Efficacy of STC in Magnetically Coupled High Frequency Power Electronics Systems: Full-Bridge DC-DC Converter

Abstract

Due to its simple gain selection and implementation procedures high-gain sliding mode control idea was introduced. Apart from achieving robustness features, the aim was to reduce product-design cycle time. To overcome its basic chattering issues, it was replaced by complex super twisting control (STC). Subsequently, the research in this field has been extensive, intense and persistent. The idea has been validated in several applications generating great hope in minds of industry experts. Its real success, however, would depend on its adoption and diffusion into industry domain, where an analysis of validating STC based products is due. In STC, selection of gains is based on worst-case values of disturbance and/or its derivative. Can such procedure ensure controller’s reliable functioning? This article proposes that such simplistic procedure of gain selection may not work for power electronics controllers where, particularly, the actuation or controlled power transfer to load is through magnetically-coupled system. Using practical approach, this article elaborates that optimally designed transformer, driven by high-gain super twisting controller, invites problem of core saturation leading to higher switching losses, poor operating duty cycle of the system and there could be problem of reliability. It further details an alternate high-gain controller that generates superior efficacy.