We have been developing a conduction cooled HTS-MRI that is driven by a power supply in order to solve the long-lasting attenuation of the screening current induced on superconducting tapes at the time of initial excitation and the difficulty with REBCO tape superconducting junctions, as well as a superconducting switch for persistent current operation. A power supply system consisting of two exciters, one for charging and discharging and the other for holding the magnet current, is proposed and developed. The supply system is equipped with a control block to compensate the magnetic field deviation caused by the screening current. We carried out a magnetic field stability experiment using a 32-H HTS-MRI magnet excited by the power supply system proposed which was equipped with specially designed micro-current control.