In order to improve the heating stability and safety of combined heat and power unit under depth peak load cycling

In this paper

Firstly

the influence of bypass heating transformation on the safety boundary of the turbine and bypass system is analyzed baesd on a 350MW supercritical coal-fired unit. On this basis

the linkage control and protection logic scheme applied to high and low pressure heating bypass valves of combined heat and power unit is formed. The scheme can realize the level limit of security parameters in the heating adjustment process of high and low pressure bypass valves

which can interlock high and low pressure bypass valves according to alarm

lock

overdrive and protection levels. Furtherly

the automatic and manual switching term of each regulating valve under special working conditions is considered. Through the practical application in the case unit

the scheme effectively improves the safety and reliability of the bypass heating system. At last

the lower limit of the unit"s electrical load can be reduced to 120.7MW when the capacity of heat supply can still be maintained at 352.1t/h

enhancing the depth peak load cycling and heat-power decoupling capacity of the unit.