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<p>This paper proposes a family of hybrid single-flying-capacitor (HSFC) inverter topologies that can generate four to eight output voltage levels. Compared to conventional hybrid-clamped (HC) and hybrid flying-capacitor (HFC) inverters, the number of FCs and power switches in the proposed topologies is significantly reduced. However, due to the reduced component counts, they lack redundant switching states, complicating capacitor voltage balancing under conventional carrier-based PWM techniques. Specifically, level-shifted PWM cannot regulate both split DC-link and FC voltages without auxiliary circuits, whereas phase-shifted PWM produces constrained performance through the mismatch between the number of voltage levels and available switch pairs. To address these challenges, a novel modified carrier-overlapped PWM (MCOPWM) strategy is developed. In this PWM method, virtual duty ratios are first derived using the conventional COPWM scheme. Then, they are transformed into actual switching signals through a logic-based gating signal generation stage. A dedicated voltage balancing method, using offset injection and state swapping, ensures effective regulation of all the capacitor voltages without additional hardware. The proposed topology and control scheme are validated through simulations of an 11&#xa0;kV / 1 MVA system and experimental results from a 4.7 kVA HSFC inverter prototype.</p>

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Capacitor voltage balancing for hybrid single-flying-capacitor multilevel inverters

  • 期刊论文

  • 发表日期：

    2026年5月5日

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  • Jonathan Pribadi,
  • Dinh Du To,
  • Min-Seok Kim,
  • Dong-Choon Lee

摘要

This paper proposes a family of hybrid single-flying-capacitor (HSFC) inverter topologies that can generate four to eight output voltage levels. Compared to conventional hybrid-clamped (HC) and hybrid flying-capacitor (HFC) inverters, the number of FCs and power switches in the proposed topologies is significantly reduced. However, due to the reduced component counts, they lack redundant switching states, complicating capacitor voltage balancing under conventional carrier-based PWM techniques. Specifically, level-shifted PWM cannot regulate both split DC-link and FC voltages without auxiliary circuits, whereas phase-shifted PWM produces constrained performance through the mismatch between the number of voltage levels and available switch pairs. To address these challenges, a novel modified carrier-overlapped PWM (MCOPWM) strategy is developed. In this PWM method, virtual duty ratios are first derived using the conventional COPWM scheme. Then, they are transformed into actual switching signals through a logic-based gating signal generation stage. A dedicated voltage balancing method, using offset injection and state swapping, ensures effective regulation of all the capacitor voltages without additional hardware. The proposed topology and control scheme are validated through simulations of an 11 kV / 1 MVA system and experimental results from a 4.7 kVA HSFC inverter prototype.