Fractional order PID control of steam generator water level for nuclear steam supply systems

The main part of nuclear powered system is the nuclear steam supply system (NSSS) to produce the steam needed for electricity or cogeneration. The NSSS mainly contains the fission reactor, based on pressurized water reactors or small modular reactors, and the steam generator. One of the most important control strategies in the NSSS is water level regulation to keep the water level of the steam generator around programmed setpoint because violation of the level jeopardizes the plant availability in making the electricity and supplying the heat for industrial applications. The appearance of fractional calculus made it possible to realize the control design requirements in optimum and efficient ways. In this paper, we proposed a gain scheduled Fractional order PID (FOPID) control system for steam generator level control system in entire operating range. Nelder-Mead tuning strategy which takes into account the desired gain- and phase- margin with integral time absolute error (ITAE) performance index has been devoted to adjust the FOPID parameters. Simulation results indicate that the new control system can enhance the transient response in contrast to the conventional PID. The performance comparison of the FOPID regulator with the classical PID shows that the fractional controller has huge superiority which is comparable with the advanced quantitative feedback theory (QFT) controller. The Nyquist stability analysis is also provided to demonstrate the favorable robust stability of the gain scheduled FOPID controller over the wide range of operating conditions.