Optimization of Frequency Feedback Control Strategy for Magnet Power Supply of EAST Fishtail Divertor

The power supply (PS) of fishtail divertor (FTD) magnet used in experimental advanced superconducting tokamak (EAST) tokamak device is multifrequency LC resonant power. In the experiment, the change of magnetic field will cause the current skin effect of the load magnet of the divertor, which will cause the shift of resonant frequency and the attenuation of current. Therefore, to ensure the output amplitude of the resonant current, the feedback control strategy based on the resonant frequency identification is adopted. Because the resonant quality factors $Q$ of the high-frequency working point are larger than the low one, the current amplitude attenuation caused by the shift of resonant frequency at the high frequency point is much greater than the low point. The resonant current error will increase greatly when the frequency of working point increases because of the resonant frequency identification control with fixed scanning space and number. Therefore, in order to improve the output current feedback control accuracy, a frequency scanning strategy based on multispaces is proposed. The effect of this frequency feedback optimal control strategy is verified by modeling and simulation.