Design Of Deceleration Pole Power Supply For Neutral Beam Injector

High-power Neutral Beam Injector(NBI)is the important method to heat and drive the plasma in controlled nuclear fusion. The deceleration pole power supply (DPPS) is an important part of the power system of NBI. The power is used to decelerate secondary electron to reflux into the source of plasma in the process of Neutral Beam extraction, and it can control electron which passed through the eyelet of the deceleration pole power supplies in the beam, and in order to improve the space-charge effect of beam. The current DPPS using SCR and diode rectifier to regulate voltage in the demestic, its ripple too high and can not solve the problem of the current overload when arcing condition. In addition, the output polarity reversal is a serious problem.This paper presents a new DPPS for NBI using the topology of high-frequency switching power supply, which controlled the digital phase-shifted PWM based on FPGA. The design can increase the capability for overload and adjustment rapidly and obtain good output waveform parameters and excellently dymatic characteristics. The HVDC platform with technology of series resonant makes the capacity for anti-overload has been increased. The mathematical model of the sinusoidal approximation fundamental component is get and is used to calculate circuit component parameters; The tetrode modulator is applied to endure the problem that high-frequency resonant switching power supply needs long time to stable output and can control the ripple under 5%, and the rise time and the fall time of pulse are no more than 20 microsecond and the turn-off protection can be achieved fast; The digital phase-shifted PWM control method based on FPGA not only makes IGBT operating in ZVS mode which can reduce the switching losses of the system and EMI, but also makes the controller performance is much higher than traditional analog IC controller. Furthermore, the protection circuits for operating in the bad conditions are designed in paper, such as short-circuit overcurrent and high-voltage isolation.At last, the preliminary prototype of the control circuit, PS platform and modulator are manufactured. The output waveforms of PS platform with resistive load show that the designs are reasonable. The voltage and current waveforms of inverter in the simulated arcing state show that protection circuit triggers reliable, series resonant circuit has strong ability of overload and the modulator output waveforms meets the design requirements. The system can be applied to NBI in the further.