| In order to develop the high-performance steady operation and fusion energy research in the China Fusion Engineering Test Reactor(CFETR),the Negative-ion-based Neutral Beam Injector(N-NBI)system is the one of the key auxiliary heating systems.The accelerator grid power supply(AGPS)is the one of the core devices to supply main energy for N-NBI system.The high input/output performance and the fast shutdown capability when breakdown occurred are required for the AGPS conversion-system(AGPS-CS).As for AGPS-CS,the power capacity and the operation requirements are high.Due to lack of design and research experience,the key technologies of AGPS-CS about the topology,the control strategy and the converter design should be studied in depth.Supported by the National Key Research and Development Program,the concept design of the CFETR N-NBI AGPS-CS and the development of the CFETR N-NBI AGPS-CS prototype were studied in this paper.The main contents and innovations are as follows:(1)The topology scheme of the CFETR N-NBI AGPS-CS has been developed.Some topologies of the typical multilevel inverter and the high-power rectifier were analyzed,the design method of the AGPS-CS topology was proposed based on the four factors: cost,performance,power capacity and reliability.According to the requirements of CFETR N-NBI AGPS,the new topology scheme of AGPS-CS based on three-level neutral point clamped(3LNPC)rectifier and the five-level cascaded neutral point clamped(5L-NPC/H)inverter was proposed.Compared with the traditional scheme in ITER,the reactive power consumption,the risk of DC-link and the complex design of inverter in parallel were improved and optimized.(2)The control strategy of the CFETR N-NBI AGPS-CS has been developed.Based on the proposed topology of the CFETR AGPS-CS,the parameters of the direct current generation were calculated.As for 3L-NPC rectifier,the control strategy based on dq current decoupling and the modulation method based on third-order harmonic injection were introduced.As for5L-NPC/H inverter,according to the characteristics of amplitude and ripple for the output voltage acquired by the time-frequency domain transformation analysis method,the control strategy based on the pre-set modulation index and feedback compensation,and the modulation method based on shift angle and duty cycle were proposed.Simulation results indicated that the proposed control strategy could meet the design parameters,the input harmonic current and reactive power were optimized,the output respond speed was improved and the output ripple voltage was reduced.(3)The design of the CFETR N-NBI AGPS-CS prototype has been developed.According to the requirements of the AGPS prototype,the topology scheme of AGPS-CS prototype based on 12-pulse thyristor rectifier and 3L-NPC inverter was proposed based on the AGPS-CS design method.The control strategy of the AGPS-CS prototype was also analyzed.The design scheme was indicted by simulation.Then,the high-power converter design technology has been developed taking the AGPS-CS prototype as research object.Based on the systematically theoretical analysis and experiment comparison,the application characteristics between Injection Enhanced Gate Transistor(IEGT)and Integrated Gate-Commutated Thyristor(IGCT)were summarized.According to the operation characteristics of N-NBI AGPS inverter,the inverter scheme based on IEGT with high reliability and strong switch-off ability was proposed.The modular design method was considered,the features from the engineering design of the converter: power stack,cooling system,control system,and auxiliary power supply system were completed,test results were indicated that the proposed AGPS-CS prototype has the operation ability.The develop and analysis of the AGPS-CS design method,the control strategy and the research of the high-power converter could be extended to other high-power and high-voltage power electronic converter and have a certain reference value for the development and operation of the CFETR N-NBI system. |
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