Open-Loop Control of Modular Multilevel Converters Using Estimation of Stored Energy

• Published in: IEEE transactions on industry applications Vol. 47; no. 6; pp. 2516 - 2524
• Main Authors: Angquist, L., Antonopoulos, A., Siemaszko, D., Ilves, K., Vasiladiotis, M., Nee, H-P
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-11-2011; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Capacitors; Controllers; Converters; Current measurement; Electric potential; Energy balance; Energy management; Internal energy; Modular; modular multilevel converter (M2C); modulation; Modulators; Multilevel; open-loop control; prototype; SRA - Energi; SRA - Energy; Steady-state; Terms—Energy balance; Voltage; Voltage control
• ISSN: 0093-9994; 1939-9367; 1939-9367
• DOI: 10.1109/TIA.2011.2168593

The internal control of a modular multilevel converter aims to equalize and stabilize the submodule capacitor voltages independent of the loading conditions. It has been shown that a submodule selection mechanism, included in the modulator, can provide voltage sharing inside the converter arm. Several procedures for controlling the total stored energy in each converter arm exist. A new approach is described in this paper. It is based on estimation of the stored energy in the arms by combining the converter electromotive force reference, the measured alternating output current, and the known direct voltage. No feedback controllers are used. Experimental verification on a three-phase 10 kVA prototype is presented along with the description of the new procedure.