Modeling and design of multi-cell buck converters using InterCell Transformers for HVDC cable diagnostic

This paper presents the design of a new application for parallel multi-cell converters. The aim is to setup a portable system that can inject a 12000 A current within 2s in the conducting core of a HVDC cable, and determinate the distribution of electrical space charge through the insulation using the Thermal Step Method (TSM). This is an original application that contributes to the study of power cable reliability. The proposed structure will be constituted of ten paralleled coupled multiphase buck converters using InterCell Transformers (ICT). The magnetic coupling used in this structure does not need the use of additional filters (inductors and capacitors), which are weighty and expensive for a portable power converter. Ultracapacitors are used as power source because they offer the ability to carry the application for on-site measurements. An analytical model is developed in order to quantify the magnetic flux through the magnetic core and to optimize the ICT design. A prototype (four-phase coupled buck converter) was built in order to validate the transient principle and to confirm the magnetic coupler analytical model results.