基于谐振频率扫描的EAST鱼尾偏滤器磁体电源反馈控制策略的研究

Study on Magnet Power Supply Feedback Control StrategyBased on Resonant Frequency Scanning of EAST Fishtail Divertor

鱼尾偏滤器是EAST托卡马克偏滤器系统的一种新型偏滤器设计,其作用是将反应中的高能带电粒子导向特定的靶板,避免粒子轰击主放电室壁。EAST托卡马克装置放电时电磁环境复杂多变,且偏滤器对磁体线圈的电流要求为频率(10~3 800 Hz)、幅值(0~5 000 A)可调的正弦电流。为满足线圈电流的精度和稳定输出的要求,提出了一种基于谐振频率的反馈控制策略并建立了电源的等效数学模型。通过理论分析和仿真,完成了电源输出电流频率反馈控制系统的设计。通过电源及磁体线圈放电实验,证明采用频率反馈控制策略,电源能在1.5 s内及时获取电磁环境干扰对等效负载特性造成的谐振网络频率偏差,并主动校正励磁电压频率,保证偏滤器磁体线圈电流的准确性。

The thermal deposition of particle beam on the divertor target plate in tokamak and the surface ablation caused by it issue that it can not be ignored.Fishtail divertor is a new divertor design of EAST Tokamak divertor system.Its function is to guide the high-energy charged particles in the reaction to a specific target plate to avoid particle bombardment on the wall of the main discharge chamber.It can be found that the thermal deposition effect under the sinusoidal deflection current is very different from that under the direct current,which will be more conducive to the distribution of the thermal deposition area of the divertor target.The current of the divertor to the magnet coil is required to be a sinusoidal current with adjustable frequency(10-3800 Hz)and amplitude(0-5000 A).The power supply adopts the frequency modulation square wave to excite LCR series resonance to realize the frequency regulation of sine wave current.When the EAST Tokamak device discharges,the electromagnetic environment is complex and changeable.Therefore,the environment will lead to the change of the load inductance value,which will make the LCR resonant frequency shift,thus causing the attenuation of the output current amplitude.By establishing the equivalent mathematical model of power supply,the generation mechanism of output current and the key factors affecting the current amplitude were obtained.To ensure the accuracy of the output current,it is necessary to ensure the amplitude of the excitation voltage and the frequency of the LCR resonant network.In order to ensure the accuracy of resonant frequency,a feedback control strategy based on resonant frequency was proposed.Through the study of frequency feedback control process and simulation with the help of ANSYS simulation software,the design of power output current frequency feedback control system was completed.On the basis of theoretical analysis and simulation verification,the frequency feedback control strategy can be implemented on the power supply.Through the discharge experiments of power supply and magnet coil,it is proved that using the frequency feedback control strategy,the power supply can timely obtain the resonance network frequency deviation caused by electromagnetic environment interference on the equivalent load characteristics in 1.5 seconds,and actively correct the excitation voltage frequency to ensure the accuracy of magnet coil current of divertor.It can be seen that the feedback control strategy based on resonant frequency identification proposed can solve the problem of output sinusoidal current amplitude attenuation due to inductance change,and has good engineering value and reference significance.