Development of PWR feedwater controller using $H-\infinity$ loop-shaping techniques

Abstract

In this thesis, a robust $\It{H-\infin}$ loop-shaping controller for the steam generator (SG) feedwater control system of the KSNP (Korean Standard Nuclear Power Plant), a 1000MWe pressurized water reactor with vertical U-tube type steam generators (UTSG) is developed. The SG feedwater control system maintains the SG water level by controlling the feedwater flowrate using feedwater control valves. In order to develop the robust $\It{H-\infin}$ controller, SG models for the control of feedwater to the KSNP UTSG are identified. As the first step of SG model identification, a precise SG mathematical thermal-hydraulic model is built using the RELAP5/MOD3 system simulation computer code. The developed RELAP5/MOD3 SG model is inadequate to be used for the design of controller due to its complexities. Thus, the SG thermal-hydraulic model needs to be simplified while maintaining required accuracy in describing the principal dynamics of the SG. For this, as the second step, a series of model experiments using the developed thermal-hydraulic model are performed in order to acquire input-output data sets representing the SG characteristics in terms of SG water level dynamics as a function of the feedwater flowrate, steam flowrate, feedwater temperature, and reactor power. As the final step, the $\Bf{Simple Process Models}$ are applied to create a simple, continuous-time process SG model for control. The input-output data sets obtained from the model experiments using the RELAP5/MOD3 SG model are utilized in developing the algorithm to describe static gain, dominating time constants, and a possible delay of transfer function of the SG system. Since the SG operating characteristics are strongly dependent on the operating power level, the SG operating range from 0 to 100% power is divided into 10 sub-operating points based on the plant operation experiences as well as the operating modes of the KNSP SG. A number of robust $\It{H-\infin}$ controllers for the SG models iden...