Research on Decoupling Control Method for Feedwater System of Steam Generator in Nuclear Power Plant

The nuclear steam generator (SG) is an important component for nuclear power plant which transfers heat from the primary side coolant to the secondary side water. Water supply system is composed of water supply pump and feed water adjusting valve, and the water level of the steam generator is adjusted by the change of feed water flow rate. Changes in regulating valve opening and feed pump speed can both affect changes of feed water flow, and unrelated regulation of the two control variables will lead to mutual effects on the regulating effect, which makes the regulating time longer and the flow control deviation larger. In order to solve the coupling problem of feed pump and feed regulating valve of feed water system, the coupling characteristic of feed pump and feed regulating valve are studied in this paper. The paper analyzes the dynamic impact characteristics of feed pump speed on feed water flow rate and pressure difference of water supply adjusting valve, and also the dynamic impact characteristics of the opening of the water supply adjusting valve on feed water flow rate and pressure difference of water supply valve. A feedforward control scheme of water supply adjusting valve is further proposed for feedwater system decoupling, and the control simulation is conducted based on a flow rate step process. The simulation results show that the feed water flow response speed after decoupling is significantly improved, and the steady-state regulation time is shortened by more than 40%. Meanwhile, the maximum control difference of the feed water regulating valve is reduced by more than 60%.