Design of a Multipulse High-Magnetic-Field System Based on Flywheel Energy Storage

The controlled pulsed high magnetic field can promote some scientific research effectively such as nuclear magnetic resonance imaging, terahertz, etc. Hence, in this paper, a multipulse high-magnetic-field system is designed by a 100-MVA/100-MJ generator at the Wuhan High Magnetic Field Center. In this system, to improve the energy utilization rate, the storage energy of the magnet would be fed back to the flywheel after each discharge shot by the 4-quadrant 12-pulse thyristor rectifier. Consideration of the difficulties of phase jump, commutation notch, varied frequency, and distorted output voltage of the generator, a novel phase-locked loop (PLL) based on the genetic algorithm (GA) is proposed. This GA PLL can not only help avoid the problem of the invert fault but also improve the accuracy of the firing angles. On the base of exact firing, a combined closed-loop with forward-feed control system is designed, which could achieve fast response and steady accuracy at the same time. The simulations and the experiments verified the feasibility of the design, and accordingly, a 5/10/15/20-T multistage pulse and 20-T multipulse are generated.