Grid Current Harmonic Suppression for Motor Drive with Reduced DC-Link Capacitance in Weak Grid

Motor drives with reduced DC-link capacitance may face grid current distortion or even instability under weak grid condition. In this paper, the small signal model of reduced DC-link capacitance drive system under weak grid condition is derived and analyzed. On this basis, an impedance reshaping method is proposed to suppress the harmonics of the grid-side current. By extracting DC-link harmonics near the LC resonant frequency and reconstructing the virtual admittance of the drive, the active damping voltage control signal is generated to suppress the harmonic of the grid-side current at the specific frequency. The THD of the grid-side current was reduced from 53% to 39%. The experiment was carried out on a 5.5kW permanent magnet motor drive platform with reduced DC-link capacitance, and the effectiveness of the control strategy was verified by experiments.