High-Definition High-Bandwidth DC/AC Power Conversion Through Binary Asymmetric Cascaded H-Bridges

It is known that cascaded H-bridges with heterogenous module voltages can, in theory, generate exponentially-refined output voltage levels and achieve high output resolutions from only one power source. However, several critical considerations have yet to be thoroughly studied, namely the controllability of module voltages under any load conditions, and how to schedule the switching states optimally. We present a scheduling algorithm and topological modifications for binary asymmetric cascaded H-bridges (ACHBs) to achieve complete sensorless operation under any load conditions while using only one power source. The scheduling algorithm cancels the energy intake of floating modules per time frame, while low-power auxiliary dc/dc circuits, which naturally emerge from the bridge structure, can correct any voltage drift without the need for voltage sensors. Rigorous analyses reveal an inherent performance tradeoff between reference-tracing accuracy and floating module voltage controllability for ACHBs in general, for which the proposed algorithm always achieves the Pareto front. The proposed ACHB and the algorithm are tested on an experimental setup with six modules and 65 output levels (i.e., effectively six bits).