Active damping of power converters with modular basic crossover correction cells

High-precision applications typically demand very-low ripple, fast response, and high efficiency. The newly proposed concept of Basic Crossover Correction Cell (B3C) aims to achieve exactly that by processing the current ripple independently from the main bulk current. As a consequence, correction cells can be constructed from lower-power switching devices with reduced stress, as compared to conventional multi-level and cascaded converters. However, to separate the ripple current from bulk, shunt inductors and DC current blocking capacitors are employed, and give rise to more complicated converter dynamics. The internal converter dynamics leads to unwanted oscillations at the output during transitory operation, and thus needs to be actively controlled to achieve fast dynamic response. The focus in this paper is on control relevant modeling of the converter and compensation of the unwanted dynamics. A revised modulation scheme is proposed for the B3C, which allows direct control of internal resonances. Two control methods employing it are discussed, i.e., distributed virtual resistance damping and observer-based state feedback. Control strategies are evaluated in simulation and compared to more conventional alternatives as state-feedback with the original modulation scheme and passive damping.