Abstract
Overspeed is more likely to occur in the process of load rejection or large disturbances for nuclear steam turbines due to the large parameter range and low steam parameters, as well as the power of the low-pressure cylinder accounting for a high proportion of the total power. It is of great significance to study the overspeed characteristics of nuclear power plants (NPPs) to ensure the safe and stable operation of the unit and power grid. According to the characteristics of NPPs, the overspeed protection model and the super-acceleration protection model were established, which were added to the speed-governing system model. The response characteristics of the reactor, thermal system, steam turbine and speed-governing system in the process of load rejection or large disturbances of the power grid were analyzed and simulated. The results were compared using the simulation software personal computer transient analyzer (PCTRAN). The simulation results showed that quickly closing both the high and medium pressure regulating valves could effectively realize frequency control when load rejection or a large grid disturbance occurred. The over-acceleration protection cooperates with the super-acceleration protection to avoid the repeated opening/closing of the valves due to overspeed protection. This could effectively reduce the impact of large disturbances on the reactor, thermal system, and turbine.
Highlights
Nuclear power generation accounts for 10.5% of the global electricity supply in 2018, according to the report of the World Nuclear Association
For large-capacity nuclear power units, brushless excitation systems [27] without brushes and collector rings are generally used in order to avoid the generator tripping due to faults in the collector rings are generally used in order to avoid the generator tripping due to faults in the operation of brushes and collector rings
By building the integrated system model of the nuclear power plants (NPPs) in MATLAB/SIMULINK, the validity of the model can be verified in various working conditions such as increasing or reducing the power, load shedding, grid frequency disturbance, and grid faults
Summary
Hunan Province Key Laboratory of Smart Grids Operation and Control, School of Electrical & Information. Engineering, Changsha University of Science & Technology, Changsha 410114, China. Received: 15 November 2019; Accepted: 24 December 2019; Published: 31 December 2019
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