Voltage-balancing method using phase-shifted PWM for the flying capacitor multilevel converter

Amer M. Y. M. Ghias, Josep Pou, Mihai Ciobotaru, Vassilios G. Agelidis

Research output: Contribution to journalArticlepeer-review

71 Citations (Scopus)


Multilevel flying capacitor (FC) converters provide natural capacitor voltage balance under phase-shifted pulse width modulation (PS-PWM). However, natural balancing may not be robust enough to maintain the voltages at the reference values, especially under certain transient conditions. Furthermore, natural balancing dynamics depend on the load and it may be very slow in some practical applications. Therefore, a more robust balancing mechanism of maintaining the FC voltages at the desired values is required. This paper proposes a new closed-loop voltage-balancing method for the multilevel FC converters using PS-PWM. The proposed method balances the voltages of the FCs by modifying the duty cycle of each switch of the FC converter using a proportional controller. The crossed effect between FC currents and duty cycles is considered and is used for optimal FC voltage balancing. Simulation and experimental results verify that the proposed voltage-balancing method is very robust to different operating conditions, such as load transients, linear/nonlinear and unbalanced loads.
Original languageEnglish
Pages (from-to)4521-4531
Number of pages11
JournalIEEE Transactions on Power Electronics
Issue number9
Publication statusPublished - Sep 2014
Externally publishedYes


  • Capacitor voltage balancing
  • flying capacitor (FC) converter
  • multilevel converter
  • phase-shifted pulse width modulation (PS-PWM)


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