NNBI射频功率源输出功率控制系统设计

Design of NNBI RF power source output power control system

设计了一种改进型射频功率源输出功率控制系统,解决了现有射频功率源使用中存在的输出功率稳定性与控制精度不足等问题,预期将应用于中国聚变工程实验堆(China Fusion Engineering Test Reactor,CFETR)负离子源中性束系统(Negative Ion Based Neutral Beam Injection System,NNBI)。采用ARM+CPLD双核设计的软、硬件分离控制结构,保障输出功率控制算法运行效率;采用数字化信号控制方法,实现输出功率的高精度控制;通过精确采样射频功率源实际输出功率和闭环功率控制方法设计,实现输出功率的高稳定性控制。对射频功率源样机进行输出功率控制系统模拟负载测试,结果表明:在额定输出功率为50 kW时,输出功率的控制精度高于0.1%、稳定性波动小于0.5%、人机交互软件功能完善。该方案预期可以搭配阻抗匹配网络满足CFETR NNBI射频功率源对输出功率控制的性能要求。

[Background]With the development of negative ion based neutral beam injection system(NNBI)for China fusion engineering test reactor(CFETR),the output power control system of its supporting the radio frequency(RF)power source is one of the key technologies to realize the improvement of its performance.[Purpose]The study aims to design an improved output power control system of RF power source to solve the problems of output power stability and insufficient control accuracy in the use of existing RF power sources.[Methods]The software and hardware separation control structure designed by ARM+CPLD dual-core were employed to ensure the operation efficiency of the output power control algorithm of the RF power source and the communication stability of the peripheral equipment.Multi-stage progressive power control method and 12-bit digital signal were adopted to control the opening and closing of RF power amplifier,so as to realize high-precision control of output power.The capacitive voltage divider method and current transformer method were combined to accurately sample the actual output power of the RF power source for implementing high-stability control of output power with a closed-loop power control method.Meanwhile,the upper computer software design of man-machine interaction based on serial communication of self-defined protocol was adopted to complete the man-machine interaction function of output power control.[Results]The control system has perfect human-computer interaction software function,and test results of the prototype RF power output power control system with simulation load show that the control accuracy of the output power is higher than 0.1%when the rated output power is 50 kW,and the stability fluctuation is less than 0.5%.[Conclusions]This scheme with impedance matching networks is expected to meet the performance requirements of CFETR NNBI RF power supply for output power control.