Introduction  The primary frequency modulation technology of thermal power units has been considered essential to ensure the power grid's safe and stable operation.

  Method  The current primary frequency modulation technology, the auxiliary primary frequency modulation technology, the coupled frequency modulation control strategy, and the potential development direction of primary frequency modulation technology were reviewed.

  Result  The results show that the primary frequency modulation technology for the unit mainly includes regulating valve pre-throttling, adjustable regenerative steam extraction frequency modulation, and condensate water throttling frequency modulation. Among them, the condensate water throttling frequency modulation technology should be the main mode. Auxiliary primary frequency modulation technology is mainly based on the fast-response rate characteristics of flywheel energy storage and battery to meet the unit input and output requirements. The focus and difficulty of coupled auxiliary frequency modulation technology are then analyzed. The system modeling and control strategy research based on frequency modulation technology can optimize the matching between unit parameters.

  Conclusion  Thus, the application status of primary frequency modulation technology in recent years is compared, and it is considered that flywheel energy storage primary frequency modulation and sliding pressure operation optimization will be the key development direction.