Research On Impact Power Compensation Strategy Of ITER Power Supply System

With the development of society,the problem of energy crisis is becoming more and more serious.Developing new energy is an effective way to solve the problem.Nuclear fusion energy is a kind of abundant and pollution-free new energy.O ver the years,relevant scientific and engineering technology research has been continuously carried out at home and abroad.The International Thermonuclear Experimental Reactor(ITER)is designed to build a sustainable combustion Tokamak fusion experimental reactor to verify the technical feasibility of the fusion reactor.The power supply system is an important part of ITER device,with a total installed capacity of 2200 MVA.It is connect to French 400 k V power grid,through step-down transformers and power conversion,and realizes the generation,driving,heating and control of plasma by driving superconducting magnets and various heating systems.Due to the strong pulse characteristics of fusion load,it brings a huge impact of active and reactive powers to the high voltage power grid.The impact power can reach several hundreds MW/Mvar in one power frequency cycle,and has strong randomness,which threatens the safe and stable operation of fusion device and power grid.Therefore,ITER is equipped with corresponding reactive power compensation devices,in order to improve the working conditions of the power grid and realize the compatibility between the power supply system and the power grid.However,the current power compensation system cannot cope with the high-parameter operating conditions of ITER in the future.Thesis focuses on the impact power compensation problem of ITER power supply system,and analyzes the perturbation characteristics of active and reactive power in the power supply system.Aiming at the problems of insufficient reactive power compensation capacity,poor dynamic performance and lack of active power impact compensation,the impulse power compensation scheme and control strategy of supercapacitor energy storage system based on modular multilevel converter(MMC-SC)are established,combined with the technology of supercapacitor energy storage and modular multilevel converter.The cooperative control with the existing reactive power compensation system is further realized.The specific research contents are as follows :First of all,according to the operation p rocess of ITER device,this paper analyzes the typical load of the ITER system during operation,and clarifies the characteristics of the impulse power under various operating conditions.Through the Matlab simulation experiment,the phenomena of the grid voltage sags,generator speed fluctuation and forced oscillation of grid power and others are researched.Aiming at the problems of power compensation in ITER system,a solution of impulse power based on energy storage multilevel converter technology is proposed.Secondly,the topology,mathematical model and compensation principle of MMC-SC are studied.In order to achieve good compensation performance,the modulation strategy of MMC-SC is analyzed,and the submodules capacitor voltage control strategy and the cooperative control strategy of MMC and bidirectional DC/DC converter are designed respectively.As a result,MMC-SC can quickly compensate the active and reactive impact power of the system.In order to improve the fault-tolerant operation ability of the system,a fault-tolerant control strategy of dynamic active standby is adopted,by reducing the voltage differences between the redundant module and the normal module,the transient effect of charging process caused by redundant switching is reduced.Finally,the installation point of the MMC-SC in the ITER system is determined considering the engineering application.According to the impact power caused by typical operation load,the main parameters of MMC-SC system are designed.Aiming at the problem of coordinated operation of MMC-SC and ITER existing SVC devices,the cooperative control method is designed,which provides an effective scheme for the impact power compensation of ITER system under high parameter operation mode.The scheme and control strategy proposed in this paper are verified by simulation.The technology can provide a reference for ITER power supply system impact power compensation,and also has a reference significance for China to carry out the independent design of domestic nuclear fusion reactor in the future.