Design and application of natural ventilation direct Air cooling (NDC) control system for 660MW unit

The back pressure of steam turbine is an important control parameter of air cooling unit. The research and design of the first natural ventilation direct air cooling (NDC) system in the world is very important for the safe and economical operation of NDC system. This paper introduces the composition of NDC system, the configuration of main measuring points and the realization of control functions. In the framework of the general structure of the control system, the NDC starting and total protection logic, exhaust pressure master, program control logic design and sector shutters control logic design are described. The step design and step switching rules of isolation valve and sector shutters are analyzed in detail, and the anti-freezing protection control strategy of NDC system is proposed. After the system is put into operation, the unit runs safely and stably, and the control system runs well, which has a certain reference for the popularization and application of the natural ventilation direct air cooling control system of the same type of unit.