New strategies with multi-model, state-feedback control and stability analysis for load-follow PWR core

Abstract

The objective of this study is to design a Pressurized Water Reactor (PWR) core load following control system for regulating the core power level and axial power difference and analyze the global stability of the system theoretically. On the basis of building a two-point based nonlinear PWR core model without boron and with the power rod and Axial Offset (AO) rod, the linearized single-variable (multi-variable) core model under Case 1 (Case 2) classified by two movable regions of power rod is constructed. For each case, by proposing the equilibrium manifold and the nonlinearity measure of the core to calculate the distribution situation of the core nonlinearity measure in the entire range of power level, linearized models of the core at ten power levels are chosen as local models of the core to substitute the nonlinear core model. Based on each local model, the state feedback control is implemented by utilizing the robust pole assignment method with an additional integrator for Case 1 and devising an integral decoupling control system with a dynamic controller for Case 2; a Kalman filter with robustness is designed as an observer for each case. The integration of the state feedback and the observer structures a local controller of the core of each case. For each case, a local model and a local controller at one of ten power levels compose a core load following control subsystem. The combination of core load following control subsystems at ten power levels is the core load following control system. The global stability theorem is deduced to define that the core load following control system for Case 1 (Case 2) is globally asymptotically stable within the whole range of power level. Finally, the core load following control system for each case is simulated and the simulation results show that the control system is effective.