Sungrow Tests Oscillation Control at 500 MW Qinghai Plant

Sungrow has successfully reproduced and suppressed wideband oscillation at a 500 MW solar-plus-storage plant in Qinghai, China, in a field test that the company described as a world first.

The test was conducted using Sungrow PV inverters deployed at the plant to examine oscillation challenges associated with increasing renewable energy penetration.

During the test, weak-grid conditions were established, and the company identified power output, system short-circuit ratio (SCR) and control parameters as three key factors contributing to oscillations. Sungrow then successfully reproduced a localized system oscillation under controlled conditions.

The company also tested the oscillation suppression performance of its PV inverters under different grid conditions. According to Sungrow, its patented grid-strength adaptation technology identified grid strength within 40 milliseconds and adjusted the inverters' control strategies to stabilize voltage and frequency.

The test also assessed grid-forming control for wideband oscillation suppression. Sungrow said its grid-forming control strategy enables stable operation across an SCR range of 1 to 40 and mitigates transient overvoltage.

Sungrow said that the field test could help renewable energy plants operate under extremely weak-grid conditions, prevent grid disconnections caused by oscillations, increase power export capacity and reduce generation losses.

The company cited previous grid incidents involving oscillations. According to Sungrow, the BorWin1 offshore HVDC project in Germany experienced oscillations at 250–350 Hz in 2014, while the Hornsea offshore wind farm in the UK experienced widespread disconnection due to subsynchronous oscillation in 2019.

Pan Nian'an, Chief Engineer and Chief Expert for Utility PV BU at Sungrow, said that the company would continue research and development in wideband oscillation suppression, grid-forming control and multi-energy coordination.