Single-Phase 5-Level Split-Midpoint Cross-Clamped (5L-SMCC) Inverter: An Alternative to the Two-Stage ANPC Topology

The conventional active neutral-point-clamped (ANPC) multilevel inverters are popular for single-phase applications owing to their advantage of mitigating high-frequency common-mode voltage (CMV). With the ac neutral connected to the midpoint of dc link, their voltage gain is restricted to only half. For boosting output voltage, a two-stage structure by adding a frontend dc-dc boost converter is commonly used. This article investigates the performance of the conventional two-stage 5-level ANPC inverter and proposes an improved topology by splitting the dc-link midpoint and cross clamping them to the dc-link capacitors. While using the same number of power devices and retaining the advantages of the conventional two-stage 5-level ANPC topology, such as high-frequency CMV mitigation and continuous dc source current, the proposed 5-level split-midpoint cross-clamped (5L-SMCC) inverter achieves several advantages, such as higher voltage gain, lower voltage across dc-link capacitors, lower inverter voltage stress, and natural voltage balancing for all capacitors without requiring any balancing controller or sensor. In addition, it saves one capacitor by eliminating the flying capacitor of the conventional 5-level ANPC inverter. The operation of the proposed 5L-SMCC inverter is thoroughly analyzed. For validation, simulation and experimental results are presented.