On reliability of medium voltage multilevel converters

In this paper, the reliability of medium voltage multilevel converters based on cascaded cells is investigated. Limits of reliability prediction and redundancy application are shown. Opportunities to leverage converter predicted reliability with redundancy are analyzed. Special attention is given to the impact of the bypass device on converter reliability. The analysis shows significant influence of redundancy on power stage failure rate reduction. At a certain redundancy level though, control hardware will play a dominant limiting role in converter reliability. The analysis also shows the existence of maximum power stage redundancy level for a given bypass failure rate. Exceeding this level results in reduction of converter reliability. This work was carried out within the frame of European FP7 program and its support is gratefully acknowledged.