Abstract: Aiming at the problem that low-order harmonics (75-125 Hz) are difficult to control due to non-linear loads such as EAST magnet power supply, an injection hybrid active filtering scheme is proposed. Based on the EAST low-order harmonic experimental platform, the topology and filtering principle of the injected hybrid active power filter device are studied. At the same time, a three-level space voltage vector modulation algorithm for reducing the midpoint potential fluctuation of the DC side is adopted. The method of obtaining the basic vector action time is given. The simulation and experimental verification of the scheme and algorithm are carried out, and the simulation results are in good agreement with the experimental results, which proves that the scheme can effectively suppress the low-order harmonics and resonance amplification produced in the operation of EAST magnet power supply.