Economic Study on Cooperative Peak Regulation of Circulating Fluidized Bed Units with Wind Power Considering Flexibility Retrofits

The transition toward new power systems requires enhanced operational flexibility, within which circulating fluidized bed (CFB) units exhibit considerable peak regulation potential. This study develops an economic optimization framework to evaluate the benefits of flexibility retrofits for CFB units operating in coordination with wind power. A representative integrated system consisting of two 300 MW CFB units and a 300 MW wind farm is analyzed to compare ramping capability enhancement, minimum load reduction, and their combined implementation. The results indicate that the combined retrofit delivers the highest overall economic benefit at the system level. Even under a highly fluctuating wind power scenario, the combined retrofit achieves complete wind power accommodation, demonstrating the effectiveness of coordinated flexibility expansion. The minimum load reduction retrofit and the ramping capability retrofit reduce wind curtailment by 81% and 13%, respectively. Moreover, the economic benefit achieved by the combined retrofit exceeds the aggregate benefit of the two independent measures by about 6%, indicating a synergistic interaction between ramping flexibility and minimum load reduction retrofit. For the studied system, minimum load reduction retrofit contributes substantially greater economic gains than ramping capability enhancement when applied individually. Sensitivity analysis further highlights the influence of coal prices and feed-in tariff structures on retrofit profitability. Compared with existing studies focusing primarily on conventional pulverized coal units, this work establishes a quantitative framework tailored to CFB-specific flexibility retrofits, providing practical support for power systems with high renewable penetration.