Double-Frequency Sampling Impact on Dynamic Model of Half-Wave Symmetric Converters

This work examines the impact of symmetric twice-per-period sampling frequency on the dynamics of AC-link power converters. A series–series resonant converter, comprising both AC and DC state variables, is considered for the analysis. The AC states, associated with the tank circuit, exhibit half-wave antisymmetry, while the input and output DC states contain double-frequency components. As a result, all DC states can be regarded as half-wave symmetric with respect to the switching period. Discrete-time (DT) modeling is an effective technique for analyzing such high-frequency converters, offering improved prediction of high-frequency dynamics. In conventional DT modeling, sampling is performed once per switching period, resulting in a full-cycle model. However, when the converter states exhibit half-wave symmetry, this property can be leveraged to develop a half-cycle model. Such a model reduces the number of subintervals and, consequently, the number of differential equations to be solved, thereby lowering computational effort. This approach necessitates twice-per-period sampling and allows control updates at twice the switching frequency. This study explores the impact of such double-frequency sampling on the frequency response of the DT model, in comparison to the conventional once-per-period-sampling. The converter dynamics are captured experimentally and compared with the dynamics of half-cycle (hc) and full-cycle (fc) DT model.