Modeling and Analysis of Operating Limits of the Differential Boost Inverter

Abstract

The differential boost inverter (DBI) is a single-stage step-up topology composed of two bidirectional boost converters whose outputs are connected in differential mode to generate an AC output voltage. The DBI poses significant modeling challenges, since all variables operate with both DC and AC components, requiring a highly complex dynamical model to accurately capture its behavior. Also, the operating range of this converter is restricted both in the modulation indexes, which are limited to the interval between 0 and 1, and in the capacitor voltage, which must always be above the input voltage. In addition, a large harmonic content in the converter variables when working at certain operating points can increase the total harmonic distortion (THD), degrading the performance. This work presents a model that considers both the DC and fundamental AC components of the converter variables. Based on this model, the allowable operating ranges for the modulation indexes and capacitor voltages are defined. Furthermore, the model is extended to determine the harmonic content of the capacitor voltage, enabling the identification of the operating ranges in which a low THD is achieved. The proposed analysis introduces a flexible DC component in the modulation, without assuming a fixed DC bias, which broadens the valid operating region and enhances the potential for THD minimization. Finally, a DBI prototype has been built to validate the model and analysis, with experimental results confirming the mathematical relationships at representative operating points.