Switching loss analysis of modulation methods used in neutral point clamped converters

Multilevel converters are used in medium voltage high power applications. In this field, switching losses are an important efficiency issue due to long term operation costs. Previous works have centered the analysis in comparing different topologies or semiconductors in relation to switching losses. However, switching loses are closely related to the modulation method employed to control the converter. Therefore, the comparison of several modulation methods applied to a single topology can provide valuable insight for designing considerations. This paper presents a switching loss estimation method for Neutral Point Clamped (NPC) multilevel converters. The estimation method is based on experimental measurements of the power semiconductors together with a linearized switching model of the converter. In addition manufacturer datasheet information is used to represent more accurately different operating conditions. The estimation method is used to compare the switching losses produced by the most common modulation methods used for NPC converters. The main purpose of the paper is to provide quantitative results to compare the different modulation methods in terms of efficiency.