Design of acceleration grid power supply for CFETR negative-ion-based neutral beam injection prototype

Abstract The planned China Fusion Engineering Test Reactor (CFETR) needs one or more Negative-ion-based Neutral Beam Injectors (N-NBIs) with a beam energy of 500 keV to heat plasma and drive current. In order to prepare for CFETR, a prototype of CFETR N-NBI is being designed to accelerate hydrogen negative ions up to 200 keV with a beam current as high as 20 A for 3600 s at max, and an Acceleration Grid Power Supply (AGPS) rated at −200 kV/25 A is needed. A single stage inverter-type high voltage power supply is adopted as AGPS of the N-NBI prototype. The AGPS mainly includes a 12 pulse rectifier based on thyristor, a dual-dc-link system rated at 5 kV, a three phase three level neutral point clamped dc/ac inverter based on injection enhanced gate transistor, a three-phase set-up transformer, a high voltage uncontrolled rectifier based on avalanche diode and a high voltage R-C dc-filter. This paper describes the design of the AGPS for CFETR N-NBI prototype, focusing on the inverter, the step-up transformer and the HV diode rectifier.