Abstract: With the popularization of renewable energy in the power system, improving the primary frequency regulation (PFR) capability of thermal power units to suppress grid frequency fluctuations is currently a difficult problem to overcome. However, the flexibility transformation of thermal power plants plays an important role in ensuring the safe and stable operation of the power grid. Traditional thermal units use coordinated control system (CCS), digital electro-hydraulic control systems (DEH), and with the transformation of condensate throttling (CT) and high-pressure heaters’ feedwater bypass (HPHFB), the fast frequency regulation characteristics of thermal units can also be improved. Therefore, this paper combines CCS, DEH, CT, and HPHFB to propose a new frequency regulation strategy. In addition, to improve the fast frequency regulation performance of thermal units, the gravitational search algorithm (GSA) and fuzzy gain scheduling control strategy are combined to suit for multiple operating conditions of thermal units, and simulation results verify the effectiveness of the improved control strategy.

Key words: primary frequency regulation, operational flexibility, gravitational search algorithm (GSA), fuzzy gain scheduling