Capacitor Damage-Based Power Routing Strategy in ISOP-DAB Converters for Smart Grid

The solid-state transformer (SST) is gaining popularity in smart grid for its high flexibility and high controllability. However, the application is limited by its low reliability and the required high maintenance costs. To improve the system reliability and optimize the maintenance schedules, power routing has been widely studied recently. Most power routing strategies allocate power among cells based only on power semiconductor devices (PSDs) damage, but ignore capacitors, another key component in power electronic converters, which may greatly weaken the ability of power routing to converge the lifetimes of cells and reduce the number of maintenances. To analyze the influence of capacitors on power routing, this paper has compared PSD damage-based power routing with the power routing strategy considering both the damage of capacitors and PSDs for the input-series-output-parallel (ISOP) connected dual active bridge (DAB) converter, and found that capacitors wear out much faster than PSDs. Therefore, a capacitor damage-based power routing strategy is proposed for the system where capacitors dominate its reliability. It can achieve the same effect as the power routing strategy considering both capacitors and PSDs, while balancing accuracy and computation time, and greatly reducing the hardware complexity. Validity of the proposed strategy is verified by simulation in MATLAB.