Multiport-Impedance-Optimization-Based Harmonic Suppression Strategy for Electrolytic Capacitorless PMSM Drives

Active damping strategies are commonly used for grid current harmonic suppression in electrolytic capacitorless motor drives. However, they lead to the increase of motor harmonics. In this letter, a multiport-impedance-optimization-based harmonic suppression strategy is proposed, which considers both grid current and motor current harmonics. A multiport impedance model is constructed, in which the rectifier voltage is served as the input, while motor current and dc-link current serve as outputs. Moreover, the impedance optimization index that quantifies harmonic content on the motor and grid sides is constructed. The voltage for regulating the port impedance is derived from the harmonic information of the system, which contains the motor torque and the dc-link voltage. An analysis is conducted on the effect of the angle of impedance regulation voltage on the impedance optimization index. The ideal angle can be determined using entropy-weighted technique for order of preference by similarity to ideal solution (TOPSIS). This enables vector synthesis of the port impedance regulation voltage under the co-optimization of port impedance, which improves the coordination between the quality of the grid current and the harmonics of the motor torque.