Research on the feedwater control of a multimodule once through steam generator parallel system

Abstract

• A complete multimodule parallel OTSG system model is established. • A coordinated control scheme for parallel feedwater of multimodule OTSG is proposed. • Feedforward can improve the response of system in flowrate disturbance. • Wrong control logic may have good control performance, but it hides great danger. Nuclear power plants mostly use the multimodule once-through steam generator (OTSG) parallel system as heat exchange equipment, but the current research mostly focuses on a single OTSG. The huge system brings great challenges to modeling and control system design. In this paper, the ODE method is used to model the main equipment of a multimodule parallel system based on mechanism. The results show that the maximum error is 3.77%. Based on the characteristics of parallel system, a new control strategy is proposed and compared with other control strategies by introducing four typical disturbances. The results show that the proposed feedwater control scheme can effectively solve the coordination between loop valve and module valve of multimodule parallel OTSG system, and the coordination between main feedwater pump and loop valve. Compared with Method 1, the response time of Method 2 in sodium temperature disturbance is shortened by 319 s and the temperature fluctuation is reduced by 1.67 times, but Method 2 has potential safety hazards. Method 1 can improve the system response speed when the sodium flowrate and water flowrate change. Compared with Method 3, the outlet sodium temperature fluctuation of Method 1 is reduced by 10 times and the adjustment time of Method 1 shortens 141.9 s in the case of feedwater flow disturbance.