Optimal Control of Load-Following Maneuvers in a Pressurized Water Reactor

Abstract

This paper formulates the problem of load-following maneuvers in a pressurized water reactor (PWR) as a nonlinear-quadratic tracking problem in accordance with optimal control theory. An one-dimensional core model is adopted. The system model with distributed parameters is converted to a lumped one by modal expansion method. A practical combination method — STMDDF, combining differential dynamic programming (DDP) with system tau method (STM), is used to solve above problem. In the course of solving this problem, the DDP is used to deal with the strong nonlinear part of the dynamic process, and STM is employed to treat the weak nonlinear part which can be linearized around nominal value, respectively. In addition, the time interval of the strong nonlinear dynamic process can be divided into several subregions. In each subregion, an appropriate nominal trajectory for DDP can be provided by STM by the application of linearized approximation treatment. As illustrated in the examples, the provided calculating method is shown to achieve rapid convergence and shorten the computation time considerably. It is also shown that the practical reactor power can closely follow the desired load demand and meanwhile axial offset as well as axial power-peaking factor can be maintained within assigned limits with relatively less control effort.