Global Asymptotic Stability of Modular Multilevel Converters

• Published in: IEEE transactions on industrial electronics (1982) Vol. 61; no. 2; pp. 603 - 612
• Main Authors: Antonopoulos, Antonios, Angquist, Lennart, Harnefors, Lennart, Ilves, Kalle, Nee, Hans-Peter
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-02-2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Asymptotic properties; Asymptotic stability; Capacitors; Converters; Dynamics; Equivalent circuits; Integrated circuits; Lyapunov stability; Mathematical analysis; Modular; modular multilevel converters (M2Cs); Multilevel; open-loop control; prototype; Prototypes; SRA - Energi; SRA - Energy; Strategy; Vectors; Voltage; Voltage control
• ISSN: 0278-0046; 1557-9948; 1557-9948
• DOI: 10.1109/TIE.2013.2254100

Modular multilevel converters require that the controller is designed so that the submodule capacitor voltages are equalized and stable, independent of the loading conditions. Assuming that the individual capacitor-voltage sharing is managed effectively, an open-loop strategy has been designed to ensure that the total amount of energy stored inside the converter always will be controlled. This strategy, using the steady-state solutions of the dynamic equations for controlling the total stored energy in each converter arm, has proven to be effective. The intention of this paper is to explain in a rigorous way the mechanism behind the suggested strategy and to prove that, when this open-loop strategy is used, the system becomes globally asymptotically stable. Experimental verification on a three-phase 10-kVA prototype is presented.