Modelling and Robust Repetitive Control of PWM DC/AC Converters

Modelling and robust repetitive controller of constant-voltage constant-frequency (CVCF) pulse-width modulated (PWM) DC/AC converter systems are studied in this paper. During the design of feedback controller, the plug-in repetitive module is considered as one part of augmented plant to achieve overall system robustness performance. To overcome the inherent drawback of linear load model, the load changes are modelled as plant uncertainties by linear fractional transformation (LFT): linear load differences are treated as structured uncertainties, and the nonlinear loads are considered as unstructured uncertainties. The robust repetitive controlled converter systems will have the robustness performance as well as periodic disturbance rejection performance in the presence of various loads. Experimental results verified the effectiveness of the proposed scheme.