Online control of current-source-type active rectifier using transfer function approach

Current-source topology AC/DC converters (buck converters) operated using pulsewidth modulation have significant drawbacks in lack of line current control and AC-side filter damping. Also, an AC-side filter is usually overrated in order to keep harmonic distortion under imposed limits. Discontinuous current at converter line inputs disables the use of current control techniques known from control of voltage-source converters. In order to overcome these problems, an online control method for the buck converter is presented in this paper. This method is based on the AC filter transfer function approach. Such an approach enables a novel solution for line-side filter optimization in the case of hysteresis line current control. This method leads to a filter with minimal apparent power (cost) and the fast and accurate converter's control response. Furthermore, a line current estimation method was developed. It uses only one current sensor at the converter DC side in order to estimate power supply currents. Suggested methods were numerically and experimentally verified.