Hybrid PWM Technique and Capacitor Voltage Balancing Control for Four-Level Asymmetrical Flying Capacitor Inverter

 This paper presents a novel hybrid PWM technique for the four-level asymmetrical hybrid flying capacitor (4L-AHFC) inverter, developed to enhance performance, simplify control, and reduce system cost compared to conventional multilevel inverter topologies. The proposed modulation strategy combines level-shifted and phase-shifted PWM methods to generate high-quality multilevel output voltage waveforms and achieve natural balancing of the flying capacitor voltages under steady-state conditions. To further address the issue of DC-link capacitor voltage imbalance, a zero-sequence voltage injection-based control algorithm is introduced, enabling active regulation of the DC-link voltages without requiring any additional balancing circuits or hardware components. Detailed simulation studies and comparative analysis with existing four-level inverter configurations demonstrate that the proposed approach significantly reduces total harmonic distortion, minimizes power losses, and lowers total standing voltage, resulting in approximately 20% cost savings over conventional hybrid flying capacitor designs. The simulation results confirm the feasibility and effectiveness of the hybrid PWM scheme and the capacitor voltage balancing strategy, making the proposed inverter an attractive solution for medium-voltage applications that demand efficient, compact, and reliable power conversion.

Keywords: Asymmetrical hybrid flying capacitor, hybrid pulse-width modulation, capacitor voltage balancing control, multilevel inverter, medium voltage application.