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Flying capacitors (FCs) are very important in multilevel inverter systems when it comes to synthesizing additional voltage levels for various medium-voltage industrial applications, including renewable energy, motor drives, and power transmission. In particular, they are responsible for forming the five-level output pole voltages in five-level hybrid active neutral-point-clamped (ANPC) topologies. This is only possible when the FCs reach their reference values (i.e., 25% of the DC-link value). When a five-level hybrid ANPC inverter operates in the high-frequency (HF) range, the output three-phase current waveforms are less distorted when compared to the low-frequency (LF) performance. Instantaneously achieving a five-level output pole voltage during HF operation is a challenging task. This is due to the large capacitance of some existing types of FCs. In this study, a novel analysis of the effects of a FC on the performance of a five-level hybrid ANPC inverter is presented with simulation and experimental validations. Film capacitors significantly enhanced system performance when compared to electrolytic capacitors due to their many advantageous features, including the ability to charge and discharge quickly during HF operation. In addition, the total harmonic distortion of the output pole voltage is significantly suppressed. Consequently, the size of the required filter can be reduced. Therefore, the proposed system is highly desirable for various industrial applications. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of a DC-link capacitor under open-switch failures in hybrid active neutral point clamped (ANPC) inverters that consist of Si-IGBTs and SiC-MOSFETs. Open-switch failures cause the current harmonic distortion of DC-link capacitors. This distorted current affects the capacitor loss increase, which in turn affects the lifetime decrement of the DC-link capacitor. These influences of open-switch failures on inverter operation have not been discussed despite the fact that they lead to secondary failures of the system. In this paper, the influence of open-switch failure is analyzed based on the current harmonics of the DC-link capacitor, which experiences the highest failure rate. Simulation and experimental results demonstrate the effects of various open-switch failure scenarios on DC-link capacitors in terms of current harmonics and lifetime. [ABSTRACT FROM AUTHOR]