Low frequency ripple current attenuation for slow corrector power supplies in the APS Upgrade

As part of the Advanced Photon Source Upgrade (APS-U), approximately one thousand bipolar power supplies were installed to power the slow corrector magnets. During the APS-U commissioning, a 1Hz harmonic was detected in the beam motion. This harmonic originates from the 480V AC grid, caused by the booster ramping power supply operating at 1 Hz. The resulting grid disturbance introduced low-frequency ripples into both the corrector magnet power supplies and the L-Bend M1/M2 supplies, leading to the observed 1 Hz beam motion. This paper proposes two methods to mitigate these ripples in the corrector supplies: setpoint compensation using repetitive control, and regulation circuit adjustments through a simple jumper reconfiguration. The second approach was adopted and applied to all slow corrector magnet power supplies. Operational data showed that the low-frequency ripples were significantly attenuated in the corrector supplies, and in combination with fine-tuning of the L-Bend M1/M2 supplies, the 1 Hz beam motion was successfully eliminated.