Fault-Tolerant Z-Source-based Isolated DC-DC Building Blocks for Mission-Critical DC Distribution Applications

This paper proposes Z-source-based isolated DC-DC building blocks with voltage gain boosting and fault tolerance capability. A modified Z-source impedance network along with a dc-dc dual active bridge (DAB) represents the main parts of the proposed topology. In addition to the Z-source impedance voltage gain feature, fault tolerance operation introduced by integrating a simple controller with the impedance network. Three operating conditions are investigated: shoot-through (ST) and non-shoot through (NST) as conventional operating conditions for Z-source impedance-based power converters, and fault handling operation. For each operating condition, a detailed mathematical representation is provided, which explains the proposed design approaches based on the specific application requirements. By taking advantage of ST state, the input dc voltage can be boosted using the Z-source impedance. For fault tolerance condition, the power switch at the input of the Z-source impedance network is replaced with a FET or an IGBT, instead of a diode, to realize fault tolerance for each building block. Simulation results are provided to validate the proposed concepts and the converter’s features. These building blocks can be very useful for mission-critical DC distribution applications such as subsea oil and gas, offshore wind, electric ships, aircrafts, etc.