Evaluation of control and modulation methods for modular multilevel converters

• Published in: 2010 International Power Electronics Conference pp. 746 - 753
• Main Authors: Siemaszko, Daniel, Antonopoulos, Antonios, Ilves, Kalle, Vasiladiotis, Michail, Ängquist, Lennart, Nee, Hans-Peter
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2010
• Subjects: Arm; Capacitors; Control systems; Controller Evaluation; Feedback Control; Leg; Modular Multilevel Converter; Open loop systems; Open-loop Control; Power electronics; Prototype; Sorting; Switching converters; Topology; Voltage control
• ISBN: 9781424453948; 1424453941
• DOI: 10.1109/IPEC.2010.5544609

The modular multilevel converter is a promising converter technology for various high-voltage high-power applications. Despite the apparent simplicity of the circuit, the inherent dynamics of the converter and the balancing of the sub-module capacitor voltages impose high requirements on the control system, which can be implemented in quite different ways. To illustrate this, and to provide a guidance for future research on the subject, this paper presents an evaluation of four different control and modulation methods. The investigation is based on experiments on a down-scaled 10 kVA converter having 10 submodules per phase leg. The main items to be investigated are dynamics within the sub-modules, arm voltages and circulating currents. It is found that the suggested open-loop control method provides the fastest arm-voltage response and that the balancing approach based on a sorting algorithm is substantially faster and less complicated to implement than the method using a dedicated voltage controller for each sub-module.