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Increased efficiency and performance from modular multilevel converters reducing costs of converters for grid-level power systems and large motor drives.
About
Summary: The use of modular multilevel converters (M2LCs) has increased recently as the cost and availability of individual semiconductor devices is restrictive in high power applications. M2LCs are a low cost alternative, utilising available lower power semiconductors to meet required high power demands, in a modular, scalable fashion. Difficulties arise in the implementation of M2LC systems, particularly circulating and balancing currents,which leads to an increased rating of individual components and a need for complex voltage balancing control algorithms. Additionally, the control of, and power supply to, each separate module becomes a limiting factor as the number of modules increase. The failure of a single module can compromise the entire system. The Solution: Researchers at the University of Auckland have implemented a number of methods to alleviate these difficulties, making M2LCs an efficient, economical and reliable choice for high power applications. Several techniques are in commercial use. An inductive power transfer (IPT) system “partially and wirelessly” transfers power to each module, using standard components, maintaining consistency and reducing circuit complexity while providing electrical isolation. A voltage correcting module (VCM) minimises voltage fluctuations across modules, countering the difficulties associated with circulating currents and reducing associated power losses. Applications: High power motor drives High-voltage direct current (HVDC) transmission Traction motors Static synchronous compensators (STATCOM) Battery energy storage systems Grid-connected converters.