Research On Coordinated Control Method Of Multi-Modular Reactors Under Load Following Maneuver

Developing advanced nuclear energy technology is one of the important measures to solve the world energy crisis.The main line of the global nuclear power plant development is divided into the development of large single nuclear reactors and the development of multi-modular nuclear reactors.The load tracking ability of a large single reactor is weak in actual operation.A good load tracking ability is the basic condition for achieving the matching between the unit capacity and the power grid demand,which improves the fuel cycle period and ensuring the safe and stable operation of nuclear power plants.Compared with a large single reactor,the multi-modular nuclear reactor adopts the operation mode of multiple modular reactors driving a group of steam turbines in parallel,which has the advantages of the higher power generation efficiency,shorter modular standard production and construction period,inherent safety characteristics.The most important is that the multi-modular nuclear reactor can quickly adapt to the demands of new power loads and the peak operation of the grid.The multi-modular nuclear reactor has the unique modular structure.For achieving fast and stable load tracking of the reactor system,it is necessary to consider not only the load distribution mode between each reactor module,but also the operation parameters of the system whether can reach the design index,which increases the difficulty of the power matching among modules and the complexity of the system control strategy.Moreover,there is the problem of mutual coupling among the modules of the multi-modular nuclear reactor.Multiple reactor modules are coupled to each other through the common secondary loop.The load change of any module not only affects its own power,but also causes the power change of other modules.Therefore,it is of great significance for the safe and stable operation of the multi-modular nuclear reactor to carry out the research on the coordinated control method between modules in load operation.Aiming at the thermal coupling problem caused by the parallel operation of multiple modules,the coordinated control method of the multi-modular nuclear reactor system under load tracking is studied in this thesis,and the control effect is simulated and verified on the full range real-time simulation platform CLEAR-I simulator.The main research contents are as follows.Firstly,aiming at the complexity of the multi-modular nuclear reactor structure,a networked structural model is established for the reactor system.Considering that a single module has the characteristics of the low rated power,compact structure and inherent safety,this thesis takes the 10MW small lead-based cooled reactor CLEAR-I as the reference design object.The lumped parameter method is used to build a single module dynamic mathematical model,including the point reactor dynamic model,core heat exchange model,heat exchanger model and air cooler model.The steady state characteristics of the reactor are analyzed and calculated,which provides the steady state parameters for the dynamic characteristics of the system.Secondly,aiming at the power matching problem between reactor modules and the complexity of the overall control strategy of the system,an automatic power controller was designed to realize the unbalanced load operation mode of the reactor.The operation mode of unbalanced load can meet the requirements of the staggered refueling of the whole reactor and the maintenance of different modules.Based on the analysis of the operation characteristics of primary and secondary circuit of the multi-modular nuclear reactor,the coordinated control loop between modules is built to realize the orderly adjustment of the load factors of each module when the reactor load changes,module refueling,maintenance or emergency shutdown occurs.Through the simulation experiments of the fault state and the variable load,the good load tracking ability of the system is verified,and the design of the multi-module operation control strategy for load tracking is completed.Thirdly,in view of the coupling problem between modules in the multi-modular nuclear reactor,the multivariable frequency domain method is used to design a coordinated control scheme for the reactor system.After diagonally dominating the transfer function matrix of the multivariable system,the decoupling design is carried out according to multiple univariate systems.Considering that the inverse diagonalization of the transfer function matrix is easier to realize,the constant diagonal dominance compensation matrix is obtained by the pseudo-diagonalization method in this paper,and then the inverse Nyquist array method is used to design the decoupling controller of the compensated system.For obtaining the transfer function matrix of the whole reactor system,the system identification of the multi-modular nuclear reactor on the full range real-time simulation platform CLEAR-I simulator was carried out by frequency response experiments.The feasibility of the coordinated control scheme is verified by the simulation experiments of the system under the condition of lifting and lowering loads.