A Novel Z-Type Modular Multilevel Converter With Capacitor Voltage Self-Balancing for Grid-Tied Applications

The modular multilevel converter (MMC) has been proven to be an effective solution for grid-tied applications with medium/high voltage ratings. The MMC contains a large amount of floating capacitors, which require the voltage balancing control. The voltage balancing control complexity is normally increased with the number of floating capacitors. As a result, the computation burden of the controller as well as the corresponding hardware cost will be high. This article proposed a novel Z-type MMC, which can achieve capacitor voltage self-balancing without any balancing control. Therefore, the overall control of the converter is significantly simplified. Both mathematical analysis and experimental results have confirmed the effectiveness of the proposed method.