Reliability Analysis Based on Markov Model, Economic Feasibility, and Efficiency Comparison for a Cascaded H-Bridge Multilevel Inverter Capable of Generating 27 Levels

A cascaded H-bridge multilevel inverter (CHBMI) can increase the number of output voltage levels by increasing the number of H-bridge modules, thereby achieving low dv/dt stress and good total harmonic distortion (THD). However, as switching devices increase due to increased H-bridge modules, control becomes complicated, and the failure rate may rise. This paper analyzes the reliability of a CHBMI that can generate 27 levels, including failures in some H-bridge modules. The Markov model of a method with 13 H-bridge modules using a swapping control algorithm (Type 1) and a form with 3 H-bridge modules with input voltage sources of Vdc, 3Vdc, and 9Vdc (Type 2) was obtained, and reliability was calculated. To analyze the effect of redundancy on reliability, a reliability analysis is also performed for the two cases where two H-bridge modules are added to Type 1. Finally, we aim to help select a 27-level inverter method by comparing economic feasibility and switching loss based on the cost model.