Admittance Reshaping Based on Adaptive Minimum Value of DC-Link Voltage for IPMSM Drive With Small Film Capacitor

The cascade system stability and grid-side power quality are significant concerns for the single-phase input interior permanent magnet synchronous motor (IPMSM) drive system with small film capacitor. The characteristic of port equivalent circuit of grid side–dc link–inverter side is analyzed, and the model of inverter-side equivalent admittance is established considering the power fluctuation and motor dynamic. The essence of the cascaded system instability is investigated, which reveals the mismatch between the front and rear ports and hence simplifies the stability judgment with Nyquist criterion. To deal with the cascade system instability and LC resonance, an admittance reshaping method based on the adaptive minimum value of dc-link voltage is proposed, which avoids extra sensors for grid current detection and maintains the inherent active damping effect of dc-link voltage. The resonance component under different cases of minimum value is analyzed in detail and is obtained based on the adaptive minimum value of dc-link voltage, which removes the phase delay and reduces inevitable compensation error to a large degree. In addition, the grid-side power quality is evaluated through the grid-side input admittance. Experimental validations have been presented to confirm the effectiveness of the proposed method.