A Hybrid Nine-Level Inverter With Reduced Components and Simplified Control

Abstract

To reduce component count and realize the self-balance of capacitors, a hybrid inverter is proposed in this article, which is the combination of a switched-capacitor (SC) cell and flying capacitor (FC) structure. Due to the introduction of FC, the inrush charging current is limited, which reduces the current stress. The significant advantages of the proposed topology are embodied in the reduced component count, simplified control, and voltage-boosting capacity. Four pairs of complementary switches, a diode, and only two capacitors are employed to generate nine levels. The FC can naturally balance at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5V_{\text {dc}}$ </tex-math></inline-formula> for a given operating cycle, enabling a sensorless operation. Therefore, the simplified control is reflected in the inherent voltage balance of capacitors and four independent control signals from the controller. Also, the system cost is greatly reduced. Self-balance, the assessment of the charging process, and loss calculation have been introduced. Afterward, quantitative comparison and loss compared with the recently proposed nine-level inverter are conducted, demonstrating the merits of reduced active components, simplified control, high cost-effectiveness, and low power loss. Finally, experimental results are given to validate the feasibility of the proposed topology.