开关型双极性电源通常用来为加速器的校正磁铁线圈提供稳定励磁电流.深圳中能高重复频率X射线自由电子激光大科学装置(Shenzhen Superconducting Soft X-ray Free Electron Laser,S3FEL)的技术指标,对校正磁铁的磁场稳定性提出更高要求.然而,校正磁铁电源工作在小电流状态时,电源开关脉宽占空比极小,会导致输出电流稳定性变差.为解决上述矛盾,提出一种串联可控双向阻抗电路的方法改善校正磁铁电源小电流工况稳定性.首先利用伯德图对串接可控双向阻抗电路进行了分析,获得了可控双向阻抗的设计依据,然后利用上海光源的校正磁铁和电源完成了实验验证,实验结果表明:串接可控双向阻抗的方法不仅能改善小电流工况的稳定性,而且实现了MOSFET的平滑切换.该电路结构简单,值得推广.
Low current stability of bipolar magnet power supply in switching mode
[Background]Bipolar magnet power supplies using switching techniques are commonly used to provide stable excitation current for correction magnet coils.Specification of the Shenzhen Superconductive Soft-X-ray Free Electron Laser(S3FEL)project requires enhanced magnetic field stability of correction magnets.However,when switching power supplies are used for correction magnets at low currents,the very narrow pulse width of the power switch leads to poor stability in the output current.[Purpose]This study aims to propose a method involving a series controllable bidirectional impedance circuit to improve the stability of low current output from the correction magnet power supply.[Methods]Firstly,the characteristics of a controllable bidirectional impedance was identified when connected in series from the power supply to the correction magnet,and a Bode diagram was applied to analyzing its features.Then,a controllable bidirectional impedance circuit was designed on the basis of simulation analysis.Finally,experimental validation was conducted using the correction magnet and power supply from Shanghai Synchrotron Radiation Facility(SSRF).[Results]The experimental results demonstrate that serially connecting controllable bidirectional impedances not only improves low current stability but also allows for smooth switching between MOSFETs and controllable bidirectional impedances.[Conclusions]The circuit design proposed in this study is simple and proves to be effective to improve the stability of bipolar magnet power supply under low current condition.
Bipolar power supplyCorrecting magnetControlled impedancePI controlBode diagram
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