Control Method of Electrolytic Capacitor-less Dual Inverter for Harmonic Compensation Under Distorted Grid Voltage

This paper proposes a harmonic compensation method using an open-ended winding IPMSM driven by an electrolytic capacitor-less dual inverter in a motor drive system. In the conventional electrolytic capacitor-less single inverter, harmonics caused by the DC-link voltage ripple frequency are superimposed on the motor phase current under a distorted input voltage. As a result, the reliability of the motor drive system is reduced, and the torque ripple causes mechanical vibration and noise. Using the proposed control method, the compensating inverter outputs the harmonic voltage superimposed on the estimated motor winding voltages. The experimental results show that compared to the conventional electrolytic capacitor-less single inverter, the proposed system reduces the maximum peak-to-peak of motor current by 8 %, and the shaft torque ripple caused by a distorted input voltage by 75 %. For motor drive systems without energy buffer that are driven under a distorted grid voltage, the proposed control method improves reliability and reduces mechanical vibration and noise.