Upgrade of the cathode HVPS system for 4.6 GHz LHCD on EAST using high speed PSM

Abstract

The 4.6GHz LHCD system is an important part of the auxiliary heating system on EAST tokamak. The cathode high voltage power supply(HVPS) is based on pulse step modulation (PSM) technology, in which 64 modules are used to output 50kVDC in series. The modulation frequency of single PSM module is 50Hz, it switch on and off every 20ms, so the regulation speed of system is limited. In the face of the interference caused by the voltage fluctuation of the grid side during the tokamak operation, the HVPS cannot make more rapid response. It means that a large fluctuation of the output voltage will be produced and output performance of microwave will be affected. In order to improve the regulation speed and anti-interference capability of system, the high frequency PSM module with 1kHz modulation frequency capability was designed to replace some of the original low frequency modules. The fluctuation of output voltage was reduced by the rapid regulation capability of the high frequency module. The experimental results show that the output voltage fluctuation rate of the upgraded power supply is reduced by 50%, which better meets the control requirements of klystron for voltage accuracy and stability, and the reliability of the system is guaranteed.