Control Strategy for Resonance Mitigation and Grid Harmonic Suppression in Three-Phase Diode Rectifier-Fed PMSM Drives With Small DC-Link Capacitance

Abstract

This article proposes a robust control strategy to minimize grid current harmonics in three-phase diode rectifier-fed permanent magnet synchronous motor (PMSM) drives featuring a small DC-link capacitance. First, a virtual impedance-based active damping scheme is introduced to emulate a series R-C damper. This suppresses LC resonance using only a DC-link voltage sensor, avoiding additional hardware. Second, a discrete-time extended state observer (ESO) is developed to estimate the rectified current, eliminating the need for grid current sensors. Specifically, the proposed observer is independent of inductance parameters, ensuring robustness against grid inductance variations. To mitigate grid current harmonics, a resonant controller with phase compensation is implemented using the estimated current, where compensation voltage References are directly derived via a current-to-voltage transformation. The stability of the integrated harmonic suppression schemes is validated through impedance-based analysis accounting for digital delays. Experimental results demonstrate that the proposed strategy effectively stabilizes the DC-link voltage while significantly minimizing grid current harmonics under varying grid conditions.