Frequency-Divided Control and Stability Analysis of Single-Phase Three-Level Flying Capacitor Boost Inverter

The single-phase three-level flying capacitor (TLFC) boost inverter is a power converter with active power decoupling without requiring additional components. However, it has the characteristic that the number of control degrees of freedom is fewer than the number of control targets, which poses a challenge to controller design. To address this issue, this article proposes a frequency-divided control method for the TLFC boost inverter. According to the frequency-divided idea, the decoupling control input of the system is divided into a dc component and an ac component design. The dc component regulates the flying capacitor’s average voltage, and the ac component suppresses the dc bus voltage’s pulsation. The proposed method can effectively suppress the double-line-frequency ripple in both the input current and the bus voltage and exhibit high robustness. Furthermore, considering that the TLFC boost inverter is a nonlinear periodic time-varying system, a single-input single-output (SISO) admittance model is developed to analyze the system’s stability under the proposed control method. Finally, a 1.5-kW hardware prototype is built to validate the effectiveness of the proposed control method and stability analysis.