Multifrequency Current Control Including Distortion-Free Saturation and Antiwindup With Enhanced Dynamics

Output-voltage saturation (OVS) in voltage source converters can produce current-control windup. Many OVS and antiwindup (AWU) methods exist for a single-frequency current controller, but they cause additional distortion when applied to multifrequency current control. The latter is important, e.g., for reducing losses in various applications or torque ripple in ac drives. In the existing strategies with distortion-free OVS and AWU for multifrequency current control, the nonlinear effect of the OVS to the hexagon (OVSH) on the dynamics is neglected. Thus, the actual system can have bad dynamics or even be unstable. This letter proposes a multifrequency current control with distortion-free OVS and AWU where this problem is solved. An internal-model-control scheme is included to remove the OVSH nonlinear effect from the control loops, yielding better dynamics. Experimental results are provided.