In order to promote the high-level integration of renewable energy and enhance the security coordination capacity of the new-type power system

it is imperative to carry out flexibility transformation on existing thermal power units in China to achieve deep peak-shaving control. This paper proposes a coupled molten salt scheme for the 660 MW supercritical unit

in which a portion of the main steam is extracted to heat the cold molten salt for heat storage

while the hot molten salt is used to heat a portion of the deaerator feed water for heat release. First

a comprehensive dynamic mathematical model of the overall system is developed and validated

and a thermal-storage flexible peak shaving control strategy is proposed for flexible deep peak-shaving. In the proposed scheme

the unit power output is mainly controlled by the extracted steam and pumping flow in the molten salt storage system when the load demand change is within peak shaving capacity

with the boiler-turbine control system as a supplement. The simulation results show that the new downward peak shaving capacity is 57.9 MW

and the peak shaving depth increment is 8.77%; the new upward peak shaving capacity is 24.43 MW

and the peak shaving depth increment is 3.7%

which effectively expands the unit’s peak shaving operation range. Moreover

the proposed flexible peak shaving control strategy can achieve fast and accurate response to a wide range of load commands and significantly reduce the impacts on the unit body

particularly on the boiler side. Meanwhile

it effectively reduces load variation frequency and extreme operating scenarios

thereby largely enhancing the safety and flexibility of unit peak shaving operation.