Generalized Enhanced PWM for Multilevel Current Source Inverters

In power electronic converter topologies, when voltage and current stresses on power devices differ while operating at the same switching frequency and enduring these stresses for equal durations, power losses cannot be evenly distributed. Consequently, devices subjected to higher voltage or current stress may have a shorter lifespan than others. Furthermore, designing an optimal cooling system (e.g., fans, heatsinks) becomes more complex in such converters. Another limitation of almost all conventional power converters is the need for dead-time in voltage source inverters (VSIs) and overlap-time in current source inverters (CSIs), which must be inserted between complementary switches. However, the presence of these intervals can increase the total harmonic distortion (THD). Furthermore, practical issues such as rising and falling delays in gate signals during switching transitions can cause shoot-through problems in VSIs and arm open-circuit fault in CSIs. To overcome these shortcomings, this article proposes a pulse-width modulation (PWM) method called generalized enhanced PWM (GE-PWM). To fully investigate the features of the proposed modulation method, a recently developed fault-tolerant five-level switching-cell current-source inverter (FT-SC²SI) was selected as a case study, and the proposed PWM was applied to it. Extensive theoretical analysis, supported by experimental results, validates the effectiveness of the proposed solution and its findings.