Transient Simulation Research On Emergency Diesel Generator In Nuclear Plant

Emergency diesel generator(EDG)set is an important device to ensure safe and reliable operation in nuclear power plants.According to IEEE387-1995 standards,when nuclear power plants in the face of emergencies,emergency generators should start within a short time,and equip the ability to load all the required loads to achieve reactor safe shutdown,while ensure that the generator terminal voltage and frequency the stability,which makes strict requirements on load response of the diesel generator in loading process.Firstly,a first domestic diesel engine18PA6 B model was developed on the simulation platform of GT-power software,and the diesel engine speed control system model was built using MATLAB/Simulink software.A mathematical model is given instead of the actual load of the generator in operation,transient simulation for a loading sequence of diesel engine was computed by coupling the two software,by comparing the simulation results in this case to the results ordered from MAN Diesel & Turbo,the accuracy of this model is verified.Secondly,used Simulink software to establish a simulation model of synchronous generator and its excitation system,and carried out the sudden50 percent rated load,unload simulation calculations,by comparing the results of 50% sudden rated load and unload test to the results of simulation,it verified the accuracy of the EDG co-simulation model.On this basis,a loading scheme was designed according to the load characteristic of loss of offsite power(LOOP)in a nuclear power plant.Parameters such as rotation speed,rack position and in-cylinder pressure of diesel engine as well as the phase voltage,current,active power etc was predicted and analyzed while the loads were increased orderly.The simulation results illustrates that this co-simulation model can predict the mechanical and electrical characteristics of the nuclear EDG sets comprehensively and also has a good dynamic response.Finally,considering the non-linear and time-variation of diesel engine speed control system,a speed control system based on Back-Propagation(BP)-PID was designed,and the two above load methods was simulated based on BP-PID.Through the simulation of loading on diesel engine at different times,it realized on-line optimization of the PID controller parameters by its self-learning and adaptive ability.Comparing with the calculation results of incremental PID,it illustrates that this simulation model is practicable and the control system based on BP-PID has a better dynamic characteristics.