Power-level control of the MHTGRs with control rods driven by stepper motors

Due to its inherent safety feature, the modular high temperature gas-cooled reactor (MHTGR) is promising to build the next generation nuclear plants which provide safe and clean power or heat. It is very clear that power-level regulation technique is important in providing safe, stable and efficient operation for the MHTGRs. Since the MHTGR dynamics is complexly nonlinear, it is necessary to develop nonlinear power-level control strategies. The stepper motor is a satisfactory choice for driving the control rods of MHTGRs, and has already been applied to under-constructed HTR-PM plant. Since every stepper motor is a nonlinear system whose dynamics deeply influences power-level control performance, it is meaningful to develop nonlinear power-level control laws of MHTGRs by considering stepper motor dynamics. Motivated by this a novel nonlinear power-level control law is proposed by regarding the MHTGR and stepper motor as a whole nonlinear system. It is proved theoretically that this newly-built power-level control provides globally asymptotic closed-loop stability by generating proper motor stator voltages. Numerical simulation results show not only the feasibility of this new controller but also the relationship between its performance and parameters.