Sungrow's representatives believe the latest test can help move oscillation control techniques beyond simulation and the laboratory, ultimately helping renewable plants remain connected under extremely weak grid conditions, reducing lost generation and increasing the amount of electricity facilities can export.
Pan Nian'an said the company plans to continue developing technologies for broadband oscillation suppression, grid-forming control and the coordination of multiple energy sources. "These efforts are aimed at supporting the stable grid integration and efficient utilisation of renewable energy, while strengthening the technological foundation for a safe and stable energy transition and next-generation power systems."
Future outlook for broadband oscillation control technology
Broadband oscillations pose a challenge to the stability of renewable energy systems, particularly where grid conditions are poor. Sungrow's successful test demonstrates not only the technical feasibility of the approach, but may also serve as a reference for other plants worldwide, helping them maintain stable operation in similar circumstances. As renewable energy becomes more widespread, the development of such technologies is essential to ensuring the safety and stability of power systems and will advance the pace of the energy transition.