Graphical Evaluation of Time-Delay Compensation Techniques for Digitally Controlled Converters

Abstract

A main design constraint of the digitally controlled power electronics converters is the time delay of control systems, which may lead to the reduced control loop bandwidth and even unstable dynamics. Numerous time-delay compensation methods have been developed, of which the model-free schemes are independent to model accuracy whereas the model-based alternatives are sensitive to system modeling. This paper first presents a graphical illustration of four model-free delay compensation techniques, where their principles and performances are intuitively elaborated and compared by means of the impulse area equivalence method. An improved time-delay compensation approach is then proposed based on additional area insertion, which provides a wider frequency of phase compensation. Finally, the dynamic response of an LCL-filtered grid-connected inverter was tested with the studied delay compensation methods. Simulations and experimental test results validate the effectiveness of the graphical comparisons and the proposed approach.