The turbine cooling air(TCA) cooling water flow control of Mitsubishi F-class gas turbine is influenced by multiple factors and the influence process is complicate. Due to the low quality of control

the TCA cooling water flow is small

causing frequent trip of the units. The TCA cooling water flow is higher than the set value with current control mode

which leads to the decrease of gas turbine output and turbine efficiency to some extent. To solve this problem

the closed-loop control method of TCA cooling water system is proposed in this paper. In this method

the process of the TCA cooling water system is optimized at first. The cooling water is returned to high-pressure drum pipeline to separate with the high-pressure feeding water pipeline

so as to ensure the control of both water flow will not affect each other. Then

by transforming the flow control valve(waste heat boiler side) from open-loop control to closed-loop control

parameters of each PID module are optimized to realize accurate regulation of cooling water flow. Finally

logical lockout conditions are added

to ensure there is only one valve regulating the TCA cooling water flow with PID mode. After the transformation

the TCA cooling water flow is more stable

the operation condition switching is more smooth

and the TCA cooling water flow can be very close to the set value.It further improves the safety

stability and economy of the combined cycle unit. The research provides a brand new idea for upgrading the TCA system of Mitsubishi F-class gas turbine.