Modeling condensate throttling to improve the load change performance of cogeneration units

摘要

The operational flexibility of coal-fired units plays an important role in the stable and safe operation of power grid under fluctuant renewable power resources. As they represent a large proportion of coal-fired units, cogeneration units need to be studied to improve the load change performance. The purpose of this study is to activate the energy storage of regenerative system by condensate throttling, which can improve the load change performance of cogeneration units. The static and dynamic models of condensate throttling were established through a mechanism analysis. And a 350 MW cogeneration unit was chosen as a case study to simulate the dynamic model under 10 operating conditions with different condensate throttled flowrates. The results reveal that the load change performance of condensate throttling is more improved when the output power is higher, the increased condensate throttled flowrate can further improve the load change performance. Moreover, the increased operational flexibility can be obtained when cogeneration units working under the sliding pressure operating condition. Finally, the maximum duration and the 1-min output power increment are also evaluated. The maximum duration is mainly influenced by the condensate throttled flowrate. And the maximum 1-min output power increment is between 4.972 MW and 22.999 MW.