A Novel Hybrid Modulation Method for a Five-Level Hybrid Clamped Converter with Low-Frequency Voltage Ripple Suppression and Harmonic Performance Enhancement

The hybrid clamped (HC) converter cannot suppress low-frequency voltage fluctuations of the DC-link capacitors at low power factors. Rather, it exhibits a slow dynamic response and high output harmonics in such scenarios. To address this limitation, this study presents a novel hybrid modulation method that maintains the natural capacitor voltage balance while combining two basic modulation strategies: one minimizes neutral-point (NP) current to suppress low-frequency fluctuations, and the other maximizes NP current to enhance the dynamic response. The method further bolsters harmonic performance through carrier redistribution. Then, the proposed method dynamically switches between two basic modulation methods based on real-time NP current optimization while calculating the required zero-sequence voltage (ZSV) for active voltage balancing. The proposed hybrid modulation method thus inherits the merits of these basic modulations. Finally, the method is validated under various experimental conditions, with the results highlighting its advantages.