Paper Infomation
Control Strategies for Modular Multilevel Converters (MMC)
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Author: Rui Luo
Abstract: Modular Multilevel Converters (MMC) have emerged as a key technology for medium- to high-voltage power conversion applications such as HVDC transmission, large-scale renewable integration, and flexible AC transmission systems. Despite their superior performance and modularity, MMCs present complex control challenges due to their multi-level structure, numerous submodules, and circulating currents. This paper comprehensively reviews advanced control strategies developed for MMCs, including fundamental current and voltage balancing controls, sophisticated switching algorithms, and multifunctional approaches addressing harmonic suppression, power factor correction, and fault tolerance. Emphasis is placed on modern methods such as model predictive control, adaptive and robust controls that accommodate system nonlinearities and parameter uncertainties. Implementation aspects, including digital control hardware and the impact of control delays, are also discussed. The paper highlights recent advancements that improve system stability, efficiency, and reliability, thus facilitating MMC deployment in evolving power grids with high renewable penetration and stringent grid code requirements.
Keywords: Modular Multilevel Converter; Control Strategies; Voltage Balancing; Circulating Current; Model Predictive Control; Harmonic Suppression; Fault-Tolerant Control
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