2-DOF Decoupled Discrete Current Control for AC Drives at Low Sampling-to-Fundamental Frequency Ratios

In high-performance drive systems, wide bandwidth and reference tracking accuracy of current control loop are fundamental requirements. The conventional PI controller provides robustness against the machine parameter mismatching and zero steady-state error, but its dynamic performance degrades at high speed due to the bandwidth limitation. In this article, a new control structure of discrete PI controller with a deadbeat response is proposed, which combines the advantage of conventional PI controller with deadbeat characteristics. The proposed controller shows a decoupled tracking performance of up to 15% of the switching frequency while also providing extra control freedom of the disturbance rejection, which effectively improves the system stability. Experiments show a reduction of oscillation by 30% compared to the conventional PI and the validity and applicability of the proposed control method for high-speed applications with low sampling-to-fundamental (S2F) frequency ratios.