Design of Phase Synchronization Unit for Active Power Filter in Superconducting Magnet Power Supply

In this dissertation, a method is given to solve the problem of phase synchronization for active power filter (APF) which is used in superconducting magnet power supply (SMPS). Firstly, the characteristics of the SMPS are introduced and the technical difficulties which will influence the phase synchronization are pointed out. Secondly, in order to solve these difficulties, the synchronization design is based on zero-cross detection, Butterworth filter and phase compensation for practical purposes. Because the APF adopts DSP as the digital controller, the phase compensation can be easily achieved by software design. In the end, the experimental results of a prototype have verified the effectiveness of the proposed design and the APF can trace the frequency and phase of primary input voltage effectively.