To achieve flexible and efficient operation of the supercritical carbon dioxide (S-CO2) power generation system across a wide load range

the off-design model of a coal-fired semi-closed S-CO2 power generation system is developed. The part-load performance of the system is studied under the basic operation mode with full-admission turbines

constant back pressure

and constant outlet temperature. Through the regulation of turbine partial admission and back pressure adjustment

system parameters are optimized. Ultimately

an efficient method using turbine partial-admission regulation and back pressure regulation in synergy is proposed for off-design operation. The results show that when operating in the low load range

the system net efficiency can be increased by reducing the turbine partial-admission degree or lowering the turbine back pressure separately

while reducing the partial-admission degree or excessively lowering the back pressure will lead to the opposite effect in the high load range. By regulating the partial-admission degree and back pressure in synergy

the net efficiency of the system can be further improved in the low load range. For the power generation unit of 600 MWe

at 30% load

the net efficiency of the system can reach 34.77%

which is 3.8 percentage points higher than that of the basic operation mode.