Research On Linear Active Disturbance Rejection Control Of Sodium-cooled Fast Reactor

The development of fast reactors is of great significance for advancing the closed cycle of nuclear fuel,promoting the sustainable development of nuclear energy,and eliminating the impact of nuclear energy on the environment.The fast reactor power regulation system is used for its start-up,shutdown,power-up,power-down and steady operation.It plays an extremely important role in the entire fast reactor control system.Improving its performance is beneficial to the safe and economic operation of the fast reactor.The sodium-cooled fast reactor(SCFR)has smaller delayed neutron fraction than that of pressurized water reactor,under the same reactivity disturbance,the reactor period is shorter and the reactor power changes faster,a controller with faster response is required.Due to higher enriched fuel and harder neutron spectrum,Doppler Effect of SCFR is smaller than thermal reactor;therefor self-equilibrium ability is weaker,so higher stability for control system is expected.Because of small specific heat and better heat conduction of sodium,large fluctuation of core outlet temperature is highly likely to occur in power level regulation transient.Strict limitation on power level overshoot is necessary.For good heat transfer between the fuel cladding and liquid sodium and the integrity of fuel pellet,temperature difference of sodium between core outlet and core inlet should be kept within a certain range.Due to reactivity temperature feedback,there is a complex coupling effect between core power level and temperature,thus power level control and outlet coolant temperature control need to address decoupling issues.Therefore,design method is of great theoretical significance and practical values,which result in a controller with better stability,faster response,smaller overshoot and stronger anti-disturbance ability.A properly designed Linear Active Disturbance Rejection Controller(LADRC)generally has better control performance,anti-disturbance ability and robustness than traditional PID,also has the advantages of simple structure and easy parameter tuning.To meet the higher performance requirements of sodium-cooled fast reactor control,the LADRCs of power level and core coolant outlet temperature are designed.In consideration of the dynamic characteristics and control quality requirements of sodium-cooled fast reactor,design of LADRCs is improved,and performance of LADRC based control is enhanced by feedback linearization and feedforward.Firstly,according to the sodium-cooled fast reactor dynamics model,the Linear Extended State Observer(LESO)design and the LADRC parameter tuning method are optimized.From fast reactor neutron dynamics kinetics and core heat transfer equations,the second order nonlinear models of relative power and coolant outlet temperature for LADRC design are derived;LESO with model information are configured based on the derived model;The range of LESO bandwidth is chosen via the time constants of the derived second order model,The range of PD bandwidth is estimated by the allowable range of deviation and actuator operating speed.Then,for the limitations of LADRC itself,the composite control strategy based on LADRC is studied.To reduce the influence of model nonlinear,a LADRC combined partial feedback linearization control scheme is proposed.To decrease the impact of coupling effect on LADRC performance,a LADRC integrated feedforward control method is presented.The improved LADRC and composite control strategies proposed above are applied to core power level control and core coolant outlet temperature control,respectively.The step disturbance of reactivity,coolant inlet temperature and flow rate are introduced to the model to verify the system's anti-disturbance capability.Simulation results demonstrate that the LESO with model information obtain better total disturbance estimation,and the corresponding LADRC have faster response and higher precision.The LADRC combined with feedback linearization and feedforward control show better anti-disturbance ability and control performance.