Load Analysis And Stability Mechanism Of Distribution Network For Tokamak Nuclear Fusion Devices

The nuclear fusion industry in China has developed rapidly in recent years with the deep participation in ITER,the establishment of Comprehensive Research Facility for Fusion Technology(CRAFT),and the gradually start of China Fusion Engineering Test Reactor(CFETR).The high availability of more and more complex nuclear fusion devices is closely related to the reliability and stability of their distribution networks.The distribution network becomes a key issue for the high availability of more and more complex nuclear fusion devices.In this dissertation,the function of Tokamak power distribution network,the model analysis on steady-state loads and pulsed loads,the research on voltage stability,and the operation mechanism of pulsed distribution networks for high-power magnet power load are analyzed.With a particular topology,control and operation design on the power distribution network of the Tokamak fusion device,new analysis methods and directions are proposed.According to the basic framework and theoretical basis of the power distribution network design for the Tokamak nuclear fusion device,four types of loads in the nuclear fusion device are cataloged and analyzed to determine the distribution network configuration.The function of the power distribution system for the Tokamak nuclear fusion device is analyzed to determine the basic topology structure.The rationality and effectiveness of the design are verified through power flow calculation,short circuit calculation,stability calculation and impact load check calculation.A single induction motor has been taken as an eample to develop the dynamic mechanism model for conventional load in the nuclear fusion device.The nameplate data are exacted,analized and integrated to the corresponding parameters to simulate the special usage of fusion technology.Thethod is verified by calculation and analysis based on the continuous power flow method,the static voltage stability of the fusion distribution network is analyzed,and the influence of different load models on the analysis results is compared.The main reasons for the transient instability of system voltage are analyzed.The calculation and time domain simulation proved that the fault clearing time and the bus power factor are the main factors to the voltage transient stability.Taking the conventional load in the Tokamak nuclear fusion device as the research object,an identification method which utilizes the nameplate data of a single induction motor and transformed into the corresponding parameters of the dynamic mechanism model is proposed.The effectiveness of the method is verified by calculation and analysis of typical loads.Based on the continuous power flow method,the static voltage stability of the fusion distribution network is analyzed,and the influence of different load models on the analysis results is compared.The main reasons for the transient instability of system voltage is analyzed.The fault clearing time and the bus power factor are proved the main factors affecting the voltage transient stability by the calculation and simulation in time domain.Self-recovery model of magnet power system identified by PSO,and combined load model of PSM high voltage power supply are developed respectively.The accuracy of the self-recovery model is verified by the EAST magnet power experiment records.The applicability of the combined load model is verified with simulation.A stability index on the short-circuit capacity of the coupling point is proposed,and some control measures are suggested to improve the stability.These provide a theoretical and operational basis for real-time monitoring of the voltage stability of the Tokamak distribution network.The comprehensive situation of the magnet power supply which is random,high power and extremely low power factor interact with the power distribution network is analyzed.With the short circuit ratio parameter,the configuration requirements of the Tokamak power distribution system for operation of the converters are proposed.A solution is proposed to reduce the mutual influence between converters.Comprehensive analysis on the impact of Tokamak distribution system configuration to converter operating conditions such as commutation gaps and harmonic currents are explored and then verified by the EAST model.The control strategies to avoid distribution network resonance over-voltage and suppress low-order harmonic amplification are put forward,which is great significance to the optimal design of Tokamak nuclear fusion device distribution network.The ITER and CFETR distribution network have been compared on fuctional requirements,loads and structures.The basic framework of the CFETR 220kV substation and distribution network is established according to the current input.The basic parameters of the Tokamak distribution network are performed by the related stability calculations.The feasibility of load distribution and reactive power compensation scheme is verified by the power flow and short circuit calculation with ETAP 12.6.0.