A New Postfault Control Method for CHB Inverter to Increase Maximum Output Voltage

Abstract

In this article, a new postfault control algorithm for cascaded H-bridge (CHB) multilevel inverter is proposed to increase the maximum available output voltage under semiconductor fault conditions. Once a semiconductor switch in an H-bridge power cell fails, instead of bypassing the faulty cell, it can be utilized to generate a voltage. However, one of the three levels (positive, negative, or zero) of the faulty cell output voltage is not available, reducing the available output voltage of the cell to half. In the proposed method, the faulty cells being utilized and combined with the neutral shift (NS) method to achieve a higher output voltage of the CHB in faulty conditions. The output voltage obtained by the proposed method is analyzed for different faulty conditions and compared with the conventional NS method. Experimental results are presented confirming the effectiveness of the proposed methods in increasing the maximum output voltage at different faulty conditions.