On the basis of the research on air cooling units with large capacity and high parameter

a multi-machine combined heating scheme is formed by adopting the high back pressure pumping and condensing heating technology and the steam extraction residual pressure utilization technology. Through high back pressure pumping and condensing heating renovation for 600 MW units

steam pumping renovation for 1 000 MW units

and adding back pressure generating units to compensate power consumption of the plant

a complete and reliable large-load heating system is established

which can improve the energy utilization efficiency

increase the heating capacity of the units

and meet the central heating requirements of regional cities. The analytical results indicate that

the operation and adjustment modes of this heating system are flexible and diverse

which can be operated by single machine with high back pressure or by double machines with high back pressure. In the case of the shutdown of any one unit

the other two units can provide an 76% heating guarantee rate. By analyzing the heating capacity of the heating system under different operation modes

a reference for operation regulation and thermoelectric load dispatch is provided. A good example is provided for the transformation of thermal power units in north China.