Modeling And Control Of Pressurizer In PWR Nuclear Power Plant

The primary circuit of nuclear power plant is a very important part of the whole nuclear power plant,and also an important part of the stable and safe operation of nuclear power plant.In the whole primary circuit,the pressurizer plays an important role in stabilizing the pressure and water level in the whole primary circuit.However,due to the complexity of the province,how to establish an accurate mathematical model of the pressurizer has always been a problem,and the control method of the pressurizer has always remained on the traditional PID controller.It has always been the accurate model of the pressurizer and the advanced control method applied to it Hot spots and difficulties in the field.In this paper,the physical structure of each component in the pressurizer and their functions in the pressurizer are analyzed.After a thorough understanding of the physical structure of the pressurizer itself,a three zone non-equilibrium mechanism model is established for the pressurizer.For some uncertain thermodynamic parameters in the mechanism model,the moving least square method is used to find them Solution.Finally,a differential equation of the pressure and water level of the pressurizer is established.The input of the pressurizer is the power of the electric heater,the flow of the spray valve,the flow of the safety valve,the difference between the charging and discharging flow.Combined with the physical parameters of the pressurizer itself,a model of the pressurizer biased to the control is finally obtained.On the established model,the open-loop verification is carried out.By observing the pressure level response curve of the model,the final curve is consistent with the actual operation of the regulator changes,and the accuracy of the mechanism model of the regulator is verified.By using the above-mentioned regulator model,the control strategies of traditional PID controller,fuzzy adaptive PID controller and segmented multi model predictive controller are compared,the final control curve is observed,and the advantages and disadvantages of each controller are compared.From the final simulation process,it can be seen that although the traditional PID controller is simple in structure and widely used,its tracking performance can meet the requirements in the face of the negative small step change of pressure and water level.When the simulation situation becomes a large step change,the traditional PID controller can not track the step change of pressure in a short time.Similarly,in the step change process of water level Compared with the traditional PID controller,the fuzzy self-adaptive PID controller has a certain degree of improvement.The steady-state error in the process of water level step has also been eliminated.In the face of the large step change of pressure,it can also realize the tracking without static difference in a short time.Finally,the multi model predictive controller is used.By selecting several pressure reference points,the piecewise state space equations are established for the pressure and water level systems respectively.Finally,the model predictive controller is established for the model of each reference point.Finally,the output of all controllers is added to the final control output using the center of gravity method.From the final simulation results,the multi model predictive controller can achieve fast tracking in the case of small step change of pressure,large step change of pressure and small step change of water level,and verify the effectiveness of the controller.