Flexible transformation of thermal power units is the key to build a new power system and achieve the goal of “carbon peak” and “carbon neutrality”. In order to promote the flexibility of thermal power units

the coupling scheme for small steam turbine drive and motor drive liquid compressed carbon dioxide energy storage system and thermal power unit is put forward

and the thermodynamic system model is established. Moreover

the heat consumption rate and energy utilization coefficient are used to evaluate the system

the thermodynamic performance of the system is compared and analyzed

and the optimal coupling scheme of energy storage is established. The researches show that

in the energy storage stage

condensate water is extracted from the outlet of the condensate pump

and the compressed heat is absorbed and returned to the outlet of No.7 low-pressure heater. In the energy release stage

steam is extracted from the exhaust of the middle pressure cylinder

and the expanded CO_2 is heated and returned to the No.5 low-added hydrophobic cooler

the coupling system has the best performance. The heat consumption rate is 48.308 k J/(k W·h) lower than that of the original system

and the energy utilization coefficient increases by 0.52 percentage point. Changing the inlet temperature and the mass flow rate of CO_2 expander can quickly change the load. After coupling with the energy storage system

the peak regulation capacity of thermal power unit increases by 17.1%

when the hot water tank is configured and the maximum heat is released

the peak regulation capacity of the unit increases by 37.4%

indicating the flexibility of thermal power unit is improved.