Three-phase Dual-active Bridge DC-DC Converter Research Articles

Modelling and compensation of dead time in three-phase dual-active bridge DC-DC converter

ABSTRACT With growing decentralized power generation, medium-voltage (MV) dc-dc converters are becoming increasingly important. A three-phase dual-active bridge (DAB3) is a promising topology for high-power MV applications. The semiconductor devices used in such converters at multi-megawatt level tend to be slow in switching. Hence, a considerable dead time between switching instants is required to avoid shoot-through in phase legs. This dead time forces the current to commutate to the freewheeling diodes and introduces a current dependence of the phase voltages. In this work, the effects of dead time on the operation of DAB3 are analysed in detail. The derived analytical expressions are used in the control development to compensate for the effects of dead time and hence achieve superior control performance. Measurements are carried out on a small-scale laboratory prototype to validate the derived operational modes and the effectiveness of the proposed dead time compensation.