Samer Saleh Hakami, Sadeq Ali Qasem Mohammed, and Kyo-Beum Lee, "An Optimized Hybrid Unipolar PWM Technique for Ripple Reduction in Flying Capacitor of 5L-ANPC Converters," IEEE Transactions on Industrial Electronics, in press. -SCI > Paper

Five-level active neutral-point-clamped (5L-ANPC) converters have emerged as promising solutions for various industrial applications owing

to their outstanding performance and control simplicity. Unipolar pulse-width-modulation (PWM) is a widely adopted control strategy for these

converters, known for its capability to generate a desired five-level output voltage while maintaining balanced dc-link and flying capacitor (FC)

voltages. However, unipolar PWM frequently results in significant ripple currents in FCs, potentially diminishing their lifespan and overall

system reliability. To address this challenge, this paper proposes current ripple-reduction strategies over a wide modulation index (MI) range.

Six ripple-elimination methods are presented and compared against the conventional unipolar PWM. These methods aim to significantly

reduce FC current ripples while ensuring acceptable levels of output voltage distortion. A hybrid switching method tailored to accommodate 

various MI operations is suggested. It can enhance the performance and reliability of these converters in various industrial applications.