Fault-Tolerant and Reliable Structure for a Cascaded Quasi-Z-Source DC–DC Converter

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Abstract
The present paper proposes a fault tolerant cascaded quasi-Z source DC-DC converter structure and investigates its reliability through a precise mathematical evaluation. In order to enhance the reliability of the suggested topology, a robust control method is considered, as well. According to the utilized control method, at the moment of fault occurrence, the defected modules are isolated from the converter by the virtue of some considered relays allowing the whole system keep working with the remained modules. Since the defected modules are eliminated from the circuit, the duty cycles of the switches will be changed through the controlling system, so that, the remained modules take the responsibility of maintaining the output voltage in the desired level. Operation principle of the converter along with the control method (consists of fault detection and elimination systems) are provided. Additionally, reliability evaluation technique is considered and, reliability comparison between the proposed, conventional and flyback structures is illustrated. Taking advantage of a laboratory built prototype, the practicality of the suggested structure is proven. The obtained results confirm higher reliability and Mean Time To Failure (MTTF) of the proposed converter compared to the conventional and flyback structures. Therefore, it could be counted as a suitable structure in sensitive industrial applications.

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