DC-Link Voltage Fluctuation Suppression Strategy for Electrolytic Capacitorless PMSM Drives Under Grid Background Harmonics

The virtual admittance reshaping strategy based on specific harmonic suppression can effectively suppress LC resonance for electrolytic capacitorless permanent magnet synchronous motor (PMSM) drives, yet its performance relies on the periodic characteristics of the DC-link voltage under ideal grid conditions. In this article, a DC-link voltage fluctuation suppression strategy based on rectified voltage harmonic disturbance decoupling is proposed. An analytical model describing the harmonic suppression capability of the traditional strategy under grid background harmonics is established, which can reveal the nonlinear disturbance mechanism of damping performance caused by the variations of grid harmonics. Different from the conventional methods, the proposed modeling method models the small signal of rectified voltage as a disturbance term. Therefore, a harmonic decoupling mechanism between the disturbance term and the closed-loop vector control system is constructed, which can enhance the capability to mitigate DC-link voltage fluctuations under grid background harmonics. Considering the incomplete decoupling problem caused by digital control delay, the decoupling branch is optimized as a virtual admittance. Meanwhile, the DC-link voltage harmonic factor is constructed to provide theoretical guidance for the parameter design of virtual admittance. Experimental results validate the effectiveness of the proposed scheme.