A comparative benchmark of digital delay compensation techniques based on a graphical approach

For a converter using the digital processor for control system, the digital time delay is a main reason to reduce the system bandwidth, leading to a relatively slow dynamic or even unstable operation. To alleviate the negative impacts of digital delays, 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 presents a graphical illustration of state-of-art model-free delay compensation techniques, where their principles and performances are intuitively and immediately elaborated and compared by means of the impulse area equivalence method. Then, 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.