Recent research in flying capacitor multilevel inverters (FCMIs) has shown that the number of voltage levels can be extended by changing the ratio of the capacitor voltages. For the three-cell FCMI, four levels of operation are expected if the traditional ratio of the capacitor voltages is 1:2:3. However, by altering the ratio, the inverter can operate as a five-, six-, seven-, or eight-level inverter. According to previous research, the eight-level case is referred to as maximally distended (or full binary combination schema) since it utilizes all possible transistor switching states. However, this case does not have enough per-phase redundancy to ensure capacitor voltage balancing under all modes of operation. In this paper, redundancy involving all phases is used along with per-phase redundancy to improve capacitor voltage balancing. It is shown that the four- and five-level cases are suitable for motor drive operation and can maintain capacitor voltage balance under a wide range of power factors and modulation indices. The six-, seven-, and eight-level cases are suitable for reactive power transfer in applications such as static var compensation. Simulation and laboratory measurements verify the proposed joint-phase redundancy control.


Electrical and Computer Engineering

Keywords and Phrases

Converter; Capacitor Voltage Balancing; Flying Capacitor; Flying Capacitor Multilevel Inverters; Inverter; Invertors; Joint-Phase Redundancy Control; Modulation Indices; Motor Drive Operation; Motor Drives; Multilevel; Power Capacitors; Power Factors; Reactive Power; Reactive Power Transfer; Rectifier; Static VAr Compensators; Static Var Compensation; Switching Convertors; Transistor Switching States; Voltage Balancing

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2006 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jan 2006