Paralleled H-Bridge Multilevel Switching-Cell Current Source Inverter

The paralleled H-bridge multilevel current source inverter (PHB-MLCSI) is widely used in industry, especially for high-power and medium-voltage applications. Even so, the risk of an open-circuit fault (OCF), which is the most common and destructive failure among all conventional CSIs also jeopardizes the reliability of the standard PHB-MLCSI. To overcome this major shortcoming, a new topology called paralleled H-bridge multilevel switching-cell current source inverter is introduced in this article. Thus, OCF is no longer an issue in the proposed topology, even if it occurs frequently or is caused by switch turn on mismatch/delay among all complementary switches in every switching cycle. The phase-shifted pulsewidth modulation (PS-PWM) method is used to control the proposed topology due to the following two reasons: 1) other PWM schemes, such as level shifted and low/fundamental frequency or half-cycle PWMs cannot overcome OCF if it occurs frequently; 2) mismatches in gating signals, tolerance in parameters of the input dc smoothing inductors (chokes), and unequal input dc voltage values are other concerns in the PHB-MLCSI that may deteriorate the performance of the converter. The PS-PWM method with redundant switching states is a proper modulation technique to handle all the aforementioned mismatch issues to an acceptable level. A variety of experimental tests are conducted to validate the feasibility of the proposed solution. Finally, a comparison is drawn between the proposed circuit and three other existing MLCSIs, further highlighting its distinctive features.