Research On Key Technologies Of Anode High-Voltage Power Supply For Electron Cyclotron System On EAST

As one of the important subsystems of Tokamak,electron cyclotron resonance heating(ECRH)system can heat plasma and drive plasma current.With the deepening of the physical experiment of EAST device,the ECRH has put forward high-frequency modulation requirements for the anode power supply(APS)from the perspective of suppressing the instability of the neoclassical tearing mode(NTM).In this paper,starting from the characteristics of high modulation,high power density and fast dynamic response of anode power supply,the topology of the power supply is proposed.Then,key technologies such as overvoltage suppression strategy of SiC MOSFET,the modeling and optimization LCC resonant circuit,and parasitic parameter analysis of high-voltage high-frequency multi-winding transformers in power supply design process are analyzed.Firstly,the design scheme of anode power supply for ECRH of major fusion devices at home and abroad is deeply studied.According to the technical specifications of the power supply,three characteristics of the anode power supply are summarized:wide output voltage,fast rise and fall,and fast dynamic response.The inverter technology,boost and output modulation technology and voltage regulation strategy in high-voltage power supply are analyzed,and the topology scheme of the APS is proposed.Secondly,in view of the overvoltage in turn-off process of SiC MOSFET,the mechanism of voltage spike in the turning off process of SiC MOSFET is studied,and a closed-loop active gate drive circuit based on dv/dt control is proposed.Based on the analysis of the control-oriented SiC MOSFET driver circuit small-signal model,the stability of dv/dt control is studied,and the influence of the key parameters of the driver circuit on the stability of the control system is analyzed by using the root locus method.A double-pulse test platform is built.The test results show that the proposed active drive circuit can effectively suppress the device overvoltage during the turn-off process at the expense of smaller switching losses compared with the traditional suppression circuit.It provides a foundation to fully utilize the advantages of high frequency and high efficiency of SiC MOSFETs.Thirdly,in order to improve the dynamic response capability of the anode power supply,two methods are proposed to improve the dynamic response capability of the power supply.Those are reducing the open-loop voltage droop and optimizing the design of the PI parameters.It is proposed to operate the LCC resonant circuit in the capacitive state,and use the state space to model the LCC resonant circuit under the capacitive operating condition.Aiming at the minimum open-loop voltage drop,the steady-state characteristics of the circuit are analyzed,and the resonance parameters are optimized.The optimized circuit is modeled by the dynamic phasor method,the system properties of the APS is analyzed,and the PI parameters are designed.The test results show that the adjustment time of the APS is reduced to 1ms.Finally,the parasitic parameters of high-frequency high-voltage multi-winding transformers are analyzed in view of the significant influence of high-frequency transformers on the characteristics of resonant converters.The multi-winding transformer structure under the condition of high isolation voltage is proposed,and the finite element analysis of 8 secondary winding structures is carried out.Besides,the relationship between parasitic parameters and winding structure is obtained.Finally,a prototype of high frequency and high voltage multi-winding transformer was designed and tested.The test results show that the designed transformer is consistent with the theory,the larger leakage inductance of the transformer can be used for the resonant circuit,and the smaller the parasitic capacitance has negligible influence on the resonance process.