Grid Current Harmonic Suppression in Low-Line Inductance Electrolytic-Capacitor-Free PMSM Drives via Frequency-Selective Enhanced ADRC

Abstract

Low-line-inductance electrolytic-capacitor-free drive systems are expected to further exploit the advantages of power density and cost. However, this design makes grid current harmonics more difficult to suppress and compromises system stability, particularly under unbalanced grid voltages. To address this issue, this paper proposes a frequency-selective enhanced ADRC rectified current regulation (FSEA-RCR) strategy. In the proposed strategy, grid current harmonics are treated as the major disturbance and ADRC is adopted to estimate and compensate the total disturbance. In addition, repetitive control is embedded into the linear state error feedback to enhance the suppression of multifrequency periodic harmonics. The controller design explicitly incorporates line inductance and DC-link capacitance to ensure effective harmonic suppression under low-line inductance. The proposed method neither requires specific harmonic extraction nor relies on distinguishing balanced and unbalanced grid conditions, making it applicable to both operating scenarios. Simulation results demonstrate that the proposed strategy effectively suppresses grid current harmonics under ${4 0 0}~\mu \mathrm{H}$ line-inductance and maintains satisfactory adaptability under different operating conditions.