Taking a 460 MW gas-steam combined cycle cogeneration unit as the object

the process of modeling and calculating the variable conditions by using Ebsilon software was studied. The accuracy and reliability of the model and the method were verified by comparing the simulation results with the design values on the heat balance diagram. It proves that the modeling method is suitable for calculation of the gas-steam combined cycle cogeneration unit. Besides

the heat supply performances of different heating extractions

ambient temperatures and load rates conditions were analyzed. The results show that

as the mass flow of the high

medium and low pressure extraction steam increases from 0 t/h to 60 t/h

the combined cycle efficiency increases by 4.24%

4.31% and 4.08%

respectively

and the heat consumption rate decreases by 193.6 kJ/(kW·h)

215.4 kJ/(kW·h)and 203.3 kJ/(kW·h). When the ambient temperature is lower than 15 ℃

the combined cycle heat rate is negatively correlated with the ambient temperature under rated heating conditions

and positively correlated when the ambient temperature is higher than 15 ℃. The reduction of the gas turbine load will shrink the operating power range of the steam turbine

and the peak shaving capacity of the unit will be weakened. When the heat supply is greater than 300 GJ/h

the combined cycle efficiency at 75% load rate will be higher than that of 100%.The results can provide data supports and theoretical guidance for the optimal operation of gas-steam combined cycle thermoelectric systems.