The article explains the heating supply technology retrofit for 135 MW and 300 MW grade units at high back pressure condition. The performance indicators of high back pressure operational conditions are obtained through performance test after retrofit. At high back pressure operational mode

the heat consumption rate of pure condensing condition is among 3690~3740 kJ/(kW·h)

the heat consumption rate of extraction steam condition is among 3690~4060 kJ/(kW·h). The effect of retrofit technology

cold end design parameters and operational parameters on performance indicators has been analyzed. For the same 135 MW grade unit

under full load condition

the difference of circulating water being 3500 t/h

the difference of condenser pressure is 15 kPa. The difference of generator power at full condition is 26.7 MW. By peak regulation capacity test during heat supply period

the peak regulation range and adaptation with high back pressure operational mode have been determined. The power load regulation capacity of 300 MW unit is 65 MW

being 22% of rated capacity before retrofit. The power load regulation capacity of 135 MW unit is 35~60 MW

being 26%~44% of rated capacity before retrofit. The reason that resulting peak regulation range narrow and peak regulation decrease also have been analyzed.