A hybrid high‐efficiency nine‐level inverter with high DC voltage utilization ratio

Abstract This paper proposes a new hybrid nine‐level inverter topology with high efficiency and high dc voltage utilization ratio, which provides a potential for renewable energy power conversion. The proposed inverter can synthesize up to nine voltage levels with only ten switching devices and a flying capacitor (FC). To improve the operation efficiency, a hybrid‐device topology based on Si and SiC is proposed. The total device cost of this inverter is much lower than the all‐SiC‐based inverter. Compared with other advanced multilevel inverters, a notable feature is the more comprehensive performance of the proposed inverter. In addition to having fewer components and higher efficiency, the dc voltage utilization ratio of the inverter is 2.5 times that of the traditional inverter such as Neutral Point Clamped (NPC), FC, and Active NPC (ANPC). A hybrid FC voltage balancing strategy based on redundancy switching states and three voltage levels step switching method is implemented to reduce FC voltage ripple. Besides, a cooperative voltage control strategy between the dc‐link capacitors and FC ensures the neutral‐point voltage balancing. The voltage stresses analysis and the design guidelines of components are discussed in detail. A comparison with some existing topologies has also been made to highlight its performance. Experimental results verify the validity of the proposed inverter topology and the control schemes.