On May 30, it was learned from Sinohydro Bureau 7 Co., Ltd. that the Maerdang Hydropower Station in Qinghai, the highest-altitude hydropower project in the Yellow River Basin, has for the first time implemented and applied large-scale hydropower unit water-depressed phase modulation technology, marking a new breakthrough in China's phase-modulation operation of large-capacity units in the hydropower sector.

The water-depressed phase modulation retrofit mainly involves adding a medium-pressure air system, a control and protection system, a power supply system, and a cooling water system to the existing units. The principle of water-depressed phase modulation technology is to close the movable guide vanes, inject compressed air into the runner chamber, and forcibly lower the water level in the draft tube so that the runner rotates in air, shifting the unit from power generation mode to phase-modulation operation. During the dry season, the unit can enter phase-modulation operation at any time as required by the system, effectively enhancing cross-regional power transmission capacity and supporting the consumption of new energy. During the flood season, the unit mainly operates in normal power generation and participates in flood control, reducing water consumption rates and greatly improving the station's regulation capability and economic benefits.

After the completion of the water-depressed phase modulation retrofit of Unit 2 at Maerdang Hydropower Station, the unit can operate stably for up to 24 hours, with the strongest phase-modulation capability in China, and all technical indicators reaching internationally leading levels. The unit operates smoothly, with all indicators superior to design values.

With the application of this technology, the regulation role of hydropower units in the Yellow River Basin can be fully leveraged, effectively enhancing the nearby voltage support level and the new energy consumption capacity by 300,000 kilowatts, and reducing power loss by approximately 70 million kilowatt-hours per year. It delivers significant economic and environmental benefits and is of great significance for enhancing system flexibility, ensuring the safe and stable operation of the power grid, and improving the power transmission capacity of the Qinghai-Henan UHV DC line.