Research On Design And Operation Optimization Of Superconducting Magnet Test Power Supply For Fusion Device

As a major national research project in china,the Comprehensive Research Facility for Fusion Technology(CRAFT)consists of world leading superconducting magnet and divertor research system.The superconducting magnet test power supply is the core unit of superconducting magnet research system,and it is essential to the experimental study of large superconducting magnets and key components of China Fusion Engineering Test Reactor(CFETR).The power supply system is characterized with wide range of output voltage and current,high inertia superconducting magnet load and complex operation mode.According to the requirements of steady-state operation,fault state operation,short-circuit overload operation and superconducting magnet test,the design and operation optimization of the power supply are studied in this paper.The main contents and innovations are summarized as follows:According to the requirements of superconducting magnet load during steady,transient and fault state operation,a superconducting magnet test power supply is designed with multiple rectification technology.The simulation mathematical model of AC/DC system is established with the distribution parameters.The operation limit of AC/DC system is studied,and the key equipment parameters are investigated to ensure the reliability of the power supply system.For the widely changed of load,the external characteristics under different operation modes of superconducting magnet test power supply are studied,and the optimal operation methods and self-adapted algorithm to single,parallel and series mode of superconducting magnet power supply are proposed to provide the test to different loads.To meet the high reliability of power supply during superconducting magnet test,the scheduling strategy and the redundancy scheme of modular power supply are explored and researched,which offer an assurance for the test of superconducting magnet and a new method for the stable operation of high-power fusion power supply.The simulations and experiments are conducted,and results validate the feasibility of the proposed methods.To resolve the current sharing problem of converters in Parallel,the circulating current mathematical model is founded with the study on the circulating current characteristics between converters.Based on the mathematical model,A current sharing control algorithm by virtual impedance restraint circulating current is proposed.With this algorithm,the synchronization of circulating current and harmonic voltage is achieved,the response performance of current sharing control is improved and the loss on the DC reactor is avoided.To short-circuit pulse operation,on the basis of research on the external characteristics of power supply in the rise process of impulse current,the linear mathematical model under short-circuit operation is established by replacing the circular arc with small bowstring.On this basis,an open-loop control strategy with controllable pulse width and amplitude is designed,and the rationality of the control strategy is verified by simulation and experiment.All design methods also provide technical support for the design and operation of the same type of high-power pulse power supply.