Reliability improvement based on optimized modulations and rotating shedding frequency in modular DAB EV chargers

Modular dual-active-bridge (DAB) converter is widely used for fast electric vehicle (EV) charging due to galvanic isolation and high power processing capability. However, the increasing high power demand for EV chargers introduces new challenges in ensuring the high reliability of power conversion systems. Various modulation techniques for DAB, such as single-phase-shift (SPS), extended-phase-shift (EPS), and dual-phase-shift (DPS), have been proposed, while the combined impact of these techniques and power sharing strategies on reliability remains underexplored. Therefore, this paper presents a comparative reliability evaluation of SPS, EPS, and DPS under the optimization schemes of minimum backflow power and peak current, along with the power sharing strategies of even sharing and module shedding with and without rotation. The results show that appropriate combinations where DPS with minimum peak current under module shedding with a rotation strategy achieve the best balance between efficiency and reliability. Furthermore, the investigation of the trade-off between rotation frequency and system-level reliability shows that high-frequency rotation leads to excessive thermal cycling and reduces the lifetime, which provides a new guideline for optimizing module shedding for increased reliability performance.