A new class of single-phase multilevel inverters

Multilevel power converters make it possible to use mature but voltage-limited power semiconductors in high voltage, high power industry and utility applications. Different from high frequency approach, the concept of direct output synthesizing provides efficient power conversion with the advantages of better harmonic cancellation and compact ac filtering. Conventional multilevel inverters, including diode-clamped, flying capacitor, and cascaded H-bridge, are well defined but become clumsy for higher levels. This paper proposes a new single-phase full-bridge multilevel topology, which requires less split-rail dc sources and significantly reduced semiconductor switch devices. An n-capacitor switching problem is proposed and analyzed, which leads to the new class of generalized multilevel structure featured with asymmetrical dc sources and maximized output levels. Cascading basic five-level cells provides another structure to build higher-level inverters with separate dc sources. The proposed multilevel inverters can be potential for solar photovoltaics and energy storage applications.