Modeling For A New Generation Of Nuclear Power Units And Simulation Study On Power-frequency Regulation Characteristics

Nuclear power unit has many characteristics,such as high nuclear safety requirement,large unit capacity,limited power regulation capability and so on.Under the background of improving proportion of nuclear power in the whole power supply and increasing complexity of China's power system,based on actual needs of power system,it is of great importance to appropriately play primary frequency regulation of nuclear power unit for improving system operation flexibility and ensuring nuclear safety and power system safe and stable operation.On the basis of in-depth understanding of a large number of domestic and foreign references,a detailed theoretical derivation on the working principle of the nuclear power unit and the overall model is done combined with several related nuclear power unit modeling projects,At the same time,the influence of the parameters of the turbine and governor model on the frequency regulation characteristics of the nuclear power units and the influence of the frequency modulation parameters on the frequency characteristics of the nuclear power units are analyzed.The main contents are as follows:(1)Aiming at the new generation of large-scale PWR nuclear power unit,the whole model of nuclear power units which are suitable for the inter-connection to power grid is established based on the mass conservation theorem and energy conservation theorem.Sub models are established in turn,including reactor neutron dynamics model,core fuel temperature model,core coolant temperature model,coolant heat/cold pipe section model,steam generator-circuit cooling,reactor power control system model,as well as steam generator saturated steam pressure model,steam turbine and electro-hydraulic speed control system model,generator model are constructed.Among them,considering the effect of the valve opening on the main steam pressure of the nuclear turbine,the modified nuclear turbine model is established.The simulation results show that the proposed model is more in line with the actual operating characteristics of nuclear power units.Finally,according to the simulation results of the power regulation response,validity of the model of nuclear power plant is verified.(2)The steam turbine model suitable for nuclear power plant is studied,and the influence of steam turbine and governor system parameters on the primary frequency modulation is simulated and analyzed.Firstly,the characteristics of nuclear turbine and thermal power turbine are studied,and the output characteristics of the steam turbine are compared.Then,the influence of steam turbine and speed regulation system parameters on the primary frequency modulation characteristics of the generator is analyzed.The results show that the frequency-modulating dead zone,frequency limiting and amplitude modulation coefficient are important factors of the frequency-modulating characteristics.(3)Based on the overall modeling of the nuclear power units,the nuclear power units are connected to single machine infinite bus system.The influence of dead zone,amplitude limiting and regulation coefficient on the power-frequency regulation characteristics of nuclear power units are analyzed empirically.The dynamic response process of the internal variables of the nuclear power unit is obtained by changing the primary frequency regulation parameters when frequency difference step happens.The power-frequency characteristics of the nuclear power units are analyzed from the aspects of the first frequency modulation effect and the thermal shock of the nuclear island part,and ultimately the three primary frequency regulation parameters of the value of the law and reasonable range are determined.