Time-Step-Adaptive-Bilinear (TSAB) Second-Order Digital Filter Design for Variable Sampling Frequency Control of Power Converter

This paper proposes a time-step-adaptive-bilinear (TSAB) digital filter design method considering the effect of the previous sampling time step on the filter response for variable sampling frequency (VSF) control. In this paper, second-order filters are carefully designed to ensure the accurate filter response as the original continuous filter under VSF with discretized integral equation accompanying prewarping. The frequency response of the digital filters and the experimental results of the single-phase totem-pole AC-DC converter show the superiority of the proposed method compared to the conventional method under randomized sampling frequency (15-35 kHz). The proposed principle has a promising potential for digital control of power converters under VFC.