Introduction Multilevel Voltage Source Modulation Fundamental Multilevel Converter Topologies Diode-Clamped Multilevel Converters • Flying-Capacitor Multilevel Converters • Cascaded H-Bridge Multilevel Converters • Multilevel H-Bridge Converters Cascaded Multilevel Converter Topologies Cascaded Multilevel Converters • Cascaded Multilevel H-Bridge Converters Multilevel Converter Laboratory Examples Three-Level Diode-Clamped Inverter • The Cascade-3/2 Inverter • The Cascade-5/3H Inverter Conclusion Introduction Multilevel power conversion was first introduced 20 years ago [1]. The general concept involves utilizing a higher number of active semiconductor switches to perform the power conversion in small voltage steps. There are several advantages to this approach when compared with traditional (two-level) power conversion. The smaller voltage steps lead to. | 6 Multilevel Converters Keith Corzine Introduction University of Wisconsin-Milwaukee Multilevel Voltage Source Modulation Fundamental Multilevel Converter Topologies Diode-Clamped Multilevel Converters Flying-Capacitor Multilevel Converters Cascaded H-Bridge Multilevel Converters Multilevel H-Bridge Converters Cascaded Multilevel Converter Topologies Cascaded Multilevel Converters Cascaded Multilevel H-Bridge Converters Multilevel Converter Laboratory Examples Three-Level Diode-Clamped Inverter The Cascade-3 2 Inverter The Cascade-5 3H Inverter Conclusion Introduction Multilevel power conversion was first introduced 20 years ago 1 . The general concept involves utilizing a higher number of active semiconductor switches to perform the power conversion in small voltage steps. There are several advantages to this approach when compared with traditional two-level power conversion. The smaller voltage steps lead to the production of higher power quality waveforms and also reduce the dv dt stresses on the load and reduce the electromagnetic compatibility EMC concerns. Another important feature of multilevel converters is that the semiconductors are wired in a series-type connection which allows operation at higher voltages. However the series connection is typically made with clamping diodes which eliminates overvoltage concerns. Furthermore since the switches are not truly series connected their switching can be staggered which reduces the switching frequency and thus the switching losses. One clear disadvantage of multilevel power conversion is the larger number of semiconductor switches required. It should be pointed out that lower voltage rated switches can be used in the multilevel converter and therefore the active semiconductor cost is not appreciably increased when compared with the two-level case. However each active semiconductor added requires associated gate drive circuitry and adds further complexity to the converter mechanical .
