Resonance Analysis and Suppression Strategy for Electrolytic Capacitor-less Permanent Magnet Synchronous Motor Drives

In the electrolytic capacitor-less PMSM drives, the LC resonance between small film capacitor in the DC bus and the inductance in the grid side is analyzed in this paper. Since the electrolytic capacitor is replaced by a small film capacitor in the DC bus, the LC resonance phenomena cannot be neglected, which will result in the underdamping characteristics of the electrolytic capacitor-less motor drives. Hence, the detailed model is established to reveal the resonance mechanism. Based on the model, a current harmonics suppression strategy is also proposed. The proposed control strategy can improve the power factor and reduce the current harmonics in the grid side. In addition, it can improve the system efficiency and enhance the stability of the drives. The proposed method is experimentally validated on an electrolytic capacitor-less PMSM drive applied in 1.5 HP variable frequency air-conditioner.