Analysis and Validation of a Novel Symmetrical Structure for Toroidal Variable Power Inductors in Energy Storage Systems

This article presents an analysis of an alternative variable inductor (VI) structure compared to the ones previously proposed in the literature. The inductor is constructed based on a toroidal core and presents some prosperous advantages, which are a reduced induced voltage in the dc bias control windings and a symmetrical operation while making use of the simplicity of a toroidal magnetic core. The proposed VI topology is applied to a specific case study: the design and implementation of a bidirectional boost converter for integration of battery energy storage systems (ESSs) into dc grids. The variation of the inductance in this application provides an extra degree of freedom in the design, which offers twofold improvement to the controlled system. On the one hand, it allows the system to keep the same impedance throughout the operation range. This guarantees that the behavior of the controlled system will remain the same and avoids the need to change the controller tuning and parameters each time the state of charge (SOC) of the battery varies. Also, on the other hand, it enables control over the voltage and current ripple through the battery without the need to install extra capacitor banks. The design, assessment, and experimental procedures of the proposed VI structure for this application case are shown in this article. The results show an improvement in the performance of the selected case study.