Current Pulsation Suppression Method Based on Power Current Closed-Loop Control for a PMSM Under Fluctuating DC-Link Voltage

For a single-phase rectifier, a common issue is that there exists a component fluctuating at twice the grid frequency in dc-link voltage due to the fluctuating input power. This fluctuating dc-link voltage causes modulation error, which induces severe phase current pulsation at low frequency. An additional
LC
filter can suppress the voltage fluctuation at the cost of increasing volume and reducing power density. The conventional software method is achieved by the modulation ratio or frequency compensation. However, the compensation methods have limited performance. In this article, a cascaded power current controller is proposed to suppress the current pulsation. The power current is constructed and used as the control target. Accordingly, the power current loop is cascaded between the speed and current loops. Maintaining a constant power current beneficially rejects the current ripple. Compared to the conventional closed-loop method, the proposed method does not need a phase-locked loop or resonant controller. Therefore, it has the ability to suppress current pulsation within a wide frequency range, and can achieve improved dynamic performance due to the fast convergence. Experimental results confirm the expected performance of the proposed method.