Disturbance Observer-Based Active Damping Control for Electrolytic Capacitor-Less PMSM Drives

The electrolytic capacitor-less permanent magnet synchronous motor (PMSM) drives have the advantages of high-power density, low cost, and long service life. However, the interaction between the LC resonance and the negative impedance characteristic of PMSM may lead to an instability issue in the drive system. The harmonic contents near the resonant frequency in the grid-side current also increase significantly. The above issues are detrimental to achieving a high input power factor and stable control of the drive system. In this article, the impedance model of the drive system is established first to analyze the stability of the system. Secondly, a novel active damping control method is proposed to improve the stability of drive system and suppress the harmonics of grid-side current. The active damping control method in electrolytic capacitor-less system requires the information of grid-side current or rectifier output current, which is usually achieved by adding a current sensor. In contrast, a super-twisting sliding mode-based disturbance observer is designed to estimate the rectifier output current, thereby further reducing the hardware cost. The effectiveness of the proposed method is verified by experimental results.